JP4474782B2 - Electric load drive - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention provides an output transistor provided in a current supply path for flowing a current to an electric load, and a transistor driving circuit for turning on / off the output transistor in accordance with a control signal for each of a plurality of electric loads to be driven. In particular, the present invention relates to an electric load driving device having a high-side output configuration in which an output transistor flows current to the electric load.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, an electronic control device for a vehicle such as an engine control device and a transmission control device mounted on an automobile controls a control target by driving various electric loads such as a relay and a solenoid according to a driving state of the vehicle. ing.
[0003]
These control devices, as means for driving the electric load, for each electric load to be driven, an output transistor provided in a current supply path of the electric load, and the output transistor are connected to a microcomputer (hereinafter referred to as a microcomputer). And a transistor drive circuit (so-called predrive circuit) that is turned on / off in response to a control signal from a dedicated IC or the like.
[0004]
Here, the output form for supplying the drive current to the electric load varies depending on the type and application of the electric load, and either the high-side output form or the low-side output form is adopted. When the output transistor is an N-channel MOSFET with a high-side output configuration, there are two current supply paths from the high potential side of the load power supply (battery voltage which is generally the potential of the positive terminal of the battery in the vehicle) to the electric load. The drain and source which are output terminals are connected in series.
[0005]
In this case, a booster circuit (hereinafter also referred to as a charge pump circuit) that boosts and outputs the voltage of the load power source (generally a battery voltage in a vehicle) to a higher voltage is provided, and a transistor drive circuit When the control signal from the microcomputer or the like is at an active level for instructing to turn on the output transistor, the output transistor is turned on by supplying the output voltage Vcp of the charge pump circuit to the gate of the output transistor.
[0006]
Further, in the case where an output transistor that is an N-channel MOSFET of a high-side output form and a transistor drive circuit are provided for each of a plurality of electric loads, the plurality of transistor drive circuits share one charge pump circuit. With such a configuration, the number of parts can be reduced, and the size and cost can be reduced.
[0007]
Therefore, a conventional configuration example of an electronic control device in which one charge pump circuit is shared by a plurality of transistor drive circuits will be specifically described with reference to FIG.
First, the electronic control unit 100 illustrated in FIG. 7 includes at least the hydraulic pressure of the main hydraulic path 102 disposed in the automatic transmission 101 as shown in FIG. 6 among the solenoids used for controlling the automatic transmission of the vehicle. A main hydraulic solenoid L1 that is a linear solenoid for adjusting the speed, and a shift solenoid L2 that supplies hydraulic pressure from the main hydraulic path 102 to the gear portion 104 of the automatic transmission 101 and changes a reduction ratio in the gear portion 104; Is driven and controlled.
[0008]
The lockup solenoid L3 in FIG. 6 is a lockup drive that causes the two clutch plates 108 provided in the torque converter 106 of the automatic transmission 101 to be hydraulically coupled to bring the automatic transmission 101 into a lockup state. The lockup solenoid L3 is actually controlled by the electronic control unit 100 together with the main hydraulic solenoid L1 and the shift solenoid L2, although the hydraulic pressure from the main hydraulic path 102 is supplied to the section 110. Then, explanation is omitted. Further, although there are actually a plurality of shift solenoids L2, a description is given here assuming that there is one.
[0009]
As shown in FIG. 7, the electronic control unit 100 is configured to control the main hydraulic solenoid L1 from the microcomputer 10 as a control unit that executes various processes for controlling the solenoids L1 and L2. A drive unit 200 for passing a current to the main hydraulic solenoid L1 in response to the output control signal S1 and for causing a current to flow to the shift solenoid L2 in response to the control signal S2 output from the microcomputer 10 to control the shift solenoid L2; The current detection resistor 12 connected between one end of the main hydraulic solenoid L1 and the ground potential (the potential of the negative terminal of the battery and corresponding to the low potential side of the load power source), and the current detection resistor 12 The potential difference generated at both ends is differentially amplified and output as a current detection signal MI representing the current value flowing through the main hydraulic solenoid L1. And a current detecting circuit 14 for.
[0010]
Drive unit 200 boosts and outputs vehicle battery voltage VB to a voltage higher than that, and drain is connected to battery voltage VB (corresponding to the high potential side of the load power source). At the same time, an output transistor T1, which is an N-channel MOSFET, is connected to the end of the main hydraulic solenoid L1 opposite to the current detection resistor 12 side and is turned on to flow current to the main hydraulic solenoid L1. An output which is an N-channel MOSFET whose drain is connected to the battery voltage VB and whose source is connected to the end of the shift solenoid L2 on the side opposite to the ground potential side. And a transistor T2.
[0011]
Furthermore, the drive unit 200 serves as a circuit for turning on / off the output transistor T1 corresponding to the main hydraulic solenoid L1 in response to the control signal S1 from the microcomputer 10, and the output voltage of the charge pump circuit CP (hereinafter also referred to as a boosted voltage). In response to Vcp, when the control signal S1 is at a high level, the boosted voltage Vcp is output from the output terminal. When the control signal S1 is at a low level, the buffer 21 has an output terminal in a high impedance state, and the buffer 21 A gate protection resistor 22 connected between the output terminal and the gate of the output transistor T1, an NPN transistor 23 whose emitter is connected to the ground potential, and between the collector of the transistor 23 and the gate of the output transistor T1. And the current limiting resistor 24 connected to the microcomputer 10 and the control signal from the microcomputer 10. S1 is by logical inversion comprises an inverting circuit 25 is supplied to the base of the transistor 23, the transistor driving circuit K1 consisting of.
[0012]
In the transistor drive circuit K1, when the control signal S1 from the microcomputer 10 becomes a high level as an active level, the output voltage Vcp of the charge pump circuit CP is supplied from the buffer 21 to the gate of the output transistor T1 through the resistor 22. The Accordingly, the drive current Ion flows from the buffer 21 to the gate of the output transistor T1 based on the output of the charge pump circuit CP, and the gate-source parasitic capacitance C of the output transistor T1 becomes a predetermined threshold voltage. The output transistor T1 is turned on. On the contrary, when the control signal S1 from the microcomputer 10 becomes a low level as a passive level, the NPN transistor 23 is turned on, and the gate-source parasitic capacitance C of the output transistor T1 is discharged. The output transistor T1 is turned off. Note that Ioff in FIG. 7 indicates a discharge current when the gate-source parasitic capacitance C of the output transistor is discharged.
[0013]
Similarly, the drive unit 200 includes a transistor drive circuit K2 having the same configuration as the transistor drive circuit K1 as a circuit for turning on / off the output transistor T2 corresponding to the shift solenoid L2 according to the control signal S2 from the microcomputer 10. I have. That is, the transistor drive circuit K2 also receives the boosted voltage Vcp from the charge pump circuit CP, and outputs the boosted voltage Vcp from the output terminal when the control signal S2 is at high level, and the control signal S2 is at low level. Sometimes the buffer 31 whose output terminal is in a high impedance state, the gate protection resistor 32 connected between the output terminal of the buffer 31 and the gate of the output transistor T2, and the NPN transistor whose emitter is connected to the ground potential 33, the current limiting resistor 34 connected between the collector of the transistor 33 and the gate of the output transistor T2, and the control signal S2 from the microcomputer 10 are logically inverted and supplied to the base of the transistor 33. And an inverting circuit 35.
[0014]
In such an electronic control device 100, the microcomputer 10 detects the driving state of the vehicle based on signals from various sensors (not shown) attached to the vehicle, and from the detected driving state to the main hydraulic solenoid L1. A target current to be flowed (in other words, a target hydraulic pressure of the main hydraulic pressure path 102 in the automatic transmission 101) is calculated. Further, the microcomputer 10 detects a current actually flowing through the main hydraulic solenoid L1 (hereinafter referred to as an actual current) based on the current detection signal MI from the current detection circuit 14, and a control signal to the transistor drive circuit K1. S1 is output at a duty ratio such that the actual current becomes the target current. That is, the microcomputer 10 outputs the control signal S1 with a duty ratio corresponding to the difference between the actual current and the target current, and feedback-controls the current flowing through the main hydraulic solenoid L1.
[0015]
In addition, regarding the shift solenoid L2, the microcomputer 10 sets the control signal S2 to the transistor drive circuit K2 to high level and starts energizing the shift solenoid L2 when the timing for changing the reduction ratio in the gear unit 104 comes. Then, when the timing at which it is considered that the change of the reduction ratio in the gear unit 104 has been completed, on / off control is performed such that the control signal S2 is made low to stop energization of the shift solenoid L2.
[0016]
[Problems to be solved by the invention]
By the way, in the case of an electric load driving device configured to supply driving power for turning on an output transistor from one charge pump circuit to a plurality of transistor driving circuits like the electronic control device 100, the charge pump circuit includes Therefore, a large-scale device with high output capability is required so that sufficient drive power can be supplied even when a plurality of connected transistor drive circuits simultaneously turn on the output transistors.
[0017]
For example, in the electronic control unit 100 of FIG. 7, as shown at time t1 of FIG. 8, the control signal S2 for the shift solenoid L2 (control signal (2)) and the control signal S1 for the main hydraulic solenoid L1 (control signal ▲) 1 ▼) change from the low level to the high level almost simultaneously. FIG. 8 illustrates a case where the control signal S1 becomes high level immediately after the control signal S2 becomes high level.
[0018]
In this case, since the drive current Ion must be supplied almost simultaneously to the gates of the two output transistors T1 and T2, the output capability (particularly the current capacity that can be output) of the charge pump circuit CP is not sufficient as shown in FIG. As a result, the output voltage Vcp of the charge pump circuit CP decreases, and the charging of the gate-source parasitic capacitance C of the output transistors T1 and T2 is delayed, and as a result, the on-state of the output transistors T1 and T2 is delayed. . In FIG. 8, “drive signal (1)” indicates the gate-source voltage of the output transistor T1, and “drive signal (2)” indicates the gate-source voltage of the output transistor T2.
[0019]
Then, since the ON time of the output transistor T1 that is duty-driven based on the control signal S1 becomes shorter than the scheduled value, the energization duty ratio of the main hydraulic solenoid L1 is temporarily reduced, and the energization of the main hydraulic solenoid L1 is reduced. The current decreases, and the duty ratio of the next cycle of the control signal S1 is corrected to a large value by the action of feedback control based on the current detection signal MI from the current detection circuit 14. For this reason, the pulsation that the energizing current of the main hydraulic solenoid L1 increases and returns to the control current value as the target current as shown in the period X of FIG. 8 occurs. The oil pressure may fluctuate unnecessarily, and the control of the automatic transmission 101 may be affected.
[0020]
Therefore, in the conventional electronic control device 100, the charge pump circuit CP needs to have a large output capability capable of quickly turning on the two output transistors T1 and T2 at the same time. There was a limit to the conversion. In other words, the charge pump circuit (boost circuit) CP is generally charged by the voltage of a plurality of stages of charging capacitors that are cumulatively charged at a predetermined frequency and the final stage of the charging capacitors, so that the boosted voltage is increased. An output capacitor for outputting Vcp. In order to increase the output capability, it is necessary to increase the capacitance of the output capacitor and the charging capacitor, or in some cases, increase the number of stages of the charging capacitor. is there.
[0021]
On the other hand, in the electronic control unit 100 of FIG. 7, for example, the resistance values of the resistors 22 and 32 are set to be large, and the driving current Ion flowing from the transistor driving circuits K1 and K2 to the gates of the output transistors T1 and T2 is reduced. It is conceivable to reduce the size of the charge pump circuit CP by setting.
[0022]
However, if the drive current Ion is simply reduced, the drive responsiveness of the output transistors T1 and T2 to the control signals S1 and S2 (that is, the output transistors T1 and T2 are turned on after the control signals S1 and S2 become high level). Reaction rate) until it is reduced, and it becomes impossible to always obtain excellent control performance. In particular, when comparing the main hydraulic solenoid L1 in which the energization current is precisely duty-controlled and the shift solenoid L2 in which the energization current is on / off controlled (binary control of energization or not), the current to the shift solenoid L2 is compared. The output response of the output transistor T2 that flows current is excellent in driving response, but if the output response of the output transistor T1 that flows current to the main hydraulic solenoid L1 is low, the accuracy of the current feedback control is affected. It is not preferable. That is, in terms of drive response, it can be said that the output transistor T1 corresponding to the main hydraulic solenoid L1 has higher priority than the output transistor T2 corresponding to the shift solenoid L2.
[0023]
In addition, setting the output capability of the charge pump circuit CP high is not only in consideration of when a plurality of output transistors are simultaneously turned on, but also includes a transistor drive circuit with a fail-safe function described below. It was also necessary for the device.
[0024]
That is, first, the transistor drive circuit detects the abnormality of the electric load to be driven from the operation state when the output transistor is turned on (for example, the current flowing through the output transistor or the heat generation of the output transistor), and controls when the abnormality is detected. Some have a fail-safe function of temporarily turning off an output transistor regardless of a signal.
[0025]
As a specific example, for example, in the transistor drive circuit for the shift solenoid L2, in order to realize the fail-safe function, when the current flowing through the output transistor becomes equal to or higher than the overcurrent determination value, a short-circuit failure of the solenoid L2 occurs. There may be provided an abnormality detection circuit that outputs an abnormality detection signal indicating that it has occurred, and a protection circuit that forcibly turns off the output transistor for a predetermined time when the abnormality detection signal is output from the abnormality detection circuit. .
[0026]
In the case of this transistor drive circuit, when the shift solenoid L2 is short-circuited, the abnormality is detected while the control signal is at the active level. The output transistor is turned off for a certain period of time (energization is cut off). The operation of abnormality detection → the output transistor is turned off for a certain time →... Is repeated, and the output transistor is periodically turned on / off. If the shift solenoid L2 returns to the normal state and no abnormality is detected. From that point on, the normal operation according to the control signal is performed. This is because, in the case of the shift solenoid L2, in the event of a short circuit failure, it is considered that it is better to continue driving while limiting energization in anticipation of return to the normal state.
[0027]
Here, in the case of a device having such a transistor drive circuit with a fail-safe function, when an abnormality occurs in the electrical load corresponding to the transistor drive circuit and the output transistor is periodically turned on / off, the charge is The output capability of the pump circuit becomes insufficient and the output voltage Vcp decreases (or tends to decrease) as compared with the normal time. As a result, other output transistors (specifically, other transistor drive circuits are supported). The drive response of the output transistor) is reduced.
[0028]
Therefore, it is necessary to set the output capability of the charge pump circuit sufficiently high so that the drive response of such other output transistors does not deteriorate, and the large-scale charge pump circuit has a high output capability. Was needed.
The present invention has been made in view of the above problems, and in an electric load driving device having a configuration in which a plurality of transistor driving circuits share one boosting circuit, the boosting circuit can be reduced in size without causing performance degradation. The purpose is to reduce costs.
[0029]
[Means for Solving the Problems and Effects of the Invention]
The electrical load driving device according to claim 1, which has been made to achieve the above object, has two output terminals connected in series to the current supply path from the high potential side of the load power source to the electrical load, as in the conventional device described above. A high-side output type output transistor that flows current to the electrical load by being turned on, and a transistor drive circuit that turns the output transistor on / off according to a control signal from the control unit, Each of the plurality of electric loads to be driven is provided with a booster circuit shared by the transistor drive circuits. The booster circuit boosts the voltage of the load power supply (load power supply voltage) to a voltage higher than that, and outputs the boosted voltage to each transistor drive circuit. Each transistor drive circuit outputs a control signal from the control unit. When the transistor is at an active level instructing to turn on the transistor, the output transistor is turned on by supplying the output voltage of the booster circuit to the gate of the output transistor corresponding to the transistor.
[0030]
In particular, in the electric load driving device according to the first aspect, the situation determination unit determines whether or not a predetermined situation in which the output voltage of the booster circuit decreases (hereinafter referred to as a voltage reduction situation) has occurred. A specific transistor drive circuit among the plurality of transistor drive circuits is supplied to the gate of the output transistor based on the output of the booster circuit while it is determined by the situation determination means that a voltage drop situation has occurred. The driving current that flows out is suppressed.
[0031]
According to this electrical load driving device, when the occurrence of the situation where the output voltage of the booster circuit is lowered (voltage drop situation) is detected by the situation determining means, the drive current that the specific transistor drive circuit flows to the output transistor is reduced. In order to suppress this, a drive current can be sufficiently supplied from another transistor drive circuit to the gate of the corresponding output transistor.
[0032]
Therefore, the transistor drive circuit KB corresponding to the output transistor TB that is allowed to have lower drive response than the output transistor TA that is turned on / off by a predetermined transistor drive circuit KA among the plurality of transistor drive circuits. If the above-mentioned specific transistor drive circuit is used, even if the output voltage of the booster circuit decreases, the drive capability for the output transistor TA having a high drive response priority is maintained. In other words, even if the output capability of the booster circuit is small and the output voltage decreases, a sufficient drive current based on the output of the booster circuit is applied to the gate of the output transistor TA that requires higher drive response. As a result, the drive response of the output transistor TA can be ensured.
[0033]
In addition, in this electric load driving device, the driving current flowing out from the specific transistor driving circuit KB to the gate of the output transistor TB is not reduced in advance, but only reduced when a voltage drop situation occurs. As a result, the drive response of the output transistor TB can be maintained at a high level during normal operation.
[0034]
Therefore, according to the electric load driving device of the first aspect, compared with the conventional device, the booster circuit can be reduced in size and cost without causing a decrease in performance. The entire apparatus can be reduced in size and cost. By the way, as described in claim 2, the situation determination means monitors the output voltage Vcp of the booster circuit, and when the output voltage Vcp is lower than a predetermined reference voltage Vref, the voltage drop situation occurs. It can be configured to determine that it is present.
[0035]
According to the electric load driving apparatus of the second aspect, since the output voltage Vcp of the booster circuit is directly monitored, when a plurality of output transistors are turned on almost simultaneously, any one of the transistor driving In addition to the case where the output transistor corresponding to the transistor drive circuit is periodically turned on / off by the above-described fail-safe function of the circuit, for example, when the load power supply voltage itself is lowered or a certain output transistor is controlled. Even if the output voltage Vcp of the booster circuit decreases due to any other factor, such as when it is frequently turned on / off, the specific transistor drive circuit KB suppresses the drive current. For this reason, it becomes possible to more surely secure the drive response of the other output transistor TA that requires higher drive response than the output transistor TB corresponding to the specific transistor drive circuit KB.
[0036]
On the other hand, in the electric load driving apparatus according to the first aspect, if any one of the plurality of transistor driving circuits has the above-described fail-safe function, the electric load driving apparatus can be configured as in the third aspect. .
That is, first, in the electric load driving device according to the third aspect, the specific transistor drive circuit KB configured to suppress the drive current includes the fail-safe means for the fail-safe function described above.
[0037]
The fail-safe means detects an abnormality of the electric load to be driven from the operating state when the output transistor TB corresponding to the transistor drive circuit KB is on, and when the abnormality is detected, the control from the control unit Regardless of the signal, the output transistor TB is temporarily turned off.
[0038]
For this reason, when the fail-safe means detects an abnormality in the electric load, the abnormality detection → the output transistor TB until the abnormality is resolved or the control signal from the control unit to the transistor drive circuit KB returns to the passive level. Is temporarily turned off → output transistor TB is turned on → abnormality detection → output transistor TB is temporarily turned off →..., And output transistor TB is periodically turned on / off. The output capability of the circuit becomes insufficient, and the output voltage Vcp of the booster circuit decreases (or is likely to decrease) than when it is normal.
[0039]
Accordingly, in the electric load driving device according to claim 3, when the fail safe means detects the abnormality, the situation determination means continues from the point in time until the fail safe means continues to detect the abnormality for a predetermined time or more. During this period, it is determined that the voltage drop situation has occurred.
[0040]
In such an electric load driving device according to claim 3, an abnormality occurs in the electric load LB connected to the output transistor TB which is turned on / off by the specific transistor driving circuit KB, and the output transistor TB becomes a fail-safe means. As a result, even if the output capability of the booster circuit becomes insufficient, the drive that flows from the specific transistor drive circuit KB to the gate of the output transistor TB Since the current is suppressed, it is possible to secure a sufficient drive current to the other output transistors.
[0041]
Next, the electric load driving device according to claim 4 has the same premise configuration as that of the electric load driving device according to claim 1. In particular, in the electric load driving device according to claim 4, a plurality of transistors are driven. A specific transistor drive circuit in the circuit is configured such that when the control signal output from the control unit to a predetermined transistor drive circuit other than the transistor drive circuit is at an active level, the gate of the output transistor is based on the output of the booster circuit. It is configured to suppress the drive current flowing out to the flow.
[0042]
In the electric load driving device according to claim 4, when the output transistor corresponding to the predetermined transistor driving circuit is turned on, the driving current supplied from the specific transistor driving circuit to the gate of the corresponding output transistor is suppressed. Will be.
[0043]
Therefore, if a transistor drive circuit corresponding to an output transistor that requires a higher drive response than an output transistor that is turned on / off by the specific transistor drive circuit is used as the predetermined transistor drive circuit, the predetermined transistor drive When the circuit and the specific transistor driving circuit try to turn on their output transistors almost simultaneously, the output capability of the booster circuit is prevented from being insufficient and the output voltage is lowered, and thus higher drive response is required. The driving capability for the output transistor to be performed (that is, the driving capability of the predetermined transistor driving circuit) is ensured.
[0044]
Also in this electric load driving device, the driving current output from a specific transistor driving circuit is not reduced in advance, but only reduced when another predetermined transistor driving circuit turns on the output transistor. Therefore, in other cases, the drive response of the output transistor corresponding to the specific transistor drive circuit can be maintained at a high level.
[0045]
Therefore, according to the electric load driving device of claim 4 as well, the booster circuit can be reduced in size and cost without causing a decrease in performance as compared with the conventional device. And cost reduction can be achieved.
[0046]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an electronic control device as an electric load driving device according to an embodiment to which the present invention is applied will be described with reference to the drawings.
First, FIG. 1 is a configuration diagram showing the configuration of the electronic control device 1 of the first embodiment.
[0047]
The electronic control device 1 also controls the drive of the main hydraulic solenoid L1 and the shift solenoid L2 in the automatic transmission 101 of the vehicle according to the driving state of the vehicle, similarly to the electronic control device 100 of FIG. Is. In FIG. 1, components and signals having the same functions as those in FIG. 7 are denoted by the same reference numerals, and detailed description thereof is omitted.
[0048]
Compared with the electronic control device 100 of FIG. 7, the electronic control device 1 of the first embodiment includes a drive unit 20 that replaces the drive unit 200. The drive unit 20 is compared with the drive unit 200 of FIG. Then, the following points (1-1) and (1-2) are different.
[0049]
(1-1): First, the drive unit 20 of the present embodiment divides a constant voltage Vs (for example, 5 V) generated based on the battery voltage VB in the electronic control device 1 to charge the charge pump circuit CP. Two series voltage dividing resistors 41 and 42 for generating a reference voltage Vref for determining whether or not the output voltage Vcp of the output voltage Vcp has decreased, and a non-inverting input terminal ( + Terminal) and the output voltage Vcp of the charge pump circuit CP is input to the inverting input terminal (− terminal), and the constant voltage corresponding to the high level is applied to the output terminal of the comparator 43. A voltage determination circuit 46 including a pull-up resistor 44 that pulls up to Vs and a feedback resistor 45 connected between the output terminal of the comparator 43 and the connection point between the voltage dividing resistors 41 and 42 is added. Been That.
[0050]
In the voltage determination circuit 46, the resistance values of the resistor 41 and the resistor 42 are R41 and R42, respectively, the resistance value obtained by connecting the resistor 42 and the resistor 45 in parallel is Ra, and the resistor 44 and the resistor 45 are connected. When the resistance value obtained by connecting the resistor 41 and the resistor 41 in parallel is Rb, and the output of the comparator 43 is at a low level, it is input to the non-inverting input terminal of the comparator 43. When the reference voltage Vref becomes the first reference voltage Vref1 of the following equation 1 and the output of the comparator 43 is at a high level (actually, the output terminal of the comparator 43 is in a high impedance state), the comparator The reference voltage Vref input to the non-inverting input terminal 43 is the second reference voltage Vref2 of the following equation 2.
[0051]
Vref1 = Vs × Ra / (R41 + Ra) Equation 1
Vref2 = Vs × R42 / (Rb + R42)> Vref1 Formula 2
Therefore, in the voltage determination circuit 46, when the output voltage Vcp of the charge pump circuit CP becomes higher than the second reference voltage Vref2, the output of the comparator 43 is surely set to the low level, and then the output voltage of the charge pump circuit CP. If Vcp becomes lower than the first reference voltage Vref1, the output of the comparator 43 changes from the low level to the high level. Once the output of the comparator 43 becomes high level, the output of the comparator 43 returns to low level only after the output voltage Vcp of the charge pump circuit CP becomes higher than the second reference voltage Vref2. It becomes. That is, in the voltage determination circuit 46, hysteresis is provided for the reference voltage Vref to the non-inverting input terminal of the comparator 43.
[0052]
(1-2): Next, the drive unit 20 of the present embodiment includes a transistor drive circuit K2 ′ instead of the transistor drive circuit K2 of FIG.
The transistor driving circuit K2 ′ includes an inverting circuit 49 that logically inverts and outputs the output of the comparator 43 of the voltage determination circuit 46 as compared with the transistor driving circuit K2 of FIG. The AND circuit 50 that outputs a logical product signal of the output and the control signal S2 from the microcomputer 10 and the output voltage (boost voltage) Vcp of the charge pump circuit CP are received, and the output terminal when the output of the AND circuit 50 is high level When the output of the AND circuit 50 is at a low level, the output terminal of the AND circuit 50 is in a high impedance state, and the gate connected between the output terminal of the buffer 51 and the gate of the output transistor T2 A protective resistor 52 is additionally provided.
[0053]
Further, in this transistor drive circuit K2 ′, the resistance value of the resistor 32 connected between the output terminal of the buffer 31 and the gate of the output transistor T2 is twice that of the resistor 32 in the transistor drive circuit K2 of FIG. Is set to a value. The resistance value of the resistor 52 connected between the output terminal of the buffer 51 and the gate of the output transistor T2 is also set to twice the resistance value of the resistor 32 in the transistor drive circuit K2 of FIG.
[0054]
In such a transistor drive circuit K2 ′, if the output of the comparator 43 of the voltage determination circuit 46 is at a low level, when the control signal S2 from the microcomputer 10 is at a high level as an active level, the output of the AND circuit 50 is Since the level is high, the boosted voltage Vcp is supplied from the two buffers 31 and 51 to the gate of the output transistor T2 via the resistors 32 and 52.
[0055]
As a result, the drive current I1 flows from the buffer 31 to the gate of the output transistor T2 via the resistor 32, and the drive current I2 flows from the buffer 51 to the gate of the output transistor T2 via the resistor 52. The drive current Ion of “I1 + I2” is supplied to the gate of the output transistor T2 based on the output of the charge pump circuit CP. Further, when the gate-source parasitic capacitance C of the output transistor T2 is charged to a predetermined threshold voltage, the output transistor T2 is turned on.
[0056]
The drive current Ion (= I1 + I2) in this case is the same value as the drive current Ion supplied from the transistor drive circuit K2 of FIG. 7 to the gate of the output transistor T2 by setting the resistance values of the resistors 32 and 52 described above. Become.
On the other hand, if the output of the comparator 43 is high level, the output of the AND circuit 50 is low level even if the control signal S2 from the microcomputer 10 is high level. Among them, the boosted voltage Vcp is supplied from only one buffer 31 to the gate of the output transistor T2 through the resistor 32.
[0057]
Then, only half the normal drive current I1 (= Ion / 2) flows from the buffer 31 to the gate of the output transistor T2 via the resistor 32, and the gate-source parasitic capacitance C of the output transistor T2 is predetermined. When the threshold voltage is charged, the output transistor T2 is turned on.
[0058]
That is, when the output of the comparator 43 is at a high level, the drive current that flows out to the gate of the output transistor T2 based on the output of the charge pump circuit CP is the output of the comparator 43 at a low level. Will be suppressed to half.
In the transistor drive circuit K2 ′, as in the transistor drive circuit K2 of FIG. 7, when the control signal S2 from the microcomputer 10 becomes low level, the NPN transistor 33 is turned on and the gate-source of the output transistor T2 is turned on. The interstitial capacitance C is discharged, and as a result, the output transistor T2 is turned off.
[0059]
The electronic control device 1 according to the first embodiment as described above basically performs the same operation as the electronic control device 100 of FIG. 7, but for example from the microcomputer 10 as shown at time t <b> 2 of FIG. 2. The control signal S2 (control signal {circle around (2)}) and the control signal S1 (control signal {circle around (1)}) change from the low level to the high level almost simultaneously and are driven almost simultaneously to the gates of the two output transistors T1 and T2. It is assumed that a situation where a current flows is generated, and as a result, the output voltage Vcp of the charge pump circuit CP is lower than the first reference voltage Vref1 described above. In FIG. 2, as in FIG. 8, “drive signal (1)” indicates the gate-source voltage of the output transistor T1, and “drive signal (2)” indicates the gate-source of the output transistor T2. Inter-voltage is shown.
[0060]
Then, the output of the comparator 43 in the voltage determination circuit 46 becomes high level, and in the transistor drive circuit K2 ′, the output of the AND circuit 50 becomes low level, and the drive current to the gate of the output transistor T2 is half of the normal value. Will be suppressed.
[0061]
For this reason, according to the electronic control device 1 of the first embodiment, even if the output capability of the charge pump circuit CP is small and the output voltage Vcp thereof is lowered, the drive response is higher than that of the output transistor T2 for the shift solenoid L2. A sufficient drive current can be supplied to the gate of the output transistor T1 for the main hydraulic solenoid L1 having a high priority based on the output of the charge pump circuit CP, and the drive response of the output transistor T1 is ensured. can do. Therefore, the pulsation of the energization current to the main hydraulic solenoid L1 as shown in the period X of FIG. 8 is prevented.
[0062]
In addition, in the electronic control apparatus 1 of the first embodiment, the charge determination circuit 46 does not reduce the drive current flowing out from the transistor drive circuit K2 ′ to the gate of the output transistor T2 in advance, but the charge pump circuit. Since it is suppressed only when it is detected that the output voltage Vcp of the CP has decreased, the drive response of the output transistor T2 with respect to the shift solenoid L2 can be maintained at a high level in a normal state.
[0063]
Therefore, according to the electronic control device 1, compared with the conventional device 100, the charge pump circuit CP can be reduced in size and cost without causing a decrease in performance. The entire electronic control unit 1 can be reduced in size and cost.
[0064]
In the first embodiment, the transistor drive circuit K2 ′ corresponding to the shift solenoid L2 corresponds to a specific transistor drive circuit. In addition, the voltage determination circuit 46 corresponds to a situation determination means, and a voltage drop situation occurs during a period in which the signal from the comparator 43 of the voltage determination circuit 46 to the inverting circuit 49 is at a high level. This corresponds to the period in which it is determined that
[0065]
Next, an electronic control device according to a second embodiment will be described with reference to FIGS.
First, FIG. 3 is a block diagram showing the configuration of the electronic control unit 54 of the second embodiment.
The electronic control unit 54 also drives the main hydraulic solenoid L1 and the shift solenoid L2 in the automatic transmission 101 of the vehicle according to the driving state of the vehicle, similarly to the electronic control units 1 and 100 of FIGS. It is something to control. In FIG. 3, components and signals having the same functions as those in FIGS. 1 and 7 are denoted by the same reference numerals, and detailed description thereof is omitted.
[0066]
The electronic control device 54 of the second embodiment includes a drive unit 56 in place of the drive unit 20 as compared with the electronic control device 1 of FIG. 1 described above, and the drive unit 56 is the drive unit 20 of FIG. And the following points (2-1) to (2-3) are different.
[0067]
(2-1): First, the voltage determination circuit 46 is not provided in the drive unit 56 of the present embodiment.
(2-2): Next, the drive unit 56 of this embodiment includes a transistor drive circuit K2 ″ instead of the transistor drive circuit K2 ′ of FIG.
[0068]
As compared with the transistor drive circuit K2 ′ of FIG. 1, the transistor drive circuit K2 ″ is preset with a load current flowing from the output transistor T2 to the shift solenoid L2 as a means for realizing the fail-safe function. When the overcurrent determination value is greater than or equal to the overcurrent detection value, an overcurrent detection circuit 58 outputs a high level signal as an overcurrent detection signal indicating that a short circuit fault has occurred in the shift solenoid L2 and an overcurrent has flowed through the output transistor T2. When the output of the overcurrent detection circuit 58 changes from the low level to the high level, the one-shot pulse output circuit 60 that outputs a high-level signal for a predetermined time Toff, and the output signal of the one-shot pulse output circuit 60 Is inverted and output, and the output of the inverter 62 and the An AND circuit 64 that outputs a logical product signal with the control signal S2 from the capacitor 10 is additionally provided. Further, in this transistor drive circuit K2 ″, the output of the AND circuit 64 is connected to the buffer 31 and It is input to each of the AND circuit 50 and the inverting circuit 35.
[0069]
In the second embodiment, the output transistor T2 has another current detection source in addition to the current output source connected to the shift solenoid L2, and this current detection source. Current flows in proportion to the current flowing through the current output source. The overcurrent detection circuit 58 is configured to determine whether or not the load current is greater than or equal to the overcurrent determination value from the current flowing through the current detection source.
[0070]
(2-3): Furthermore, when the output of the overcurrent detection circuit 58 becomes high level, the output becomes low level at that time, and then the drive unit 56 of the present embodiment only has a predetermined time Ts. If the output of the overcurrent detection circuit 58 continues to be at a low level, the output of the timer circuit 66 that returns to the high level and the output of the overcurrent detection circuit 58 are input to the set terminal (S). Is input to the reset terminal (R), and the output of the SR latch 68 is logically inverted, and an inverting circuit 70 is output to the microcomputer 10 as a diagnosis signal DS indicating whether the shift solenoid L2 is abnormal or not. Has been added. The output of the SR latch 68 is input to the inverting circuit 49 of the transistor drive circuit K2 ″.
[0071]
The set terminal and the reset terminal of the SR latch 68 are both high active input terminals. The predetermined time Ts timed by the timer circuit 66 is the fixed time Toff when the one-shot pulse output circuit 60 outputs a high-level signal (that is, the pulse width of the high-level signal output by the one-shot pulse output circuit 60). ) Is set to a sufficiently longer time than, for example, 10 times the predetermined time Toff.
[0072]
In such an electronic control unit 54 of the second embodiment, when the short-circuit failure has not occurred in the shift solenoid L2 and the output of the overcurrent detection circuit 58 remains normal, the transistor drive circuit K2 " 1 operates in exactly the same way as the transistor drive circuit K2 'when the output of the comparator 43 is at a low level in the drive unit 20 of Fig. 1. That is, in this normal state, the one-shot pulse output circuit 60 and the SR latch are operated. This is because both of the outputs of 68 and 68 remain at low level, and the control signal S2 from the microcomputer 10 is supplied to each of the buffer 31, the AND circuit 50, and the inverting circuit 35.
[0073]
On the other hand, when the output transistor T2 is turned on, a short circuit failure occurs in the shift solenoid L2, and the current flowing from the output transistor T2 to the shift solenoid L2 is detected as an overcurrent detection circuit 58 as shown at time t3 in FIG. The overcurrent judgment value at is exceeded.
[0074]
Then, in the transistor drive circuit K2 ″, a high-level overcurrent detection signal is output from the overcurrent detection circuit 58, and the output signal from the one-shot pulse output circuit 60 to the inverting circuit 62 becomes high level for a certain time Toff. As a result, regardless of the control signal S2, the output of the AND circuit 64 becomes low level for a certain time Toff, and the output transistor T2 is forcibly turned off.
[0075]
When the predetermined time Toff elapses, the output of the AND circuit 64 returns to the high level and the output transistor T2 is turned on again. If the short-circuit failure of the shift solenoid L2 is not eliminated at that time, the output The energization current from the transistor T2 to the shift solenoid L2 again exceeds the overcurrent determination value, and the output transistor T2 is forcibly turned off for a certain time Toff.
[0076]
For this reason, when a short circuit failure occurs in the shift solenoid L2, the transistor drive circuit K2 "causes the" short circuit failure by the overcurrent detection circuit 58 while the control signal S2 from the microcomputer 10 is at a high level as shown in FIG. Detection → By the action of the one-shot pulse output circuit 60, the inverting circuit 62, and the AND circuit 64, the output transistor T2 is turned off (energization cut off) for a predetermined time Toff → the output transistor T2 is turned on (energization resumed) → by the overcurrent detection circuit 58 The operation of “short failure detection → the output transistor T2 is turned off for a predetermined time Toff →...” Is repeated, and the output transistor T2 is periodically turned on / off.
[0077]
In FIG. 4, as in FIGS. 2 and 8, “drive signal (1)” indicates the gate-source voltage of the output transistor T1, and “drive signal (2)” indicates the output transistor T2. The gate-source voltage is shown.
In the second embodiment, when the short-circuit failure of the shift solenoid L2 is detected by the overcurrent detection circuit 58 of the transistor drive circuit K2 ″ and the output transistor T2 is periodically turned on / off, From the time when the short circuit failure is detected until the short circuit failure is not detected continuously for a predetermined time Ts counted by the timer circuit 66 (that is, the output of the overcurrent detection circuit 58 continues to be at the low level for the predetermined time Ts or more. Until the output of the SR latch 68 becomes high level. As a result, as shown in FIG. 4, the diagnosis signal DS from the inverting circuit 70 to the microcomputer 10 becomes low level indicating abnormality.
[0078]
In the second embodiment, when the diagnostic signal DS becomes low level, the microcomputer 10 determines that the shift solenoid L2 has a short circuit failure and executes a predetermined fail-safe process.
Here, when the output transistor T2 is periodically turned on / off by the fail-safe function of the transistor drive circuit K2 ″, the output capability of the charge pump circuit CP becomes insufficient and the boosted voltage Vcp becomes lower than normal. As a result, the drive response of the other output transistor T1 is lowered.
[0079]
Therefore, in the second embodiment, the output of the SR latch 68 is input to the inverting circuit 49 of the transistor drive circuit K2 ″, and while the output of the SR latch 68 is at the high level (that is, the overcurrent detection circuit 58 is 1 is output from the transistor drive circuit K2 ″ in the same manner as when the output of the comparator 43 becomes high level in the drive unit 20 of FIG. The drive current flowing out to the gate of the transistor T2 is suppressed to half of the normal time.
[0080]
For this reason, according to the electronic control unit 54 of the second embodiment, a short failure occurs in the shift solenoid L2, and the output transistor T2 is periodically turned on / off by the fail-safe function of the transistor drive circuit K2 ″. As a result, even if the output capability of the charge pump circuit CP becomes insufficient, it is possible to prevent the boosted voltage Vcp from greatly decreasing as illustrated by the dotted line in the sixth stage of FIG. As a result, a sufficient drive current to the other output transistor T1 can be secured.
[0081]
Therefore, the drive response of the other output transistor T1 can be ensured without using the charge pump circuit CP having a large output capability, and the performance is reduced as in the electronic control device 1 of the first embodiment. Minimization and cost reduction can be achieved without incurring.
[0082]
In the second embodiment, the overcurrent detection circuit 58, the one-shot pulse output circuit 60, the inverting circuit 62, and the AND circuit 64 are provided in a fail-safe manner provided in a transistor drive circuit K2 ″ as a specific transistor drive circuit. In addition, the timer circuit 66 and the SR latch 68 correspond to a situation determination means, and a voltage drop situation occurs during a period in which the output of the SR latch is at a high level. This corresponds to the determined period.
[0083]
Next, an electronic control device according to a third embodiment will be described with reference to FIG.
FIG. 5 is a configuration diagram showing the configuration of the electronic control unit 72 of the third embodiment. The electronic control device 72 also sets the main hydraulic solenoid L1 and the shift solenoid L2 in the automatic transmission 101 of the vehicle to the vehicle operating state, similarly to the electronic control devices 1, 54, 100 of FIGS. The drive is controlled according to the above. In FIG. 5, components and signals having the same functions as those in FIGS.
[0084]
As shown in FIG. 5, the electronic control device 72 of the third embodiment includes a drive unit 74 that replaces the drive unit 20 as compared with the electronic control device 1 of FIG. 1 described above. Compared with the drive unit 20 of FIG. 1, the following points (3-1) and (3-2) are different.
[0085]
(3-1): First, the voltage determination circuit 46 is not provided in the drive unit 74 of the present embodiment.
(3-2): The control signal S1 from the microcomputer 10 to the transistor drive circuit K1 is input to the inverting circuit 49 of the transistor drive circuit K2 ′.
[0086]
In such an electronic control device 72 of the third embodiment, when the control signal S1 from the microcomputer 10 becomes high level and the output transistor T1 having a high drive response priority is turned on by the transistor drive circuit K1, As in the case where the output of the comparator 43 becomes high level in the drive unit 20 of FIG. 1, the drive current flowing from the transistor drive circuit K2 ″ to the gate of the output transistor T2 is suppressed to half of the normal time. .
[0087]
For this reason, when the two output transistors T1 and T2 are turned on at the same time, the output capability of the charge pump circuit CP is prevented from being insufficient, and the drive capability for the output transistor T1 for which higher drive response is required. (That is, the drive capability of the transistor drive circuit K1) is ensured.
[0088]
Also in the electronic control unit 72 of the third embodiment, the transistor drive circuit K1 does not narrow down the drive current output to the gate of the output transistor T2 in advance, but the transistor drive circuit K1 outputs the output transistor T1. Therefore, the drive response of the output transistor T2 can be maintained at a high level in other cases.
[0089]
Therefore, also with this electronic control device 72, compared with the conventional device 100, the charge pump circuit CP can be reduced in size and cost without incurring a decrease in performance. The entire control device 72 can be reduced in size and cost.
[0090]
In the third embodiment, the transistor drive circuit K2 ′ corresponding to the shift solenoid L2 corresponds to the specific transistor drive circuit according to claim 4, and the transistor drive circuit K1 corresponding to the main hydraulic solenoid L1 is This corresponds to the predetermined transistor drive circuit according to claim 4.
[0091]
As mentioned above, although one Embodiment of this invention was described, it cannot be overemphasized that this invention can take a various form.
For example, the method of the third embodiment can be additionally applied to the electronic control device 1 of the first embodiment or the electronic control device 54 of the second embodiment. That is, in the electronic control units 1 and 54 of FIG. 1 or FIG. 3, the AND circuit 50 is a three-input AND circuit, and the control signal S1 from the microcomputer 10 is logically inverted at the input terminal to which the AND circuit is added. What is necessary is just to comprise so that it may input.
[0092]
On the other hand, in the electronic control unit 1 of the first embodiment, the voltage determination circuit 46 directly monitors the output voltage Vcp of the charge pump circuit CP, and when the output voltage Vcp is lower than the reference voltage, a voltage drop situation occurs. Although it is determined that the voltage has occurred, for example, when both the control signals S1 and S2 from the microcomputer 10 are at a high level, it may be determined that a voltage drop situation has occurred. That is, when the two output transistors T1 and T2 are simultaneously turned on, the output voltage Vcp of the charge pump circuit CP is considered to decrease.
[0093]
As a specific configuration example in this case, for example, in the electronic control unit 1 of FIG. 1, an AND circuit that receives both control signals S <b> 1 and S <b> 2 from the microcomputer 10 is used instead of the voltage determination circuit 46. What is necessary is just to comprise so that it may provide as a determination means and the output of the AND circuit may be input into the inversion circuit 49 of transistor drive circuit K2 '.
[0094]
However, if the output voltage Vcp of the charge pump circuit CP is directly monitored and determined as in the first embodiment, when the output transistors T1 and T2 are turned on at the same time, or the fail safe of the transistor drive circuit Depending on the function, not only when the output transistor corresponding to the transistor drive circuit is periodically turned on / off, for example, when the battery voltage VB itself decreases, or when the output transistor T2 is frequently turned on / off for control purposes. Even if the output voltage Vcp of the charge pump circuit CP decreases due to any other factor, such as when the transistor is driven, the transistor drive circuit K2 ′ suppresses the drive current, and the surface of the drive response is higher than that of the output transistor T2. The drive response of the output transistor T1 having a high priority can be ensured more reliably. This is preferable.
[0095]
On the other hand, the present invention can be applied in the same manner even when the electric load to be driven is an electric load other than the main hydraulic solenoid L1 and the shift solenoid L2. Further, the present invention can be applied not only to a vehicle device.
[Brief description of the drawings]
FIG. 1 is a configuration diagram illustrating a configuration of an electronic control device according to a first embodiment.
FIG. 2 is a time chart showing the operation of the electronic control device of the first embodiment.
FIG. 3 is a configuration diagram illustrating a configuration of an electronic control device according to a second embodiment.
FIG. 4 is a time chart showing the operation of the electronic control device of the second embodiment.
FIG. 5 is a configuration diagram illustrating a configuration of an electronic control device according to a third embodiment.
FIG. 6 is an explanatory diagram for explaining a solenoid used for controlling an automatic transmission of a vehicle.
FIG. 7 is a configuration diagram illustrating a conventional configuration example of an electronic control device.
FIG. 8 is a time chart for explaining a problem of the conventional apparatus.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1,54,72 ... Electronic control apparatus 10 ... Microcomputer 12 ... Resistance for electric current detection
14 ... Current detection circuit 20, 56, 74 ... Drive unit
T1, T2 ... Output transistor CP ... Charge pump circuit (boost circuit)
K1, K2 ', K2 "... transistor drive circuit
21, 31, 51 ... buffer 23, 33 ... NPN transistor
22, 24, 32, 34, 41, 42, 44, 45, 52 ... resistance
25, 35, 49, 62, 70 ... inverting circuit 43 ... comparator
46 ... Voltage determination circuit 50, 64 ... AND circuit 58 ... Overcurrent detection circuit
60 ... One-shot pulse output circuit 66 ... Timer circuit
68 ... SR latch L1 ... Main hydraulic solenoid
L2 ... Shift solenoid

Claims (4)

Two output terminals are connected in series to the current supply path from the high potential side of the load power supply to the electric load, and a voltage higher than the voltage of the load power supply (hereinafter referred to as the load power supply voltage) is supplied to the gate and turned on. An output transistor for flowing current to the electrical load;
A booster circuit that boosts and outputs the load power supply voltage to a voltage higher than the load power supply voltage;
A circuit for turning on / off the output transistor in response to a control signal from the control unit, and when the control signal is at an active level instructing to turn on the output transistor, a gate of the output transistor is connected to the gate of the output transistor; A transistor drive circuit for turning on the output transistor by supplying an output voltage;
And the output transistor and the transistor drive circuit are provided for each of a plurality of electric loads to be driven,
A situation determination means for determining whether or not a predetermined situation in which the output voltage of the booster circuit decreases (hereinafter referred to as a voltage reduction situation) has occurred;
A specific transistor drive circuit of the plurality of transistor drive circuits is configured to output the output transistor based on the output of the booster circuit while the state determination unit determines that the voltage drop state is occurring. Configured to suppress the drive current flowing out to the gate,
An electric load driving device characterized by the above. The electric load driving device according to claim 1,
The situation determination means includes
Monitoring the output voltage of the booster circuit and determining that the voltage drop situation has occurred when the output voltage is lower than a predetermined reference voltage;
An electric load driving device characterized by the above. The electric load driving device according to claim 1,
The specific transistor driving circuit includes:
Detecting an abnormality in the electric load to be driven from the operating state when the output transistor is on, and when detecting the abnormality, comprises fail-safe means for temporarily turning off the output transistor regardless of the control signal,
The situation determination means includes
When the fail-safe means detects the abnormality, it is determined that the voltage drop situation has occurred from that point until the fail-safe means continues to detect the abnormality for a predetermined time or longer,
An electric load driving device characterized by the above. Two output terminals are connected in series to the current supply path from the high potential side of the load power supply to the electric load, and a voltage higher than the voltage of the load power supply (hereinafter referred to as the load power supply voltage) is supplied to the gate and turned on. An output transistor for flowing current to the electrical load;
A booster circuit that boosts and outputs the load power supply voltage to a voltage higher than the load power supply voltage;
A circuit for turning on / off the output transistor in response to a control signal from the control unit, and when the control signal is at an active level instructing to turn on the output transistor, a gate of the output transistor is connected to the gate of the output transistor; A transistor drive circuit for turning on the output transistor by supplying an output voltage;
And the output transistor and the transistor drive circuit are provided for each of a plurality of electric loads to be driven,
A specific transistor drive circuit of the plurality of transistor drive circuits outputs an output of the booster circuit when a control signal output from the control unit to a predetermined transistor drive circuit other than the transistor drive circuit is at the active level. Is configured to suppress the drive current flowing out to the gate of the output transistor based on
An electric load driving device characterized by the above.

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