JP2008293057A - Load drive circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a load drive circuit in which time for diagnosing failure in a relay is shortened. <P>SOLUTION: A control means implements a first drive means for making first switching means and second switching means to be in an ON state at starting, and a second drive means for driving only the second switching means after the first driving means, then detects abnormality in the circuit based on a voltage of a main power supply line after implementing the first drive means or implementing the second drive means. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a load drive circuit that controls a load (such as a motor) that applies a steering force or a braking force to a vehicle.

Conventionally, in a load control device of a brake control system, failure diagnosis of a power source and a relay connected to the load is performed by driving the load and discharging the electric charge of the capacitor.
JP 2001-138882 A

  However, in the above prior art, since the ON check is performed after the relay OFF check, it takes time to discharge the capacitor once before the OFF check. Therefore, there is a problem that the diagnosis time becomes long.

  The present invention has been made paying attention to the above problem, and an object of the present invention is to provide a load drive circuit in which the failure diagnosis time of the relay is shortened.

  To achieve the above object, according to the present invention, a power source, first switching means provided downstream of the power source, power storage means provided downstream of the first switching means, and parallel to the power storage means are provided. And a second switching means provided in parallel to the power storage means, and a voltage monitor provided in parallel to the load and the second switching means. And a control means for outputting a monitoring result of the voltage monitoring means, wherein the storage means, the second switching means, and a load drive circuit in which the downstream side of the voltage monitoring means is connected to the ground, Includes first driving means for turning on the first and second switching means at the time of system startup, and the first switching means after the first driving means. And a second driving means for turning off only, the first, on the basis of the monitoring result of said voltage monitoring means obtained when running the second driving means, it was decided to detect an abnormality in the circuit.

  Therefore, it is possible to provide a load drive circuit that shortens the failure diagnosis time of the relay.

  Hereinafter, the best mode for realizing a load driving circuit of the present invention will be described based on an embodiment shown in the drawings.

[System configuration]
Example 1 will be described with reference to FIGS. FIG. 1 is a system configuration diagram of a brake control device to which the load driving circuit according to the first embodiment is applied. The brake control device according to the first embodiment is a four-wheel brake-by-wire system, and includes two first and second hydraulic units HU1 and HU2 that control the hydraulic pressure independently of the operation of the brake pedal BP by the driver. Yes.

  The ECU 1 also includes a main ECU 300 that calculates target wheel cylinder pressures P * fl to P * rr for the wheels FL to RR, and first and second sub-drives that drive the first and second hydraulic pressure units HU1 and HU2. ECUs 100 and 200 are provided.

  The first and second hydraulic units HU 1 and HU 2 are driven by the first and second sub ECUs 100 and 200 based on a command from the main ECU 300. The brake pedal BP is applied with a reaction force by a stroke simulator S / Sim connected to the master cylinder M / C.

  The first and second hydraulic units HU1, HU2 are connected to the master cylinder M / C through oil passages A1, A2, and are connected to the reservoir RSV through oil passages B1, B2. The oil passages A1 and A2 are provided with first and second M / C pressure sensors MC / Sen1 and MC / Sen2.

  The first and second hydraulic pressure units HU1 and HU2 are hydraulic actuators that include a pump, a motor, and an electromagnetic valve, and independently generate hydraulic pressure. The first hydraulic unit HU1 performs hydraulic control of the FL and RR wheels, and the second hydraulic unit HU2 performs hydraulic control of the FR and RL wheels.

  That is, the wheel cylinders W / C (FL to RR) are directly increased in pressure by pumps that are two hydraulic pressure sources. Since the wheel cylinder W / C is directly pressurized by the first and second pumps without using the accumulator, the gas in the accumulator does not leak into the oil passage at the time of failure. Further, the first pump increases the pressure on the FL and RR wheels, and the second pump increases the pressure on the FR and RL wheels, thereby forming a so-called X pipe.

  The first and second hydraulic units HU1 and HU2 are provided separately. By using a separate body, even if a leak occurs in one hydraulic unit, the braking force is secured by the other unit. The first and second hydraulic units HU1 and HU2 may be integrally provided, the electrical circuit configuration may be integrated into one place, the harness and the like may be shortened, and the layout may be simplified.

[Main ECU]
The main ECU 300 is a host CPU that calculates target wheel cylinder pressures P * fl to P * rr generated by the first and second hydraulic units HU1 and HU2. The main ECU 300 is connected to the first and second power sources BATT1 and BATT2, and is provided to operate if either BATT1 or BATT2 is normal, and is connected to other control units CU1 to CUN1 connected by an ignition signal IGN or CAN3. It is activated by an activation request from CU6.

  The main ECU 300 has stroke signals S1, S2 from the first and second stroke sensors S / Sen1, S / Sen2, and M / C pressures Pm1, Pm2 from the first and second M / C pressure sensors MC / Sen1, MC / Sen2. Entered.

  The wheel speed VSP, yaw rate Y, and front and rear G are also input to the main ECU 300. Further, the detection value of the liquid amount sensor L / Sen provided in the reservoir RSV is input, and it is determined whether the brake-by-wire control by driving the pump can be executed. The stop lamp switch STP. The operation of the brake pedal BP is detected from the signal from the SW regardless of the stroke signals S1 and S2 and the M / C pressures Pm1 and Pm2.

  In the main ECU 300, two first and second CPUs 310 and 320 for performing calculations are provided. The first and second CPUs 310 and 320 are connected to the first and second sub ECUs 100 and 200 by CAN communication lines CAN1 and CAN2 (second communication means), and the first and second sub ECUs 100 and 200 are connected via the first and second sub ECUs 100 and 200, respectively. Pump discharge pressures Pp1 and Pp2 and actual wheel cylinder pressures Pfl to Prr are input to the second CPUs 310 and 320, respectively. The CAN communication lines CAN1 and CAN2 are connected to each other and a duplex system is assembled for backup.

  Based on the input stroke signals S1, S2, M / C pressures Pm1, Pm2, and actual wheel cylinder pressures Pfl to Prr, the first and second CPUs 310 and 320 calculate target wheel cylinder pressures P * fl to P * rr, The data is output to the first and second sub ECUs 100 and 200 via the CAN communication lines CAN1 and CAN2.

  The first CPU 310 calculates the target wheel cylinder pressures P * fl to P * rr of the first and second hydraulic pressure units HU1 and HU2 together, and the second CPU 320 may be used for backup of the first CPU 310, and is not particularly limited.

  Also, the main ECU 300 activates the first and second sub ECUs 100 and 200 via the CAN communication lines CAN1 and CAN2. The first and second sub ECUs 100 and 200 are independently activated. However, the first and second sub ECUs 100 and 200 may be activated simultaneously with one signal, and there is no particular limitation. Moreover, it is good also as starting by the ignition switch IGN.

  ABS (control to increase / decrease braking force to avoid wheel lock), VDC (control to increase / decrease braking force to prevent side slip when vehicle behavior is disturbed), TCS (control to suppress idling of drive wheels), etc. During the vehicle behavior control, the wheel speed VSP, the yaw rate Y, and the front and rear G are taken together to control the target wheel cylinder pressures P * fl to P * rr. During the VDC control, a warning is issued to the driver by the buzzer BUZZ. The VDC switch VDC. The control can be switched ON / OFF by the intention of the driver.

  Further, the main ECU 300 is connected to the other control units CU1 to CU6 through the CAN communication line CAN3, and performs cooperative control. The regenerative brake control unit CU1 regenerates braking force and converts it into electric power, and the radar control unit CU2 performs inter-vehicle distance control. The EPS control unit CU3 is a control unit for the electric power steering apparatus.

  The ECM control unit CU4 is an engine control unit, and the AT control unit CU5 is an automatic transmission control unit. Further, the meter control unit CU6 controls the meter. The wheel speed VSP input to the main ECU 300 is output to the ECM control unit CU4, the AT control unit CU5, and the meter control unit CU6 via the CAN communication line CAN3.

  The power sources of the ECUs 100, 200, 300 are first and second power sources BATT1, BATT2. First power supply BATT1 is connected to main ECU 300 and first sub ECU 100, and second power supply BATT2 is connected to main ECU 300 and second sub ECU 200.

[Sub ECU]
The first and second sub ECUs 100 and 200 are provided integrally with the first and second hydraulic units HU1 and HU2. In addition, it is good also as a separate body according to a vehicle layout.

  The first and second sub ECUs 100 and 200 include target wheel cylinder pressures P * fl to P * rr output from the main ECU 300, and pump discharge pressures Pp1 and P2 from the first and second hydraulic pressure units HU1 and HU2. Pp2, actual wheel cylinder pressures Pfl, Prr and Pfr, Prl are input.

  Pumps in the first and second hydraulic pressure units HU1, HU2 so as to achieve the target wheel cylinder pressures P * fl-P * rr based on the input pump discharge pressures Pp1, Pp2 and the actual wheel cylinder pressures Ffl-Prr, Hydraulic control is performed by driving a motor and a solenoid valve. The first and second sub ECUs 100 and 200 may be separate from the first and second hydraulic units HU1 and HU2.

  Once the target wheel cylinder pressures P * fl to P * rr are input, the first and second sub ECUs 100 and 200 are servos that control to converge to the previous input value until a new target value is input. The control system is configured.

  Further, the first and second sub ECUs 100 and 200 convert the currents from the power sources BATT1 and BATT2 into the valve driving currents I1 and I2 and the motor driving voltages V1 and V2 of the first and second hydraulic units HU1 and HU2, respectively. 1. Output to the second hydraulic unit HU1, HU2.

[Master cylinder and stroke simulator]
The stroke simulator S / Sim is built in the master cylinder M / C and generates a reaction force of the brake pedal BP. The master cylinder M / C is provided with a switching valve Can / V for switching communication / blocking between the master cylinder M / C and the stroke simulator S / Sim.

  The switching valve Can / V is opened / closed by the main ECU 300, and can be quickly transferred to the manual brake when the brake-by-wire control ends or when the first and second sub ECUs 100 and 200 fail. The master cylinder M / C is provided with first and second stroke sensors S / Sen1, S / Sen2. Stroke signals S1 and S2 of the brake pedal BP are output to the main ECU 300.

[Load drive circuit]
FIG. 2 is a load drive circuit diagram of the first sub ECU 100 and the first hydraulic unit HU1 in the first embodiment. Since the same applies to the second sub ECU 200 and the second hydraulic unit HU2, only the first sub ECU 100 will be described. The solenoid 30 that is a load is a solenoid of one of the plurality of solenoid valves provided in the first hydraulic unit HU1.

  The load drive circuit includes a first power supply BATT1, a load drive relay 10 (first switching means), a first power supply relay 20 (second switching means), a solenoid 30 (load), a capacitor 40 (power storage means), and a voltage monitor 50 ( Voltage monitoring means), a main power supply line L, and first and second power supply lines L1 and L2.

  The first power supply relay 20 is connected to the downstream side of the first power supply BATT1, and the solenoid 30, the voltage monitor 50, and the noise absorbing capacitor 40 are connected in parallel to the downstream side of the first power supply relay 20, respectively. Both ends of the first power supply line L1 are connected to the main power supply line L, and a capacitor 40 is interposed.

  The second power supply line L2 is provided in parallel to the first power supply line L1 and connected to the main power supply line L, and the solenoid 30 and the load driving relay 10 are interposed. A first power relay 20 is provided on the main power line L.

  The load drive relay 10 is connected in series downstream of the solenoid 30, and the capacitor 40, the load drive relay 10, and the voltage monitor 50 are connected downstream of the first power supply BATT 1. As a result, the voltage of the solenoid 30 is detected by the voltage monitor 50. Each relay 10, 20 is driven by the first CPU 310 in the main ECU 300, and the monitor value of the voltage monitor 50 is output to the first CPU 310.

[Circuit diagnosis]
(Power relay ON diagnosis)
FIG. 3 is a diagram showing a change with time of the voltage monitor value V when the first power supply relay 20 is ON. If both the first power supply relay 20 and the capacitor 40 are normal, the voltage monitor value V after the diagnosis time t seconds is a value equal to or greater than the threshold value _VA . When the first power supply relay 20 is fixed to OFF or the capacitor 40 is abnormal, the voltage monitor value V after t seconds becomes equal to or less than the threshold value _VA .

(Power relay OFF diagnosis)
FIG. 4 is a diagram showing a change with time of the voltage monitor value V when the first power supply relay 20 is OFF. The first power supply relay 20 is turned off at time t1, and the diagnosis of the load driving relay 10 is completed at time t2. The amount of decrease in the voltage monitor value V between times t1 and t2 is indicated by ΔV.

If the load drive circuit is normal, because the minimum value of the drop amount [Delta] V at the time of diagnosis [Delta] V _B, the maximum value is [Delta] V _C, drop [Delta] V in the normal is in the range of ΔV B _{<ΔV <ΔV C} . Therefore, when ΔV is out of this range, it is diagnosed that the load driving circuit is abnormal.

In the case of 0 ≦ ΔV ≦ ΔV _B , the amount of decrease ΔV is small and the discharge speed of the capacitor 40 is slow. Therefore, an open failure of the solenoid 30 (always non-conducting state), the load driving relay 10 being fixed to OFF, or the first power supply relay 20 being fixed to ON can be considered.

  In the case of an open failure of the solenoid 30, there is no charge discharge destination, so the capacitor 40 is spontaneously discharged and the discharge rate is slow. On the other hand, when the first power supply relay 20 is fixed to ON, the capacitor 40 is not discharged, and there is a possibility that the drop amount ΔV = 0.

When ΔV _C ≦ ΔV, the drop amount ΔV is large and the discharge speed of the capacitor 40 is fast. For this reason, a short circuit failure of the load driving relay 10 or a short circuit failure of the capacitor 40 can be considered.

  When the load driving relay 10 is short-circuited, a larger current flows than usual, so that the discharge speed of the capacitor 40 is increased. On the other hand, since the charge is lost when the capacitor 40 fails, the discharge speed increases.

  Therefore, first, the load drive relay 10 and the first power supply relay 20 are turned ON at the time of system startup (first drive means), and based on the voltage of the voltage monitor 50 after the first drive means or after the second drive means, Detect abnormalities in the circuit.

That is, if the power monitor ON diagnosis is performed and the voltage monitor value V after t seconds is equal to or less than the threshold value V _A , it is diagnosed that the first power relay 20 is fixed OFF or the capacitor 40 is abnormal.

Thereafter, only the first power supply relay 20 is driven (second drive means), and the power supply relay OFF diagnosis is performed. If the voltage drop amount ΔV is within the range of ΔV _B <ΔV <ΔV _C , it is determined that the circuit is normal. In the case of 0 ≦ ΔV ≦ ΔV _B , it is determined that the solenoid 30 is in an open failure (always non-conductive state) or the first power supply relay 20 is stuck on. When ΔV _C ≦ ΔV, it is determined that the load driving relay 10 is short-circuited or the capacitor 40 is short-circuited.

  By performing the ON diagnosis before the OFF diagnosis, it is not necessary to discharge the residual charge of the capacitor 40 before the power relay ON diagnosis, leading to a reduction in time corresponding to the charge discharge time. Further, since the load drive relay 10 is turned on to consume residual charges when the power supply relay 20 is turned off, the power supply relay 20 OFF diagnosis and the drive diagnosis of the load drive relay 10 are performed simultaneously to further reduce the time.

  Further, the CPU 310 cuts off the power supply relay 20 when the load driving relay 10 fails. As a result, when the load drive relay 10 that drives the load fails, the power supply relay 20 immediately turns off the power to ensure fail-safety.

[Circuit diagnosis processing]
FIG. 5 is a flowchart showing the flow of the circuit diagnosis process. Hereinafter, each step will be described.

  In step S101, the first power supply BATT1 is turned on, and the process proceeds to step S102.

  In step S102, the first CPU 310 is initialized, and the process proceeds to step S103.

  In step S103, relay diagnosis is started, and the process proceeds to step S104.

  In step S104, the first power supply relay 20 is turned on, and the process proceeds to step S105.

  In step S105, the load driving relay 10 is turned on, the residual charge in the capacitor 40 is consumed by the solenoid 30, and the process proceeds to step S106. By consuming the residual charge in advance, it is prevented that the first power supply relay 20 is erroneously detected as ON due to the residual charge when the first power supply relay 20 is fixed OFF.

In step S106, it is determined whether or not the voltage monitor value V after t seconds> the threshold value V _A (see FIG. 3). If YES, the process proceeds to step S108, and if NO, the process proceeds to step S107.

  In step S107, it is diagnosed that the first power supply relay 20 is abnormal or the capacitor 40 is short-circuited, and the control is terminated.

  In step S108, the first power supply relay 20 is turned off, and the process proceeds to step S109.

In step S109, it is determined whether or not ΔV _B <voltage monitor value drop amount ΔV <ΔV _C (see FIG. 4). If YES, the process proceeds to step S110, and if NO, the process proceeds to step S112.

  In step S110, the first power supply relay 20 is diagnosed as normal, and the process proceeds to step S111.

  In step S111, the relay diagnosis is finished and the control is finished.

Whether step is S112 in 0 ≦ _V ≦ V _B is determined, the process proceeds to step S113 if YES, the process proceeds to step S114 if NO.

  In step S113, it is diagnosed that one of the first power supply relay 20 is fixed ON, the solenoid 30 (load) is open, or the load drive relay 10 is open, and the control is terminated.

  In step S114, it is diagnosed that the load driving relay 10 is short-circuited or the capacitor 40 is broken, and the control is terminated.

[Comparison of changes over time in circuit diagnosis]
FIG. 6 is a time chart of the load driving circuit diagnosis in the first embodiment of the present invention and FIG. 7 in the conventional example. Both indicate normal times. The conventional load driving circuit is the same as that of the first embodiment.

(Time t11)
At time t11, the first CPU 310 is activated in both the first embodiment and the conventional example.

(Time t12)
At time t12, relay diagnosis is started in Embodiment 1 of the present application, and both the load driving relay 10 and the first power supply relay 20 are turned on, and the voltage monitor value V increases (ON diagnosis). a voltage monitor value V> threshold _{V A} between t12 to t13.
On the other hand, in the conventional example, the load driving relay 10 is turned on while the first power supply relay 20 is off.

(Time t13)
At time t13, in the first embodiment of the present invention, the relay ON diagnosis ends, the first power supply relay 20 is turned OFF, and the voltage monitor value V decreases (OFF diagnosis). The load driving relay 10 is turned on as it is.
On the other hand, in the conventional example, the load driving relay 10 is turned off.

(Time t14)
At time t14, in the first embodiment of the present application, the relay OFF diagnosis is completed, and the first power supply relay 20 is turned ON again. Between time t13 and t14, the relationship of ΔV _B <voltage monitor value V <ΔV _C is maintained, whereby the first power supply relay 20 is diagnosed as normal and the power supply relay diagnosis control ends.
In contrast, in the conventional example, both the load driving relay 10 and the first power supply relay 20 are turned on.

(Time t15)
At time t15, the relay OFF diagnosis in the conventional example is finished, the first power supply relay 20 is turned on again, and the power supply relay diagnosis control is finished. In the conventional example, since the relay OFF diagnosis is performed at the time t12 and then the ON diagnosis is performed at the time t14, the diagnosis control takes longer time than the first embodiment of the present application. That is, in Embodiment 1 of the present application, the diagnosis control time is shortened.

[Effect of Example 1]
(1) First power supply BATT1, load drive relay 10 (first switching means) provided downstream of first power supply BATT1, capacitor 40 (power storage means) provided downstream of load drive relay 10, and capacitor 40 And a solenoid 30 (load) provided in parallel with the power supply relay 20, a power supply relay 20 (second switching means) provided in parallel with the capacitor 40 and in parallel with the capacitor 40, and the solenoid 30 and the power supply relay 20, a voltage monitor 50 (voltage monitoring means) provided in parallel with the CPU 20 and a CPU 310 (control means) for outputting the monitoring result of the voltage monitor 50 are provided, and the condenser 40, the power supply relay 20, and the downstream side of the voltage monitor 50 are provided. In the load driving circuit in which is connected to the ground GND, the CPU 310 performs the first power supply relay at the system startup. Obtained when the first and second drive means are executed, comprising first drive means for turning on 20 and second drive means for turning off only the load drive relay 10 after the first drive means. Based on the monitoring result of the voltage monitor 50, an abnormality in the circuit is detected.

  By performing the ON diagnosis before the OFF diagnosis, it is not necessary to discharge the residual charge of the capacitor 40 before the power relay ON diagnosis, and the diagnosis time corresponding to the charge discharge time can be shortened. Further, since the load drive relay 10 is turned on to consume residual charge when the power supply relay 20 is turned off, the power supply relay 20 diagnosis and the drive diagnosis of the load drive relay 10 can be performed at the same time, thereby further reducing the time.

  (2) The CPU 310 detects an off failure of the load driving relay 10 or a short circuit of the capacitor 40 based on the monitoring result of the voltage monitor 50 obtained during the execution of the first driving means. As a result, it can be diagnosed that the first power supply relay 20 is fixed OFF or the capacitor 40 is abnormal.

  (3) The CPU 310 detects either an on failure of the load drive relay 10, a failure of the power supply relay 20, or a failure of the solenoid 30 based on the monitoring result of the voltage monitor 50 obtained during the execution of the second drive means. It was decided.

Thereby, if it is in the range of ΔV _B <ΔV <ΔV _C , it can be determined that the circuit is normal. In the case of 0 ≦ ΔV ≦ ΔV _B , it is determined that the solenoid 30 has an open failure (normally non-conducting state), the load driving relay 10 is fixed OFF, or the first power supply relay 20 is fixed ON. If ΔV _C ≦ ΔV, It can be determined that the load driving relay 10 is short-circuited or the capacitor 40 is malfunctioning.

  (4) The CPU 310 cuts off the power supply relay 20 when the load drive relay 10 fails. When the load drive relay 10 that drives the load fails, the power supply relay 20 immediately turns off the power, thereby ensuring fail-safe property.

  (6) The CPU 310 controls the hydraulic pressures of the wheel cylinders W / C (FL to RR) and the wheel cylinders W / C (FL to RR) provided on the wheels FL to RR. A CPU 310 of a brake control device including HU1 and HU2 (hydraulic actuators), and a target wheel cylinder pressure P * (fl to rr) of the wheel cylinder W / C (FL to RR) based on the brake operation amount of the driver. ) (Target hydraulic pressure) is calculated, and this target wheel cylinder pressure P * (fl to rr) and the actual wheel cylinder pressure P (fl to rr) (actual hydraulic pressure) of the wheel cylinder W / C (FL to RR) are calculated. Based on this, the first and second hydraulic units HU1, HU2 were controlled.

  Even in the brake-by-wire control device, the load driving circuit of the present application can be applied.

  A second embodiment will be described with reference to FIGS. Since the basic configuration is the same as that of the first embodiment, only different points will be described. In the first embodiment, only one power supply relay 20 is connected to the first power supply BATT1, but in the second embodiment, a plurality of relays are provided to configure a precharge relay.

[Load Drive Circuit in Embodiment 2]
FIG. 8 is a load drive circuit diagram according to the second embodiment. The second embodiment includes a precharge relay 60 provided in parallel with the first power supply relay 20 in addition to the load driving circuit of the first embodiment.

  A resistor 70 is provided on the + side of the precharge relay 60, and the resistor 70 and the precharge relay 60 constitute a precharge circuit. The precharge relay 60 is also driven by the first CPU 310.

  When the capacity of the capacitor 40 is large, when the first power supply relay 20 is turned on, a current suddenly flows into the capacitor 40, which may shorten the life of the first power supply relay 20 or destroy other elements. Therefore, first, a small current is caused to flow into the capacitor 40 through the precharge circuit, and then the first power supply relay 20 is turned on.

[Circuit Diagnosis Processing in Embodiment 2]
FIG. 9 is a flowchart showing the flow of the circuit diagnosis process in the second embodiment. In the second embodiment, since the precharge circuit is provided, the precharge relay 60 is turned on before the first power supply relay 20 is turned on. Other points are the same as in the first embodiment.

(Steps S201 to S203)
This is the same as steps S101 to S103 in the first embodiment.

  In step S203a, the precharge relay 60 is turned on, and the process proceeds to step S204.

(Step S204)
This is the same as step S104 in the first embodiment.

  In step S204a, the precharge relay 60 is turned OFF, and the process proceeds to step S205.

(Steps S205 to S214)
This is the same as steps S105 to S114 in the first embodiment.

[Circular change of circuit diagnosis in Example 2]
FIG. 10 is a time chart of the load drive circuit diagnosis in the second embodiment (normal time).

(Time t21)
The first CPU 310 is activated at time t21.

(Time t22)
At time t22, relay diagnosis is started. In the second embodiment, the precharge relay 60 is turned on and the power supply monitor value V increases (ON diagnosis). a voltage monitor value V> threshold _{V A} between T22～t23.

(Time t23)
At time t23, relay diagnosis is started, both the load drive relay 10 and the first power supply relay 20 are turned on, and the power supply monitor value V increases. Accordingly, the precharge relay 60 is turned off.

(Time t24)
At time t24, the relay ON diagnosis ends, the first power supply relay 20 is turned OFF, and the power supply monitor value V decreases (OFF diagnosis). The load driving relay 10 is turned on as it is.

(Time t25)
At time t24, the relay OFF diagnosis ends, and the first power supply relay 20 is turned ON again. Between time t24 and t25, the relationship of ΔV _B <power monitor value V <ΔV _C is maintained, whereby the first power relay 20 is diagnosed as normal and power relay diagnostic control is terminated.

[Effect of Example 2]
(5) The first power supply BATT1 is further provided with a precharge relay 60 (third switching means) provided in parallel with the power supply relay 20. By providing the precharge relay 60, overcurrent can be prevented.
(Other examples)

The best mode for carrying out the present invention has been described based on the embodiments. However, the specific configuration of the present invention is not limited to the embodiments, and the design does not depart from the gist of the invention. Any changes and the like are included in the present invention.

It is a system configuration figure of a brake control device to which a load drive circuit is applied. 2 is a power supply circuit diagram of a main ECU and a first sub ECU in Embodiment 1. FIG. It is a figure which shows the time-dependent change of the voltage monitor value V at the time of ON of a 1st power supply relay. This is a change with time of the voltage monitor value V when the power supply relay is OFF. 3 is a flowchart illustrating a flow of circuit diagnosis processing according to the first embodiment. It is a time chart of the load drive circuit diagnosis in this-application Example 1 (at the time of normal). It is a time chart of the load drive circuit diagnosis in a prior art example (at the time of normal). FIG. 6 is a load drive circuit diagram in Embodiment 2. 12 is a flowchart illustrating a flow of circuit diagnosis processing in the second embodiment. It is a time chart of the load drive circuit diagnosis in Example 2 (at the time of normal).

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Load drive relay 20 Power supply relay 30 Solenoid 40 Capacitor 50 Voltage monitor 60 Precharge relay 70 Resistance 100,200 1st, 2nd sub ECU
300 Main ECU
310 Main CPU
A1, A2 Oil passage B1, B2 Oil passage BATT1, BATT2 First and second power supply BP Brake pedal BUZZ Buzzer CAN1-CAN3 Communication line CU1-CU6 Control unit Can / V Switching valve HU1, HU2 First, second hydraulic pressure unit IGN. SW ignition switch L main power supply line L1, L2 first, second power supply line L / Sen fluid quantity sensor M / C master cylinder first, second motor MC / Sen1, 2, first, second master cylinder pressure sensor first , Second pump RSV reservoir S / Sen1, S / Sen2 stroke sensor S / Sim stroke simulator STP. SW Stop lamp switch VDC. SW switch W / C Wheel cylinder

Claims (6)

Power supply,
First switching means provided downstream of the power source;
Power storage means provided downstream of the first switching means;
A load provided in parallel with the power storage means;
Second switching means provided in series downstream of the load and provided in parallel to the power storage means;
Voltage monitoring means provided in parallel with the load and the second switching means;
And a control means for outputting a monitoring result of the voltage monitoring means,
In a load driving circuit in which the downstream side of the power storage means, the second switching means, and the voltage monitoring means is connected to the ground,
The control means includes
First driving means for turning on both the first and second switching means at the time of system startup, and second driving means for turning off only the first switching means after the first driving means,
An abnormality in the circuit is detected based on a monitoring result of the voltage monitoring unit obtained when the first and second driving units are executed. The load driving circuit according to claim 1,
The control means detects an off failure of the first switching means or a short circuit of the power storage means based on a monitoring result of the voltage monitoring means obtained during the execution of the first driving means. circuit. In the load driving circuit according to claim 1 or 2,
The control means is either on-failure of the first switching means, failure of the second switching means, or failure of the load based on the monitoring result of the voltage monitoring means obtained during the execution of the second drive means. A load driving circuit characterized by detecting the above. The load driving circuit according to any one of claims 1 to 3,
The load driving circuit, wherein the control means cuts off the energization of the second switching means when the first switching means fails. The load driving circuit according to any one of claims 1 to 3,
A load driving circuit, further comprising third switching means provided in parallel with the second switching means for the power source. The load driving circuit according to any one of claims 1 to 3,
The control means includes
A wheel cylinder provided on the wheel;
A control means of a brake control device comprising a hydraulic actuator for controlling the hydraulic pressure of the wheel cylinder,
A load driving circuit, wherein a target hydraulic pressure of the wheel cylinder is calculated based on a brake operation amount of a driver, and the hydraulic actuator is controlled based on the target hydraulic pressure and an actual hydraulic pressure of the wheel cylinder.

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