JP4652876B2 - Driver switching method and driver switching device - Google Patents

Description

  The present invention relates to a driver switching method and a driver switching device that are preferably used when switching between an internal driver incorporated in an integrated circuit (abbreviation: IC) and an external driver outside the IC, for example.

  FIG. 27 is a diagram showing a step-up switching power supply circuit 110 when driving a built-in driver according to the prior art. FIG. 28 is a diagram showing a step-up switching power supply circuit 120 in driving a conventional external driver. A driver such as a step-up switching element used in the step-up switching power supply circuit is incorporated in an integrated circuit (abbreviation: IC) 111 in order to reduce manufacturing steps and manufacturing costs. If the output current exceeds a predetermined output current, the driver built in the IC 111 (hereinafter sometimes referred to as “built-in driver”) 112 increases the loss of the driver and cannot be used. In addition, since the size of the driver that can be built in the IC 111 is limited, when a large-scale driver exceeding the size is required, there is a disadvantage that the driver cannot be built in the IC 111. Therefore, as shown in FIG. 28, an external driver 113 can be connected to the outside of the IC 111. The IC 111 includes a pre-driver (hereinafter sometimes referred to as “built-in pre-driver”) 115 for driving the internal driver 112 and a pre-driver (hereinafter referred to as “external pre-driver”) for driving the external driver 113. 116). The built-in pre-driver 115 and the external pre-driver 116 (hereinafter may be collectively referred to as “pre-driver”) are complementary metal oxide semiconductors (abbreviated as CMOS).

  When the built-in driver 112 and the external driver 113 are driven without switching, when the built-in pre-driver 115 is driven, that is, when the built-in driver 112 is driven, a through current indicated by an arrow E in FIG. The unnecessary current flows through the external pre-driver 116. When the external pre-driver 116 is driven, that is, when the external driver 113 is driven, an unnecessary current such as a through current indicated by an arrow F in FIG. As described above, when an unnecessary current such as a through current flows through the pre-driver, problems such as generation of noise and increase in current consumption occur. Therefore, in order to prevent the occurrence of the problem, a function for switching and driving the built-in driver 112 and the external driver 113 is required. In the conventional technology, the IC 111 is provided with a dedicated switching setting terminal so that the built-in driver 112 and the external driver 113 are switched and driven, or the IC 111 and an external microcomputer are communicably connected, and a command transmitted from the microcomputer is transmitted. The internal driver 112 and the external driver 113 are switched and driven based on the above. Techniques relating to such switching are described in Patent Document 1 and Patent Document 2. The conventional technique described in Patent Document 1 is configured to switch between a peripheral device and a computer by using a semiconductor switching element such as a field effect transistor (abbreviation: FET). The conventional technique described in Patent Document 2 is configured to switch the changeover switch to a predetermined first position or second position in order to extract a transmission signal from the output of the differential amplifier.

Japanese Patent Laid-Open No. 7-175561 JP-A-8-70234

  As described above, in the step-up switching power supply circuit according to the prior art, the internal driver 112 and the external driver 113 are switched and driven by providing a dedicated terminal for switching setting in the IC 111, or the microcomputer 111 is communicably connected to the microcomputer. The built-in driver 112 and the external driver 113 are switched and driven based on a command transmitted from the IC 111. However, when considering that a driver having as many functions as possible is built in the IC 111, the switching setting If the IC 111 is provided with a dedicated terminal used only for this purpose, the number of components increases, and problems such as a driver with many desired functions added cannot be built in the IC 111. Further, when the built-in driver 112 and the external driver 113 are switched and driven based on a command transmitted from an external microcomputer, the driver is not switched until communication with the microcomputer is started, and the built-in driver is undesirably built. The driver 112 and the external driver 113 may be driven, and a through current may flow through the pre-driver and noise may be generated. Further, in the case of communication, there may be a problem that switching to an undesired driver due to a communication error occurs.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a driver switching method and a driver switching device capable of switching either one of a built-in driver and an external driver to the other without increasing the number of parts and suppressing generation of unnecessary current and noise. Is to provide.

The present invention is a driver switching method for switching and driving a built-in driver built in an integrated circuit and an external driver outside the integrated circuit,
The driver switching method is characterized in that the connection state between the ground terminal and the ground of the built-in driver is monitored, and either the built-in driver or the external driver is switched to the other and driven according to the connection state.

The present invention is characterized in that a resistor is provided between the ground terminal and the power source.
According to the present invention, a current source is provided between the ground terminal and the power source.

  The present invention is characterized in that the state is set to any one of a built-in driver drive state, an external driver drive state, and a drive stop state of the built-in driver and the external driver according to the voltage of the ground terminal. .

  The present invention is characterized in that either one of the built-in driver and the external driver is switched to the other in accordance with the current flowing through the ground terminal.

  The present invention is characterized in that the internal driver driving state, the external driver driving state, and the internal driver driving state and the external driver driving state are set according to the current flowing through the ground terminal. To do.

  Further, the present invention is characterized in that the built-in driver and the external driver are constituted by n-channel MOS transistors.

The present invention is also a driver switching method for switching and driving a built-in driver built in an integrated circuit and an external driver external to the integrated circuit,
A driver switching method characterized by monitoring a connection state between a power supply terminal and a power supply of the built-in driver and switching one of the built-in driver and the external driver to the other according to the connection state.

According to the present invention, a resistor is provided between the power supply terminal and the ground.
According to the present invention, a current source is provided between the power supply terminal and the ground.

  The present invention is characterized in that, according to the voltage of the power supply terminal, one of a built-in driver drive state, an external driver drive state, and a drive stop state of the built-in driver and the external driver is set. .

  The present invention is characterized in that either one of the built-in driver and the external driver is switched to the other and driven in accordance with the current flowing through the power supply terminal.

  Further, the present invention is characterized in that it is set to any one of a built-in driver drive state, an external driver drive state, and a drive stop state of the built-in driver and the external driver according to the current flowing through the power supply terminal. To do.

  According to the present invention, the built-in driver and the external driver are constituted by p-channel MOS transistors.

Further, the present invention is a driver switching device for switching and driving a built-in driver built in an integrated circuit and an external driver outside the integrated circuit,
The driver switching is configured to monitor the connection state between the ground terminal of the built-in driver and the ground, and switch either the built-in driver or the external driver to the other in accordance with the connection state. Device.

Further, the present invention is a driver switching device for switching and driving a built-in driver built in an integrated circuit and an external driver outside the integrated circuit,
The driver switching is configured to monitor a connection state between a power supply terminal of the built-in driver and a power supply, and switch one of the built-in driver and the external driver to the other according to the connection state. Device.

  According to the present invention, the connection state between the ground terminal of the built-in driver built in the integrated circuit (abbreviation: IC) and the ground is monitored, and either the built-in driver or the external driver is switched to the other according to the connection state. Switch to drive. For example, the voltage of the built-in driver's ground terminal (hereinafter sometimes simply referred to as “ground terminal”) is monitored, and when the ground terminal and the ground are connected and the voltage of the ground terminal is less than the threshold, the built-in driver is driven. If so, the internal driver is driven as it is, and if the external driver is driven, the external driver is switched to the internal driver to drive the internal driver. When the ground terminal is connected to the power supply side and the voltage of the ground terminal is equal to or higher than the threshold, the external driver is driven as it is if the external driver is driven, and the built-in driver is switched to the external driver if the internal driver is driven Drive the external driver. As described above, in the present invention, either the built-in driver or the external driver can be switched to the other and driven in accordance with the voltage of the ground terminal provided in the IC. Therefore, unlike a method of switching a built-in driver and an external driver by newly providing a dedicated driver switching terminal in the IC as in the prior art, it is not necessary to provide a dedicated driver switching terminal in the IC. Without increasing the number of components provided in the IC, either the built-in driver or the external driver can be switched to the other and driven.

  In addition, since either one of the built-in driver and the external driver can be switched and driven, the other driver can be prevented from being driven when either the built-in driver or the external driver is driven. Therefore, when driving the built-in driver, it is possible to prevent an unnecessary current such as a through current from flowing through the external pre-driver for driving the external driver. Further, when the external driver is driven, it is possible to prevent an unnecessary current such as a through current from flowing through the built-in pre-driver for driving the built-in driver. As a result, it is possible to suppress the occurrence of problems such as the occurrence of noise due to unnecessary current and an increase in current consumption.

  In addition, according to the present invention, by providing a resistor between the ground terminal of the built-in driver and the power supply, the ground terminal voltage can be stabilized even when the ground terminal is opened due to poor solder contact or disconnection. It can be made. In other words, the voltage at the ground terminal becomes unstable, and the switching from one of the built-in driver and the external driver to the other becomes abnormal, that is, undesirably from either the built-in driver or the external driver to the other. It is possible to prevent switching. In addition, by providing a resistor between the ground terminal and the power supply, it is not necessary to connect the ground terminal to the power supply when driving the external driver. Even when the ground terminal is open, the built-in driver can be switched to the external driver. An external driver can be driven.

  In addition, according to the present invention, by providing a current source between the ground terminal of the built-in driver and the power supply, the ground terminal voltage can be stabilized even when the ground terminal is opened due to poor contact or disconnection of the solder. Can do. In other words, the voltage at the ground terminal becomes unstable, and the switching from one of the built-in driver and the external driver to the other becomes abnormal, that is, undesirably from either the built-in driver or the external driver to the other. It is possible to prevent switching. In addition, by providing a current source between the ground terminal and the power supply, there is no need to connect the ground terminal to the power supply when driving an external driver, and switching from the built-in driver to the external driver is possible even when the ground terminal is open. The external driver can be driven.

  According to the present invention, the internal driver driving state for driving the internal driver, the external driver driving state for driving the external driver, and the driving for stopping the driving of the internal driver and the external driver according to the voltage of the ground terminal of the internal driver. One of the stopped states is set. For example, when the ground terminal is connected to the ground and the voltage of the ground terminal is less than the first threshold, if the internal driver is driven, the internal driver is driven as it is, and if the external driver is driven, the internal driver drive state The built-in driver is driven by setting to switch to the built-in driver. If the drive is stopped, the built-in driver is driven by setting to switch to the built-in driver drive state.

  When the ground terminal is connected to the power supply side and the voltage of the ground terminal is equal to or higher than the second threshold, if the external driver is driven, the external driver is driven as it is, and if the built-in driver is driven, the external driver is driven. The external driver is driven by setting to switch, and the external driver is driven by setting to switch to the external driver driving state if the driving is stopped. Further, when the ground terminal is connected to the power supply side and the voltage of the ground terminal is not less than the first threshold value and less than the second threshold value, if the driving of the built-in driver and the external driver is stopped, the driving is stopped as it is, and the built-in driver and the external driver are stopped. If either one of the drivers is driven, the drive is stopped by setting to switch to the drive stop state.

  As described above, the built-in driver drive state or external driver drive state can be set according to the voltage of the ground terminal of the built-in driver, and the built-in driver and external driver drive stop state can also be set. When there is a request to drive neither the driver nor the external driver, the driving stop state can be immediately set. As described above, since a desired driver can be immediately set to the drive or drive stop state in accordance with the voltage of the ground terminal, it is possible to prevent the occurrence of noise and the increase in current consumption.

  According to the present invention, either one of the built-in driver and the external driver is switched to the other and driven according to the current flowing through the ground terminal of the built-in driver. For example, when the current flowing through the ground terminal is less than the threshold, if the external driver is driven, the external driver is driven as it is, and if the internal driver is driven, the internal driver is switched to the external driver to drive the external driver. When the current flowing through the ground terminal is equal to or greater than the threshold value, if the internal driver is driven, the internal driver is driven as it is, and if the external driver is driven, the external driver is switched to the internal driver to drive the internal driver.

  As described above, in the present invention, either the built-in driver or the external driver can be switched to the other and driven in accordance with the current flowing through the ground terminal provided in the IC. Therefore, unlike a method of switching a built-in driver and an external driver by newly providing a dedicated driver switching terminal in the IC as in the prior art, it is not necessary to provide a dedicated driver switching terminal in the IC. Without increasing the number of components provided in the IC, either the built-in driver or the external driver can be switched to the other and driven.

  In addition, since either one of the built-in driver and the external driver can be switched and driven, the other driver can be prevented from being driven when either the built-in driver or the external driver is driven. Therefore, when driving the built-in driver, it is possible to prevent an unnecessary current such as a through current from flowing through the external pre-driver for driving the external driver. Further, when the external driver is driven, it is possible to prevent an unnecessary current such as a through current from flowing through the built-in pre-driver for driving the built-in driver. As a result, it is possible to suppress the occurrence of problems such as the occurrence of noise due to unnecessary current and an increase in current consumption.

  According to the present invention, the internal driver driving state for driving the internal driver, the external driver driving state for driving the external driver, and the driving of the internal driver and the external driver are stopped according to the current flowing through the ground terminal of the internal driver. One of the drive stop states is set. For example, when the current flowing through the ground terminal is less than the first threshold, if the external driver is driven, the external driver is driven as it is, and if the built-in driver is driven, the external driver is set to be switched to the external driver driving state. If the drive is stopped, the external driver is driven by setting to switch to the external driver drive state.

  When the current flowing through the ground terminal is equal to or greater than the second threshold, the built-in driver is driven as it is if the built-in driver is driven, and the built-in driver is set to switch to the built-in driver drive state if the external driver is driven. If the drive is stopped, the setting is made to switch to the built-in driver drive state, and the built-in driver is driven. When the current flowing through the ground terminal is not less than the first threshold value and less than the second threshold value, if the driving of the internal driver and the external driver is stopped, the driving is stopped as it is, and either the internal driver or the external driver is driven. If so, the driver is stopped by setting to switch to the drive stop state.

  As described above, according to the current flowing through the ground terminal of the internal driver, it can be set to the internal driver drive state or the external driver drive state, and also can be set to the drive stop state of the internal driver and the external driver. When there is a request to drive neither the built-in driver nor the external driver, the drive stop state can be immediately set. As described above, since a desired driver can be immediately set to the drive or drive stop state in accordance with the current flowing through the ground terminal, it is possible to prevent the occurrence of noise and the increase in current consumption.

  Further, according to the present invention, even when the built-in driver and the external driver are composed of n-channel MOS transistors, it is not necessary to newly provide a dedicated terminal for driver switching in the IC, so that the number of components provided in the IC is increased. Instead, either the built-in driver or the external driver can be switched to the other and driven. Accordingly, it is possible to prevent an unnecessary current such as a through current from flowing through the pre-driver, and it is possible to suppress the occurrence of problems such as the occurrence of noise and an increase in current consumption due to the unnecessary current.

  Further, according to the present invention, the connection state between the power supply terminal of the built-in driver built in the integrated circuit (abbreviation: IC) and the power supply is monitored, and either the built-in driver or the external driver is connected to the other according to this connection state. Switch to drive. For example, the voltage of the power supply terminal of the built-in driver (hereinafter sometimes simply referred to as “power supply terminal”) is monitored. When the power supply terminal and the power supply are connected and the voltage of the power supply terminal is equal to or higher than the threshold value, the built-in driver is driven. If so, the internal driver is driven as it is, and if the external driver is driven, the external driver is switched to the internal driver to drive the internal driver. When the power supply terminal is connected to the ground and the voltage of the power supply terminal is less than the threshold, if the external driver is driven, the external driver is driven as it is, and if the internal driver is driven, switch from the internal driver to the external driver. Drive an external driver. As described above, according to the present invention, either the built-in driver or the external driver can be switched to the other and driven in accordance with the voltage of the power supply terminal provided in the IC. Therefore, unlike a method of switching a built-in driver and an external driver by newly providing a dedicated driver switching terminal in the IC as in the prior art, it is not necessary to provide a dedicated driver switching terminal in the IC. Without increasing the number of components provided in the IC, either the built-in driver or the external driver can be switched to the other and driven.

  In addition, since either one of the built-in driver and the external driver can be switched and driven, the other driver can be prevented from being driven when either the built-in driver or the external driver is driven. Therefore, when driving the built-in driver, it is possible to prevent an unnecessary current such as a through current from flowing through the external pre-driver for driving the external driver. Further, when the external driver is driven, it is possible to prevent an unnecessary current such as a through current from flowing through the built-in pre-driver for driving the built-in driver. As a result, it is possible to suppress the occurrence of problems such as the occurrence of noise due to unnecessary current and an increase in current consumption.

  Further, according to the present invention, by providing a resistor between the power supply terminal of the built-in driver and the ground, the power supply terminal voltage can be stabilized even when the power supply terminal is opened due to poor contact of solder or disconnection. It can be made. In other words, the voltage at the power supply terminal becomes unstable and the switching from one of the built-in driver and the external driver to the other becomes abnormal, that is, undesirably from either the built-in driver or the external driver to the other. It is possible to prevent switching. In addition, by providing a resistor between the power supply terminal and the power supply, it is not necessary to connect the power supply terminal to the ground when driving the external driver, and even when the power supply terminal is open, the built-in driver can be switched to the external driver. The driver can be driven.

  Further, according to the present invention, by providing a current source between the power supply terminal of the built-in driver and the ground, the voltage of the power supply terminal can be reduced even if the power supply terminal is opened due to poor contact or disconnection of the solder. Can be stabilized. In other words, the voltage at the power supply terminal becomes unstable and the switching from one of the built-in driver and the external driver to the other becomes abnormal, that is, undesirably from either the built-in driver or the external driver to the other. It is possible to prevent switching. In addition, by providing a current source between the power supply terminal and the power supply, it is not necessary to connect the power supply terminal to the ground when driving the external driver, and even when the power supply terminal is open, the built-in driver can be switched to the external driver. An external driver can be driven.

  Further, according to the present invention, the internal driver driving state for driving the internal driver, the external driver driving state for driving the external driver, and the driving for stopping the driving of the internal driver and the external driver according to the voltage of the power supply terminal of the internal driver. One of the stopped states is set. For example, when the power supply terminal is connected to the ground and the voltage of the power supply terminal is less than the first threshold, if the external driver is driven, the external driver is driven as it is, and if the built-in driver is driven, the external driver is driven. The external driver is driven by setting to switch, and the external driver is driven by setting to switch to the external driver driving state if the driving is stopped. When the power supply terminal and the power supply are connected and the voltage of the power supply terminal is equal to or higher than the second threshold, if the internal driver is driven, the internal driver is driven as it is, and if the external driver is driven, the internal driver is driven. The setting for switching is made to drive the built-in driver, and if the drive is stopped, the setting to switch to the built-in driver driving state is made to drive the built-in driver. When the voltage of the power supply terminal is not less than the first threshold value and less than the second threshold value, if the driving of the built-in driver and the external driver is stopped, the driving is stopped as it is, and either the built-in driver or the external driver is driven. If so, the driver is stopped by setting to switch to the drive stop state.

  As described above, the built-in driver drive state or external driver drive state can be set according to the voltage of the power supply terminal of the built-in driver, and the built-in driver and external driver drive stop state can also be set. When there is a request to drive neither the driver nor the external driver, the driving stop state can be immediately set. As described above, since a desired driver can be immediately set to the drive or drive stop state in accordance with the voltage of the power supply terminal, it is possible to prevent the occurrence of noise and the increase in current consumption.

  Further, according to the present invention, either the built-in driver or the external driver is switched to the other and driven in accordance with the current flowing through the power supply terminal of the built-in driver. For example, when the current flowing through the power supply terminal is less than the threshold value, if the external driver is driven, the external driver is driven as it is. If the internal driver is driven, the internal driver is switched to the external driver to drive the external driver. When the current flowing through the power supply terminal is equal to or greater than the threshold, if the internal driver is driven, the internal driver is driven as it is. If the external driver is driven, the external driver is switched to the internal driver to drive the internal driver.

  As described above, according to the present invention, either the built-in driver or the external driver can be switched to the other and driven in accordance with the current flowing through the power supply terminal of the built-in driver provided in the IC. Therefore, unlike a method of switching a built-in driver and an external driver by newly providing a dedicated driver switching terminal in the IC as in the prior art, it is not necessary to provide a dedicated driver switching terminal in the IC. Without increasing the number of components provided in the IC, either the built-in driver or the external driver can be switched to the other and driven.

  In addition, since either one of the built-in driver and the external driver can be switched and driven, the other driver can be prevented from being driven when either the built-in driver or the external driver is driven. Therefore, when driving the built-in driver, it is possible to prevent an unnecessary current such as a through current from flowing through the external pre-driver for driving the external driver. Further, when the external driver is driven, it is possible to prevent an unnecessary current such as a through current from flowing through the built-in pre-driver for driving the built-in driver. As a result, it is possible to suppress the occurrence of problems such as the occurrence of noise due to unnecessary current and an increase in current consumption.

  According to the present invention, the internal driver driving state for driving the internal driver, the external driver driving state for driving the external driver, and the driving of the internal driver and the external driver are stopped according to the current flowing through the power supply terminal of the internal driver. One of the drive stop states is set. For example, when the current flowing through the power supply terminal is less than the first threshold, if the external driver is driven, the external driver is driven as it is, and if the built-in driver is driven, the external driver is set to switch to the external driver driving state. If the drive is stopped, the external driver is driven by setting to switch to the external driver drive state.

  When the current flowing through the power supply terminal is equal to or greater than the second threshold, the built-in driver is driven as it is if the built-in driver is driven, and the built-in driver is switched to the built-in driver drive state if the external driver is driven. If the drive is stopped, the internal driver is set to switch to the internal driver drive state, and the internal driver is driven. When the current flowing through the power supply terminal is not less than the first threshold and less than the second threshold, if the driving of the internal driver and the external driver is stopped, the driving is stopped as it is, and either the internal driver or the external driver is driven. If so, the driver is stopped by setting to switch to the drive stop state.

  As described above, according to the current flowing through the power supply terminal of the internal driver, it can be set to the internal driver drive state or the external driver drive state, and also can be set to the drive stop state of the internal driver and the external driver. When there is a request to drive neither the built-in driver nor the external driver, the drive stop state can be immediately set. As described above, since a desired driver can be immediately set to the drive or drive stop state in accordance with the current flowing through the power supply terminal, it is possible to prevent the occurrence of noise and the increase in current consumption.

  Further, according to the present invention, even when the built-in driver and the external driver are constituted by p-channel MOS transistors, it is not necessary to newly provide a dedicated terminal for driver switching in the IC, so that the number of components provided in the IC is increased. Instead, either the built-in driver or the external driver can be switched to the other and driven. Accordingly, it is possible to prevent an unnecessary current such as a through current from flowing through the pre-driver, and it is possible to suppress the occurrence of problems such as the occurrence of noise and an increase in current consumption due to the unnecessary current.

  According to the present invention, the connection state between the ground terminal of the built-in driver built in the integrated circuit (abbreviation: IC) and the ground is monitored, and either the built-in driver or the external driver is connected to the other according to the connection state. Switch to drive. For example, the voltage of the built-in driver's ground terminal (hereinafter sometimes simply referred to as “ground terminal”) is monitored, and when the ground terminal and the ground are connected and the voltage of the ground terminal is less than the threshold, the built-in driver is driven. If so, the internal driver is driven as it is, and if the external driver is driven, the external driver is switched to the internal driver to drive the internal driver. When the ground terminal is connected to the power supply side and the voltage of the ground terminal is equal to or higher than the threshold, the external driver is driven as it is if the external driver is driven, and the built-in driver is switched to the external driver if the internal driver is driven Drive the external driver. As described above, in the present invention, either the built-in driver or the external driver can be switched to the other and driven in accordance with the voltage of the ground terminal provided in the IC. Therefore, unlike a device for switching a built-in driver and an external driver by newly providing a dedicated terminal for driver switching in the IC as in the prior art, it is not necessary to provide a dedicated terminal for switching the driver in the IC. One of the built-in driver and the external driver can be switched to the other and driven without increasing the number of components provided.

  In addition, since either one of the built-in driver and the external driver can be switched and driven, the other driver can be prevented from being driven when either the built-in driver or the external driver is driven. Therefore, when driving the built-in driver, it is possible to prevent an unnecessary current such as a through current from flowing through the external pre-driver for driving the external driver. Further, when the external driver is driven, it is possible to prevent an unnecessary current such as a through current from flowing through the built-in pre-driver for driving the built-in driver. As a result, it is possible to suppress the occurrence of problems such as the occurrence of noise due to unnecessary current and an increase in current consumption.

  Further, according to the present invention, the connection state between the power supply terminal of the built-in driver built in the integrated circuit (abbreviation: IC) and the power supply is monitored, and either the built-in driver or the external driver is connected to the other according to this connection state. Switch to drive. For example, the voltage of the power supply terminal of the built-in driver (hereinafter sometimes simply referred to as “power supply terminal”) is monitored. When the power supply terminal and the power supply are connected and the voltage of the power supply terminal is equal to or higher than the threshold value, the built-in driver is driven. If so, the internal driver is driven as it is, and if the external driver is driven, the external driver is switched to the internal driver to drive the internal driver. When the power supply terminal is connected to the ground and the voltage of the power supply terminal is less than the threshold, if the external driver is driven, the external driver is driven as it is, and if the internal driver is driven, switch from the internal driver to the external driver. Drive an external driver. As described above, according to the present invention, either the built-in driver or the external driver can be switched to the other and driven in accordance with the voltage of the power supply terminal provided in the IC. Therefore, unlike a device for switching a built-in driver and an external driver by newly providing a dedicated terminal for driver switching in the IC as in the prior art, it is not necessary to newly provide a dedicated terminal for switching the driver in the IC. Without increasing the number of components provided in the IC, either the built-in driver or the external driver can be switched to the other and driven.

  In addition, since either one of the built-in driver and the external driver can be switched and driven, the other driver can be prevented from being driven when either the built-in driver or the external driver is driven. Therefore, when driving the built-in driver, it is possible to prevent an unnecessary current such as a through current from flowing through the external pre-driver for driving the external driver. Further, when the external driver is driven, it is possible to prevent an unnecessary current such as a through current from flowing through the built-in pre-driver for driving the built-in driver. As a result, it is possible to suppress the occurrence of problems such as the occurrence of noise due to unnecessary current and an increase in current consumption.

  Hereinafter, a plurality of modes for carrying out the present invention will be described. In each embodiment, portions corresponding to the matters described in the preceding embodiment are denoted by the same reference numerals, and redundant description may be omitted. When only a part of the configuration is described, the other parts of the configuration are the same as those described in the preceding section. Not only the combination of the parts specifically described in each embodiment, but also the embodiments can be partially combined as long as the combination does not hinder.

  FIG. 1 is an electric circuit diagram showing a simplified configuration of the driver switching device 1 according to the first embodiment of the present invention, and is an electric circuit diagram when driving a built-in driver. FIG. 2 is an electric circuit diagram showing a simplified configuration of the driver switching device 1, and is an electric circuit diagram when driving an external driver. The driver switching devices 1, 30, 40, and 50 according to the first to fourth embodiments of the present invention described below are non-insulated boost switching power supply circuits (hereinafter sometimes referred to as “boost switching power supply circuits”). Consists of. In the following description, the “driver switching device” may be referred to as a “boost switching power supply circuit”. The step-up switching power supply circuit 1 boosts the output voltage from the voltage generated in the battery 2 toward a predetermined voltage by the switching operation of the switching element. The step-up switching power supply circuit 1 is used, for example, in a power supply section of an ignition circuit for inflating an airbag embedded in a handle and an instrument panel in an airbag device as an occupant protection device mounted on a vehicle. It is done.

  First, the step-up switching power supply circuit 1 when the built-in driver is driven will be described. The step-up switching power supply circuit 1 includes a battery 2, and a coil 3 and a diode 4 are connected in series between the battery 2 and the output terminal 6. One end of the coil 3 is connected to the battery 2, the other end of the coil 3 is connected to the anode of the diode 4, and the cathode of the diode 4 is connected to the output terminal 6.

  A capacitor 5 having the other end connected to the ground is connected between the cathode of the diode 4 and the output terminal 6. A connection point between the cathode of the diode 4 and the positive terminal of the capacitor 5 is connected to the output terminal 6. A connection point between the other end of the coil 3 and the anode of the diode 4 is connected to a second terminal 19 of an integrated circuit (abbreviated as IC) 7 as shown in FIG. The IC 7 includes a signal source 11, a changeover switch 12, a built-in pre-driver 14, an external pre-driver 15, a built-in driver 16 and an inverter 17. The changeover switch 12 includes a switch piece 13, a first contact 13a, and a second contact 13b. The second terminal 19 of the IC 7 is connected to a built-in driver 16 built in the IC 7. The built-in driver 16 of the present embodiment is realized by an n-channel MOS field effect transistor (abbreviation: MOSFET) that functions as a switching element. In the following description, the internal driver 16 may be referred to as an internal MOSFET 16. The second terminal 19 is connected to the drain of the built-in MOSFET 16. The source of the built-in MOSFET 16 is connected to a ground terminal (hereinafter sometimes simply referred to as “ground terminal”) 21 of the built-in MOSFET 16, and the ground terminal 21 is connected to the ground.

The first terminal 18 of the IC 7 is connected to a DC power source (hereinafter sometimes referred to as “power source”) 8. The first terminal 18 is connected to a power supply unit 15 a of a pre-driver 15 (hereinafter also referred to as “external pre-driver”) 15 for driving an external driver 22 outside the IC 7. The external pre-driver 15 of the present embodiment is a complementary MOS (
Complementary Metal Oxide Semiconductor (abbreviation: CMOS) is realized, and the external driver 22 is realized by an n-channel MOSFET that functions as a switching element. In the following description, the external driver 22 may be referred to as an external MOSFET 22. The input unit 15 b of the external pre-driver 15 is connected to the second contact 13 b of the changeover switch 12. The output unit 15 c of the external pre-driver 15 is connected to the third terminal 20 of the IC 7. The first terminal 18 is connected to a power supply unit 14 a of a pre-driver (hereinafter sometimes referred to as “built-in pre-driver”) 14 for driving a built-in MOSFET 16 built in the IC 7. The built-in pre-driver 14 is realized by CMOS. The input part 14 b of the built-in pre-driver 14 is connected to the first contact 13 a of the changeover switch 12. The output part 14 c of the built-in pre-driver 14 is connected to the gate of the built-in MOSFET 16.

  A connection point between the input terminal 17 a of the inverter 17 and the source of the built-in MOSFET 16 is connected to the ground terminal 21. The changeover switch 12 is connected to a signal source 11 that generates a pulse signal. The inverter 17 monitors the voltage of the ground terminal 21 based on a signal corresponding to the voltage of the ground terminal 21 input from the input terminal 17 a, in other words, detects the voltage and switches the switching mode of the changeover switch 12. Is output from the output terminal 17b. In the present embodiment, based on a signal output from the output terminal 17b of the inverter 17, the switch piece 13 of the changeover switch 12 is connected to one of the first contact 13a and the second contact 13b and turned on (ON). ) So that the switching mode can be switched. When the switch piece 13 is connected to the first contact 13a, the built-in MOSFET 16 is driven.

  Next, the step-up switching power supply circuit 1 when driving an external driver will be described. When the switch piece 13 of the changeover switch 12 is connected to the second contact 13b, the external MOSFET 22 is driven. When the external MOSFET 22 is driven, the connection point between one end of the coil 3 and the anode of the diode 4 is connected to the drain of the external MOSFET 22 as shown in FIG. The source of the external MOSFET 22 is connected to the ground, and the gate of the external MOSFET 22 is connected to the third terminal 20 of the IC 7. The ground terminal 21 is connected to the power supply 8. A breakdown preventing diode 23 is connected between the drain and source of the built-in MOSFET 16 and the external MOSFET 22 (hereinafter may be collectively referred to as “MOSFET”). More specifically, the anode of the breakdown preventing diode 23 is connected to the source of the MOSFET, and the cathode of the breakdown preventing diode 23 is connected to the drain of the MOSFET. Since the film of the gate portion of the MOSFET is vulnerable to overvoltage and has high impedance, it may be destroyed by static electricity. As described above, the MOSFET 23 is prevented from being destroyed by connecting the destruction preventing diode 23 to the MOSFET.

  A DC voltage of the battery 2 is applied to the coil 3 of the step-up switching power supply circuit 1. The signal source 11 of the IC 7 generates and outputs a pulse signal having a predetermined cycle. For example, when the switch piece 13 of the changeover switch 12 is connected to the first contact 13 a as shown in FIG. 1, the pulse signal output from the signal source 11 is input to the input unit 14 b of the built-in pre-driver 14. A high level signal or a low level signal is output from the output unit 14 c of the built-in pre-driver 14, and the signal is input to the gate of the built-in MOSFET 16. The built-in MOSFET 16 performs a switching operation that repeats conduction and interruption based on an input signal. The coil 3 repeats grounding and opening by repeating the conduction and interruption of the built-in MOSFET 16. As a result, a high voltage having the same cycle as that of the signal output from the signal source 11 is generated from the coil 3. The high voltage is smoothed by the capacitor 5. More specifically, the capacitor 5 smoothes the output voltage of the coil 3 generated in a pulse shape in response to the switching operation of the built-in MOSFET 16. The capacitor 5 accumulates electric charge when the output voltage of the coil 3 is equal to or higher than the specified voltage, and discharges electric charge when the output voltage is lower than the output voltage. The output voltage smoothed by the capacitor 5 is supplied from the output terminal 6 to, for example, an ignition circuit of an air bag squib. When the coil 3 becomes a high voltage by the battery 2, the current tends to flow backward to the battery 2 side, but the diode 4 is configured to prevent the current from flowing backward. The operation of the step-up switching power supply circuit 1 when the switch piece 13 of the changeover switch 12 is connected to the second contact 13b and the external MOSFET 22 is driven is the same as the operation when the built-in MOSFET 16 is driven. Description is omitted.

  Next, a driver switching method for switching and driving the built-in driver 16 and the external driver 22 in the first embodiment will be described. FIG. 3 is a flowchart showing an example of an operation procedure of the driver switching method according to the first embodiment of the present invention. The operation procedure of the driver switching method is started when, for example, the ignition switch of the vehicle is turned on. In step a1, the built-in pre-driver 14 determines whether or not the built-in driver 16 is driven. If it is driven, the process proceeds to step a2. In step a2, the inverter 17 determines whether or not the voltage at the ground terminal 21 is less than the threshold value. If the voltage is less than the threshold value, the process proceeds to step a3. The voltage below the threshold is, for example, the ground voltage, and the voltage above the threshold is, for example, the power supply voltage. In step a3, after the built-in pre-driver 14 drives the built-in MOSFET 16 which is a built-in driver, all operation procedures are terminated.

  In step a4, the switch piece 13 of the changeover switch 12 switches from the connection state with the first contact 13a to the connection state with the second contact 13b based on the signal output from the inverter 17, and proceeds to step a5. In step a5, after the external pre-driver 15 drives the external MOSFET 22 which is an external driver, all operation procedures are terminated. In step a6, the external pre-driver 15 determines whether or not the external driver 22 is driven. If it is driven, the process proceeds to step a7. If not, the process returns to step a1. In step a7, the inverter 17 determines whether or not the voltage at the ground terminal 21 is less than the threshold value. If the voltage is less than the threshold value, the process proceeds to step a8. In step a8, the switch piece 13 of the changeover switch 12 switches from the connection state with the second contact 13b to the connection state with the first contact 13a based on the signal output from the inverter 17, and proceeds to step a9. In step a9, after the built-in pre-driver 14 drives the built-in MOSFET 16 which is a built-in driver, all operation procedures are terminated.

  As described above, according to the first embodiment, the voltage of the ground terminal 21 is monitored by the inverter 17, and when the ground terminal 21 and the ground are connected and the voltage of the ground terminal 21 is less than the threshold value, the built-in MOSFET 16 Is driven as it is, and if the external MOSFET 22 is driven, the external MOSFET 22 is switched to the internal MOSFET 16 to drive the internal MOSFET 16. When the ground terminal 21 is connected to the power supply side and the voltage of the ground terminal 21 is equal to or higher than the threshold value, the external MOSFET 22 is driven as it is, and the internal MOSFET 16 is switched from the internal MOSFET 16 to the external MOSFET 22 when the internal MOSFET 16 is driven. The external MOSFET 22 is driven. As described above, in this embodiment, either the built-in MOSFET 16 or the external MOSFET 22 can be switched to the other and driven in accordance with the voltage of the ground terminal 21 provided in the IC 7. Therefore, unlike the conventional technique in which a dedicated driver switching terminal is newly provided in the IC 7 and the built-in MOSFET 16 and the external MOSFET 22 are switched, there is no need to newly provide a dedicated driver switching terminal in the IC 7. Without increasing the number of components provided in the IC 7, either the built-in MOSFET 16 or the external MOSFET 22 can be switched to the other and driven.

  In addition, since either one of the built-in MOSFET 16 and the external MOSFET 22 can be switched and driven, the other can be reliably driven when either the built-in MOSFET 16 or the external MOSFET 22 is driven. Therefore, when the built-in MOSFET 16 is driven, it is possible to prevent unnecessary current such as a through current indicated by a broken arrow A in FIG. 1 from flowing to the external pre-driver 15 for driving the external MOSFET 22. Further, when the external MOSFET 22 is driven, unnecessary current such as a through current indicated by a broken arrow B in FIG. 2 can be prevented from flowing to the built-in pre-driver 14 for driving the built-in MOSFET 16. As a result, it is possible to suppress the occurrence of problems such as the occurrence of noise due to unnecessary current and an increase in current consumption.

  FIG. 4 is an electric circuit diagram showing a simplified configuration of the driver switching device 1. FIG. 5 is an electric circuit diagram showing a simplified configuration of the driver switching device 1. As shown in FIG. 1 described above, when the built-in MOSFET 16 is driven, the ground terminal 21 is connected to the ground. When the built-in MOSFET 16 is driven, if the ground terminal 21 is opened due to poor solder contact or disconnection, the voltage of the ground terminal 21 rises, and the switch piece 13 of the changeover switch 12 is connected to the first contact 13a. To the connection state with the second contact 13b. As a result, the driving state of the built-in MOSFET 16 is switched to the driving state of the external MOSFET 22. When the driving state of the external MOSFET 22 is switched, the built-in MOSFET 16 is turned off, whereby the voltage at the ground terminal 21 drops to the ground voltage, and the driving state of the external MOSFET 22 is switched to the driving state of the built-in MOSFET 16. As the built-in MOSFET 16 is driven again, when the ground terminal 21 is opened, the voltage at the ground terminal 21 becomes unstable, causing the abnormal switching operation of the MOSFET as described above, and generating unnecessary noise. Troubles such as doing.

  Therefore, in this embodiment, a resistor 25 is provided between the ground terminal 21 and the power supply 8 as shown in FIG. Specifically, one end of the resistor 25 is connected to the power supply 8 via the first terminal 18, and the connection point between the other end of the resistor 25 and the source of the built-in MOSFET 16 is connected to the ground terminal 21. As described above, the resistor 25 is provided between the ground terminal 21 of the built-in MOSFET 16 and the power supply 8, and this resistor 25 functions as a so-called pull-up resistor, and the potential of the ground terminal 21 is set to the power supply potential via the resistor 25. As a result, even when a problem that the ground terminal 21 is opened occurs, the voltage of the ground terminal 21 can be stabilized. In other words, the voltage at the ground terminal 21 becomes unstable, and switching from one of the built-in MOSFET 16 and the external MOSFET 22 to the other becomes abnormal, that is, one of the built-in MOSFET 16 and the external MOSFET 22 is undesirably switched to the other. Can be prevented. Further, by providing the resistor 25 between the ground terminal 21 and the power supply 8, it is not necessary to connect the ground terminal 21 to the power supply 8 side when driving the external MOSFET 22, and even when the ground terminal 21 is open, the built-in MOSFET 16 The external MOSFET 22 can be driven by switching from the external MOSFET 22 to the external MOSFET 22.

  In the present embodiment, the ground terminal 21 of the built-in MOSFET 16 is prevented in order to prevent a problem that the voltage at the ground terminal 21 becomes unstable and an abnormal switching operation of the MOSFET is caused to cause unnecessary noise. A current source 26 may be provided between the power supplies 8 as shown in FIG. Specifically, one end of the current source 26 is connected to the power supply 8 via the first terminal 18, and the connection point between the other end of the current source 26 and the source of the built-in MOSFET 16 is connected to the ground terminal 21. As a result, the potential of the ground terminal 21 can be kept constant. Therefore, the voltage of the ground terminal 21 can be stabilized, and the same effect as when the resistor 25 is provided as shown in FIG. 4 can be achieved.

  FIG. 6 is an electric circuit diagram showing a simplified configuration of the driver switching device 30 according to the second embodiment of the present invention. In the present embodiment, only the driver switching device 30 when the built-in driver is driven is shown for easy understanding. When the external driver is driven, the external driver 22 is connected to the third terminal 20 of the IC 7 as in the driver switching device 1 shown in FIG. In the present embodiment, a three-contact selector switch 31 is provided in place of the two-contact selector switch 12 of the first embodiment. The changeover switch 31 includes a switch piece 32, a first contact 32a, a second contact 32b, and a third contact 32c. In the present embodiment, a comparator 33 is provided instead of the inverter 17 of the first embodiment. The first contact 32a of the changeover switch 31 is connected to the input unit 14b of the built-in predriver 14, the second contact 32b is connected to the input unit 15b of the external predriver 15, and the third contact 32c is connected to both. It has not been. A connection point between the non-inverting input terminal 33 a of the comparator 33 and the source of the built-in MOSFET 16 is connected to the ground terminal 21. The first inverting input terminal 33 b of the comparator 33 is connected to the first power supply 34, and the second inverting input terminal is connected to the second power supply 35.

  The comparator 33 according to the present embodiment monitors the voltage of the ground terminal 21 and outputs a signal for switching the switching mode of the changeover switch 31 from the output terminal 33d based on a signal corresponding to the voltage of the ground terminal 21. . In the present embodiment, based on the signal output from the output terminal 33d of the comparator 33, the switch piece 32 of the changeover switch 31 is connected to any one of the first contact 32a to the third contact 32c and turned on ( ON) is configured so that the switching mode can be switched. When the switch piece 32 is connected to the first contact 32a, the built-in driver driving state in which the built-in MOSFET 16 is driven is set. When the switch piece 32 is connected to the second contact 32b, an external driver driving state in which the external MOSFET 22 is driven is set. When the switch piece 32 is connected to the third contact 32c, the driving stop state is set in which the driving of the internal MOSFET 16 and the external MOSFET 22 is stopped.

  Next, a driver switching method for switching and driving the built-in driver 16 and the external driver 22 in the second embodiment will be described. FIG. 7 is a flowchart showing an example of an operation procedure of the driver switching method according to the second embodiment of the present invention. FIG. 8 is a flowchart showing an example of an operation procedure of the driver switching method according to the second embodiment of the present invention. The operation procedure of the driver switching method shown in FIGS. 7 and 8 is started, for example, when an ignition switch of the vehicle is turned on. It is assumed that the first threshold value in the present embodiment is a value smaller than the second threshold value. In step b1, the built-in pre-driver 14 determines whether or not the built-in driver 14 is driven. If it is driven, the process proceeds to step b2. If not, the process proceeds to step b9. In step b2, the comparator 33 determines whether or not the voltage at the ground terminal 21 is less than the first threshold value. If the voltage is less than the first threshold value, the process proceeds to step b3. . The first threshold is a value corresponding to 1/3 of the power supply voltage, for example. In step b3, after the built-in pre-driver 14 drives the built-in MOSFET 16 which is a built-in driver, all the operation procedures are finished.

  In step b4, the comparator 33 determines whether or not the voltage of the ground terminal 21 is equal to or higher than the second threshold value. If the voltage is equal to or higher than the second threshold value, the process proceeds to step b5. It is determined that the voltage is greater than or equal to the first threshold and less than the second threshold, and the process proceeds to step b7. The second threshold is a value corresponding to 2/3 of the power supply voltage, for example. In step b5, the switch piece 32 of the changeover switch 31 switches from the connection state with the first contact 32a to the connection state with the second contact 32b based on the signal output from the output terminal 33d of the comparator 33, and drives the external driver. The state is set and the process proceeds to step b6. In step b6, after the external pre-driver 15 drives the external MOSFET 22 that is an external driver, all operation procedures are terminated. In step b7, the switch piece 32 of the changeover switch 31 switches from the connection state with the first contact 32a to the connection state with the third contact 32c based on the signal output from the output terminal 33d of the comparator 33, and the built-in driver 16 The drive stop state is set and the process proceeds to step b8. In step b8, after the built-in pre-driver 14 stops driving the built-in MOSFET 16, all operation procedures are terminated.

  In step b9, the external pre-driver 15 determines whether or not the external driver 22 is driven. If it is driven, the process proceeds to step b10. If it is not driven, both the internal and external drivers 16 and 22 are driven. It is determined that it is not driven, and the process proceeds to step c1 in FIG. In step b10, the comparator 33 determines whether or not the voltage at the ground terminal 21 is less than the first threshold value. If the voltage is less than the first threshold value, the process proceeds to step b11, and if not less than the first threshold value, the process proceeds to step b13. . In step b11, the switch piece 32 of the changeover switch 31 switches from the connection state with the second contact 32b to the connection state with the first contact 32a based on the signal output from the output terminal 33d of the comparator 33, and the built-in driver is driven. The state is set and the process proceeds to step b12. In step b12, after the built-in pre-driver 14 drives the built-in MOSFET 16 which is a built-in driver, all operation procedures are completed.

  In step b13, the comparator 33 determines whether or not the voltage at the ground terminal 21 is equal to or higher than the second threshold value. If the voltage is equal to or higher than the second threshold value, the process proceeds to step b14. It is determined that the voltage is greater than or equal to the first threshold value and less than the second threshold value, and the process proceeds to step b15. In step b14, after the external pre-driver 15 drives the external MOSFET 22, all operation procedures are terminated. In step b15, the switch piece 32 of the changeover switch 31 switches from the connection state with the second contact 32b to the connection state with the third contact 32c based on the signal output from the output terminal 33d of the comparator 33, and the external driver 22 The drive stop state is set, and the process proceeds to step b16. In step b16, after the external pre-driver 15 stops driving the external MOSFET 22, all operation procedures are terminated.

  In step c1 of FIG. 8, the comparator 33 determines whether or not the voltage of the ground terminal 21 is less than the first threshold value. If the voltage is less than the first threshold value, the process proceeds to step c2. Proceed to c4. In step c2, the switch piece 32 of the changeover switch 31 switches from the connection state with the third contact 33c to the connection state with the first contact 32a based on the signal output from the output terminal 33d of the comparator 33, and the built-in driver is driven. The state is set and the process proceeds to step c3. In step c3, after the built-in pre-driver 14 drives the built-in MOSFET 16, all operation procedures are terminated.

  In step c4, the comparator 33 determines whether or not the voltage at the ground terminal 21 is equal to or higher than the second threshold value. If the voltage is equal to or higher than the second threshold value, the process proceeds to step c5. It is determined that the voltage is greater than or equal to the first threshold and less than the second threshold, and the process proceeds to step c7. In step c5, the switch piece 32 of the changeover switch 31 switches from the connection state with the third contact 32c to the connection state with the second contact 32b based on the signal output from the output terminal 33d of the comparator 33, and drives the external driver. The state is set and the process proceeds to step c6. In step c6, after the external pre-driver 15 drives the external MOSFET 22, all operation procedures are terminated. In step c7, the switch piece 32 of the changeover switch 31 maintains the connection state with the third contact 32c, thereby maintaining the drive stop state of the built-in MOSFET 16 and the external MOSFET 22 and finishing all the operation procedures.

  As described above, according to the second embodiment, when the ground terminal 21 is connected to the ground, and the voltage of the ground terminal 21 is less than the first threshold value, the built-in MOSFET 16 is driven as it is, If the external MOSFET 22 is driven, the setting to switch to the built-in driver driving state is performed to drive the built-in MOSFET 16, and if the driving is stopped, the setting to switch to the built-in driver driving state is set to drive the built-in MOSFET 16.

  When the ground terminal 21 is connected to the power supply 8 side and the voltage of the ground terminal 21 is equal to or higher than the second threshold value, the external MOSFET 22 is driven as it is, and the built-in MOSFET 16 is driven to the external driver driving state. The external MOSFET 22 is driven by setting to switch, and the external MOSFET 22 is driven by setting to switch to the external driver driving state if the driving is stopped. Further, when the ground terminal 21 is connected to the power supply 8 side and the voltage of the ground terminal 21 is not less than the first threshold value and less than the second threshold value, if the driving of the built-in MOSFET 16 and the external MOSFET 22 is stopped, the driving is stopped as it is. If either one of the MOSFET 16 and the external MOSFET 22 is driven, the driving of the MOSFET is stopped by setting to switch to the driving stop state.

  As described above, the built-in driver driving state or the external driver driving state can be set in accordance with the voltage of the ground terminal 21, and the built-in driver and the external driver can be stopped. When there is a request to drive none of the external MOSFETs 22, the drive stop state can be immediately set. As described above, since a desired driver can be immediately set to a drive or drive stop state in accordance with the voltage of the ground terminal 21, it is possible to prevent the occurrence of noise and the increase in current consumption.

  FIG. 9 is an electric circuit diagram showing a simplified configuration of the driver switching device 40 according to the third embodiment of the present invention. In the present embodiment, only the driver switching device 40 at the time of driving the built-in driver is shown for easy understanding. When the external driver is driven, the external driver 22 is connected to the third terminal 20 of the IC 7 as in the driver switching device 1 shown in FIG. In the present embodiment, unlike the first and second embodiments in which the built-in driver 16 and the external driver 22 are switched and driven according to the voltage of the ground terminal 21, the current flows through the ground terminal 21. Thus, the built-in driver 16 and the external driver 22 are switched and driven. The IC 7 of the present embodiment further includes a current mirror circuit 41, a pull-up resistor 45, and a threshold setting resistor (hereinafter sometimes referred to as “threshold resistor”) in addition to the circuit elements included in the IC 7 of the first embodiment. 46 is comprised. The current mirror circuit 41 includes an input side transistor 42 and an output side transistor 43 which are a pair of PNP bipolar transistors. The emitters and bases of the input-side transistor 42 and the output-side transistor 43 are connected in common, and the commonly connected base is connected to the collector of the input-side transistor 42. The commonly connected emitters are connected to a power supply 8. When the current I flows between the emitter and collector of the input transistor 42, the base-emitter voltage of the output transistor 43 and the base-emitter voltage of the input transistor 42 become the same. A current proportional to the current I flows between the collectors.

  A pull-up resistor 45 is connected to the collector of the input side transistor 42. By connecting the pull-up resistor 45, as described in the first embodiment, even when the ground terminal 21 is opened, the voltage of the ground terminal 21 can be stabilized, and the built-in MOSFET 16 is undesirably. Further, switching from one of the external MOSFETs 22 to the other can be prevented. A connection point between the other end of the pull-up resistor 45 and the source of the built-in MOSFET 16 is connected to the ground terminal 21. The collector of the output side transistor 43 is connected to a threshold resistance 46 whose other end is connected to the ground. A connection point between the input terminal 17 a of the inverter 17 and the collector of the output side transistor 43 is connected to a threshold resistance 46. The threshold resistance 46 is a resistance provided for setting a threshold current. When a current flows through the threshold resistor 46, the value of the current flowing through the threshold resistor 46 is detected by measuring the voltage generated across the threshold resistor 46. In the present embodiment, the detected current value flowing through the threshold resistance 46 is set as a threshold value. The inverter 17 detects the value of the current flowing through the ground terminal 21, compares the detected current value with the threshold value, and outputs a signal for switching the switching mode of the changeover switch 12 from the output terminal 17b. In the present embodiment, the built-in driver 16 and the external driver 22 are switched and driven according to the signal output from the output terminal 17b.

  Next, a driver switching method for switching and driving the built-in driver 16 and the external driver 22 in the third embodiment will be described. FIG. 10 is a flowchart showing an example of the operation procedure of the driver switching method according to the third embodiment of the present invention. The operation procedure of the driver switching method is started when, for example, the ignition switch of the vehicle is turned on. Since the operations of Step d1, Steps d3 to d6 and Steps d8 and d9 are the same as those of Step a1, Steps a3 to a6 and Steps a8 and a9 of the flowchart shown in FIG. 3, description thereof will be omitted. In step d2, the inverter 17 determines whether or not the current flowing through the ground terminal 21 is equal to or greater than the threshold value. If it is equal to or greater than the threshold value, the process proceeds to step d3. In step d7, the inverter 17 determines whether or not the current flowing through the ground terminal 21 is equal to or greater than the threshold value. If it is equal to or greater than the threshold value, the process proceeds to step d8.

  As described above, according to the third embodiment, when the current flowing through the ground terminal 21 is less than the threshold value, if the external MOSFET 22 is driven, the external MOSFET 22 is driven as it is. If the internal MOSFET 16 is driven, the internal MOSFET 16 starts driving. The external MOSFET 22 is driven by switching to the external MOSFET 22. When the current flowing through the ground terminal 21 is equal to or greater than the threshold value, if the internal MOSFET 16 is driven, the internal MOSFET 16 is driven as it is. If the external MOSFET 22 is driven, the external MOSFET 22 is switched to the internal MOSFET 16 to drive the internal MOSFET 16.

  As described above, in the present embodiment, either the built-in MOSFET 16 or the external MOSFET 22 can be switched to the other and driven in accordance with the current flowing through the ground terminal 21 provided in the IC 7. Therefore, unlike the conventional technique in which a dedicated driver switching terminal is newly provided in the IC 7 and the built-in MOSFET 16 and the external MOSFET 22 are switched, there is no need to newly provide a dedicated driver switching terminal in the IC 7. Without increasing the number of components provided in the IC 7, either the built-in MOSFET 16 or the external MOSFET 22 can be switched to the other and driven.

  In addition, since either one of the built-in MOSFET 16 and the external MOSFET 22 can be reliably switched to the other and driven, the external pre-driver 15 can be driven when the built-in MOSFET 16 is driven, as in the first embodiment. It is possible to prevent an unnecessary current such as a through current from flowing through, and to prevent an unnecessary current such as a through current from flowing through the built-in pre-driver 14 when the external MOSFET 22 is driven. As a result, it is possible to suppress the occurrence of problems such as the occurrence of noise due to unnecessary current and an increase in current consumption.

  FIG. 11 is an electric circuit diagram showing a simplified configuration of the driver switching device 50 according to the fourth embodiment of the present invention. In the present embodiment, only the driver switching device 50 when the built-in driver is driven is shown for easy understanding. When the external driver is driven, the external driver 22 is connected to the third terminal 20 of the IC 7 as in the driver switching device 1 shown in FIG. In the present embodiment, similarly to the second embodiment described above, a three-contact changeover switch 31 including a first contact 32a, a second contact 32b, and a third contact 32c is replaced with an IC 7 instead of a two-contact changeover switch. Provided. In the present embodiment, as in the second embodiment described above, the comparator 33 is provided in the IC 7 instead of the inverter 17. The first contact 32a of the changeover switch 31 is connected to the input unit 14b of the built-in predriver 14, the second contact 32b is connected to the input unit 15b of the external predriver 15, and the third contact 32c is connected to both. It has not been. The non-inverting input terminal 33 a of the comparator 33 is connected to a connection point between the collector of the output-side transistor 43 of the current mirror circuit 41 and one end of the threshold setting resistor 46. The first inverting input terminal 33 b of the comparator 33 is connected to the first power supply 34, and the second inverting input terminal 33 c is connected to the second power supply 35.

  The comparator 33 according to the present embodiment outputs a signal for switching the switching mode of the changeover switch 31 based on a signal corresponding to the current flowing through the ground terminal 21 input to the non-inverting input terminal 33a. In the present embodiment, based on the signal output from the output terminal 33d of the comparator 33, the switch piece 32 of the changeover switch 31 is connected to any one of the first contact 32a to the third contact 32c and turned on ( ON) is configured so that the switching mode can be switched. When the switch piece 32 is connected to the first contact 32a, the built-in driver driving state in which the built-in MOSFET 16 is driven is set. The ground terminal 21 in the internal driver driving state is connected to the ground. When the switch piece 32 is connected to the second contact 32b, an external driver driving state in which the external MOSFET 22 is driven is set. The ground terminal 21 in the external driver driving state is opened. When the switch piece 32 is connected to the third contact 32c, the driving stop state is set in which the driving of the internal MOSFET 16 and the external MOSFET 22 is stopped. The ground terminal 21 in the drive stop state is connected to the ground via a so-called pull-down resistor.

  Next, a driver switching method for switching and driving the built-in driver 16 and the external driver 22 in the fourth embodiment will be described. FIG. 12 is a flowchart showing an example of the operation procedure of the driver switching method according to the fourth embodiment of the present invention. FIG. 13 is a flowchart illustrating an example of an operation procedure of the driver switching method according to the fourth embodiment of the present invention. The operation procedure of the driver switching method is started when, for example, the ignition switch of the vehicle is turned on. It is assumed that the first threshold value in the present embodiment is a value smaller than the second threshold value. The operations of steps e1, e3, steps e5-e9, steps e11, e12 and steps e14-e16 in FIG. 12 are the same as steps b1, b3, steps b5-b9, steps b11, b12 in the flowchart shown in FIG. Since this is the same operation as steps b14 to b16, the description is omitted. 13 are the same as steps c2 and c3 and steps c5 to c7 in the flowchart shown in FIG. 8, and thus the description thereof is omitted.

  In step e2, the comparator 33 determines whether or not the current flowing through the ground terminal 21 is equal to or greater than the second threshold value. If it is equal to or greater than the second threshold value, the process proceeds to step e3. move on. In step e4, the comparator 33 determines whether or not the current flowing through the ground terminal 21 is less than the first threshold value. If it is less than the first threshold value, the process proceeds to step e5. Is determined to be less than or equal to the first threshold and less than the second threshold, and the process proceeds to step e7. In step e10, the comparator 33 makes the same determination as in step e2. If the current flowing through the ground terminal 21 is equal to or greater than the second threshold value, the process proceeds to step e11. If not, the process proceeds to step e13. In step e13, the comparator 33 makes the same determination as in step e4. If the current flowing through the ground terminal 21 is less than the first threshold value, the process proceeds to step e14. It is determined that it is greater than or equal to one threshold value and less than the second threshold value, and the process proceeds to step e15. In step e9, if the external pre-driver 15 determines that the external driver 22 is not driven, the process proceeds to step f1 in FIG. In step f1 of FIG. 13, the comparator 33 determines whether or not the current flowing through the ground terminal 21 is greater than or equal to the second threshold. If it is greater than or equal to the second threshold, the process proceeds to step f2, and if not greater than the second threshold. Proceed to step f4. In step f4, the comparator 33 determines whether or not the current flowing through the ground terminal 21 is less than the first threshold value. If it is less than the first threshold value, the process proceeds to step f5. Is determined to be less than or equal to the first threshold and less than the second threshold, and the process proceeds to step f7.

  As described above, according to the fourth embodiment, when the current flowing through the ground terminal 21 is less than the first threshold value, if the external MOSFET 22 is driven, the external MOSFET 22 is driven as it is, and if the built-in MOSFET 16 is driven, the external MOSFET 22 is driven. The external MOSFET 22 is driven by setting to switch to the driver driving state, and the external MOSFET 22 is driven by setting to switch to the external driver driving state if the driving is stopped. When the current flowing through the ground terminal 21 is equal to or greater than the second threshold, if the built-in MOSFET 16 is driven, the built-in MOSFET 16 is driven as it is, and if the external MOSFET 22 is driven, the built-in driver driving state is set to drive the built-in MOSFET 16. If the drive is stopped, the internal MOSFET 16 is driven by setting to switch to the internal driver drive state. When the current flowing through the ground terminal 21 is not less than the first threshold value and less than the second threshold value, if the driving of the internal and external MOSFETs 16 and 22 is stopped, the driving is stopped as it is, and either the internal or external MOSFETs 16 or 22 is stopped. If is driven, the setting to switch to the drive stop state is made to stop the MOSFET drive.

  As described above, the built-in driver drive state or the external driver drive state can be set according to the current flowing through the ground terminal 21, and the built-in and external driver drive stop states can be set. When there is a request to drive neither of the MOSFETs 16 and 22, the driving stop state can be immediately set. As described above, since a desired driver can be immediately set to the drive or drive stop state in accordance with the current flowing through the ground terminal 21, it is possible to prevent the occurrence of noise and the increase in current consumption.

  FIG. 14 is an electric circuit diagram showing a simplified configuration of the driver switching device 60 according to the fifth embodiment of the present invention, and is an electric circuit diagram when the built-in driver is driven. FIG. 15 is an electric circuit diagram showing a simplified configuration of the driver switching device 60, and is an electric circuit diagram when driving an external driver. Driver switching devices 60, 80, 90, and 100 according to fifth to eighth embodiments of the present invention described below are non-insulated step-down switching power supply circuits (hereinafter, sometimes referred to as “step-down switching power supply circuits”). Consists of. In the following description, the “driver switching device” may be referred to as a “step-down switching power supply circuit”. The step-down switching power supply circuit 60 steps down the output voltage from a voltage generated in the battery toward a predetermined voltage by switching of the switching element. Similar to the step-up switching power supply circuit, the step-down switching power supply circuit is used, for example, in an airbag device as an occupant protection device mounted on a vehicle.

First, the step-down switching power supply circuit 60 when the built-in driver is driven will be described. The step-down switching power supply circuit 60 includes the battery 2 and is connected to the battery 2, the first terminal 62 of the IC 61, and the power supply terminal (hereinafter sometimes simply referred to as “power supply terminal”) 65 of the built-in driver 67 built in the IC 61. Has been. The built-in driver 67 of this embodiment includes a p-channel MOS field effect transistor (Metal Oxide) that functions as a switching element.
This is realized by a semiconductor field effect transistor (abbreviation: MOSFET). In the following description, the internal driver 67 may be referred to as an internal MOSFET 67. The IC 61 includes a signal source 11, a changeover switch 12, a built-in predriver 14, an external predriver 15, and an inverter 17. The changeover switch 12 includes a switch piece 13, a first contact 13a, and a second contact 13b. The first terminal 62 of the IC 61 is connected to the power supply unit 15 a of the external pre-driver 15. The input unit 15 b of the external pre-driver 15 is connected to the second contact 13 b of the changeover switch 12. The output unit 15 c of the external pre-driver 15 is connected to the second terminal 63 of the IC 61.

  The first terminal 62 is connected to the power supply unit 14 a of the built-in pre-driver 14. The input part 14 b of the built-in pre-driver 14 is connected to the first contact 13 a of the changeover switch 12. The output part 14 c of the built-in pre-driver 14 is connected to the gate of the built-in MOSFET 67. A connection point between the drain of the built-in MOSFET 67 and the input terminal 17 a of the inverter 17 is connected to the power supply terminal 65. The source of the built-in MOSFET 67 is connected to the third terminal 64 of the IC 61. The changeover switch 12 is connected to a signal source 11 that generates a pulse signal. The inverter 17 monitors the voltage of the power supply terminal 65 based on a signal corresponding to the voltage of the input power supply terminal 65, in other words, detects the voltage and outputs a signal for switching the switching mode of the changeover switch 12 to the output terminal. Output from 17b. In the present embodiment, based on a signal output from the output terminal 17b of the inverter 17, the switch piece 13 of the changeover switch 12 is connected to one of the first contact 13a and the second contact 13b and turned on (ON). ) So that the switching mode can be switched. When the switch piece 13 is connected to the first contact 13a, the built-in MOSFET 67 is driven.

  The coil 3 is connected between the third terminal 64 and the output terminal 6. One end of the coil 3 is connected to the cathode of the diode 4 and the anode of the diode 4 is connected to the ground. A connection point between the cathode of the diode 4 and one end of the coil 3 is connected to the third terminal 64. A capacitor 5 is connected to the other end of the coil 3. A connection point between the positive terminal of the capacitor 5 and the other end of the coil 3 is connected to the output terminal 6, and a negative terminal of the capacitor 5 is connected to the ground.

  Next, the step-down switching power supply circuit 60 when driving an external driver will be described. When the switch piece 13 of the changeover switch 12 is connected to the second contact 13b, the external driver 68 connected to the IC 61 is driven. The external driver 68 of the present embodiment is realized by a p-channel MOSFET that functions as a switching element. In the following description, the external driver 68 may be referred to as an external MOSFET 68. When the external MOSFET 68 is driven, the second terminal 63 is connected to the gate of the external MOSFET 68 as shown in FIG. The drain of the external MOSFET 68 is connected to the battery 2, and the source of the external MOSFET 68 is connected to the cathode of the diode 4. A connection point between the source of the external MOSFET 68 and the cathode of the diode 4 is connected to one end of the coil 3. The power terminal 65 is connected to the ground. Also in the step-down switching power supply circuit, as in the case of the step-up switching power supply circuit described above, a diode for preventing breakdown is provided between the drain and the source of the internal MOSFET 67 and the external MOSFET 68 (hereinafter may be collectively referred to as “MOSFET”). 23 is connected. More specifically, the anode of the breakdown preventing diode 23 is connected to the source of the MOSFET, and the cathode of the breakdown preventing diode 23 is connected to the drain of the MOSFET. This prevents the MOSFET from being destroyed.

  When the switch piece 13 of the changeover switch 12 is connected to the first contact 13 a, the pulse signal output from the signal source 11 is input to the input unit 14 b of the built-in pre-driver 14. When power is supplied from the battery 2, the built-in predriver 14 outputs a high level signal or a low level signal from the output unit 14 c of the built-in predriver 14. The signal output from the output unit 14 c is input to the gate of the built-in MOSFET 67. The built-in MOSFET 67 performs a switching operation that repeats conduction and interruption based on an input signal. In step-down switching power supply circuit 60, the input DC voltage signal is converted into a square wave by a switching operation by a switching element such as built-in MOSFET 67, and the square wave is smoothed using a low-pass filter and a DC voltage signal is output. . The low-pass filter of the present embodiment is an LC type low-pass filter configured by the coil 3 and the capacitor 5. When the built-in MOSFET 67 is conductive, a current flows through the coil 3, the capacitor 5 is charged, and the voltage at the output terminal 6 rises. When the built-in MOSFET 67 changes from the conductive state to the cut-off state, no current is supplied to the coil 3 from the battery 2 side, and the electrical energy accumulated in the coil 3 is supplied to the output terminal 6 via the diode 4. The electric charge accumulated in the capacitor 5 is also supplied to the output terminal 6. As a result, the voltage at the output terminal 6 is lower than the voltage at the battery 2. The diode 4 is a flywheel diode for allowing the current accumulated in the coil 3 to flow when the built-in MOSFET 67 is in a cut-off state. The operation of the step-down switching power supply circuit 60 when the switch piece 13 of the changeover switch 12 is connected to the second contact 13b and the external MOSFET 68 is driven is the same as the operation when the built-in MOSFET 67 is driven. Description is omitted.

  Next, a driver switching method for switching and driving the built-in driver 67 and the external driver 68 in the fifth embodiment will be described. FIG. 16 is a flowchart showing an example of the operation procedure of the driver switching method according to the fifth embodiment of the present invention. The operation procedure of the driver switching method is started when, for example, the ignition switch of the vehicle is turned on. The driver switching method in the present embodiment is similar to the driver switching method in the first embodiment. In the first embodiment, the built-in MOSFET 16 and the external MOSFET 22 are switched and driven according to the voltage of the ground terminal 21, whereas in the present embodiment, the built-in MOSFET 67 is driven according to the voltage of the power supply terminal 65. And the external MOSFET 68 are switched and driven. Each operation of step g1, steps g3 to g6 and steps g8 and g9 in FIG. 16 is the same as step a1, steps a3 to a6 and steps a8 and a9 of the flowchart shown in FIG. Omitted. In step g2, the inverter 17 determines whether or not the voltage at the power supply terminal 65 is equal to or higher than the threshold value. If the voltage is equal to or higher than the threshold value, the process proceeds to step g3. In step g7, the inverter 17 determines whether or not the voltage at the power supply terminal 65 is equal to or higher than the threshold value. If the voltage is equal to or higher than the threshold value, the process proceeds to step g8.

  As described above, according to the fifth embodiment, the voltage at the power supply terminal 65 is monitored by the inverter 17, and the power supply terminal 65 and the battery 2 are connected. If the MOSFET 67 is driven, it is driven as it is, and if the external MOSFET 68 is driven, the external MOSFET 68 is switched to the built-in MOSFET 67 to drive the built-in MOSFET 67. When the power supply terminal 65 is connected to the ground and the voltage of the power supply terminal 65 is less than the threshold value, if the external MOSFET 68 is driven, it is driven as it is, and if the built-in MOSFET 67 is driven, the built-in MOSFET 67 is switched to the external MOSFET 68 The MOSFET 68 is driven. As described above, according to the present embodiment, either the built-in MOSFET 67 or the external MOSFET 68 can be switched to the other and driven in accordance with the voltage of the power supply terminal 65 provided in the IC 61. Therefore, unlike the conventional technique in which a dedicated driver switching terminal is newly provided in the IC 61 and the built-in MOSFET 67 and the external MOSFET 68 are switched, there is no need to newly provide a dedicated driver switching terminal in the IC 61. Without increasing the number of components provided in the IC 61, either the built-in MOSFET 67 or the external MOSFET 68 can be switched to the other and driven.

  Further, since either the internal MOSFET 67 or the external MOSFET 68 can be switched to the other and driven, when the internal MOSFET 67 is driven, an unnecessary current such as a through current indicated by an arrow C in FIG. Can be prevented from flowing to the external pre-driver 15 for driving. Further, when the external MOSFET 68 is driven, unnecessary current such as a through current indicated by an arrow D in FIG. 15 can be prevented from flowing to the built-in pre-driver 14 for driving the built-in MOSFET 67. As a result, it is possible to suppress the occurrence of problems such as the occurrence of noise due to unnecessary current and an increase in current consumption.

  FIG. 17 is an electric circuit diagram showing a simplified configuration of the driver switching device 60. FIG. 18 is an electric circuit diagram showing a simplified configuration of the driver switching device 60. As shown in FIG. 14 described above, the power supply terminal 65 is connected to the battery 2 when the internal MOSFET 67 is driven. When the built-in MOSFET 67 is driven, if the power supply terminal 65 is opened due to poor solder contact or disconnection, the voltage of the power supply terminal 65 drops, and the switch piece 13 of the changeover switch 12 is connected to the first contact 13a. Is switched to the connection state with the second contact 13b. As a result, the driving state of the built-in MOSFET 67 is switched to the driving state of the external MOSFET 68. When switching to the driving state of the external MOSFET 68, the built-in MOSFET 67 is turned off, whereby the voltage at the power supply terminal 65 rises, and the driving state of the external MOSFET 68 is switched to the driving state of the built-in MOSFET 67. Then, as the built-in MOSFET 67 is driven again, the voltage at the power supply terminal 65 becomes unstable due to the opening of the power supply terminal 65, causing the abnormal switching operation of the MOSFET as described above, and generating unnecessary noise. Troubles such as doing.

  Therefore, in this embodiment, a resistor 70 is provided between the power supply terminal 65 and the ground as shown in FIG. Specifically, one end of the resistor 70 is connected to the power supply terminal 65, and the other end of the resistor 70 is connected to the ground. By providing the resistor 70 between the power supply terminal 65 and the ground in this way, the voltage of the power supply terminal 65 can be stabilized even when a problem that the power supply terminal 65 is opened occurs. In other words, the voltage at the power supply terminal 65 becomes unstable, and the switching from one of the built-in MOSFET 67 and the external MOSFET 68 to the other becomes abnormal. Can be prevented.

  Further, in the present embodiment, in order to prevent such a problem that the voltage at the power supply terminal 65 becomes unstable and an abnormal switching operation of the MOSFET is caused and unnecessary noise is generated, the power supply terminal 65 of the built-in MOSFET 67 is prevented. A current source 71 may be provided between the grounds as shown in FIG. Specifically, one end of the current source 71 is connected to the power supply terminal 65, and the other end of the current source 71 is connected to the ground. As a result, the potential of the power supply terminal 65 can be made constant. Therefore, the voltage of the power supply terminal 65 can be stabilized, and the same effect as the case where the resistor 70 is provided as shown in FIG. 17 can be achieved.

  FIG. 19 is an electric circuit diagram showing a simplified configuration of a driver switching device 80 according to the sixth embodiment of the present invention. In the present embodiment, only the driver switching device 80 when the built-in driver is driven is shown for easy understanding. When the external driver is driven, the external driver 68 is connected to the second terminal 63 of the IC 61 in the same manner as the driver switching device 60 shown in FIG. In this embodiment, a three-contact selector switch 31 is provided instead of the two-contact selector switch 12 of the fifth embodiment. The changeover switch 31 includes a switch piece 32, a first contact 32a, a second contact 32b, and a third contact 32c. In the present embodiment, a comparator 33 is provided instead of the inverter 17 of the fifth embodiment described above. The first contact 32a of the changeover switch 31 is connected to the input unit 14b of the built-in predriver 14, the second contact 32b is connected to the input unit 15b of the external predriver 15, and the third contact 32c is connected to both. It has not been. A connection point between the non-inverting input terminal 33 a of the comparator 33 and the drain of the built-in MOSFET 67 is connected to the power supply terminal 65. The first inverting input terminal 33 b of the comparator 33 is connected to the first power supply 34, and the second inverting input terminal 33 c is connected to the second power supply 35.

  The comparator 33 according to the present embodiment monitors the voltage of the power supply terminal 65 and outputs a signal for switching the switching mode of the changeover switch 31 from the output terminal 33d based on a signal corresponding to the voltage of the power supply terminal 65. . In the present embodiment, based on the signal output from the output terminal 33d of the comparator 33, the switch piece 32 of the changeover switch 31 is connected to any one of the first contact 32a to the third contact 32c and turned on ( ON) is configured so that the switching mode can be switched. When the switch piece 32 is connected to the first contact 32a, the built-in driver driving state in which the built-in MOSFET 67 is driven is set. When the switch piece 32 is connected to the second contact 32b, the external driver driving state in which the external MOSFET 68 is driven is set. When the switch piece 32 is connected to the third contact 32c, the driving stop state is set in which the driving of the built-in MOSFET 67 and the external MOSFET 68 is stopped.

  Next, a driver switching method for switching and driving the internal driver 67 and the external driver 68 in the sixth embodiment will be described. FIG. 20 is a flowchart showing an example of an operation procedure of the driver switching method according to the sixth embodiment of the present invention. FIG. 21 is a flowchart showing an example of the operation procedure of the driver switching method according to the sixth embodiment of the present invention. The operation procedure of the driver switching method shown in FIGS. 20 and 21 is started, for example, when the ignition switch of the vehicle is turned on. The driver switching method in the present embodiment is similar to the driver switching method in the second embodiment. In the second embodiment, the built-in MOSFET 16 and the external MOSFET 22 are switched and driven according to the voltage of the ground terminal 21, whereas in the present embodiment, the built-in MOSFET 67 is driven according to the voltage of the power supply terminal 65. And the external MOSFET 68 are switched and driven. Steps h1, h3, steps h5-h9, steps h11, h12 and steps h14-h16 in FIG. 20 are the same as steps b1, b3, steps b5-b9, steps b11, b12 in the flowchart shown in FIG. Since this is the same operation as steps b14 to b16, the description thereof is omitted. 21 are the same as steps c2 and c3 and steps c5 to c7 in the flowchart shown in FIG. 8, and thus the description thereof is omitted. In the present embodiment, the first threshold value is a value corresponding to 1/3 of the battery voltage, and the second threshold value is a value corresponding to 2/3 of the battery voltage.

  In step h2, the comparator 33 determines whether or not the voltage of the power supply terminal 65 is equal to or higher than the second threshold value. If the voltage is equal to or higher than the second threshold value, the process proceeds to step h3. . In step h4, the comparator 33 determines whether or not the voltage of the power supply terminal 65 is less than the first threshold value. If the voltage is less than the first threshold value, the process proceeds to step h5. It is determined that the voltage is greater than or equal to the first threshold value and less than the second threshold value, and the process proceeds to step h7. In step h10, the comparator 33 determines whether or not the voltage at the power supply terminal 65 is equal to or higher than the second threshold value. If the voltage is equal to or higher than the second threshold value, the process proceeds to step h11. In step h13, the comparator 33 determines whether or not the voltage at the power supply terminal 65 is less than the first threshold value. If it is less than the first threshold value, the process proceeds to step h14. Is greater than or equal to the first threshold value and less than the second threshold value, the process proceeds to step h15. In step h9, if the external pre-driver 15 determines that the external driver 68 is not driven, the process proceeds to step k1 in FIG. In step k1 of FIG. 21, the comparator 33 determines whether or not the voltage of the power supply terminal 65 is equal to or higher than the second threshold value. Proceed to k4. In step k4, the comparator 33 determines whether or not the voltage at the power supply terminal 65 is less than the first threshold value. If the voltage is less than the first threshold value, the process proceeds to step k5. It is determined that the voltage is greater than or equal to the first threshold and less than the second threshold, and the process proceeds to step k7.

  As described above, according to the sixth embodiment, when the power supply terminal 65 is connected to the ground and the voltage of the power supply terminal 65 is less than the first threshold, if the external MOSFET 68 is driven, the external MOSFET 68 is driven as it is. If the MOSFET 67 is driven, the external MOSFET 68 is driven by setting to switch to the external driver driving state, and if the driving is stopped, the external MOSFET 68 is driven by setting to switch to the external driver driving state. When the power supply terminal 65 and the battery 2 are connected and the voltage of the power supply terminal 65 is equal to or higher than the second threshold value, the internal MOSFET 67 is driven as it is, and the external MOSFET 68 is driven to the internal driver drive state. The built-in MOSFET 67 is driven by setting to switch, and if the drive is stopped, the built-in MOSFET 67 is driven by setting to switch to the built-in driver drive state. When the voltage of the power supply terminal 65 is not less than the first threshold value and less than the second threshold value, if the driving of the internal MOSFET 67 and the external MOSFET 68 is stopped, the driving is stopped as it is, and either the internal MOSFET 67 or the external MOSFET 68 is driven. If so, the setting for switching to the drive stop state is made to stop the MOSFET drive. As described above, the built-in driver driving state or the external driver driving state can be set according to the voltage of the power supply terminal 65, and the built-in and external driver driving stopped states can be set. , 68 can be immediately stopped when there is a request to prevent them from being driven. As described above, since a desired driver can be immediately set to the drive or drive stop state in accordance with the voltage of the power supply terminal 65, the cause of noise and the increase in current consumption can be prevented in advance.

  FIG. 22 is an electric circuit diagram showing a simplified configuration of the driver switching device 90 according to the seventh embodiment of the present invention. In the present embodiment, only the driver switching device 90 at the time of driving the built-in driver is shown for easy understanding. When the external driver is driven, the external driver 68 is connected to the second terminal 63 of the IC 61 in the same manner as the driver switching device 60 shown in FIG. In the present embodiment, unlike the above-described fifth and sixth embodiments in which the built-in driver 67 and the external driver 68 are switched and driven according to the voltage of the power supply terminal 65, according to the current flowing through the power supply terminal 65. Thus, the built-in driver 67 and the external driver 68 are switched and driven. The IC 61 of the present embodiment further includes a current mirror circuit 91, a resistor 95, and a threshold setting resistor (hereinafter also referred to as “threshold resistor”) 96 in addition to the circuit elements included in the IC 61 of the fifth embodiment. It is prepared for. The current mirror circuit 91 includes an input side transistor 92 and an output side transistor 93 which are a pair of NPN type bipolar transistors. The emitters of the input side transistor 92 and the output side transistor 93 are respectively connected to the ground, and the bases of the input side transistor 92 and the output side transistor 93 are commonly connected. The commonly connected bases are connected to the collector of the output side transistor 93. A connection point between the collector of the input side transistor 92 and the other end of the threshold resistor 96 is connected to the input terminal 17 a of the inverter 17. When the current J flows between the collector and emitter of the output side transistor 93, the base-emitter voltage of the output side transistor 93 and the base-emitter voltage of the input side transistor 92 become the same. A current proportional to the current J flows between the emitters.

  A resistor 95 is connected between the collector of the output side transistor 93 and the power supply terminal 65. By connecting the resistor 95, as described in the fifth embodiment, the voltage of the power supply terminal 65 can be stabilized even when the power supply terminal 65 is opened. Switching from one of the MOSFETs 68 to the other can be prevented. A connection point between one end of the resistor 95 and the drain of the built-in MOSFET 67 is connected to the power supply terminal 65. A connection point between the collector of the input side transistor 92 and the input terminal 17 a of the inverter 17 is connected to the threshold resistance 96. In the present embodiment, the inverter 17 compares the value of the current flowing through the power supply terminal 65 with the threshold set by the threshold resistor 96, and outputs a signal for switching the switching mode of the changeover switch 12 from the output terminal 17b. . In the present embodiment, the built-in driver 67 and the external driver 68 are switched and driven according to the signal output from the output terminal 17b.

  Next, a driver switching method for switching and driving the built-in driver 67 and the external driver 68 in the seventh embodiment will be described. FIG. 23 is a flowchart illustrating an example of an operation procedure of the driver switching method according to the seventh embodiment of the present invention. The operation procedure of the driver switching method is started when, for example, the ignition switch of the vehicle is turned on. Since the operations of Step m1, Steps m3 to m6 and Steps m8 and m9 are the same as those of Step a1, Steps a3 to a6 and Steps a8 and a9 of the flowchart shown in FIG. In step m2, the inverter 17 determines whether or not the current flowing through the power supply terminal 65 is greater than or equal to the threshold value. If it is greater than or equal to the threshold value, the process proceeds to step m3, and if less than the threshold value, the process proceeds to step m4. In step m7, the inverter 17 determines whether or not the current flowing through the power supply terminal 65 is equal to or greater than the threshold value. If it is equal to or greater than the threshold value, the process proceeds to step m8.

  As described above, according to the seventh embodiment, when the current flowing through the power supply terminal 65 is less than the threshold, if the external MOSFET 68 is driven, the external MOSFET 68 is driven as it is, and if the internal MOSFET 67 is driven, the internal MOSFET 67 starts driving. The external MOSFET 68 is driven by switching to the external MOSFET 68. When the current flowing through the power supply terminal 65 is equal to or greater than the threshold value, if the internal MOSFET 67 is driven, the internal MOSFET 67 is driven as it is. If the external MOSFET 68 is driven, the external MOSFET 68 is switched to the internal MOSFET 67 to drive the internal MOSFET 67.

  As described above, in the present embodiment, either the built-in MOSFET 67 or the external MOSFET 68 can be switched to the other and driven in accordance with the current flowing through the power supply terminal 65 provided in the IC 61. Therefore, similarly to the fifth embodiment, there is no need to newly provide a dedicated terminal for driver switching in the IC 61 as in the prior art, so that the built-in MOSFET 67 and the external MOSFET 68 are not increased without increasing the number of components provided in the IC 61. Either one of them can be switched to the other and driven.

  Further, since either one of the built-in MOSFET 67 and the external MOSFET 68 can be switched and driven, the built-in pre-driver 14 and the external pre-driver 15 do not require a through current or the like as in the fifth embodiment. Current can be prevented from flowing, and the occurrence of problems such as noise and increased current consumption due to the unnecessary current can be suppressed.

  FIG. 24 is an electric circuit diagram showing a simplified configuration of the driver switching apparatus 100 according to the eighth embodiment of the present invention. In the present embodiment, only the driver switching device 100 when the built-in driver is driven is shown for easy understanding. When the external driver is driven, the external driver 68 is connected to the second terminal 63 of the IC 61 in the same manner as the driver switching device 60 shown in FIG. In the present embodiment, similarly to the above-described sixth embodiment, instead of the two-contact change-over switch, the three-contact change-over switch 31 including the first contact 32a, the second contact 32b, and the third contact 32c is replaced with an IC 61. Provided. In the present embodiment, as in the sixth embodiment described above, the IC 33 is provided with the comparator 33 instead of the inverter 17. The first contact 32a of the changeover switch 31 is connected to the input unit 14b of the built-in predriver 14, the second contact 32b is connected to the input unit 15b of the external predriver 15, and the third contact 32c is connected to both. It has not been. A connection point between the collector of the input side transistor 92 of the current mirror circuit 91 and the other end of the threshold setting resistor 96 is connected to the non-inverting input terminal 33 a of the comparator 33. The first inverting input terminal 33 b of the comparator 33 is connected to the first power supply 34, and the second inverting input terminal 33 c is connected to the second power supply 35.

  The comparator 33 of the present embodiment outputs a signal for switching the switching mode of the changeover switch 31 from the output terminal 33d based on a signal corresponding to the current flowing through the power supply terminal 65 input to the non-inverting input terminal 33a. Output. In the present embodiment, based on the signal output from the output terminal 33d of the comparator 33, the switch piece 32 of the changeover switch 31 is connected to any one of the first contact 32a to the third contact 32c and turned on ( ON) is configured so that the switching mode can be switched. When the switch piece 32 is connected to the first contact 32a, the built-in driver driving state in which the built-in MOSFET 67 is driven is set. The power supply terminal 65 in the built-in driver driving state is connected to the battery 2. When the switch piece 32 is connected to the second contact 32b, an external driver driving state in which the external MOSFET 68 is driven is set. The power supply terminal 65 in the external driver driving state is opened. When the switch piece 32 is connected to the third contact 32c, the driving stop state is set in which the driving of the built-in MOSFET 67 and the external MOSFET 68 is stopped. The power supply terminal 65 in the drive stop state is connected to the battery 2 via a so-called pull-up resistor.

  Next, a driver switching method for switching and driving the built-in driver 67 and the external driver 68 in the eighth embodiment will be described. FIG. 25 is a flowchart showing an example of an operation procedure of the driver switching method according to the eighth embodiment of the present invention. FIG. 26 is a flowchart illustrating an example of an operation procedure of the driver switching method according to the eighth embodiment of the present invention. The operation procedure of the driver switching method shown in FIGS. 26 and 27 is started, for example, when the ignition switch of the vehicle is turned on. It is assumed that the first threshold value in the present embodiment is a value smaller than the second threshold value. The operations of steps n1, n3, steps n5-n9, steps n11, n12 and steps n14-n16 in FIG. 25 are the same as steps b1, b3, steps b5-b9, steps b11, b12 in the flowchart shown in FIG. Since this is the same operation as steps b14 to b16, the description is omitted. 26 are the same as steps c2 and c3 and steps c5 to c7 in the flowchart shown in FIG. 8, and thus the description thereof is omitted.

  In step n2, the comparator 33 determines whether or not the current flowing through the power supply terminal 65 is greater than or equal to the second threshold value. If it is greater than or equal to the second threshold value, the process proceeds to step n3. move on. In step n4, the comparator 33 determines whether or not the current flowing through the power supply terminal 65 is less than the first threshold value. If it is less than the first threshold value, the process proceeds to step n5. Is determined to be less than or equal to the first threshold and less than the second threshold, and the process proceeds to step n7. In step n10, the comparator 33 makes the same determination as in step n2, and if the current flowing through the power supply terminal 65 is greater than or equal to the second threshold, the process proceeds to step n11, and if not greater than the second threshold, the process proceeds to step n13. In step n13, the comparator 33 makes the same determination as in step n4. If the current flowing through the power supply terminal 65 is less than the first threshold value, the process proceeds to step n14. It is determined that the value is greater than or equal to one threshold value and less than the second threshold value, and the process proceeds to step n15. If the external pre-driver 15 determines in step n9 that the external driver 68 is not driven, the process proceeds to step p1 in FIG. In step p1 of FIG. 26, the comparator 33 determines whether or not the current flowing through the power supply terminal 65 is greater than or equal to the second threshold. If it is greater than or equal to the second threshold, the process proceeds to step p2, and if not greater than the second threshold. Proceed to step p4. In step p4, the comparator 33 determines whether or not the current flowing through the power supply terminal 65 is less than the first threshold value. If it is less than the first threshold value, the process proceeds to step p5. Is determined to be less than or equal to the first threshold and less than the second threshold, and the process proceeds to step p7.

  As described above, according to the eighth embodiment, when the current flowing through the power supply terminal 65 is less than the first threshold value, if the external MOSFET 68 is driven, it is driven as it is, and if the built-in MOSFET 67 is driven, the external MOSFET 68 is driven. The external MOSFET 68 is driven by setting to switch to the driver driving state, and the external MOSFET 68 is driven by setting to switch to the external driver driving state if the driving is stopped. When the current flowing through the power supply terminal 65 is equal to or greater than the second threshold value, if the built-in MOSFET 67 is driven, the built-in MOSFET 67 is driven as it is, and if the external MOSFET 68 is driven, the built-in driver driving state is set to drive the built-in MOSFET 67. If the drive is stopped, the setting is made to switch to the built-in driver drive state, and the built-in MOSFET 67 is driven. When the current flowing through the power supply terminal 65 is not less than the first threshold value and less than the second threshold value, if the driving of the internal MOSFET 67 and the external MOSFET 68 is stopped, the driving is stopped as it is, and either the internal MOSFET 67 or the external MOSFET 68 is driven. If so, the setting to switch to the drive stop state is made to stop the MOSFET drive.

  As described above, the built-in driver drive state or the external driver drive state can be set according to the current flowing through the power supply terminal 65, and the built-in and external driver drive stop states can be set. any MOSFET67,68 of can be set to immediately drive stop state if there is a request so as not to drive. As described above, since a desired driver can be immediately set to the drive or drive stop state in accordance with the current flowing through the power supply terminal 65, it is possible to prevent the occurrence of noise and the increase in current consumption.

  Each above-mentioned embodiment is only illustration of this invention, and can change a structure within the scope of the invention. In the first embodiment described above, the inverter 17 is used to detect the voltage of the ground terminal 21, and the fifth embodiment describes the case where the inverter 17 is used to detect the voltage of the power supply terminal 65. The voltages at the ground terminal 21 and the power supply terminal 65 may be detected using a comparator, MOSFET, bipolar transistor, or the like. In the third embodiment described above, the case where the current flowing through the ground terminal 21 is detected using the inverter 17 and the current flowing through the power supply terminal 65 is detected using the inverter 17 is described in the seventh embodiment. However, the current flowing through the ground terminal 21 and the power supply terminal 65 may be detected using a comparator, MOSFET, bipolar transistor, or the like.

  In the first to fourth embodiments described above, the case where the built-in driver and the external driver are configured by n-channel MOSFETs has been described, but in other embodiments of the present invention, the driver is configured by an NPN-type bipolar transistor. Also good. In the above-described fifth to eighth embodiments, the case where the built-in driver and the external driver are configured by p-channel MOSFETs has been described. However, in other embodiments of the present invention, they are configured by PNP-type bipolar transistors. Also good. As described above, in other embodiments of the present invention, even when the built-in driver and the external driver are constituted by an NPN-type bipolar transistor and a PNP-type bipolar transistor, they can be implemented in the same manner as the above-described embodiments. And similar effects can be obtained.

  In the above-described embodiment, the case where the present invention is applied to the step-up switching power source and the step-down switching power source used for the power source of the airbag device has been described. However, the present invention is not limited to the power source of the airbag device. Any electronic device that performs various controls by switching and driving can be implemented in the same manner as in the above-described embodiment, and the same effects can be obtained.

The first is in the form of embodiment drivers switching device 1 of the configuration of the present invention is an electric circuit diagram schematically showing. FIG. 3 is an electric circuit diagram showing a simplified configuration of the driver switching device 1. It is a flowchart which shows an example of the operation | movement procedure of the driver switching method in the 1st Embodiment of this invention. FIG. 3 is an electric circuit diagram showing a simplified configuration of the driver switching device 1. FIG. 3 is an electric circuit diagram showing a simplified configuration of the driver switching device 1. It is an electric circuit diagram which simplifies and shows the structure of the driver switching apparatus 30 which is the 2nd Embodiment of this invention. It is a flowchart which shows an example of the operation | movement procedure of the driver switching method in the 2nd Embodiment of this invention. It is a flowchart which shows an example of the operation | movement procedure of the driver switching method in the 2nd Embodiment of this invention. It is an electric circuit diagram which simplifies and shows the structure of the driver switching apparatus 40 which is the 3rd Embodiment of this invention. It is a flowchart which shows an example of the operation | movement procedure of the driver switching method in the 3rd Embodiment of this invention. It is an electric circuit diagram which simplifies and shows the structure of the driver switching apparatus 50 of the 4th Embodiment of this invention. It is a flowchart which shows an example of the operation | movement procedure of the driver switching method in the 4th Embodiment of this invention. It is a flowchart which shows an example of the operation | movement procedure of the driver switching method in the 4th Embodiment of this invention. It is an electric circuit diagram which simplifies and shows the structure of the driver switching apparatus 60 which is the 5th Embodiment of this invention. 4 is an electric circuit diagram showing a simplified configuration of a driver switching device 60. FIG. It is a flowchart which shows an example of the operation | movement procedure of the driver switching method in the 5th Embodiment of this invention. 4 is an electric circuit diagram showing a simplified configuration of a driver switching device 60. FIG. 4 is an electric circuit diagram showing a simplified configuration of a driver switching device 60. FIG. It is an electric circuit diagram which simplifies and shows the structure of the driver switching apparatus 80 which is the 6th Embodiment of this invention. It is a flowchart which shows an example of the operation | movement procedure of the driver switching method in the 6th Embodiment of this invention.

It is a flowchart which shows an example of the operation | movement procedure of the driver switching method in the 6th Embodiment of this invention. It is an electric circuit diagram which simplifies and shows the structure of the driver switching apparatus 90 which is the 7th Embodiment of this invention. It is a flowchart which shows an example of the operation | movement procedure of the driver switching method in the 7th Embodiment of this invention. It is an electric circuit diagram which simplifies and shows the structure of the driver switching apparatus 100 which is the 8th Embodiment of this invention. It is a flowchart which shows an example of the operation | movement procedure of the driver switching method in the 8th Embodiment of this invention. It is a flowchart which shows an example of the operation | movement procedure of the driver switching method in the 8th Embodiment of this invention. It is a figure which shows the step-up type switching power supply circuit 110 at the time of a built-in driver drive of the prior art. It is a figure which shows the pressure | voltage rise type switching power supply circuit 120 at the time of the external driver drive of a prior art.

Explanation of symbols

1, 30, 40, 50, 60, 80, 90, 100 Driver switching device 2 Battery 3 Coil 4 Diode 5 Capacitor 6 Output terminal 7, 61 Integrated circuit (IC)
8 Power supply 11 Signal source 12, 31 Changeover switch 13, 32 Switch piece 14 Built-in pre-driver 15 External pre-driver 16, 67 Built-in driver (built-in MOSFET)
17 Inverter 18, 62 First terminal 19, 63 Second terminal 20, 64 Third terminal 21 Ground terminal 22, 68 External driver (external MOSFET)
25, 70 Resistance 26, 71 Current source 33 Comparator 65 Power supply terminal

Claims (16)

A driver switching method for switching and driving a built-in driver built in an integrated circuit and an external driver outside the integrated circuit,
A driver switching method characterized by monitoring a connection state between a ground terminal of the built-in driver and the ground, and switching one of the built-in driver and the external driver to the other according to the connection state.   2. The driver switching method according to claim 1, wherein a resistor is provided between the ground terminal and the power source.   2. The driver switching method according to claim 1, wherein a current source is provided between the ground terminal and a power source.   2. The internal driver driving state, the external driver driving state, and the driving stop state of the internal driver and the external driver are set according to the voltage of the ground terminal. Driver switching method.   2. The driver switching method according to claim 1, wherein one of the built-in driver and the external driver is switched to the other and driven in accordance with a current flowing through the ground terminal.   2. The internal driver driving state, the external driver driving state, and the internal driver driving state or the external driver driving state are set according to the current flowing through the ground terminal. Driver switching method.   7. The driver switching method according to claim 1, wherein the built-in driver and the external driver are configured by n-channel MOS transistors. A driver switching method for switching and driving a built-in driver built in an integrated circuit and an external driver external to the integrated circuit,
A driver switching method characterized by monitoring a connection state between a power supply terminal and a power supply of the built-in driver and switching one of the built-in driver and the external driver to the other according to the connection state.   9. The driver switching method according to claim 8, wherein a resistor is provided between the power supply terminal and the ground.   9. The driver switching method according to claim 8, wherein a current source is provided between the power supply terminal and the ground.   9. The internal driver driving state, the external driver driving state, and the driving stop state of the internal driver and the external driver are set according to the voltage of the power supply terminal. Driver switching method.   9. The driver switching method according to claim 8, wherein one of the built-in driver and the external driver is switched to the other and driven in accordance with a current flowing through the power supply terminal.   9. The internal driver driving state, the external driver driving state, and the driving stop state of the internal driver and the external driver are set according to a current flowing through the power supply terminal. Driver switching method.   The driver switching method according to claim 8, wherein the built-in driver and the external driver are configured by p-channel MOS transistors. A driver switching device for switching and driving a built-in driver built in an integrated circuit and an external driver outside the integrated circuit,
The driver switching is configured to monitor the connection state between the ground terminal of the built-in driver and the ground, and switch either the built-in driver or the external driver to the other in accordance with the connection state. apparatus. A driver switching device for switching and driving a built-in driver built in an integrated circuit and an external driver outside the integrated circuit,
The driver switching is configured to monitor a connection state between a power supply terminal of the built-in driver and a power supply, and switch one of the built-in driver and the external driver to the other according to the connection state. apparatus.

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