JP6563266B2 - Vehicle power supply control device - Google Patents

Description

  The present invention relates to a vehicle power supply control device that turns on / off power supply from a vehicle power supply to a load by a power MOSFET.

  In a power supply box (hereinafter referred to as a unit) that distributes power in a vehicle, the use of semiconductors is expanding in order to meet demands for weight reduction and power saving. In order to further reduce the size, the use of IPD (Intelligent Power Device), which is a device in which a configuration of a conventional predriver + MOSFET (such as a device) or a driver and a control circuit having a protection function is integrated, is expanding. Many of these devices have a built-in low-voltage cutoff function to prevent overheating due to an increase in on-resistance when the voltage drops.

  Here, since the starter flows a large current, the terminal voltage of the battery decreases due to the internal resistance of the battery. As described above, in the vehicle, a phenomenon occurs in which the voltage temporarily decreases when the engine is started (particularly during cranking). There are loads that need to be operated even during cranking when the voltage temporarily drops in the vehicle, and in order to operate these, it is necessary to avoid the low voltage cutoff function.

  Therefore, a proposal has been made that a negative voltage is generated and applied to the gate of the P-channel power MOSFET from when the starter switch is turned on until the start of the engine is completed. According to this proposal, even if the power supply voltage decreases due to cranking, the gate-source voltage of the P-channel power MOSFET is maintained at a voltage higher than the gate threshold voltage, and the power supply from the power supply to the load is not shut off. (For example, patent document 1).

JP 2013-241036 A

  However, the temporary drop in the power supply voltage does not occur only when the engine is started. For example, when a short current flows due to a rare short circuit that occurs between a power supply and a load, the power supply voltage may temporarily decrease. In this case as well, it is necessary to avoid the low voltage cutoff function and to continue the power supply from the power source to the load, as in the case of engine startup.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to turn on / off power supply from a power source to a load by a switching device having a low voltage cutoff function, even if the power source voltage temporarily decreases. An object of the present invention is to provide a vehicular power supply control device that can always ensure power supply from a power supply to a load.

In order to achieve the above object, a vehicle power supply control device according to a first aspect of the present invention comprises:
Using a switching device with a low voltage cutoff function the output voltage of the power supply of the vehicle to force off semiconductors switching element when a threshold voltage (e.g., 3V) or less, the power supply to the load of the vehicle from the power supply in the power supply control apparatus for turning on and off based on the on control signal of the semiconductor switching element,
An auxiliary power source that is provided independently of the power source and outputs a constant voltage (for example, 5V) that is lower than a rated output voltage (for example, 12V) of the power source and higher than the threshold voltage (for example, 3V);
A power supply voltage detector for detecting an output voltage of the power supply;
A capacitor charged by the power source;
The capacitor is connected to the power supply when the detection voltage of the power supply voltage detection unit is equal to or higher than a reference voltage (for example, 8V) between the rated output voltage (for example, 12V) and the constant voltage (for example, 5V). A connection for disconnecting the capacitor from the power source, ground and the GND terminal of the switching device when the detection voltage is between the reference voltage (eg, 8V) and the threshold voltage (eg, 3V);
When the detection voltage is equal to or lower than the threshold voltage (for example, 3V), a negative charge having a potential difference corresponding to the reference voltage (for example, 8V) from the constant voltage (for example, 5V) due to the charge of the capacitor. A voltage (for example, −3 V) is generated and applied to the GND terminal, and the control based on the potential of the GND terminal by the potential difference between the negative voltage and the potential of the GND terminal before the application of the negative voltage. A negative voltage generator that lowers the potential of the signal;
It is characterized by providing.

  According to the vehicle power supply control device of the first aspect of the present invention, the connecting portion connects the capacitor to the power supply while the output voltage of the power supply is equal to or higher than the reference voltage (for example, 8V). For this reason, the capacitor in which the output voltage of the power supply is lower than the reference voltage (for example, 8V) and the connection portion is insulated from the power supply is in a state of storing charges corresponding to the reference voltage (for example, 8V). Since this capacitor is also insulated from the ground and the GND terminal of the switching device, the capacitor stores a charge corresponding to a reference voltage (for example, 8 V).

  Thereafter, when the output voltage of the power supply further decreases to a threshold voltage (for example, 3 V), a control signal for the semiconductor switching element is output in the switching device. At this time, a potential difference corresponding to the charge stored in the capacitor with respect to a constant voltage (for example, 5V) of the auxiliary power source, that is, a negative voltage (for example, −3V) having a potential difference corresponding to the reference voltage (for example, 8V) is generated. , Applied to the GND terminal of the switching device. As a result, the potential of the control signal based on the potential of the GND terminal is lowered by the potential difference between the potential of the GND terminal and the negative voltage before application of the negative voltage.

  For this reason, even if the output voltage of the power supply is temporarily lowered to a low potential so that the low voltage cutoff function operates, the control potential of the semiconductor switching element that is output is lowered accordingly, The signal can be a potential when the output voltage of the power source substantially exceeds a threshold voltage (for example, 3 V).

  As a result, when the power supply from the power supply to the load is turned on / off by the switching device having a low voltage cutoff function, it is possible to always ensure the power supply from the power supply to the load even if the power supply voltage is temporarily lowered.

  The vehicle power supply control device according to the second aspect of the present invention is the vehicle power supply control device according to the first aspect of the present invention, wherein the reference voltage (for example, 8V) is equal to the constant voltage (for example, 5V). The potential difference is larger than the threshold voltage (for example, 3 V).

  According to the vehicle power supply control device according to the second aspect of the present invention, in the vehicle power supply control device according to the first aspect of the present invention, the potential difference (8V) between the reference voltage (for example, 8V) and the constant voltage (for example, 5V). −5V = 3V) is larger than the potential difference (5V−3V = 2V) between the constant voltage (5V) and the threshold voltage (for example, 3V).

  For this reason, even if the output voltage of the power supply is lower than the threshold voltage (for example, 3V), a negative voltage (for example, −3V) having a potential difference corresponding to the reference voltage (for example, 8V) with respect to the constant voltage (5V). ) Has a potential difference (2V − (− 3V) = 6V) equal to or higher than a threshold voltage (for example, 3V) with respect to the output voltage (for example, 2V) of the power supply.

  Therefore, even if the output voltage (for example, 2V) of the power supply is temporarily lowered, the potential of the GND terminal of the switching device serving as a reference for the control signal of the semiconductor switching element is lowered accordingly, and the control signal is output. The semiconductor switching element at the time can be reliably turned on.

  Note that, in the vehicle power supply control device according to the first or second aspect of the present invention, the connection portion and the negative voltage generation portion are the capacitors as in the vehicle power supply control device according to the third aspect of the present invention. A positive electrode side switching unit that switches a positive electrode connection destination between the power source and the auxiliary power source, and a negative electrode side switching unit that switches a negative electrode connection destination of the capacitor between the ground and the GND terminal of the switching device, It can be set as the structure which has the switching control part which controls the switching state of the said positive electrode side switching part and the said negative electrode side switching part according to the detection voltage of the said power supply voltage detection part.

  According to the present invention, when the power supply from the power supply to the load is turned on / off by the switching device having a low voltage cutoff function, the power supply from the power supply to the load is always secured even if the power supply voltage is temporarily lowered. Can do.

1 is a circuit diagram showing a fundamental configuration of a vehicle power supply control device according to an embodiment of the present invention. 2 is a timing chart showing the relationship between the output voltage of the power supply of FIG. 1 and the potential of the GND terminal of an intelligent power device (IPD) corresponding to a low voltage drive load. (A)-(c) is explanatory drawing which shows the circuit state of the negative voltage production | generation part according to the output voltage of the power supply of FIG. FIG. 2 is a circuit diagram illustrating a schematic configuration of a bias voltage switching unit in FIG. 1. It is a circuit diagram which shows the fundamental structure of the vehicle power supply control apparatus which concerns on other embodiment of this invention.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram showing a basic configuration of a power supply control device according to an embodiment of the present invention.

  The power supply control device 1 of the present embodiment (corresponding to the vehicle power supply control device in the claims) is connected to the main electric wire 5 from the power supply BATT mounted on a vehicle (not shown) to the loads 31, 32,. It is used as a so-called power supply box that supplies electric power through branched electric wires 51, 52,.

  In the present embodiment, the load 31 is assumed to be an electrical component such as a headlight. Further, the loads 32,..., 3n are electrical components that need to be driven even at a low voltage, such as electrical components of a control system or auxiliary machinery.

  Then, the power supply control device 1 is an intelligent power device (IPD) 131, 132,..., 13n that turns on / off the power supply from the branch wires 51, 52,. Equivalent to a switching device in claims) and a control unit 11 for controlling the operation thereof.

  The controller 11 operates with the constant voltage source 15 (corresponding to the auxiliary power supply in the claims) by the constant voltage (for example, 5V) of FIG. 2 generated from the output voltage of the power supply BATT, and loads 31, 32,. , The control signals for the corresponding IPDs 131, 132,..., 13n are output.

Each of the IPDs 131, 132,..., 13n incorporates a P-channel power MOSFETa (corresponding to a semiconductor switching element in claims) and a driver circuit b thereof. When the gate-source voltage exceeds the gate threshold voltage (Vlow, for example, 3 V, corresponding to the threshold voltage in the claims) of FIG. 2 due to the input of the drive signal to the gate, the P-channel power MOSFET a -Conduction between sources due to decrease in on-resistance. Each of the IPDs 131, 132,..., 13n supplies power from the power source BATT to the loads 31, 32,.

  Each of the IPDs 131, 132,..., 13n has a low voltage cutoff function. This low-voltage cutoff function is a function that cuts off the power supply to the loads 31, 32,..., 3n in order to prevent overheating due to an increase in the on-resistance of the semiconductor switching element when the power supply voltage of the power supply BATT decreases. is there.

  In the IPDs 131, 132,..., 13n of the present embodiment, when the source potential of the P-channel power MOSFETa is lowered to the gate threshold voltage (Vlow) in FIG. -The source is interrupted. Therefore, the operation of the P-channel power MOSFETa is a low voltage cutoff function that cuts off the power supply to the loads 31, 32,..., 3n when the power supply voltage of the power supply BATT drops to the gate threshold voltage (Vlow). We are using. However, when an N-channel power MOSFET is used as the semiconductor switching element, a similar low voltage cutoff function can be realized with another configuration.

  Therefore, in the following description, each of the IPDs 131, 132,..., 13n simply turns off the semiconductor switching element when the power supply voltage of the power supply BATT drops below the threshold voltage (Vlow), and loads 31, 32, .., 3n only on the premise of having a low voltage cutoff function to cut off the power supply to 3n, whether or not each IPD 131, 132,..., 13n uses a P-channel power MOSFET as a semiconductor switching element. It will not be specified.

  In a vehicle (not shown) in which the power supply control device 1 of the present embodiment is used, the starter motor consumes a large amount of power when cranking the engine at the time of starting. At this time, the power supply voltage of the power supply BATT temporarily decreases greatly. When the power supply voltage of the power supply BATT decreases, the low voltage cutoff function of the IPDs 131, 132,..., 13n operates to turn off the semiconductor switching element a, and the power supply from the power supply BATT to the loads 31, 32,. Will be.

  The occurrence of such a phenomenon is particularly problematic for the loads 32,..., 3n that need to be driven even at a low voltage. These loads 32,..., 3n need to ensure power supply even if the power supply voltage of the power supply BATT is greatly reduced temporarily.

  Therefore, the power supply control device 1 according to the present embodiment has the operating voltage detection unit 7, the low voltage detection unit 9, the negative voltage detection unit 7 in order to ensure the power supply to the loads 32,..., 3n even when the power supply voltage of the power supply BATT decreases. A voltage generation unit 17 and a bias voltage switching unit 19 are provided.

  The negative voltage generation unit 17 (corresponding to the negative voltage generation unit and the connection unit in the claims) connects the capacitor C, the switch SW1 that connects the positive electrode of the capacitor C to the power source BATT, and the negative electrode of the capacitor C to GND (ground) And a switch SW5 that connects the positive electrode of the capacitor C to the output side of the constant voltage source 15.

  The capacitor C is charged by the output voltage of the power supply BATT when the positive electrode is connected to the power supply BATT when the switch SW1 is turned on and the negative electrode is connected to GND (ground) when the switch SW3 is turned on.

  Further, when the switch SW5 is turned on while the switches SW1 and SW3 are turned off and disconnected from the power supply BATT, the capacitor C is switched from the power supply BATT to the output side of the constant voltage source 15 and the negative electrode is connected. Is disconnected from GND (ground). In this state, a potential obtained by subtracting the voltage corresponding to the charge of the capacitor C from the constant voltage (for example, 5 V) of the constant voltage source 15 appears on the negative electrode of the capacitor C.

  The operating voltage detector 7 (corresponding to the power supply voltage detector and the switching controller in the claims) detects the output voltage of the power supply BATT before the constant voltage source 15 generates the constant voltage. The operating voltage detection unit 7 has a detected voltage that is higher than the constant voltage by the constant voltage source 15 and lower than the rated output voltage (for example, 12V) of the power supply BATT, and is equal to or higher than the reference voltage (Vmin, for example, 8V) in FIG. In some cases, the operating voltage detector 7 turns on the switches SW1 and SW3 of the negative voltage generator 17 as shown in FIG.

  At this time, the switch SW5 of the negative voltage generator 17 is turned off by the low voltage detector 9 described later. For this reason, the capacitor C is charged at the reference voltage Vmin or higher when the output voltage of the power supply BATT is higher than the reference voltage Vmin (for example, 8 V).

  When the detected voltage falls below the reference voltage Vmin, the operating voltage detector 7 turns off the switches SW1 and SW3 of the negative voltage generator 17 as shown in FIG. 3B.

  On the other hand, the low voltage detection unit 9 (corresponding to the power supply voltage detection unit and the switching control unit in the claims) detects the output voltage of the power supply BATT, and the detected voltage exceeds the threshold voltage Vlow (for example, 3V). If so, the switch SW5 of the negative voltage generator 17 is turned off.

  For this reason, when the output voltage of the power supply BATT is between the threshold voltage Vlow and the reference voltage Vmin (for example, 8V), the capacitor C is stored in a state where charges corresponding to the reference voltage Vmin (for example, 8V) are stored. Insulated from BATT.

  Further, when the detected voltage is equal to or lower than the threshold voltage Vlow (eg, 3V), the low voltage detection unit 9 turns on the switch SW5 of the negative voltage generation unit 17 as shown in FIG. At this time, the switches SW1 and SW3 of the negative voltage generator 17 are turned off by the operating voltage detector 7. Therefore, the capacitor C has a positive electrode connected to the output side of the constant voltage source 15 in a state where charges corresponding to the reference voltage Vmin (for example, 8 V) are stored. Then, a negative potential (for example, −3 V) obtained by subtracting a voltage (for example, 8 V) corresponding to the charge of the capacitor C from a constant voltage (for example, 5 V) of the constant voltage source 15 appears at the negative electrode of the capacitor C.

  Incidentally, the GND terminal of the IPD 131 corresponding to the load 31 shown in FIG. 1 is connected to GND (ground). The GND terminal of the driver circuit b is connected to the GND terminal. Therefore, the driver circuit b of the IPD 131 sets the semiconductor switching element a in accordance with the potential difference between the control signal input (IN) potential corresponding to the control signal from the control unit 11 directed to the IPD 131 and the potential of the GND terminal. Turn on and off.

  Specifically, the driver circuit b of the IPD 131 receives the control signal input (IN) when the control signal input from the control unit 11 to the IPD 131 is not input and the potential of the control signal input (IN) is the GND (ground) potential. ) And the GND terminal potential (GND (earth) potential) does not exceed the threshold voltage Vlow, so that the semiconductor switching element a is turned off.

  Further, in the driver circuit b of the IPD 131, the potential difference between the potential of the control signal input (IN) and the potential of the GND terminal (GND (ground) potential) exceeds the threshold voltage Vlow by the input of the control signal from the control unit 11. Then, the semiconductor switching element a is turned on.

  On the other hand, as shown in the timing chart of FIG. 2, the output terminal of the power supply BATT has a threshold voltage (for example, 3V) at the GND terminals of the IPDs 132,. In the period of (1) and (2) exceeding, since the negative voltage generation unit 17 is in the circuit state shown in FIG. 3A or 3B, the direction from the GND terminal toward GND (ground) is changed. It is connected to GND (ground) via a diode D1 which is a forward direction. The GND terminal of the driver circuit b is connected to the GND terminal.

  Further, as shown in FIG. 2, the GND terminals of the IPDs 132,..., 13n have the negative voltage generation unit 17 in the period (3) in which the output voltage of the power supply BATT is equal to or lower than the threshold voltage Vlow (for example, 3V). Since it is in the circuit state shown in FIG. 3C, it is connected to the negative electrode of the capacitor C via a diode D3 whose forward direction is from the GND terminal to the negative electrode of the capacitor C.

  Therefore, when the output voltage of the power supply BATT exceeds the threshold voltage Vlow (for example, 3V), the driver circuit b of the IPDs 132,..., 13n has a potential between the potential of the control signal input (IN) and the potential of the GND terminal. The semiconductor switching element a is turned on / off according to the potential difference.

  The driver circuits b of the IPDs 132,..., 13n are connected to the potential of the control signal input (IN) and the GND terminal when the output voltage of the power supply BATT is equal to or lower than the threshold voltage Vlow (for example, 3V). The semiconductor switching element a is turned on / off according to a potential difference with a negative potential (for example, −3 V) appearing at the negative electrode of the capacitor C.

  Specifically, when the output voltage of the power supply BATT exceeds a threshold voltage Vlow (for example, 3 V), the driver circuit b of the IPDs 132,..., 13n has no control signal input and the control signal input (IN) Since the potential difference between the potential of the control signal input (IN) and the potential of the GND terminal (GND (earth) potential) does not exceed the threshold voltage Vlow, the semiconductor switching element a Turn off.

  Further, the driver circuit b of the IPDs 132,..., 13n receives a control signal input and the potential difference between the potential of the control signal input (IN) and the potential of the GND terminal (GND (ground) potential) exceeds the threshold voltage Vlow. Then, the semiconductor switching element a is turned on.

  On the other hand, when the output voltage of the power supply BATT is equal to or lower than the threshold voltage Vlow (for example, 3V), the driver circuit b of the IPDs 132,..., 13n has no control signal input and the potential of the control signal input (IN) is GND. When the potential is (earth) potential, the potential difference between the potential of the control signal and the potential of the GND terminal reverse-biased to a negative potential (for example, −3 V) does not exceed the threshold voltage Vlow, so the semiconductor switching element a is turned off.

  In addition, the driver circuit b of the IPDs 132,. When the voltage Vlow is exceeded, the semiconductor switching element a is turned on.

  As described above, the IPDs 132,..., 13n change the potential of the GND terminal to which the ground of the driver circuit b is connected to GND (depending on whether or not the output voltage of the power supply BATT exceeds the threshold voltage Vlow (for example, 3V). Switching between (ground) potential and negative potential (eg -3V). Therefore, it is necessary to switch the reference potential of the control signal input to the control signal input (IN) between a GND (ground) potential and a negative potential (for example, −3 V) in accordance with the potential of the GND terminal.

  Therefore, the bias voltage switching unit 19 switches the potential of the control signal from the control unit 11 toward the IPDs 132,..., 13n in accordance with the potentials of the GND terminals of the IPDs 132,.

  As shown in the circuit diagram of FIG. 4, the bias voltage switching unit 19 has a pnp transistor Q1. A plurality of transistors Q1 are provided in the bias voltage switching section 19 corresponding to each IPD 132,. The emitter of each transistor Q1 is connected to the output side of the constant voltage source 15, and the collector is connected to the GND terminal of the corresponding IPD 132,..., 13n and the control signal input (IN).

  The bias voltage switching unit 19 does not receive a control signal from the control unit 11 directed to the IPDs 132,..., 13n, and while the base potential of the corresponding transistor Q1 is higher than the GND (ground) potential, Since the collector-emitter of Q1 is cut off, no control signal is output to the corresponding IPD 132,..., 13n.

  When the base potential of the corresponding transistor Q1 is reverse-biased to the GND (ground) potential by the input of the control signal from the control unit 11 toward the IPDs 132,. Since the collector-emitter is electrically connected, a control signal is output to the corresponding IPD 132,.

  At this time, if the potential of the GND terminal of the corresponding IPD 132,..., 13n is the GND (ground) potential, the potential of the control signal output from the bias voltage switching unit 19 to the corresponding IPD 132,. To the same potential as the control signal input to the bias voltage switching unit 19.

On the other hand, if the potential of the GND terminal of the corresponding IPD 132,..., 13n is a negative potential (for example, −3 V), the potential of the control signal output to the driver circuit b of the corresponding IPD 132,. Is a potential based on a potential that is reduced by a potential difference between a GND (ground) potential and a negative potential (for example, −3 V) of the control signal input from the control unit 11 to the bias voltage switching unit 19.

  As described above, the bias voltage switching unit 19 switches the potential serving as the reference of the control signal from the control unit 11 in accordance with the potential of the GND terminal of the IPDs 132,..., 13n, thereby preventing the IPDs 132,. can do.

That is, even though the control signal is not input to the IPDs 132,..., 13n, the potential of the GND terminals of the IPDs 132,..., 13n is switched from the GND (ground) potential to the negative potential (for example, −3V). Thus, the potential of the control signal input (IN) of the IPDs 132,..., 13n does not rise relatively with respect to the potential of the GND terminal ( the gate potential of the P- channel power MOSFETa is relative to the source potential) .

For this reason, when the output voltage of the power supply BATT falls below the threshold voltage Vlow (for example, 3V) , the semiconductor switching element a is erroneously linked with the switching of the potentials of the GND terminals of the IPDs 132,. is turned Te (P-channel drain of the power MOSFETa - you conduct incorrectly-source) can be prevented.

  According to the power supply control device 1 of the embodiment described above, the output voltage of the power supply BATT is lower than the reference voltage Vmin when the capacitor C is charged while the output voltage of the power supply is equal to or higher than the reference voltage Vmin (for example, 8V). Then, the power supply BATT is disconnected, and when the output voltage of the power supply BATT further falls below a threshold voltage (for example, 3V), the positive electrode of the capacitor C is connected to the constant voltage source 15.

  Then, a negative potential (for example, −3 V) having a potential difference corresponding to a charge (for example, 8 V) corresponding to the charge of the capacitor C with respect to a constant voltage (for example, 5 V) output from the constant voltage source 15 is generated at the negative electrode of the capacitor C. Thus, the potential of the GND terminal of the IPD 132,..., 13n corresponding to the low voltage drive loads 32,.

Thus, lowered output voltage of the power supply BATT until a threshold voltage Vlow (e.g. 3V), GND of the control unit 11 (ground) control signal is IPD132 potential, ..., 13n (gate of P-channel power MOSFETa) be entered, IPD132, ..., the semiconductor switching element a does not exceed the potential and potential difference between the potential of the GND terminal threshold voltage Vlow (e.g. 3V) of the control signal input 13n (iN) is not turned on in , 13n, the potential of the control signal from the control unit 11 is lowered from the GND (ground) potential by the negative voltage of the GND terminal of the IPDs 132,. And the potential of the GND terminal can be set to a threshold voltage Vlow (for example, 3 V) or more.

  Thus, when the power supply from the power supply BATT to the loads 32,..., 3n is turned on / off by the semiconductor switching elements a of the IPDs 131,. It is possible to always ensure power supply to 32,.

  Further, the configuration for switching the potentials of the GND terminals of the IPDs 131,..., 13n according to the output voltage of the power supply BATT can be provided in units of the IPDs 131,. As described above, an increase in circuit scale can be suppressed to a necessary minimum by providing only the IPDs 132,..., 13n corresponding to the low voltage drive loads 32,.

  Instead of the switch SW1 of the negative voltage generator 17, the direction from the power supply BATT toward the positive electrode of the capacitor C is forward as in the power supply control device 1 according to another embodiment of the present invention shown in the circuit diagram of FIG. The diode D5 may be used.

  In the above-described embodiment, the potential difference (8V-5V = 3V) between the reference voltage (for example, 8V) and the constant voltage (for example, 5V) is changed to the potential difference between the constant voltage (5V) and the threshold voltage Vlow (for example, 3V). Although larger than (5V-3V = 2V), the magnitude relationship between both potential differences may be reversed or eliminated.

  Further, in the above-described embodiment, the IPD 131, 132,..., 13n including the semiconductor switching element a and the driver circuit b are used. However, the present invention uses the semiconductor switching element a provided separately from the driver circuit b. The present invention can also be applied to the case where the power supply to the load 3 is controlled.

  In these, the present invention can also be applied when an N-channel power MOSFET is used as the semiconductor switching element a instead of the P-channel power MOSFET.

  INDUSTRIAL APPLICABILITY The present invention is extremely useful when performing power supply control in which power supply from a vehicle power supply to a load is turned on / off by a switching device having a low voltage cutoff function.

1 Power supply control device (vehicle power supply control device)
31,..., 3 n Load 5 Main wire 51, 52,..., 5 n Branch wire 7 Operating voltage detector (power supply voltage detector, switching controller)
9 Low voltage detector (power supply voltage detector, switching controller)
11 Control part 131, ..., 13n Intelligent power device (IPD, switching device)
15 Constant voltage source (auxiliary power supply)
17 Negative voltage generator (connector)
19 Bias voltage switching part a P-channel power MOSFET (semiconductor switching element)
b Driver circuit BATT Power supply C Capacitor SW1, SW5 Switch (Positive side switching part)
SW3 switch (negative-side switching part)
Vmin Reference voltage Vlow Gate threshold voltage (threshold voltage)

Claims (3)

Using a switching device with a low voltage cutoff function the output voltage of the power supply of the vehicle to force off semi conductor switching elements when: the threshold voltage, the semiconductor switching the power supply to the load of the vehicle from the power supply in the power supply control apparatus for turning on and off based on the control signal of the element,
An auxiliary power source provided independently of the power source and outputting a constant voltage lower than the rated output voltage of the power source and higher than the threshold voltage;
A power supply voltage detector for detecting an output voltage of the power supply;
A capacitor charged by the power source;
When the detection voltage of the power supply voltage detection unit is equal to or higher than a reference voltage between the rated output voltage and the constant voltage, the capacitor is connected to the power supply, and the detection voltage is the reference voltage and the threshold. A connection for disconnecting the capacitor from the power source, ground and the GND terminal of the switching device when between
When the detected voltage is equal to or lower than the threshold voltage, a negative voltage having a potential difference corresponding to the reference voltage with respect to the constant voltage is generated by the charge of the capacitor and applied to the GND terminal. A negative voltage generation unit that reduces the potential of the control signal based on the potential of the GND terminal by a potential difference between the negative voltage and the potential of the GND terminal before application of the negative voltage;
A vehicle power supply control device comprising:   The vehicle power supply control device according to claim 1, wherein the reference voltage has a potential difference from the constant voltage larger than the threshold voltage.   The connection unit and the negative voltage generation unit include a positive-side switching unit that switches a connection destination of the positive electrode of the capacitor between the power source and the auxiliary power source, and a connection destination of the negative electrode of the capacitor is grounded and the switching device. A negative-side switching unit that switches between the GND terminal and a switching control unit that controls a switching state of the positive-side switching unit and the negative-side switching unit according to a detection voltage of the power supply voltage detection unit; The vehicle power supply control device according to claim 1 or 2.

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