JP2018160972A - Control device of motor drive circuit and diagnostic method of motor drive circuit - Google Patents

Abstract

A power supply relay circuit is prevented from being erroneously detected as being stuck on due to the electric charge accumulated in a capacitor connected between a power supply line of an inverter and a ground point. A control device sets a q-axis voltage to zero and a d-axis voltage to a predetermined non-zero voltage in a power relay circuit consisting of a power relay and a reverse connection protection relay in an OFF operation state. The charge is discharged through the windings of the motor, and when the state in which the current flows through the windings of the motor continues longer than a predetermined time in the discharging operation state, it is determined that the power relay circuit is stuck on. Then, when the control device determines that the power relay circuit is stuck on, the controller turns on the lower arm of the inverter by setting the q-axis voltage and the d-axis voltage to zero from the discharge operation state, thereby reducing the surge current to the ground point. Suppresses surge voltage by letting it escape to the side. [Selection drawing] Fig. 2

Description

  The present invention relates to a motor drive circuit control device and a motor drive circuit diagnosis method, and more particularly, to a technique for detecting the presence or absence of an on-fixation abnormality of a power relay circuit connected between an inverter and a power source.

  In Patent Document 1, in the electric power steering apparatus, the charge accumulated in the capacitor for absorbing current ripple is set to zero as the target value of the q-axis current in the control of the switching element of the inverter, and the target value of the d-axis current is not zero. It is disclosed that the value is discharged through the winding of the motor.

JP 2008-094342 A

By the way, the power supply relay circuit connected between the power supply and the inverter includes a first power supply relay including a semiconductor switching element having a parasitic diode for conducting a current in a direction from the inverter to the power supply, a first power supply relay, and the inverter. And a second power supply relay (reverse connection protection relay) composed of a semiconductor switching element having a parasitic diode that conducts current in the direction from the power supply to the inverter.
Here, the control device for the motor drive circuit determines whether the first power relay and the second power relay are turned off based on whether or not the first power relay is turned on abnormally (abnormality that remains in the on state even if the first power relay is turned off). Thus, it is possible to detect based on whether or not the voltage between the first power relay and the second power relay exceeds the set voltage.
However, in the motor drive circuit in which the capacitor is connected between the power supply line between the power supply relay circuit and the inverter and the grounding point, electric charge is accumulated in the capacitor and the second power supply relay is fixed on. And even if the 1st power supply relay was in the OFF state, the voltage between the 1st power supply relay and the 2nd power supply relay became high, and there was a problem of detecting ON sticking abnormality of the 1st power supply relay accidentally.

  SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and a motor drive circuit control device and a motor that can suppress erroneous detection of an on-fixation abnormality of a power supply relay circuit due to the electric charge accumulated in a capacitor. An object of the present invention is to provide a diagnostic method for a drive circuit.

  Therefore, the motor drive circuit control device according to the present invention has, as one aspect thereof, an inverter that is configured by connecting switching elements in a multiphase bridge, and is connected between the inverter and the power source, and an inverter that energizes the windings of the motor. And a capacitor connected between a power supply line between the power relay circuit and the inverter and a ground point, and a control device for a motor drive circuit, wherein the power relay circuit is turned off. Operating the switching element of the inverter in an operating state, discharging means for discharging the charge accumulated in the capacitor through the winding of the motor; and a current in the winding of the motor in a discharging operation state by the discharging means Diagnostic means for detecting an on-fixation abnormality of the power relay circuit when the flowing state continues for longer than a predetermined time.

  Moreover, the diagnosis method of the motor drive circuit according to the present invention includes, as one aspect thereof, an inverter that is configured by connecting switching elements in a multiphase bridge connection, and that is connected between the inverter and the power source. And a capacitor connected between a power supply line between the power supply relay circuit and the inverter and a ground point, wherein the power supply relay circuit is turned off. A first step of operating the switching element of the inverter in an operating state and discharging the charge accumulated in the capacitor through the winding of the motor; and a state in which a current flows through the winding of the motor in the discharging operation state Includes a second step of detecting an on-fixation abnormality of the power supply relay circuit when the power supply relay circuit continues for longer than a predetermined time.

  According to the above invention, a current flows through the motor winding by discharging the electric charge accumulated in the capacitor. If the current continues to flow through the motor winding even after the capacitor discharge is finished, turn off the motor. It can be estimated that the power relay circuit is actually in the on state and power is supplied from the power source to the inverter.

It is a circuit diagram which shows the motor drive circuit in embodiment of this invention. It is a flowchart which shows the on-fixation diagnostic process of the power supply relay in embodiment of this invention. It is a time chart for demonstrating generation | occurrence | production of the surge voltage in embodiment of this invention. It is a time chart for demonstrating the surge countermeasure process in embodiment of this invention.

Embodiments of the present invention will be described below.
FIG. 1 is a circuit diagram showing an embodiment of a motor drive circuit according to the present invention.
The motor 12 constitutes an electric actuator such as an electric power steering device for a vehicle and a variable compression ratio mechanism for an internal combustion engine.

The motor 12 is a three-phase permanent magnet synchronous motor including a U-phase coil, a V-phase coil, and a W-phase coil, and is driven by a motor drive circuit 21.
The motor drive circuit 21 includes an inverter 22, a driver 23 for the inverter 22, a capacitor 24, a power relay circuit 25, a driver 26 for the power relay circuit 25, and the like.

The motor drive circuit 21 is controlled by a microcomputer 27 as a control device. The microcomputer 27 includes a processor, a memory, and the like.
The inverter 22 is a three-phase bridge circuit including three sets of switching elements that drive the U phase, the V phase, and the W phase of the motor 12 for each phase via the drive lines 28U, 28V, and 28W. Consists of N-channel MOSFETs 31-36.

In the MOSFETs 31 and 32, the drain and source are connected in series between the power supply line 37 and one end of the current detection resistor 38, and one end of the drive line 28 U is connected to the connection point between the MOSFET 31 and the MOSFET 32.
The MOSFETs 33 and 34 are connected in series between the drain and source between the power supply line 37 and one end of the current detection resistor 38, and one end of the drive line 28 </ b> V is connected to a connection point between the MOSFET 33 and the MOSFET 34.

In addition, the drains and sources of the MOSFETs 35 and 36 are connected in series between the power supply line 37 and one end of the current detection resistor 38, and one end of the drive line 28 </ b> W is connected to a connection point between the MOSFET 35 and the MOSFET 36.
The other end of the current detection resistor 38 is grounded, detects a current flowing through the inverter 22 (DC bus current of the inverter 22), and supplies a detection signal S to the microcomputer 27.
Here, the diodes D1-D6 connected in the forward direction between the source and drain in each MOSFET 31-36 are parasitic diodes.

The power line 37 is connected to the battery BA as a power source via the power relay circuit 25.
A capacitor 24 is connected between the power supply line 37 and the ground point.
Capacitor 24 assists power supply from battery BA to inverter 22 and removes noise components such as surge current.

The power relay circuit 25 is configured by connecting the drain and source of an N-channel MOSFET 39 as a power relay (first power relay) and an N-channel MOSFET 40 as a reverse connection protection relay (second power relay) in series. The
The MOSFET 39 is a semiconductor switching element having a parasitic diode D13 that conducts current in the direction from the inverter 22 to the battery BA. The MOSFET 40 connected between the MOSFET 39 and the inverter 22 is in the direction from the battery BA to the inverter 22. It is a semiconductor switching element which has the parasitic diode D14 which conducts this current.

If the power supply relay circuit 25 is composed of only the MOSFET 39, the circuit may be damaged due to current flowing through the parasitic diode D13 when the polarity of the power supply (battery BA) is mistakenly connected.
Therefore, by providing the MOSFET 40 having the parasitic diode D14 whose direction of conducting current is opposite to that of the parasitic diode D13 of the MOSFET 39, it is possible to prevent the current from flowing through the parasitic diode even when the power source is reversely connected. The circuit can be protected from reverse connection.

The driver 23 drives MOSFETs 31, 33, and 35 that are upstream drive elements (upper arms) in the inverter 22, and MOSFETs 32, 34, and 36 that are downstream drive elements (lower arms), respectively. And a low-side driver section.
The gates of the MOSFETs 31, 33, and 35 are connected to the output terminals of the High side driver unit, and the MOSFETs 31, 33, and 35 are individually turned on / off by the microcomputer 27.
The gates of the MOSFETs 32, 34, and 36 are connected to the output terminals of the low-side driver unit, and the MOSFETs 32, 34, and 36 are individually turned on / off by the microcomputer 27.

Further, the gates of MOSFETs 39 and 40 constituting the power supply relay circuit 25 are connected to the output terminal of the driver 26, and the MOSFETs 39 and 40 are individually controlled to be turned on / off by the microcomputer 27.
The microcomputer 27 inputs the detection signal S of the current detection resistor 38 and drives and controls each switching element of the inverter 22 by complementary three-phase PWM control using the phase current of each phase detected based on the detection signal S.

Hereinafter, one aspect of the control of the inverter 22 by the microcomputer 27 will be described.
The microcomputer 27 detects the phase current detection values Iu, Iv, and Iw detected based on the detection signal S of the current detection resistor 38, based on the motor angle (magnetic pole position) θ at that time, and the biaxial rotational coordinate system (d− (q coordinate system) real currents Id and Iq.

Further, the microcomputer 27 calculates a d-axis command current and a q-axis command current according to the command torque, and a command voltage in the dq coordinate system based on the d-axis and q-axis command current, the angular velocity, and the actual currents Id and Iq. Vq and Vd are determined, and the determined command voltages Vq and Vd are converted into three-phase command voltages Vu, Vv, and Vw.
Further, the microcomputer 27 generates three sets of complementary drive pulse signals by PWM control using the three-phase command voltages Vu, Vv, and Vw as modulated waves, and these drive pulse signals are supplied to the gates of the switching elements of the inverter 22. By outputting, the rotation of the motor 12 is controlled.

Further, the microcomputer 27 has a function (diagnostic means) for diagnosing whether or not the MOSFET 39 (first power relay) constituting the power relay circuit 25 has an on-fixation abnormality (abnormality that remains in the on state even if the operation is turned off) It is provided as software.
The flowchart of FIG. 2 shows one aspect of the process of diagnosing the presence or absence of the on-fixation abnormality of the MOSFET 39, which is performed by the microcomputer 27.
The diagnostic process shown in the flowchart of FIG. 2 is executed as an initial process when the microcomputer 27 is powered on.

First, the microcomputer 27 determines whether or not a diagnosis condition is satisfied in step S101.
The microcomputer 27 is, for example, in a diagnostic condition when the voltage of the battery BA (power supply voltage) is within a predetermined voltage range including a standard voltage and is in a voltage stable state in which the elapsed time has exceeded a predetermined time since the power is turned on. Is determined.
Before the start of diagnosis is before the motor 12 starts to be driven, all the MOSFETs 31-36 of the inverter 22 are turned off, and the MOSFETs 39, 40 constituting the power supply relay circuit 25 are also turned off.

When the microcomputer 27 determines that the diagnosis condition is satisfied in step S101, the microcomputer 27 proceeds to step S102, and the operation state (discharge operation state) of the motor drive circuit 21 for discharging the charge accumulated in the capacitor 24 is reached. It is determined whether or not the duration time is longer than the predetermined time TH1.
Here, the microcomputer 27 proceeds from step S102 to step S103 when the discharge operation is not started, and also proceeds from step S102 to step S103 when the duration time of the discharge operation is within the predetermined time TH1.

In step S103, the microcomputer 27 sets the q-axis voltage Vq when the motor 12 is driven by the voltage from the inverter 22 to 0V, and sets the d-axis voltage Vd to a predetermined voltage other than 0V (predetermined voltage> 0V). By controlling the inverter 22 so that the q-axis voltage Vq and the d-axis voltage Vd are applied to the motor 12, the electric charge accumulated in the capacitor 24 is discharged through the winding of the motor 12.
In other words, the microcomputer 27 has a function (discharge means) for operating the switching element of the inverter 22 while the power supply relay circuit 25 is turned off and discharging the electric charge accumulated in the capacitor 24 through the winding of the motor 12. As prepared.

  The motor 12 does not rotate by setting the q-axis voltage Vq to 0V, but by setting the d-axis voltage Vd to a predetermined voltage that is not 0V, the motor 12 stops in two or three phases according to the rotor angle θ. Since the inverter 22 is controlled so that a current flows, and the power supply from the battery BA is cut off by the turning-off operation of the power relay circuit 25, the charge accumulated in the capacitor 24 is turned on. 36 and the motor 12 windings are discharged.

  Here, when the d-axis voltage Vd in the discharge operation state is high, a large current flows through the winding of the motor 12, and when the d-axis voltage Vd in the discharge operation state is low, the current flows through the winding of the motor 12. However, the time required for discharging the electric charge accumulated in the capacitor 24 becomes longer. Therefore, the d-axis voltage Vd in the discharge operation state is adapted as a voltage value that shortens the time for discharge as much as possible while suppressing the current flowing in the winding of the motor 12 within an allowable range. Stored in advance.

The predetermined time TH1 for which the microcomputer 27 continues the discharge operation state is set in advance based on the time expected to be required from the start of discharge of the charge accumulated in the capacitor 24 to the end of discharge. Is remembered.
The microcomputer 27 sets the predetermined time TH1 to a different value according to the capacity of the capacitor 24, the d-axis command voltage Vd at the time of discharge, and the like. Further, the microcomputer 27 can estimate the charge accumulated in the capacitor 24 and change the predetermined time TH1 longer as the charge accumulation amount increases.

The microcomputer 27 discharges the electric charge accumulated in the capacitor 24 as described above, and in step S104, the MOSFETs 31-36 of the inverter 22 are all turned off from the discharge operation state to end the discharge operation state. In this case, it is determined whether or not the condition is that the surge voltage is generated, in other words, whether or not the surge countermeasure processing is required.
The microcomputer 27 is detected by the current detection resistor 38 in a state in which the discharge from the capacitor 24 is expected to be almost completed when the duration of the discharge operation state approaches the predetermined time TH1 (immediately before the discharge operation end timing). When the current flowing through the inverter 22 (the DC bus current of the inverter 22) exceeds a predetermined current value, it is determined that the condition is for generating a surge voltage.

Note that the determination process of the microcomputer 27 in step S104 is to determine whether or not current continues to flow through the windings of the inverter 22 and the motor 12 at the discharge operation end timing. The value is set to a value larger than 0 A considering the variation of the current detection value by the current detection resistor 38.
If the discharge from the capacitor 24 has actually ended and no power is supplied from the battery BA to the motor 12, no large surge voltage is generated even if all the MOSFETs 31-36 of the inverter 22 are turned off.

  The microcomputer 27 holds the MOSFETs 39 and 40 of the power supply relay circuit 25 in the off operation state in the discharging process. However, when the MOSFET 39 is fixed on, the battery BA is connected to the motor 12 via the parasitic diode D14 of the MOSFET 40. Since the electric power is supplied, the current continues to flow to the winding of the motor 12 via the inverter 22 even after the time when the discharge of the electric charge from the capacitor 24 is expected to end. The discharge will not progress.

  When all the MOSFETs 31-36 of the inverter 22 are turned off from the discharge operation state (time t2 in FIG. 3), the parasitic diodes D2, D4, D6 of the MOSFETs 32, 34, 36 are connected to the downstream side of the inverter 22 (the ground point side). ) And current is prevented from flowing to the battery BA side by the parasitic diode D14 of the MOSFET 40 (reverse connection protection relay), so that it was stored in the winding of the motor 12 during the discharging operation. A surge voltage is generated by energy.

  In other words, in the discharge operation state in which the microcomputer 27 discharges the electric charge from the capacitor 24, the state in which the current flows through the windings of the inverter 22 and the motor 12 is longer than the time when the discharge from the capacitor 24 is expected to be almost completed. When continuing for a long time, it can be determined that the power is supplied from the battery BA, that is, the on-fixing abnormality of the MOSFET 39 of the power relay circuit 25 is occurring. Further, the microcomputer 27 can predict that a surge voltage will be generated when the MOSFET 31-36 of the inverter 22 is all turned off as a process for terminating the discharge operation as it is due to the occurrence of the on-fixation abnormality of the MOSFET 39. .

  Note that the microcomputer 27 detects a state in which current continues to flow through the windings of the inverter 22 and the motor 12 (surge voltage generation condition, MOSFET 39 on-fixing abnormality) based on the current detected by the current detection resistor 38. In addition, when the upstream voltage of the inverter 22 detected by the voltage sensor 41 exceeds a predetermined voltage (predetermined voltage> 0 V), a current flows in the inverter 22 and the winding of the motor 12 due to the occurrence of the ON-fixing abnormality of the MOSFET 39. It can be determined that the condition for generating the surge voltage is satisfied.

When the microcomputer 27 determines in step S104 that the surge voltage is generated when the discharge operation is terminated, that is, the power is supplied from the battery BA to the inverter 22 due to the on-fixing abnormality of the MOSFET 39, and the discharge operation is performed. Accordingly, when it is estimated that the current continues to flow through the windings of the inverter 22 and the motor 12, the process proceeds to step S105.
In step S105, the microcomputer 27 determines the occurrence of an on-fixation abnormality for the MOSFET 39, stores a history of detecting the on-fixation abnormality of the MOSFET 39, outputs a diagnostic signal indicating the occurrence of the on-fixation abnormality to the outside, The implementation of fail-safe processing for coping with the on-fixing abnormality of the MOSFET 39 is set.

On the other hand, when the microcomputer 27 determines in step S104 that it is not a condition for generating a surge voltage when the discharge operation is terminated, that is, when the time when the discharge is expected to end has elapsed from the start of the discharge. When no current flows through the winding of the motor 12, it is assumed that the MOSFET 39 is normally turned off and the discharge from the capacitor 24 is normally completed, and a surge countermeasure process described later is performed. This routine is terminated without any processing.
In step S105, the microcomputer 27 detects the on-fixation abnormality of the MOSFET 39, and then proceeds to step S106 where the duration of the operation state (surge countermeasure operation state) of the motor drive circuit 21 for releasing the surge current is a predetermined time TH2. It is judged whether it is longer than.

If the duration of the surge countermeasure operation state is within the predetermined time TH2, the microcomputer 27 proceeds to step S107 (surge countermeasure means) to release the surge current to the battery BA side (power supply side) or the grounding point side. The motor drive circuit 21 is operated.
That is, the microcomputer 27 turns on the MOSFET 39 when the current continues to flow through the windings of the inverter 22 and the motor 12 when the operation for discharging the electric charge accumulated in the capacitor 24 is performed for a predetermined time TH1. When a sticking abnormality is detected and an on-sticking abnormality of the MOSFET 39 is detected, the discharge operation state is shifted to the surge countermeasure operation state, and the surge countermeasure operation state is continued for a predetermined time TH2.

The microcomputer 27 turns on all the MOSFETs 32, 34, and 36 that are downstream drive elements of the inverter 22 to flow a surge current to the ground point side and / or turns on the MOSFET 40 (reverse connection protection relay). By causing the surge current to return to the battery BA side, the surge voltage is suppressed.
Here, as shown in FIG. 4, the microcomputer 27 sets the q-axis voltage Vq to 0V and the d-axis voltage Vd to a predetermined voltage other than 0V as described above, and applies the voltage as a discharging operation. The inverter 22 is PWM-controlled, and at time t2 when a predetermined time TH1 has elapsed from the start of discharge at time t1, the inverter 22 is shifted to PWM control of the inverter 22 in which the q-axis voltage Vq and the d-axis voltage Vd are 0V. MOSFETs 32, 34, and 36, which are downstream drive elements, can be turned on by complementary control.

  When the downstream drive elements of all phases of the inverter 22 are turned on, a surge current flows from the winding of the motor 12 to the grounding point via the downstream drive element and is stored in the winding of the motor 12 during the discharging operation. Surge voltage due to the generated energy is suppressed. When the MOSFET 40 (reverse connection protection relay) is turned on, a surge current is returned from the winding of the motor 12 to the battery BA through the parasitic diodes D1, D3, D5, the MOSFET 40, and the MOSFET 39 of the upstream drive element. The surge voltage caused by the energy stored in the winding of the motor 12 is suppressed.

When the microcomputer 27 diagnoses the on-fixation abnormality of the MOSFET 39, the microcomputer 27 shifts from the discharge operation state to the surge countermeasure operation state described above and continues the surge countermeasure operation state for a predetermined time TH2, so that the generation of the surge voltage is suppressed. It is possible to suppress damage to circuit components such as the capacitor 24 and the MOSFETs 31 to 36 due to the surge voltage.
The microcomputer 27 sets the predetermined time TH2 for continuing the surge countermeasure operation state to a longer time as the energy stored in the winding of the motor 12 during the discharge operation increases. Here, the energy stored in the windings of the motor 12 during the discharging operation changes according to the set value of the d-axis voltage Vd in the discharging operation.

Although the contents of the present invention have been specifically described above with reference to the preferred embodiments, it is obvious that those skilled in the art can take various modifications based on the basic technical idea and teachings of the present invention. is there.
The motor 12 includes a first winding group and a second winding group. The first winding group is driven by the first inverter and the second winding group is driven by the second inverter. In such a system, discharge operation, diagnosis processing, and surge countermeasure operation can be performed for each inverter.

In addition, the diagnosis process by performing the discharge operation is not limited to the configuration that is performed when the power is turned on, and can be performed, for example, when the operation of the apparatus that uses the motor 12 as an electric actuator is stopped.
Further, in the control device (microcomputer 27), when the capacitor 24 is in the discharging state and the MOSFET 39 and the MOSFET 40 of the power supply relay circuit 25 are in the OFF operation state, the voltage between the MOSFET 39 and the MOSFET 40 is higher than the set voltage. When it is high, it is possible to detect an on-fixation abnormality of the MOSFET 39. In other words, according to the diagnostic processing illustrated in the flowchart of FIG. 2, it is possible to diagnose whether or not the MOSFET 39 is on-fixed abnormally while the electric charge is accumulated in the capacitor 24.

Further, a phase relay is provided in each of the drive lines 28U, 28V, 28W of the inverter 22, and the control device (microcomputer 27) turns off the phase relay and detects the battery BA when the on-fixing abnormality of the MOSFET 39 is detected. From being energized to the windings of the motor 12.
Further, the switching element of the motor drive circuit 21 is not limited to the field effect transistor FET, and other semiconductor switching elements such as an IGBT (Insulated Gate Bipolar Transistor) can be employed.

Here, the technical idea that can be understood from the above-described embodiment will be described below.
The motor drive circuit control device, as one aspect thereof, is configured by connecting a switching element to a multiphase bridge, an inverter energizing the windings of the motor, and a power relay circuit connected between the inverter and the power source, And a capacitor connected between a power supply line between the power relay circuit and the inverter and a ground point, and a control device for a motor drive circuit, wherein the power relay circuit is in an off-operation state of the inverter. Discharging means for operating the switching element to discharge the electric charge accumulated in the capacitor through the winding of the motor, and a state in which a current flows through the winding of the motor in a discharging operation state by the discharging means from a predetermined time And a diagnostic means for detecting an on-fixation abnormality of the power relay circuit when the power relay circuit continues for a long time.

  In a preferred aspect of the motor drive circuit control device, the power supply relay circuit includes a first power supply relay comprising a semiconductor switching element having a parasitic diode for conducting a current in a direction from the inverter toward the power supply, and the first power supply. A second power supply relay comprising a semiconductor switching element connected between the relay and the inverter and having a parasitic diode for conducting a current in a direction from the power supply toward the inverter; and the diagnosis means includes the first power supply relay. An operation for detecting an on-fixation abnormality of the power supply relay and releasing a surge current from the discharge operation state by the discharge means to the power supply side or the grounding point side when the diagnosis unit detects an on-fixation abnormality of the first power supply relay A surge countermeasure means for shifting to the state is further included.

In another preferred aspect, the surge countermeasure means turns on the lower switching elements of all phases of the inverter.
In still another preferred aspect, the surge countermeasure means controls the switching element of the inverter so that the q-axis voltage and the d-axis voltage become zero.

In still another preferred aspect, the surge countermeasure means turns on the second power supply relay.
In still another preferred aspect, the surge countermeasure means holds an operation state for suppressing a surge voltage for a predetermined time.
In still another preferred aspect, the discharging means controls the switching element of the inverter so that the q-axis voltage becomes a predetermined voltage which is zero and the d-axis voltage is not zero.

  In addition, a diagnosis method for a motor drive circuit includes a multi-phase bridge connection of switching elements, an inverter for energizing a motor winding, a power relay circuit connected between the inverter and a power source, and the power relay And a capacitor connected between a power supply line between the circuit and the inverter and a ground point, and a diagnosis method for a motor drive circuit, wherein the switching element of the inverter is turned off when the power relay circuit is turned off. A first step of operating and discharging the electric charge accumulated in the capacitor through the winding of the motor, and when a state in which a current flows through the winding of the motor in the discharging operation state continues longer than a predetermined time And a second step of detecting an on-fixing abnormality of the power relay circuit.

  In a preferred aspect of the method for diagnosing the motor drive circuit, the power supply relay circuit includes a first power supply relay including a semiconductor switching element having a parasitic diode for conducting a current in a direction from the inverter toward the power supply, and the first power supply. A second power supply relay comprising a semiconductor switching element connected between the relay and the inverter and having a parasitic diode for conducting a current in a direction from the power source toward the inverter; and the second step includes the second step A first power supply relay on-fixation abnormality is detected, and when the first power supply relay on-fixation abnormality is detected, a third operation is performed to shift from a discharge operation state to an operation state in which a surge current is released to the power supply side or the grounding point side. The method further includes a step.

DESCRIPTION OF SYMBOLS 12 ... Motor, 21 ... Motor drive circuit, 22 ... Inverter, 23 ... Driver, 27 ... Microcomputer (control apparatus), 25 ... Power supply relay circuit, 31-36 ... MOSFET, 39 ... MOSFET (power supply relay, 1st power supply relay) ), 40 ... MOSFET (reverse connection protection relay, second power supply relay), BA ... battery (power supply)

Claims (9)

An inverter configured by connecting switching elements to a multiphase bridge, energizing a winding of a motor, a power relay circuit connected between the inverter and a power source, and a power line between the power relay circuit and the inverter A motor drive circuit control device comprising a capacitor connected between and a grounding point,
Discharging means for operating the switching element of the inverter in an off operation state of the power relay circuit and discharging the electric charge accumulated in the capacitor through the winding of the motor;
A diagnostic means for detecting an on-fixation abnormality of the power relay circuit when a state in which a current flows through the winding of the motor in a discharging operation state by the discharging means continues for a longer time than a predetermined time;
A control device for a motor drive circuit. The power supply relay circuit is connected between a first power supply relay comprising a semiconductor switching element having a parasitic diode for conducting a current in a direction from the inverter toward the power supply, and between the first power supply relay and the inverter, A second power relay comprising a semiconductor switching element having a parasitic diode for conducting a current in a direction from the power source toward the inverter;
The diagnostic means detects an on-fixation abnormality of the first power relay,
When the diagnostic means detects an on-fixation abnormality of the first power supply relay, it further includes surge countermeasure means for shifting from a discharge operation state by the discharge means to an operation state in which a surge current is released to the power supply side or the ground point side The motor drive circuit control device according to claim 1.   The motor drive circuit control device according to claim 2, wherein the surge countermeasure means turns on lower switching elements of all phases of the inverter.   The motor drive circuit control device according to claim 2, wherein the surge countermeasure means controls the switching element of the inverter so that the q-axis voltage and the d-axis voltage become zero.   The motor drive circuit control device according to claim 2, wherein the surge countermeasure means turns on the second power supply relay.   The motor drive circuit control device according to any one of claims 2 to 5, wherein the surge countermeasure means holds an operation state for suppressing a surge voltage for a predetermined time.   7. The motor drive circuit according to claim 1, wherein the discharge unit controls the switching element of the inverter so that the q-axis voltage is zero and the d-axis voltage is a predetermined voltage that is not zero. Control device. An inverter configured by connecting switching elements to a multiphase bridge, energizing a winding of a motor, a power relay circuit connected between the inverter and a power source, and a power line between the power relay circuit and the inverter And a capacitor connected between a ground point and a motor drive circuit comprising a diagnosis method,
A first step of operating the switching element of the inverter in an off operation state of the power relay circuit to discharge the electric charge accumulated in the capacitor through the winding of the motor;
A second step of detecting an on-fixing abnormality of the power relay circuit when a state in which a current flows through the winding of the motor in the discharging operation state continues for a longer time than a predetermined time;
A method for diagnosing a motor drive circuit. The power supply relay circuit is connected between a first power supply relay comprising a semiconductor switching element having a parasitic diode for conducting a current in a direction from the inverter toward the power supply, and between the first power supply relay and the inverter, A second power relay comprising a semiconductor switching element having a parasitic diode for conducting a current in a direction from the power source toward the inverter;
The second step detects an on-fixation abnormality of the first power relay,
And further including a third step of transitioning from a discharge operation state to an operation state in which a surge current is released to the power supply side or the grounding point side when an on-fixation abnormality of the first power supply relay is detected.
The motor drive circuit diagnosis method according to claim 8.