JP2015033233A - Method for detecting anomaly in power supply circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for detecting an anomaly in a power supply circuit which permits an inverter to be started in a short time by shortening the time to detect an open anomaly in a power relay.SOLUTION: A CPU of a control circuit 10 switches on a precharge relay 4 to start precharging a smoothing capacitor 11 with a discharge circuit 7 turned on. If a voltage Vd of the smoothing capacitor 11 is lower than a predetermined value after a predetermined time passes, the precharge relay 4 is switched off and anomaly handling is performed. If the voltage Vd is equal to or higher than the predetermined value, the precharging is continued and, on completion of charging, the precharge relay 4 is switched off. A power relay 6 is switched on, and after a voltage monitoring timer counts up to a charge time T', if the voltage Vd is equal to or lower than a precharge voltage Vb, the power relay 6 is switched off and anomaly handling is performed. If the voltage Vd is higher than the precharge voltage Vb, the discharge circuit 7 is turned off and the process is finished to exit the flow.

Description

  The present invention relates to an abnormality detection method for a power supply circuit included in a vehicle motor control device.

  Conventionally, a relay is generally used to control power supply from a high voltage battery to an electric motor or the like. For example, in an electric vehicle such as a hybrid vehicle or an electric vehicle, a power relay is provided between the battery and the inverter to control power supply from the high-voltage battery to the inverter that is the load circuit, and the battery and the inverter are connected. And the opening is performed by the power relay according to the vehicle control state. In such a case, in order to charge a large-capacity smoothing capacitor from the battery, a large inrush current flows instantaneously, and the contact of the power relay may be welded. In order to prevent the current relay from being switched off by switching the power relay due to the welding of the contacts, a power circuit having a precharge circuit for precharging the smoothing capacitor before switching the power relay on is proposed. (For example, refer to Patent Document 1).

JP 2001-128305 A

  In such a power supply circuit, the precharge circuit includes a precharge resistor for limiting an inrush current and a precharge relay connected in series to the precharge resistor, and the precharge relay is switched on to turn on the inverter. Precharge the smoothing capacitor connected to. After the smoothing capacitor is precharged, the power supply relay connected in parallel with the precharge circuit is switched on, and then the battery is connected to the inverter. Then, after the power relay is switched on, the precharge relay is switched off.

  However, when the power relay cannot be turned on normally, the voltage precharged in the smoothing capacitor gradually decreases. For this reason, the voltage at the rear end (output) side of the power supply relay may be monitored to determine whether the contact is open (open). However, since the smoothing capacitor is connected, the voltage gradually decreases and takes time to decrease to the determination value. Therefore, it is necessary to determine the voltage after a certain period of time has elapsed. As a result, since it takes time to determine whether to open check the power supply relay, if the power supply relay is normal, the time required for starting the inverter becomes long, and there is a possibility that the motor drive cannot be started early.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a power circuit abnormality detection method capable of shortening the detection time of a power relay open abnormality and starting an inverter in a short time. It is in.

  In order to solve the above-mentioned problem, the invention according to claim 1 is a power source that opens and closes a connection between a DC power source that drives an electric motor and a motor driving circuit that includes a plurality of switching elements and supplies a driving current to the electric motor. A relay, a smoothing capacitor connected between a power line and a ground line between the power relay and the motor drive circuit, and absorbing a current ripple; a connection between the DC power source and the smoothing capacitor bypassing the power relay A precharge circuit that opens and closes and precharges the smoothing capacitor, and a discharge circuit that is connected in parallel to the smoothing capacitor and discharges the charge accumulated in the smoothing capacitor through a discharge resistor by closing a discharge switch. In a power supply circuit abnormality detection method that is applied to a power supply circuit comprising and detects the presence or absence of abnormality of the power relay, Whether the charging voltage of the smoothing capacitor has increased after a predetermined time has elapsed after the power supply relay has been closed after the precharge circuit has been opened and the discharge circuit is on. The gist of the present invention is to detect the presence or absence of an open abnormality of the power relay.

  According to the above configuration, when the power supply relay is switched on while the discharge circuit is on, the charging voltage of the smoothing capacitor rapidly rises to the voltage of the DC power supply. By setting this charging time as a standby time until voltage detection is performed and abnormality detection is started, it is possible to detect abnormality of the power relay. When an open abnormality occurs in the power supply relay, the DC power supply is not connected to the smoothing capacitor and the discharge circuit, so that the voltage precharged to the smoothing capacitor rapidly decreases via the discharge resistor when the discharge circuit is on. Thereby, the open abnormality of the power supply relay can be detected in a short time by monitoring the charging voltage of the smoothing capacitor. As a result, it is possible to reliably detect a failure and to safely consume the electrical energy accumulated in the electric motor and the power supply circuit and to avoid the occurrence of an electric shock accident of the driver. Further, since an open abnormality of the power supply relay is detected using an existing smoothing capacitor discharge circuit, it is not necessary to add a dedicated circuit component.

  According to a second aspect of the present invention, in the power supply circuit abnormality detection method according to the first aspect, the precharge circuit opens and closes a precharge resistor for limiting an inrush current, and the DC power supply and the precharge resistor are opened and closed. The precharge relay is connected in series and is provided in parallel with the power supply relay.

  According to the above configuration, the precharge circuit and the power relay are provided in parallel, and the power relay of the power relay is monitored by monitoring the decrease in the charging voltage of the smoothing capacitor when the power relay after the smoothing capacitor is precharged. Open abnormality can be detected in a short time. Further, when an open abnormality occurs in the power supply relay, the precharge relay can be used instead of the power supply relay, and the vehicle can be safely moved and retracted without stopping the electric motor.

  According to a third aspect of the present invention, in the power supply circuit abnormality detection method according to the second aspect, the precharge voltage of the smoothing capacitor is set by a voltage dividing circuit constituted by the precharge resistor and the discharge resistor. This is the gist.

  According to the above configuration, the smoothing capacitor is precharged to the precharge voltage set by the voltage dividing circuit formed by the precharge resistor and the discharge resistor, and the charging voltage of the smoothing capacitor is increased by switching on the power supply relay. Is accelerated. For this reason, by setting the charging time as a standby time until the abnormality detection of the power relay is started, the time until the abnormality is determined by monitoring the voltage of the smoothing capacitor after the power relay is switched on is shortened. The Thereby, if the voltage rise of the smoothing capacitor is not observed within a certain time, it can be determined that there is an abnormality, and an open abnormality of the power supply relay can be detected in a short time. In addition, the amount of increase in the charging voltage can be arbitrarily set by the voltage dividing circuit, so the surge generated when switching the precharge relay and the power supply relay is suppressed by the combination of the resistance values of the precharge resistor and the discharge resistor. be able to.

  According to the present invention, it is possible to provide a power circuit abnormality detection method capable of shortening the detection time of an open abnormality of the power relay and monitoring the inverter in a short time by monitoring the voltage increase of the smoothing capacitor.

The figure which shows schematic structure of the drive system of the vehicle carrying the vehicle motor control apparatus containing the power supply circuit which concerns on one Embodiment of this invention. The figure which shows the circuit structure of the motor control apparatus for vehicles containing the power supply circuit of FIG. The flowchart which shows the process sequence of the open abnormality detection of the power supply relay performed with a control circuit. The graph which shows the voltage-time characteristic of a smoothing capacitor when an open abnormality generate | occur | produces in a power supply relay.

Next, a power supply circuit of a motor control device mounted on a vehicle according to an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram showing a schematic configuration of a vehicle drive system equipped with a vehicle motor control device 15 including a power supply circuit 2 according to an embodiment of the present invention. As shown in FIG. 1, a vehicle (for example, a hybrid vehicle or an electric vehicle) drives a DC power source (hereinafter referred to as a high voltage battery) 13, a vehicle control unit 18, a rear wheel drive unit 20, and a rear wheel 19. A vehicle motor control device (ECU, hereinafter referred to as a motor control device) 15 that controls the electric motor 1 to be used is provided. The rear wheel drive unit 20 includes an electric motor 1, a reduction gear (differential gear) 16, and a clutch 17, and the clutch 17 is installed at the final stage of the reduction gear 16. For example, a three-phase brushless motor is used as the electric motor 1 for the drive source. The electric motor 1 is a permanent magnet type such as an IPM motor having an embedded magnet type rotor in which a permanent magnet is embedded and fixed in a rotor core, and an SPM motor having a surface magnet type rotor in which a permanent magnet is fixed to the surface of the rotor core. A synchronous motor is used.

  The high-voltage battery 13 is a high-voltage (for example, 245 V) DC power source, and is composed of, for example, a chargeable / dischargeable secondary battery such as nickel metal hydride or lithium ion, and is disposed behind the rear seat of the vehicle. The motor control device 15 boosts the DC voltage received from the high-voltage battery 13 to a higher voltage (for example, 500 V, etc.) in the power supply circuit 2 according to the specifications of the inverter 12 that is a motor drive circuit (or remains unboosted) ) And supply to the inverter 12. Further, the motor control device 15 supplies and charges the high-voltage battery 13 with the electric power generated by the electric motor 1 during regenerative braking of the electric motor 1. The motor control device 15 is mounted, for example, under the rear seat of the vehicle.

  Further, the motor control device 15 includes a control circuit (signal processing circuit) 10 that controls the rear wheel drive unit 20 and the like. The control circuit 10 is connected to an auxiliary power source (hereinafter referred to as a low voltage battery) 14 having a low voltage (for example, 12V), receives a command from the vehicle control unit 18 that controls the driving of the vehicle, and connects the clutch 17. Thus, the driving force generated by driving the electric motor 1 is transmitted to the rear wheel 19. Further, when a higher DC voltage is required, the motor control device 15 boosts the DC voltage of the high-voltage battery 13 by a boost converter (not shown) and stabilizes it by the smoothing capacitor 11 (see FIG. 2). A power supply circuit 2, a control circuit 10, and an inverter 12 are included.

  Next, FIG. 2 is a diagram showing a circuit configuration of the motor control device 15 including the power supply circuit 2 of FIG. The power supply circuit 2 shown in FIG. 2 is connected to the positive and negative output sides of the high-voltage battery 13, and controls the power supply relay 6 that controls the power supply to the inverter 12, and the large-capacity smoothing before the power supply relay 6 is turned on. The precharge circuit 3 that precharges the capacitor 11 and the power supply relay 6 are turned off in order to dissipate power during regenerative braking (deceleration) of the electric motor 1, and then the electric charge accumulated in the smoothing capacitor 11 is discharged. And a discharge circuit 7. An inverter 12 is connected in parallel to the smoothing capacitor 11, and the electric motor 1 is connected via the inverter 12. The precharge circuit 3 and the power supply relay 6 are controlled by the control circuit 10.

  The precharge circuit 3 has a precharge relay 4 and a precharge resistor 5 connected in series. This precharge circuit 3 is connected in parallel to the contact of the power relay 6, and when the power relay 6 is in an off state, the precharge relay 4 is switched on to precharge the smoothing capacitor 11 while limiting the inrush current. . The precharge resistor 5 is an inrush prevention resistor (for example, 100Ω) that limits the inrush current of the smoothing capacitor 11. The precharge resistor 5 prevents a large inrush current from flowing immediately after the power supply relay 6 is switched on, and the smoothing capacitor 11 is precharged via the precharge resistor 5 when the power supply relay 6 is in the off state. Is done.

  The power supply relay 6 is a power switch that is arranged in the power supply circuit 2 and switches whether the smoothing capacitor 11 and the inverter 12 are connected to the high voltage battery 13 or not, and is a relay having a mechanically movable contact. The power supply relay 6 is turned on (conductive state) when the motor control device 15 is operating, and is turned off (non-conductive state) when stopped. Further, the power supply relay 6 precharges the smoothing capacitor 11 by switching on the precharge relay 4 of the precharge circuit 3 in the off state. After the smoothing capacitor 11 is precharged, the power relay 6 is switched from OFF to ON, and the high voltage battery 13 is directly connected to the inverter 12. Thereafter, the precharge relay 4 is switched off.

  The smoothing capacitor 11 is provided between a power supply line 21 and a ground (ground) line 22. The smoothing capacitor 11 supplies power to the inverter 12 from both the high voltage battery 13 and the power supply relay 6 in a state where the power supply relay 6 is switched on. In particular, the smoothing capacitor 11 instantaneously supplies high power to the inverter 12. Specifically, the smoothing capacitor 11 accumulates electric charge, and discharges the accumulated electric charge when the current flowing from the high voltage battery 13 to the inverter 12 is insufficient. Thus, the smoothing capacitor 11 functions as a capacitor that absorbs current ripple and smoothes the power supply voltage for driving the electric motor 1. Further, in the power supply circuit 2 of the present embodiment, after the power supply relay 6 is turned off, the charge accumulated in the smoothing capacitor 11 is discharged through the discharge circuit 7.

  The discharge circuit 7 is formed by connecting a discharge switch (for example, IGBT, MOSFET, etc.) 9 and a discharge resistor (for example, 500Ω) 8 in series. It is provided in between. When the power supply relay 6 is cut off and the driving of the electric motor 1 is stopped, the electric charge accumulated in the smoothing capacitor 11 is discharged through the discharge resistor 8 by turning on the discharge switch 9, and the voltage of the smoothing capacitor 11 is discharged. Vd decreases rapidly.

  In FIG. 2, the electric motor 1 is a three-phase brushless motor having three-phase windings (U-phase winding, V-phase winding, and W-phase winding, not shown). The high voltage battery 13 is a high voltage DC power source that is connected to the inverter 12 and drives the electric motor 1.

  The inverter 12 includes six switching elements (for example, IGBT, MOSFET, etc.) U1, U2, V1, V2, W1, and W2. The three circuits in which the six switching elements U1, U2, V1, V2, W1, and W2 are connected in series and two upper and lower arms (for example, U1 and U2) are formed include a power line 21 and a ground line. 22 in parallel. Each connection point of the switching elements of the upper and lower arms is directly connected to one end of the U-phase winding, the V-phase winding, and the W-phase winding. The other end of the three-phase winding of the electric motor 1 is connected to a common connection point (neutral point, not shown).

  The control circuit 10 controls switching elements U1, U2, V1, V2, W1, and W2 included in the inverter 12. More specifically, the control circuit 10 determines the three-phase drive current (U-phase current, V-phase current, and W-phase current) to be supplied to the electric motor 1 based on the input data (rotation angle and the like). A target value (target current) is determined, and a PWM signal for matching the current (each phase current value) detected by a current sensor (not shown) with the target current is output. The PWM signal of each phase output from the control circuit 10 is supplied to the gate terminals of the switching elements U1, U2, V1, V2, W1, and W2 included in the inverter 12, respectively. Note that a control voltage (for example, 12 V) serving as a power source for the control circuit 10 is supplied from the low voltage battery 14. The low voltage battery 14 may be equipped with an auxiliary battery, or may be supplied with power from the high voltage battery 13 via a DC / DC converter or the like.

Next, an abnormality detection method for the power supply relay 6 in this embodiment will be described.
FIG. 3 is a flowchart showing a processing procedure for detecting an open abnormality of the power supply relay 6 executed by the control circuit 10, and FIG. It is a graph. Open abnormality detection of the power supply relay 6 is performed by the control circuit 10 when the vehicle control is stopped, that is, when the motor control device 15 that drives the electric motor 1 is started. In the present embodiment, a CPU (not shown) in the control circuit 10 reads a program stored in the ROM, and executes each process of steps S301 to S311 shown in the flowchart of FIG. The processing in the flowchart shown below is executed at predetermined time intervals.

  In FIG. 4, the voltage Vd of the smoothing capacitor 11 is normally precharged to the precharge voltage Vb before the power supply relay 6 is turned on. As shown in FIG. 4, after the power supply relay 6 is switched on, when the power supply relay 6 is normal, the voltage Vd of the smoothing capacitor 11 has a voltage characteristic indicated by a solid line and is immediately charged to the battery voltage Va of the high-voltage battery 13. At this time, the charging time to the battery voltage Va is represented by a charging time T ′.

  Here, when an open abnormality occurs in the power supply relay 6, the voltage Vd of the smoothing capacitor 11 has a voltage characteristic indicated by a broken line when the discharge circuit 7 is not turned on, and gradually decreases. At this time, the standby time until the detection of the open abnormality is expressed as a discharge time T during which the voltage Vd decreases to the determination value Vt. On the other hand, when the discharge circuit 7 is turned on, a voltage characteristic indicated by a one-dot chain line is obtained, and the voltage Vd is rapidly lowered by discharging through the discharge resistor 8. Therefore, the standby time until the abnormality detection of the power supply relay 6 can be made shorter when the charging time T ′ in this embodiment is set than when the discharging time T is set (charging time T ′ <discharge). Time T). As a result, it becomes possible to start detection of an open abnormality of the power relay 6 in a short time.

  As shown in FIG. 3, the CPU of the control circuit 10 in the motor control device 15 first switches on the discharge switch 9 to turn on the discharge circuit 7 (step S301). Subsequently, the precharge relay 4 is switched on (step S302), and the precharge of the smoothing capacitor 11 is started.

  Next, the CPU determines whether or not the voltage Vd of the smoothing capacitor 11 has risen above a predetermined value after a predetermined time has elapsed (step S303). When the voltage Vd is smaller than the predetermined value (step S303: NO), it is determined that an open abnormality has occurred in the precharge relay 4, and the precharge relay 4 is switched off to stop the precharge. Subsequently, after the abnormality process is executed (step S311), the flow is exited. When the voltage Vd is equal to or higher than the predetermined value (step S303: YES), the process proceeds to step S304.

  If it is determined that the smoothing capacitor 11 is normally precharged, the precharge is continued. When the charge is completed, the precharge relay 4 is switched off (step S304), and the precharge is stopped. At this time, the precharge voltage Vb after the precharge is finished is expressed by Vb = Va × (Rb / (Ra + Rb)) (where Va> Vb, Va is the power supply voltage of the high-voltage battery 13, and Ra and Rb are the precharge voltages, respectively. (Represents resistance values of the charge resistor 5 and the discharge resistor 8).

  Subsequently, the power supply relay 6 is switched on (step S305), and a voltage monitoring timer that counts the charging time T ′ (see FIG. 4) of the smoothing capacitor 11 to monitor the voltage Vd starts counting (step S306). .

  Next, the CPU determines whether or not the voltage monitoring timer has expired (step S307). If the time has not expired (step S307: NO), the CPU loops this step until the time expires and sets the set time. Let it pass. If the count time of the voltage monitoring timer has elapsed until the normal charging time T ′ that is the set time (step S307: YES), the CPU determines whether or not the voltage Vd of the smoothing capacitor 11 is greater than the precharge voltage Vb (step S307). S308) is determined.

  Here, when the voltage Vd is equal to or lower than the precharge voltage Vb (step S308: NO), it is determined that an open abnormality has occurred in the power supply relay 6 because no voltage increase is observed, and the power supply relay 6 is switched off to supply power. Is stopped and abnormal processing is executed (step S310), and then the flow is exited. If the voltage Vd is greater than the precharge voltage Vb (step S308: YES), since the voltage rises, it is determined that the power supply relay 6 is normal, the discharge switch 9 is turned off and the discharge circuit 7 is turned off (step (step S308). S309), this process is terminated and the flow is exited.

  Next, the operation and effect of the abnormality detection method for the power supply circuit 2 included in the motor control device 15 according to the present embodiment configured as described above will be described.

  According to the above configuration, the smoothing capacitor 11 is connected in parallel to the inverter 12 in the power supply circuit 2 connected between the high-voltage battery (DC power supply) 13 and the inverter (motor drive circuit) 12. The smoothing capacitor 11 is precharged while limiting the inrush current via the precharge circuit 3 before the power supply relay 6 is switched on when the discharge circuit 7 is on. The precharge circuit 3 and the power supply relay 6 are provided in parallel, and the voltage Vd of the smoothing capacitor 11 is divided from the battery voltage Va by a voltage dividing circuit formed by the precharge resistor 5 and the discharge resistor 8. The precharge voltage Vb is precharged. After the precharge is completed, the precharge relay 4 is switched off and then the power supply relay 6 is switched on. When the power supply relay 6 is switched on, the voltage Vd of the smoothing capacitor 11 immediately rises to the battery voltage Va at the charging time T ′. Here, for example, a charging time T ′ can be set as a standby time until the voltage Vd is monitored and abnormality detection of the power supply relay 6 is started.

  When an open abnormality has occurred in the power supply relay 6 in this state, the high voltage battery 13 is not connected to the smoothing capacitor 11 and the discharge circuit 7, so that the discharge switch 9 is turned on and the discharge circuit 7 is in the on state. The voltage Vd charged in the smoothing capacitor 11 rapidly decreases from the precharge voltage Vb through the discharge resistor 8. For this reason, as a standby time until it is determined whether or not the voltage Vd of the smoothing capacitor 11 has decreased, the discharge circuit 7 shorter than the discharge time T (determination value Vt or less) when the discharge circuit 7 is in the OFF state is used. The charging time T ′ when in the on state can be set. However, when the power supply relay 6 is in an open abnormality, the voltage Vd of the smoothing capacitor 11 decreases more rapidly than when the discharge circuit 7 is not added by turning on the discharge circuit 7.

  Thereby, after the power supply relay 6 is switched on, the voltage Vd of the smoothing capacitor 11 can be monitored in a short charging time T ′, so that an open abnormality of the power supply relay 6 can be detected in a short time. As a result, the startup time of the inverter 12 can be shortened. As a result, when an abnormality is detected in the power supply relay 6, the abnormality is surely detected, and the electric energy accumulated in the electric motor 1 or the smoothing capacitor 11 in the power supply circuit 2 is safely consumed, so that the driver The occurrence of electric shock accidents can be avoided.

  Further, when an open abnormality occurs in the power supply relay 6, the precharge relay 4 can be used instead of the power supply relay 6 and the vehicle can be safely moved and retracted without stopping the electric motor 1. . Furthermore, since the existing discharge circuit 7 of the smoothing capacitor 11 is used, the time for detecting the open abnormality of the power supply relay 6 can be shortened without adding a dedicated circuit component. On the other hand, by forming a voltage dividing circuit with the precharge resistor 5 and the discharge resistor 8, the amount of increase in the voltage Vd of the smoothing capacitor 11 can be arbitrarily set. Therefore, the precharge relay 4 and the power relay can be selected depending on the combination of the respective resistance values. Surge generated when switching 6 can be suppressed.

  As described above, according to the embodiment of the present invention, by detecting the voltage increase of the smoothing capacitor, the detection time of the open abnormality of the power relay is shortened, and the abnormality detection method of the power circuit that can start the inverter in a short time Can provide.

  As mentioned above, although embodiment which concerns on this invention was described, this invention can also be implemented with another form.

  In the above embodiment, the power supply relay 6 and the precharge relay 4 are controlled to be turned on / off by using a normal relay (mechanical type). However, the present invention is not limited to this. May be turned on / off by using a plurality of such devices. Further, a mechanical relay may be used for the discharge switch 9.

  In the above-described embodiment, the control circuit is configured so that a code indicating an abnormality content (open failure) can be displayed on a warning display unit or a failure diagnosis device of the vehicle in the abnormality process when the open abnormality of the power supply relay 6 or the precharge relay 4 is detected. Processing such as saving in a memory area in the memory 10 may be performed.

  In the above embodiment, the process of detecting the short circuit abnormality of the power supply relay 6 and the precharge relay 4 by monitoring the voltage Vd of the smoothing capacitor 11 in the same way as the open abnormality detection is shown in the flowchart of FIG. It may be executed before processing.

  In the above-described embodiment, the example in which the present invention is applied to the inverter 12 for driving the rear wheel drive unit 20 of the vehicle has been described. However, the present invention is not limited to this. You may make it apply to inverters, such as a steering device and an electric brake device, or another vehicle-mounted power converter device. Moreover, you may apply to the inverter which drives the motor for driving | running | working of a hybrid vehicle or an electric vehicle.

1: electric motor, 2: power supply circuit, 3: precharge circuit, 4: precharge relay,
5: Precharge resistor, 6: Power relay, 7: Discharge circuit, 8: Discharge resistor,
9: discharge switch, 10: control circuit, 11: smoothing capacitor,
12: Inverter (motor drive circuit), 13: High voltage battery (DC power supply),
14: Low-voltage battery, 15: Motor controller (ECU), 16: Reducer,
17: Clutch, 18: Vehicle control unit, 19: Rear wheel,
20: Rear wheel drive unit, 21: Power line, 22: Ground (ground) line,
U1, U2, V1, V2, W1, W2: switching elements,
Va: battery voltage (power supply voltage), Vb: precharge voltage,
Vd: smoothing capacitor voltage, Vt: judgment value, T: discharge time (discharge circuit off),
T ′: charging time (discharge circuit on), Ra: precharge resistance value, Rb: discharge resistance value

Claims (3)

A power supply relay that opens and closes a connection between a DC power source that drives the electric motor and a motor drive circuit that includes a plurality of switching elements and supplies a drive current to the electric motor;
A smoothing capacitor connected between a power line and a ground line between the power relay and the motor drive circuit to absorb current ripple;
A precharge circuit that bypasses the power relay and opens and closes a connection between the DC power supply and the smoothing capacitor to precharge the smoothing capacitor;
A discharge circuit connected in parallel to the smoothing capacitor and discharging the charge accumulated in the smoothing capacitor through a discharge resistor by a closing operation of a discharge switch, and the presence or absence of abnormality of the power relay In the abnormality detection method of the power supply circuit to be detected,
Whether the charging voltage of the smoothing capacitor has increased after a predetermined time has elapsed after the power supply relay is closed after the discharge circuit is on and the precharge circuit is opened. An abnormality detection method for a power supply circuit, wherein the presence or absence of an open abnormality of the power supply relay is detected. In the power supply circuit abnormality detection method according to claim 1,
In the precharge circuit, a precharge resistor that limits an inrush current and a precharge relay that opens and closes the DC power supply and the precharge resistor are connected in series and provided in parallel with the power supply relay. An abnormality detection method for a power supply circuit. The abnormality detection method for a power supply circuit according to claim 2,
An abnormality detection method for a power supply circuit, wherein a precharge voltage of the smoothing capacitor is set by a voltage dividing circuit composed of the precharge resistor and the discharge resistor.

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