Power supply device and electric power steering device

Abstract

The power supply device includes: a direct-current power supply (13); an inverter (42A, 42B) that supplies electric power from the direct-current power supply; a capacitor (CA1, CA2, CB1, CB2) that is connected in parallel with the inverter between the direct-current power supply and the inverter; a reverse connection protection circuit (44A, 44B) that is connected between the direct-current power supply and the capacitor and that blocks a current flowing from the capacitor to the direct-current power supply in a positive electrode side power line (Lpa) of the direct-current power supply; and an overvoltage protection circuit (45A, 45B) that controls a voltage across the capacitor to be below a prescribed voltage in a case where the voltage across the capacitor becomes above the prescribed voltage.

Description

TECHNICAL FIELD

[0001] The present application relates to a power supply device and an electric power assisted steering device. BACKGROUND

[0002] In the following Patent Literature 1, a power supply device is described, which has a smoothing capacitor that smoothes a voltage after rectification by a rectification circuit, a detection circuit that detects the voltage, and a cut-off circuit that connects the rectification circuit to the smoothing capacitor when the voltage detected by the detection circuit is less than a voltage determination value, and disconnects the rectification circuit from the smoothing capacitor when the voltage detected by the detection circuit is equal to or more than the voltage determination value.

[0003] In the following Patent Literature 2, an overvoltage protection circuit is described, which repeatedly performs charging and discharging of a capacitor by causing a transistor to perform switching operation in accordance with a terminal voltage of the capacitor when a power supply voltage rises above a target value, and limits the terminal voltage to a voltage value between an upper limit value and a lower limit value of a protection set voltage.

[0004] PRIOR ART DOCUMENTS

[0005] PATENT LITERATURE

[0006] Patent Literature 1: Japanese Patent Application Publication No. 2021-061682

[0007] Patent Literature 2: Japanese Patent Application Publication No. 2009-106055 SUMMARY

[0008] PROBLEMS TO BE SOLVED BY THE INVENTION

[0009] In a power supply device that has an inverter supplied with electric power from a direct current power supply, in order to prevent a failure in a case where the polarity of the direct current power supply is erroneously connected in reverse, a reverse connection protection circuit that prevents a current from flowing from the inverter side to the direct current power supply side is sometimes provided between the direct current power supply and the inverter. When a pulse signal is repeatedly applied to a power supply line of such a power supply device, a voltage across a capacitor connected in parallel with the inverter between the direct current power supply and the inverter rises, and becomes a main cause of a capacitor failure. Such application of a pulse signal is performed, for example, by a transient emission test, a voltage withstand pulse test (ISO 7632-2 test).

[0010] By the application of a pulse signal, electric charges repeatedly flow into the capacitor, and the reverse connection protection circuit hinders discharging of the capacitor, so the electric charges gradually accumulate in the capacitor. As a result, the voltage across the capacitor exceeds a withstand voltage and becomes a main cause of a capacitor failure.

[0011] The present application has an object to prevent the voltage across a capacitor connected in parallel with an inverter between a direct-current power supply and the inverter from becoming excessively large even if a pulse signal is repeatedly applied to a power supply line from the direct-current power supply, in a case where a reverse connection protection circuit that blocks current flowing from the inverter side to the direct-current power supply side is provided between the inverter and the direct-current power supply.

[0012] Means for solving the problem

[0013] To achieve the above object, a power supply device of one embodiment of the present application includes a direct-current power supply, an inverter supplied with electric power from the direct-current power supply, a capacitor connected in parallel with the inverter between the direct-current power supply and the inverter, a reverse connection protection circuit connected between the direct-current power supply and the capacitor, which blocks current flowing from the capacitor to the direct-current power supply in a positive electrode side power supply line of the direct-current power supply, and an overvoltage protection circuit that controls the voltage across the capacitor to be lower than a predetermined voltage in a case where the voltage across the capacitor is higher than or equal to the predetermined voltage.

[0014] An electric power assisted steering device of another embodiment of the present application includes the above-described power supply device and an electric motor driven by the inverter of the power supply device, and imparts a steering assist force to a steering system of a vehicle by the electric motor.

[0015] Effects of the Invention

[0016] According to the present application, the voltage across the capacitor connected in parallel with the inverter between the direct-current power supply and the inverter can be prevented from becoming excessively large even if a pulse signal is repeatedly applied to a power supply line from the direct-current power supply. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 is a functional block diagram of a control operation device.

[0018] Figure 2 is a functional block diagram of an electronic control unit (ECU).

[0019] Figure 3 is a functional block diagram of a control operation device.

[0020] Figure 4 (a) and (b) of FIG. 10 are functional block diagrams each showing a first example and a second example of an overvoltage protection circuit.

[0021] Figure 5 is a functional block diagram of an electronic control unit.

[0022] Figure 6 is a functional block diagram of an electronic control unit.

[0023] Figure 7 is a configuration diagram showing an outline of a third modification example of an electronic control unit.

[0024] Figure 8 is a configuration diagram showing an outline of a first modification example of an electric power steering apparatus.

[0025] Figure 9 is a configuration diagram showing an outline of a second modification example of an electric power steering apparatus.

[0026] Figure 10 is a configuration diagram showing an outline of a third modification example of an electric power steering apparatus. DETAILED DESCRIPTION

[0027] With reference to the accompanying drawings, embodiments of the present application are explained in detail.

[0028] In addition, the embodiments of the present application shown below exemplify devices, methods for embodying the technical idea of the present application, but the technical idea of the present application is not limited to the configurations of components, arrangements, and the like described below. The technical idea of the present application can be applied to various modifications within the technical scope defined by the technical solutions recited in the scope of claims.

[0029] (Structure)

[0030] Figure 1 is a configuration diagram showing an outline of an example of an electric power steering (EPS) apparatus of the embodiment. A steering shaft (steering shaft, handle shaft) 2 of a steering wheel (steering handle) 1 is connected to steering wheels 8L, 8R via a reduction gear (worm) 3 constituting a reduction mechanism, universal joints 4a, 4b, a pinion rack mechanism 5, tie rods 6a, 6b, and further via hub units 7a, 7b.

[0031] The pinion rack mechanism 5 has a pinion 5a connected to a pinion shaft that transmits a steering force from the universal joint 4b and a rack 5b engaged with the pinion 5a, and converts rotational motion transmitted to the pinion 5a to linear motion in the vehicle width direction by the rack 5b.

[0032] A torque sensor 10 that detects a steering torque Th is provided at the steering shaft 2. In addition, a steering angle sensor 14 that detects a steering angle θh of the steering wheel 1 is provided at the steering shaft 2.

[0033] In addition, a motor 20 that assists the steering force of the steering wheel 1 is coupled to the steering shaft 2 via a reduction gear 3. The motor 20 can be, for example, a multiphase motor. In the following description, an example of a three-phase motor having a double winding in which first and second system coils are wound in the same motor housing and a rotor common to both systems is rotated by the coils of the two systems will be described, but the motor 20 can also be a motor other than a double winding motor, and the number of phases of the motor 20 can not be three. A plurality of motors 20 that assist the steering force of the steering wheel 1 can also be coupled to the same steering shaft 2.

[0034] Power is supplied from a battery 13 to an electronic control unit (ECU: Electronic Control Unit) 30 that controls the electric power steering apparatus, and an ignition signal is input via an ignition switch 11. The battery 13 and the ECU 30 are examples of the "power supply device" described in the technical solution.

[0035] The ECU 30 performs an operation of a current command value of an assist control command based on the steering torque Th detected by the torque sensor 10, the vehicle speed Vh detected by the vehicle speed sensor 12, and the steering angle θh detected by the steering angle sensor 14, and controls the current supplied to the motor 20 (the A-phase current I1a, the B-phase current I1b, the C-phase current I1c of the first system coil, and the A-phase current I2a, the B-phase current I2b, the C-phase current I2c of the second system coil) by a voltage control command value obtained by applying compensation or the like to the current command value. The ECU 30 is an example of the "motor control device" described in the technical solution.

[0036] Furthermore, the steering angle sensor 14 is not essential, and the steering angle θh can be calculated by adding the torsion angle of the torsion bar of the torque sensor 10 to the product of the gear ratio of the reduction gear 3 and the motor rotation angle θm obtained from a rotation angle sensor 23a that detects the rotation angle of the rotation shaft of the motor 20. The rotation angle sensor 23a can be, for example, a resolver that detects the rotation position of the motor, or a magnetic sensor that detects the magnetic field of a magnet attached to the rotation shaft of the motor 20. In addition, the steering angle of the steering wheels 8L, 8R can be used instead of the steering angle θh. The steering angle can be detected, for example, by detecting the displacement amount of the rack 5b.

[0037] The ECU 30 includes, for example, a computer including a processor and a storage device, and the like, peripheral components. The processor can be, for example, a CPU (Central Processing Unit) or an MPU (Micro-Processing Unit).

[0038] The storage device can be any of a semiconductor storage device, a magnetic storage device, and an optical storage device. The storage device can include a register, a cache memory, a memory such as a ROM (Read Only Memory) and a RAM (Random Access Memory) used as a main storage device, and the like.

[0039] The functions of the ECU 30 described below are realized, for example, by a processor of the ECU 30 executing a computer program stored in a storage device.

[0040] Furthermore, the ECU 30 can also be formed by a dedicated hardware for executing each information processing described below.

[0041] For example, the ECU 30 can include a logic circuit of functionality set in a general semiconductor integrated circuit. For example, the ECU 30 can have a programmable logic device (PLD: Programmable Logic Device) such as a field programmable gate array (FPGA: Field-Programmable Gate Array) or the like.

[0042] Figure 2 is a configuration diagram summarizing an example of the ECU 30 of the embodiment. The ECU 30 is provided with the motor rotation angle detection circuit 23, the control operation device 31a, the first motor current cutoff circuit 33A and the second motor current cutoff circuit 33B, the first gate drive circuit 41A, the second gate drive circuit 41B, the first power conversion circuit 42A, the second power conversion circuit 42B, the first reverse connection protection circuit 44A and the second reverse connection protection circuit 44B, and the overvoltage protection circuit 45A, 45B.

[0043] The power wiring PWa that transmits electric power from the battery 13 via the connector CNT is connected to the ECU 30. The positive side power line Lpa of the power wiring PWa is connected to the control operation device 31a via a noise filter circuit such as an EMC (Electromagnetic Compatibility) filter formed by a choke coil La and ceramic capacitors Cal, Ca2, and is branched at a branching point Pb to be connected to the first reverse connection protection circuit 44A and the second reverse connection protection circuit 44B, respectively.

[0044] One end of the choke coil La is connected to the positive side power line Lpa and one end of the ceramic capacitor Cal, and the other end of the choke coil La is connected to one end of the ceramic capacitor Ca2, the control operation device 31a, and the branching point Pb, and the other ends of the ceramic capacitors Cal, Ca2 are grounded. On the other hand, the negative side line of the power wiring PWa is connected to a ground line of the ECU 30.

[0045] The signals of the steering torque Th detected by the torque sensor 10, the vehicle speed Vh detected by the vehicle speed sensor 12, and the steering angle θh detected by the steering angle sensor 14 are transmitted to the control operation device 31a via the connector CNT.

[0046] The control operation device 31a operates a current command value, which is a control target value of the drive current of the motor 20, based on at least the steering torque Th, and outputs a voltage control command value V1a, V1b, V1c, V2a, V2b, V2c, which is obtained by applying compensation or the like to the current command value, to the first gate drive circuit 41A and the second gate drive circuit 41B. The voltage control command values V1a, V1b, V1c are an A-phase voltage control command value, a B-phase voltage command value, and a C-phase voltage command value of the first system coil, respectively, and the voltage control command values V2a, V2b, V2c are an A-phase voltage control command value, a B-phase voltage command value, and a C-phase voltage command value of the second system coil, respectively.

[0047] The first reverse connection protection circuit 44A includes a field effect transistor (FET) QC that connects or cuts off the positive electrode side power supply line Lpa and the first power conversion circuit 42A. The source of the FET QC is connected to the positive electrode side power supply line Lpa, and the drain is connected to the drains of the FETs Q1, Q3, and Q5 of the first power conversion circuit 42A. The control operation device 31a outputs a control signal SpA that controls the conduction and the cutoff of the first reverse connection protection circuit 44A to the first gate drive circuit 41A. The first gate drive circuit 41A outputs a gate signal of the FET QC according to the control signal SpA, and controls the conduction and the cutoff of the FET QC.

[0048] The anode of the parasitic diode of the FET QC is connected to the positive electrode side power supply line Lpa, and the cathode is connected to the first power conversion circuit 42A, so when the FET QC is cut off, the current flowing through the positive electrode side power supply line from the first power conversion circuit 42A side to the battery 13 side is blocked. As a result, even if the polarity of the battery 13 is connected in reverse by mistake, the first power conversion circuit 42A can be protected from damage.

[0049] Further, the second reverse connection protection circuit 44B has a FET QD that connects or cuts off the positive side power supply line Lpa and the second power conversion circuit 42B. The source of the FET QD is connected to the positive side power supply line Lpa, and the drain is connected to the drains of the FETs Q1, Q3, and Q5 of the second power conversion circuit 42B. The control operation device 31a outputs a control signal SpB that controls the energization and cutoff of the second reverse connection protection circuit 44B to the second gate drive circuit 41B. The second gate drive circuit 41B outputs a gate signal of the FET QD in accordance with the control signal SpB, and controls the on-off of the FET QD.

[0050] The anode of the parasitic diode of the FET QD is connected to the positive side power supply line Lpa, and the cathode is connected to the second power conversion circuit 42B, so when the FET QD is cut off, the current flowing through the positive side power supply line from the first power conversion circuit 42A side to the battery 13 side is blocked. As a result, even if the polarity of the battery 13 is reversely connected by mistake, the second power conversion circuit 42B can be protected from damage.

[0051] The first gate drive circuit 41A forms six gate signals that are pulse width modulated (PWM) based on the voltage control command values V1a, V1b, V1c and the carrier signal of the triangular wave when the voltage control command values V1a, V1b, V1c are input from the control operation device 31a. Further, the gate signals are output to the first power conversion circuit 42A.

[0052] The second gate drive circuit 41B forms six gate signals that are pulse width modulated (PWM) based on the voltage control command values V2a, V2b, V2c and the carrier signal of the triangular wave when the voltage control command values V2a, V2b, V2c are input from the control operation device 31a. Then, the gate signals are output to the second power conversion circuit 42B.

[0053] The first power conversion circuit 42A has an inverter that has three switching arms SWAa, SWAb, and SWAc that are composed of FETs as switching elements, and electrolytic capacitors CA1, CA2.

[0054] The switching arms SWAa, SWAb, and SWAc are connected in parallel to each other. The switching arm SWAa of the A phase has FETs Q1, Q2 connected in series, the switching arm SWAb of the B phase has FETs Q3, Q4 connected in series, and the switching arm SWAc of the C phase has FETs Q5, Q6 connected in series.

[0055] The gate signal output from the first gate drive circuit 41A is input to the gates of the FETs Q1 to Q6, and by this gate signal, the A-phase current Ila, the B-phase current Ilb, and the C-phase current Ile are caused to flow from the connection points between the FETs of the respective switching arms SWAa, SWAb, and SWAc to the A-phase winding, the B-phase winding, and the C-phase winding of the first system coil of the motor 20 via the first motor current interruption circuit 33A.

[0056] The electrolytic capacitors CA1, CA2 have a noise removal function and a power supply assistance function with respect to the first power conversion circuit 42A. The electrolytic capacitors CA1, CA2 may, for example, be hybrid capacitors that employ an electrolyte in which a conductive polymer and an electrolyte are fused.

[0057] The second power conversion circuit 42B has an inverter having three switching arms SWBa, SWBb, SWBc composed of FETs as switching elements, and electrolytic capacitors CB1, CB2.

[0058] The switching arms SWBa, SWBb, and SWBc are connected in parallel to each other. The switching arm SWBa of the A phase has the FETs Q1, Q2 connected in series, the switching arm SWBb of the B phase has the FETs Q3, Q4 connected in series, and the switching arm SWBc of the C phase has the FETs Q5, Q6 connected in series.

[0059] The gate signal output from the second gate drive circuit 41B is input to the gates of the FETs Q1 to Q6, and by this gate signal, the A-phase current I2a, the B-phase current I2b, and the C-phase current I2c are caused to flow from the connection points between the FETs of the respective switching arms SWBa, SWBb, and SWBc to the A-phase winding, the B-phase winding, and the C-phase winding of the second system coil of the motor 20 via the second motor current interruption circuit 33B.

[0060] The electrolytic capacitors CB1, CB2 have a noise removal function and a power supply assistance function with respect to the second power conversion circuit 42B. The electrolytic capacitors CA1, CA2 may, for example, be hybrid capacitors.

[0061] Further, the first power conversion circuit 42A and the second power conversion circuit 42B can be power conversion circuits that supply three-phase currents to two different motors that respectively generate steering assist forces that assist steering of the steering wheel 1. For example, the two different motors can be coupled to the same steering shaft 2 via a reduction gear.

[0062] Current detection circuits 39Al, 39Bl, 39Cl are provided at the source side of each of the FETs Q2, Q4, Q6 of the lower side arms of the switching arms SWAa, SWAb, SWAc that form the first power conversion circuit 42A. The current detection circuits 39Al, 39Bl, 39Cl detect the downstream side currents of the switching arms SWAa, SWAb, SWAc as the A-phase current, B-phase current, C-phase current of the first system coil, respectively, and output their detection values I lad, I lbd, I l cd.

[0063] Current detection circuits 39A2, 39B2, 39C2 are provided at the source side of each of the FETs Q2, Q4, Q6 of the lower side arms of the switching arms SWBa, SWBb, SWBc that form the second power conversion circuit 42B. The current detection circuits 39A2, 39B2, 39C2 detect the downstream side currents of the switching arms SWBa, SWBb, SWBc as the A-phase current, B-phase current, C-phase current of the second system coil, respectively, and output their detection values I2ad, I2bd, I2cd.

[0064] The first motor current cutoff circuit 33A has three FETs QA1, QA2, QA3 for current cutoff. The source of the FET QA1 is connected to the connection point of the FETs Q1, Q2 of the switching arm SWAa of the first power conversion circuit 42A, and the drain is connected to the A-phase winding of the first system coil of the motor 20. The source of the FET QA2 is connected to the connection point of the FETs Q3, Q4 of the switching arm SWAb, and the drain is connected to the B-phase winding of the first system coil. The source of the FET QA3 is connected to the connection point of the FETs Q5, Q6 of the switching arm SWAc, and the drain is connected to the C-phase winding of the first system coil.

[0065] The control operation device 31a outputs a control signal SmA that controls the conduction and cutoff of the first motor current cutoff circuit 33A to the first gate drive circuit 41A. The first gate drive circuit 41A outputs the gate signals of the FETs QA1 to QA3 in accordance with the control signal SmA, and turns on or off the A-phase current I la, B-phase current I lb, C-phase current I lc that flows from the first power conversion circuit 42A to the motor 20.

[0066] The second motor current cutoff circuit 33B has three FETs QB1, QB2, and QB3 for current cutoff. The source of the FET QB1 is connected to the connection point of the FETs Q1 and Q2 of the switching arm SWBa of the second power conversion circuit 42B, and the drain is connected to the A-phase winding of the second system coil of the motor 20. The source of the FET QB2 is connected to the connection point of the FETs Q3 and Q4 of the switching arm SWBb, and the drain is connected to the B-phase winding of the second system coil. The source of the FET QB3 is connected to the connection point of the FETs Q5 and Q6 of the switching arm SWBc, and the drain is connected to the C-phase winding of the second system coil.

[0067] The control operation device 31a outputs a control signal SmB that controls energization and cutoff of the second motor current cutoff circuit 33B to the second gate drive circuit 41B. The second gate drive circuit 41B outputs gate signals of the FETs QB1 to QB3 in accordance with the control signal SmB, and turns on or off the A-phase current I2a, the B-phase current I2b, and the C-phase current I2c flowing from the second power conversion circuit 42B to the motor 20.

[0068] The motor rotation angle detection circuit 23 acquires a detection value from the rotation angle sensor 23a, and detects a motor rotation angle θm that is the rotation angle of the rotation shaft of the motor 20. The motor rotation angle detection circuit 23 outputs the motor rotation angle θm to the control operation device 31a.

[0069] The control operation device 31a acquires detection values I1ad, I1bd, and I1cd of the A-phase current, the B-phase current, and the C-phase current of the first system coil, and detection values I2ad, I2bd, and I2cd of the A-phase current, the B-phase current, and the C-phase current of the second system coil, via an A / D conversion section not shown.

[0070] Figure 3 is a block diagram of an example of the functional structure of the control operation device 31a. Furthermore, only the functional structure of the coil of the first system that drives the motor 20 is described in Figure 3 , but the functional structure of the coil of the second system also has the same structure.

[0071] The control operation device 31a has a current command value operation section 60, subtractors 62 and 63, a current limit section 64, a proportional-integral (PI) control section 65, a two-phase / three-phase conversion section 66, a three-phase / two-phase conversion section 67, and an angular velocity conversion section 68, and drives the motor 20 by vector control.

[0072] The current command value operation section 60 operates the q-axis current command value Iq and the d-axis current command value Id to be supplied to the motor 20, based on the steering torque Th, the vehicle speed Vh, the motor rotation angle θm of the motor 20, and the rotation angular velocity ω of the motor 20.

[0073] On the other hand, the detection values I1ad, I1bd, I1cd of the A-phase current, the B-phase current, and the C-phase current of the first system coil of the motor 20 detected by the current detection circuits 39A1, 39B1, 39C1 are converted into the d-q2-axis currents id, iq by the three-phase / two-phase conversion section 67.

[0074] The subtractors 62, 63 calculate the q-axis deviation current Δq0 and the d-axis deviation current Δd0 by subtracting the fed-back currents iq, id from the q-axis current command value Iq and the d-axis current command value Id, respectively.

[0075] The current limiter 64 limits the upper limit values of the q-axis deviation current Δq0 and the d-axis deviation current Δd0. The limited q-axis deviation current Δq and the d-axis deviation current Δd are input to the PI control section 65.

[0076] The PI control section 65 calculates the voltage command values vq, vd that make the q-axis deviation current Δq and the d-axis deviation current Δd zero, respectively. The two-phase / three-phase conversion section 66 converts the voltage command values vd, vq into the A-phase voltage command value V1a, the B-phase voltage command value V1b, and the C-phase voltage command value V1c of the first system of the motor 20, respectively, and outputs them to the first gate drive circuit 41A.

[0077] The angular velocity conversion section 68 calculates the rotation angular velocity ω of the motor 20 based on the time change of the motor rotation angle θm. These motor rotation angle θm and rotation angular velocity ω are input to the current command value operation section 60 and used for vector control.

[0078] Referring again to Figure 2 The overvoltage protection circuit 45A is connected in parallel to the first reverse connection protection circuit 44A to the connection points Pca1 and Pca2. The connection point Pca1 is a point at which the first reverse connection protection circuit 44A is connected to the positive electrode side power supply line Lpa, and the connection point Pca2 is a point at which the first reverse connection protection circuit 44A is connected to the electrolytic capacitors CA1, CA2.

[0079] The overvoltage protection circuit 45A prevents the voltage across the electrolytic capacitors CA1, CA2 from becoming excessively large, for example, from becoming above the withstand voltage of the electrolytic capacitors CA1, CA2, in a state in which the FET QC of the first reverse connection protection circuit 44A is off and a pulse signal is repeatedly applied to the positive electrode side power supply line Lpa.

[0080] The application of such an impulse signal is performed, for example, by a transient emission test, a voltage withstand pulse test (ISO 7632-2 test). The ISO 7632-2 test is sometimes implemented in both the on state and the off state of the FET QC of the first reverse connection protection circuit 44A.

[0081] As shown in the circuit structure as shown in Figure 2 In the case where no rectifying element that prevents current from flowing from the battery 13 side to the electrolytic capacitors CA1, CA2 side of the positive electrode side power supply line Lpa is present, if an impulse signal is applied to the positive electrode side power supply line Lpa, in the case where the FET QC of the first reverse connection protection circuit 44A is on, charge flows into the electrolytic capacitors CA1, CA2 via the channel of the FET QC, and in the case where the FET QC is off, charge flows into the electrolytic capacitors CA1, CA2 via the parasitic diode.

[0082] At this time, in the case where the FET QC is off, the parasitic diode of the FET QC hinders discharge of the electrolytic capacitors CA1, CA2. As a result, charge gradually accumulates in the electrolytic capacitors CA1, CA2. Thus, when the voltage across the electrolytic capacitors CA1, CA2 exceeds the withstand voltage, this becomes a main cause of failure of the electrolytic capacitors CA1, CA2.

[0083] Therefore, in the case where the voltage VR across the electrolytic capacitors CA1, CA2 is equal to or greater than a prescribed voltage, the overvoltage protection circuit 45A controls the voltage VR across the electrolytic capacitors CA1, CA2 to be equal to or less than the prescribed voltage. For example, the overvoltage protection circuit 45A can be a discharge circuit that, in the case where the voltage VR across the electrolytic capacitors CA1, CA2 is equal to or greater than a prescribed voltage, discharges the charge accumulated in the electrolytic capacitors CA1, CA2 to control the voltage VR across the electrolytic capacitors CA1, CA2 to be equal to or less than the prescribed voltage.

[0084] Likewise, the overvoltage protection circuit 45B is connected in parallel to the second reverse connection protection circuit 44B at the connection points Pcb1 and Pcb2. The connection point Pcb1 is a point at which the second reverse connection protection circuit 44B is connected to the positive electrode side power supply line Lpa side, and the connection point Pcb2 is a point at which the second reverse connection protection circuit 44B is connected to the electrolytic capacitors CB1, CB2 side.

[0085] In the case where an impulse signal is repeatedly applied to the positive electrode side power supply line Lpa in the state where the FET QD of the second reverse connection protection circuit 44B is off, the overvoltage protection circuit 45B prevents the voltage across the electrolytic capacitors CB1, CB2 from becoming excessively large.

[0086] Figure 4 (a) and Figure 4(b) of FIG. 10 is a structural view showing an outline of a first example and a second example of the overvoltage protection circuit 45B. The overvoltage protection circuit 45B can also have the same structure as the overvoltage protection circuit 45A.

[0087] Referring to Figure 4 (a) of FIG. 10. The overvoltage protection circuit 45A includes a P-channel FET Q10 as a switching element connected between the connection point Pca2 and the ground line to connect or cut off the connection point Pca2 and the ground line, and a discharge resistor R1 connected in series between the FET Q10 and the ground line. A gate electrode as a control electrode of the FET Q10 is connected to the connection point Pca1. A source electrode as a first main electrode of the FET Q10 is connected to the connection point Pca2. A drain electrode as a second main electrode of the FET Q10 is connected to the ground line via the discharge resistor R1. A Zener diode Z can be connected between the gate electrode and the source electrode of the FET Q10, which protects so that a gate-source voltage does not exceed a withstand voltage. In addition, a protection resistor R2 can be connected between the gate electrode of the FET Q10 and the connection point Pca1.

[0088] Referring to Figure 4 (b) of FIG. 10. Figure 4 The overvoltage protection circuit 45A of (b) of FIG. 10 has a PNP transistor Q20 as a switching element connected between the connection point Pca2 and the ground line to connect or cut off the connection point Pca2 and the ground line. The discharge resistor R1 is connected in series between the transistor Q20 and the ground line. A base electrode as a control electrode of the transistor Q20 is connected to the connection point Pca1. An emitter electrode as a first main electrode of the transistor Q20 is connected to the connection point Pca2. A collector electrode as a second main electrode of the transistor Q20 is connected to the ground line via the discharge resistor R1. A Zener diode Z can be connected between the base electrode and the emitter electrode of the transistor Q20, which protects so that a base-emitter voltage does not exceed a withstand voltage. In addition, a protection resistor R2 can be connected between the base electrode of the FET Q20 and the connection point Pca1.

[0089] Hereinafter, an example of the operation of the overvoltage protection circuit 45A in a case where a pulse signal is repeatedly applied to the positive-side power line Lpa in a state where the FET QC of the first reverse connection protection circuit 44A is cut off (for example, in a case where an ISO 7632-2 test is performed) will be described.

[0090] First, in an initial state before the application of the pulse signal, the FET QC of the first reverse connection protection circuit 44A is controlled to be off. In this state, the battery voltage VBAT of the battery 13, the power supply voltage VBATSYS at the output of the noise filter circuit (the connection point between the choke coil La and the ceramic capacitor Ca2), and the voltage VR across the electrolytic capacitors CA1, CA2 are equal. The values of VBAT, VBATSYS, and VR in the initial state are denoted as "initial value Vo".

[0091] Thereafter, when the pulse signal for testing is applied to the power supply wiring PWa, the battery voltage VBAT and the power supply voltage VBATSYS fluctuate due to the pulse signal. In addition, the voltage variation of the power supply voltage VBATSYS is smaller than that of the battery voltage VBAT due to the influence of the load of the noise filter circuit, the control operation device 31a, and the like.

[0092] Due to the voltage fluctuation of the power supply voltage VBATSYS, charges are accumulated in the electrolytic capacitors CA1, CA2 via the parasitic diode of the FET QC of the first reverse connection protection circuit 44A. As a result, when the application of one pulse signal ends, the battery voltage VBAT and the power supply voltage VBATSYS return to the initial value Vo, but the voltage VR across the electrolytic capacitors CA1, CA2 becomes higher than the initial value Vo. Therefore, when the pulse signal is repeatedly applied, the voltage VR gradually rises.

[0093] Thereafter, by applying the pulse signal, the voltage VR continues to rise, and the sum of the negative gate threshold voltage Vth (<0) of the FET Q10 and the voltage VR becomes higher than the power supply voltage VBATSYS (VR + Vth > VBATSYS). Alternatively, the voltage VR is higher than the sum of the threshold voltage Vth between the base and the emitter of the transistor Q20 and the power supply voltage VBATSYS.

[0094] Then, the FET Q10 or the transistor Q20 becomes in the on state, and the charges of the electrolytic capacitors CA1, CA2 flow to the ground line via the FET Q10 or the transistor Q20, the discharge resistor Rl, and the electrolytic capacitors CA1, CA2 are discharged. Thus, the voltage VR is reduced. That is, when the voltage between the connection point Pcal and the connection point Pca2 becomes the absolute value |Vth| or more of the threshold voltage of the FET Q10 or the transistor Q20, the overvoltage protection circuit 45A discharges the electrolytic capacitors CA1, CA2.

[0095] After that, when the sum of the threshold voltage Vth of the gate of the FET Q10 and the voltage VR across both terminals becomes lower than the power supply voltage VBATSYS (VR + Vth ≤ VBATSYS), the FET Q10 is turned off. Alternatively, when the voltage VR across both terminals becomes lower than the sum of the threshold voltage Vth of the transistor Q20 and the power supply voltage VBATSYS, the FET Q10 is turned off. Thus, the discharging of the electrolytic capacitors CA1, CA2 ends.

[0096] Thereafter, with the application of the pulse signal, the FET Q10 or the transistor Q20 repeatedly turns on and off, and thus the voltage VR across both terminals is stabilized at a value that is the sum of the power supply voltage VBATSYS and the absolute value |Vth| of the threshold voltage. That is, when the voltage between the connection point Pca1 and the connection point Pca2 becomes equal to or higher than the absolute value |Vth| of the threshold voltage of the FET Q10 or the transistor Q20, the overvoltage protection circuit 45A controls the voltage VR across both terminals to be lower than the sum of the power supply voltage VBATSYS and the absolute value |Vth| of the threshold voltage. Thus, it is possible to prevent the voltage VR across both terminals of the electrolytic capacitors CA1, CA2 from becoming excessively large (e.g., exceeding the withstand voltage of the electrolytic capacitors CA1, CA2).

[0097] (Modified example)

[0098] (1) Figure 5 is a configuration diagram that shows an outline of a first modified example of the ECU 30. The electric power steering apparatus can also be provided with, as the battery 13, a first battery that supplies electric power to the first electric power conversion circuit 42A via the first electric power wiring PWa and a second battery that supplies electric power to the second electric power conversion circuit 42B via the second electric power wiring PWb, respectively.

[0099] The positive-side power supply line Lpa of the first electric power wiring PWa is connected to the control arithmetic device 31a via a noise filter circuit formed by the choke coil La and the ceramic capacitors Ca1, Ca2, and is connected to the first reverse connection protection circuit 44A.

[0100] The positive-side power supply line Lpb of the second electric power wiring PWb is connected to the control arithmetic device 31b via a noise filter circuit formed by the choke coil Lb and the ceramic capacitors Cb1, Cb2, and is connected to the second reverse connection protection circuit 44B.

[0101] One end of the choke coil Lb is connected to the positive-side power supply line Lpb and one end of the ceramic capacitor Cb1, and the other end of the choke coil Lb is connected to one end of the ceramic capacitor Cb2 and the control arithmetic device 31b, and the other ends of the ceramic capacitors Cb1, Cb2 are grounded. On the other hand, the negative-side line of the second electric power wiring PWb is connected to the ground line of the ECU 30.

[0102] The signals of the steering torque Th detected by the torque sensor 10, the vehicle speed Vh detected by the vehicle speed sensor 12, and the steering angle θh detected by the steering angle sensor 14 are transmitted to the control operation devices 31a, 31b via the connector CNT.

[0103] The control operation device 31a operates a current command value, which is a control target value of the drive current of the motor 20, based on at least the steering torque Th, and outputs a voltage control command value V1a, V1b, V1c, which is obtained by applying compensation or the like to the current command value, to the first gate drive circuit 41A. In addition, a control signal SpA that controls the first reverse connection protection circuit 44A and a control signal SmA that controls the first motor current cutoff circuit 33A are generated and output to the first gate drive circuit 41A.

[0104] The control operation device 31b operates a current command value, which is a control target value of the drive current of the motor 20, based on at least the steering torque Th, and outputs a voltage control command value V2a, V2b, V2c, which is obtained by applying compensation or the like to the current command value, to the second gate drive circuit 41B. In addition, a control signal SpB that controls the second reverse connection protection circuit 44B and a control signal SmB that controls the second motor current cutoff circuit 33B are generated and output to the second gate drive circuit 41B.

[0105] Further, it can also be configured that the control operation device 31a and the control operation device 31b are combined into a single control operation device, and the power is supplied from the positive side power line Lpa of the first power wiring PWa or the positive side power line Lpb of the second power wiring PWb.

[0106] (2) Figure 6 is a structure diagram that shows an outline of a second modification example of the ECU 30. The second modification example of the ECU 30 combines the first reverse connection protection circuit 44A and the second reverse connection protection circuit 44B to have a single first reverse connection protection circuit 44A. The positive side power line Lpa of the power wiring PWa is branched between the first reverse connection protection circuit 44A and the first gate drive circuit 41A, and connected to the first gate drive circuit 41A and the second gate drive circuit 41B, respectively.

[0107] The overvoltage protection circuit 45A, which prevents the both-end voltage VR of the electrolytic capacitor CA1, CA2, CB1, CB2 from becoming excessively large, is connected in parallel to the first reverse connection protection circuit 44A. That is, the number of overvoltage protection circuits can be the same as the number of reverse connection protection circuits.

[0108] (3) Figure 7 is a structure diagram that shows an outline of a third modification example of the ECU 30. The third modification example of the ECU 30 drives the motor 20 by a single inverter. Therefore, only theFigure 2 The first motor current cutoff circuit 33A and the second motor current cutoff circuit 33B, the first gate drive circuit 41A and the second gate drive circuit 41B, the first power conversion circuit 42A and the second power conversion circuit 42B, the first reverse connection protection circuit 44A and the second reverse connection protection circuit 44B, the first overvoltage protection circuit 45A among the first motor current cutoff circuit 33A, the first gate drive circuit 41A, the first power conversion circuit 42A, the first reverse connection protection circuit 44A, and the overvoltage protection circuit 45A included in the structure shown.

[0109] (4) In the above description, an example in which the rotation angle detection device of the present application is applied to an electric power steering device of a column assist type called a so-called upstream assist type is described, but the rotation angle detection device of the present application can also be applied to an electric power steering device of a so-called downstream assist type. Hereinafter, as an example of the electric power steering device of the downstream assist type, a structure example in which the rotation angle detection device of the present application is applied to an electric power steering device of a single pinion assist type, a rack assist type, and a double pinion assist type will be described.

[0110] Further, in the case of the downstream assist type, in order to prevent a waterproof countermeasure, the motor 20, the rotation angle sensor 23a, and the ECU 30 can not be separate bodies, but can be an MCU (Motor Control Unit) of an integrated structure as shown by a dotted line in FIG. 1. Figures 8-10

[0111] Figure 8 A structure example in which the rotation angle detection device of the present application is applied to an electric power steering device of a single pinion assist type is shown. The steering wheel 1 is connected to one of the universal joints 4a of the intermediate shaft via the steering shaft 2. In addition, the input side shaft 4c of the torsion bar (not shown) is connected to the other universal joint 4b.

[0112] The pinion rack mechanism 5 is provided with a pinion (secondary gear) 5a, a rack bar (rack) 5b, and a pinion shaft 5c. The input side shaft 4c and the pinion rack mechanism 5 are connected by a torsion bar (not shown) that twists due to a difference in the rotation angle between the input side shaft 4c and the pinion rack mechanism 5. The torque sensor 10 electromagnetically measures the twist angle of the torsion bar as the steering torque Th of the steering wheel 1.

[0113] The motor 20 that assists the steering force of the steering wheel 1 is connected to the pinion shaft 5c via the reduction gear 3, and the rotation angle sensor 23a calculates the rotation angle information of the motor rotation shaft of the motor 20 as in the above embodiment.

[0114] (5) Figure 9 ​A configuration example of applying the rotation angle detection device of the present application to an electric power assisted steering device of a rack assist type is shown. A helical groove (not shown) is formed on the outer peripheral surface of the rack bar 5b, and a helical groove (not shown) of the same lead is also formed on the inner peripheral surface of the nut 81. A ball screw is formed by arranging a plurality of rolling bodies in the rolling path formed by these helical grooves.

[0115] A belt 84 is wound around a drive pulley 82 coupled to the rotation shaft 20a of the motor 20 that assists the steering force of the steering wheel 1 and a driven pulley 83 coupled to the nut 81, and the rotational motion of the rotation shaft 20a is converted into the straight motion of the rack bar 5b. The rotation angle sensor 23a calculates the rotation angle information of the motor rotation shaft of the motor 20 as in the above embodiment.

[0116] (6) Figure 10 A configuration example of applying the rotation angle detection device of the present application to an electric power assisted steering device of a double pinion assist type is shown. The electric power assisted steering device of the double pinion assist type has, in addition to the pinion shaft 5c and the pinion 5a, a second pinion shaft 85 and a second pinion 86, and the rack bar 5b has first rack teeth (not shown) that mesh with the pinion 5a and second rack teeth (not shown) that mesh with the second pinion 86.

[0117] The second pinion shaft 85 is coupled to the motor 20 that assists the steering force of the steering wheel 1 via the reduction gear 3, and the rotation angle sensor 23a calculates the rotation angle information of the motor rotation shaft of the motor 20 as in the above embodiment.

[0118] (EFFECTS OF THE EMBODIMENTS)

[0119] (1) The power supply device of the embodiment has: a direct current power supply; an inverter that supplies electric power from the direct current power supply; a capacitor that is connected in parallel with the inverter between the direct current power supply and the inverter; a reverse connection protection circuit that is connected between the direct current power supply and the capacitor and that blocks electric current flowing from the capacitor to the direct current power supply in the positive electrode side power supply line of the direct current power supply; and an overvoltage protection circuit that controls the voltage across the capacitor to be below a prescribed voltage in the case where the voltage across the capacitor becomes above the prescribed voltage.

[0120] Thus, in the power supply device provided with the reverse connection protection circuit that blocks electric current flowing from the inverter side to the direct current power supply side, even if a pulse signal is repeatedly applied to the power supply line, it is possible to prevent the voltage across the capacitor connected in parallel with the inverter from becoming excessively large.

[0121] Therefore, as the capacitor connected in parallel with the inverter, a capacitor with a lower withstand voltage can be used. A capacitor with a low withstand voltage has a large electrostatic capacity compared with a capacitor with a high withstand voltage, and therefore the number of capacitors required to ensure the same capacity can be reduced. Thus, the number of components, cost, and mounting area can be reduced.

[0122] (2) The overvoltage protection circuit can be a circuit that controls the voltage across both terminals to be below a prescribed voltage in a case where the voltage between the connection point of the reverse connection protection circuit and the DC power supply and the connection point of the reverse connection protection circuit and the capacitor becomes above a threshold value. Thus, the voltage across both terminals of the capacitor can be prevented from becoming excessively large.

[0123] (3) The overvoltage protection circuit can be a switching element provided between the positive electrode of the capacitor and the ground line and turned on in a case where the voltage across both terminals of the capacitor becomes above a prescribed voltage. For example, the switching element can be a P-channel field effect transistor or a PNP transistor. Thus, the overvoltage protection circuit can be implemented with a simple structure.

[0124] (4) The control terminal of the switching element can be connected to the connection point of the reverse connection protection circuit to the DC power supply, the first main electrode of the switching element can be connected to the connection point of the reverse connection protection circuit to the capacitor, and the second main electrode of the switching element can be connected to the ground line via a discharge resistor. Thus, the switching element can be controlled to be turned on or off in accordance with the voltage across both terminals of the capacitor.

[0125] (5) The prescribed voltage can be less than the withstand voltage of the capacitor. Thus, the main cause of failure of the capacitor due to the voltage across both terminals of the capacitor exceeding the withstand voltage can be avoided.

[0126] (6) The capacitor can be, for example, a hybrid capacitor. Thus, the mounting area of the capacitor can be further reduced.

[0127] (7) A rectifying element that blocks current flowing from the DC power supply to the capacitor in the positive electrode side power line of the DC power supply can not be provided. Even if such a rectifying element is not provided, the voltage across both terminals of the capacitor can be prevented from becoming excessively large by the overvoltage protection circuit. For example, a switching element including a parasitic diode that blocks current flowing from the DC power supply to the capacitor in the positive electrode side power line can not be provided.

[0128] Explanation of Reference Signs

[0129] 1 steering wheel, 2 steering shaft, 3 reduction gear, 4a, 4b universal joint, 4c input side shaft, 5 pinion rack mechanism, 5a pinion (secondary gear), 5b rack bar (rack), 5c pinion shaft, 6a, 6b tie rod, 7a, 7b hub unit, 8L, 8R steering wheel, 10 torque sensor, 11 ignition switch, 12 vehicle speed sensor, 13 battery, 14 steering angle sensor, 20 motor, 23 motor rotation angle detection circuit, 30 electronic control unit (ECU), 31a, 31b control arithmetic device, 33A first motor current cutoff circuit, 33B second motor current cutoff circuit, 39A1, 39A2, 39B1, 39B2, 39C1, 39C2 current detection circuit, 41A first gate drive circuit, 41B second gate drive circuit, 42A first electric power conversion circuit, 42B second electric power conversion circuit, 44A first reverse connection protection circuit, 44B second reverse connection protection circuit, 45A, 45B overvoltage protection circuit, 60 current command value arithmetic portion, 62, 63 subtracter, 64 current limiter, 65 PI control portion, 66 two-phase / three-phase conversion portion, 67 three-phase / two-phase conversion portion, 68 angular velocity conversion portion, 81 nut, 82 drive pulley, 83 driven pulley, 84 belt, 85 second pinion shaft, 86 second pinion.

Claims

1. A power supply device characterized by comprising: The power supply device includes: a direct-current power supply; an inverter supplied with electric power from the direct-current power supply; a capacitor connected in parallel with the inverter between the direct-current power supply and the inverter; a reverse connection protection circuit connected between the direct-current power supply and the capacitor, which blocks a current flowing from the capacitor to the direct-current power supply in a positive electrode side power line of the direct-current power supply; and an overvoltage protection circuit that controls a voltage across the capacitor to be below a predetermined voltage in a case where the voltage across the capacitor is above the predetermined voltage, the overvoltage protection circuit controls the voltage across the capacitor to be below the predetermined voltage in a case where a voltage between a connection point at which the reverse connection protection circuit is connected to the direct-current power supply and a connection point at which the reverse connection protection circuit is connected to the capacitor is above a threshold value.

2. The power supply device according to claim 1, wherein the overvoltage protection circuit includes a switching element provided between a positive electrode of the capacitor and a ground line, which is turned on in a case where the voltage across the capacitor is above the predetermined voltage.

3. The power supply device according to claim 2, wherein the switching element is a P-channel type field effect transistor.

4. The power supply device according to claim 2, wherein the switching element is a PNP type transistor.

5. The power supply device according to claim 2, wherein a control terminal of the switching element is connected to the connection point at which the reverse connection protection circuit is connected to the direct-current power supply, a first main electrode of the switching element is connected to the connection point at which the reverse connection protection circuit is connected to the capacitor, and a second main electrode of the switching element is connected to the ground line via a discharge resistor.

6. The power supply device according to claim 1, wherein the predetermined voltage is smaller than an electric voltage resistance of the capacitor.

7. The power supply device according to claim 1, wherein the capacitor is a hybrid capacitor.

8. The power supply device according to claim 1, wherein a rectifying element that blocks a current flowing from the direct-current power supply to the capacitor in the positive electrode side power line of the direct-current power supply is not provided. The electric power assisted steering device includes:

9. An electric power steering apparatus characterized by comprising: the power supply device according to any one of claims 1 to 8; and an electric motor driven by the inverter of the power supply device, the electric motor imparts a steering assist force to a steering system of a vehicle. The electric power assisted steering device includes: the power supply device according to any one of claims 1 to 8; and an electric motor driven by the inverter of the power supply device, the electric motor imparts a steering assist force to a steering system of a vehicle.

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