Motor driver device

Abstract

Motor driver device comprising: an inverter circuit (1) for supplying current to an electric motor (M), a power supply relay (5, 17) provided on a power supply line (13) for supplying current from a power supply (14) to the inverter circuit (1), a phase relay (3U, 3V, 3W) provided on a driver line (11U, 11V, 11W) between the inverter circuit (1) and the electric motor (M) and formed by a semiconductor switching element, a driver circuit (8) connected to the phase relay (3U, 3V, 3W) and the power supply relay (5, 17) to drive the phase relay (3U, 3V, 3W) and the power supply relay (5, 17), a first control line (15) connecting the driver circuit (8) to the phase relay (3U, 3V, 3W), a first overvoltage protection device (4U, 4V, 4W, 4Ua, 4Va, 4Wa), which are located at a position between a motor-side conductor section of the driver line (11U, 11V,11W) between the electric motor (M) and the phase relay (3U, 3V, 3W) and the first control line (15) is provided and configured to protect the phase relay (3U, 3V, 3W) from overvoltage; a first current reduction device (19, 19U, 19V, 19W, 4Ub, 4Vb, 4Wb) to reduce leakage current flowing from the electric motor (M) into the first control line (15); a second control line (16) connecting the driver circuit (8) to the power supply relay (5, 17); a charge accumulation device (21) provided on an inverter-side line section of the power supply line (13) between the inverter circuit (1) and the power supply relay (5, 17); a second overvoltage protection device (18) connected to a position between the second control line (16) and the is connected to the inverter-side line section, and a second current reduction device (20) for reducing a leakage current,which flows from the charge accumulation device (21) into the second control line (16).

Description

Background of the invention 1. Field of invention The present invention relates to a motor driver device for driving an electric motor and in particular to a motor driver device with a driver circuit for driving a power supply relay and a phase relay, which provide a fail-safe function. 2. Description of the state of the art The Japanese patent application, publication number 2011-244611, describes a motor driver device using a pulse width modulation (PWM) control method. This motor driver device comprises an inverter circuit driven by a PWM signal with a predetermined duty cycle and a fail-safe circuit located between the inverter circuit and a motor. The inverter circuit is formed by a so-called three-phase bridge, in which each switching element performs an on / off operation in accordance with the PWM signal to supply a drive voltage from the inverter circuit, through the fail-safe circuit, to each phase of the motor. If, for example, an abnormality occurs, the fail-safe circuit interrupts the power supply from the inverter circuit to the motor to stop the motor, thus performing a fail-safe function. The switching elements of the inverter circuit and the fail-safe circuit can, for example, be N-channel MOSFETs. In the motor driver device of the aforementioned patent document, the MOSFETs of the fail-safe circuit are each individually switched ON / OFF by a fail-safe driver unit. A mechanical relay is used as the power supply relay, which is controlled to open / close by a control unit. The patent document states that a semiconductor switching element can be used instead of the mechanical relay, but the circuit design is based on the use of a mechanical switch, which is controlled separately from the MOSFETs of the fail-safe circuit. However, if the MOSFETs of the failover circuit are configured for individual ON / OFF control, the circuit design of the failover circuit becomes complex. And because the failover driver circuit is separate from the control unit, the problem arises that the number of components is larger, making cost savings difficult to achieve. German patent application DE 198 42 438 A1 describes a driver unit for an electric motor with two motor driver circuits arranged in parallel, each comprising a bridge circuit consisting of switching devices. A power switch is provided between each bridge circuit and a power supply. Furthermore, a function switch is provided between each bridge circuit and the motor. The two bridge circuits are configured to provide redundancy when driving the electric motor. The arrangement is also designed to prevent the motor from operating as a generator in the event of a faulty bridge circuit. US patent application US 2011 / 0285335A1 describes a motor driver device comprising an inverter circuit, a fail-safe circuit located between the inverter circuit and the motor, and a fail-safe driver unit for outputting a control signal to a semiconductor switching element of the fail-safe circuit. A power supply circuit is connected to the inverter circuit via an inverter driver unit comprising an amplifier circuit and a driver circuit. A relay is provided within the power supply circuit, between a power source and the inverter driver circuit. A grounded capacitor is located between the relay and the inverter driver circuit. The German patent application DE 102 57 453 A1 describes a driver circuit, in particular for an electric motor, with a transistor-based inverter. The German patent application DE 197 02 136 A1 describes an electronic circuit breaker with an N-channel power MOSFET. The US patent application with publication number US 2007 / 0268048A1 describes a control circuit for a power supply, wherein a MOSFET is arranged between a DC power supply and a load circuit, such that the body diode is arranged between drain and source in the forward direction. The US patent application with publication number US 2013 / 0 015 797 A1 describes an electronic control circuit for a vehicle with an integrated semiconductor circuit and a microcomputer. Summary of the invention It is an object of the present invention to provide a motor driver device which can achieve a simplification of the circuit design, a reduction in the number of components and a resulting cost reduction. This problem is solved by a motor driver device according to claim 1. Other tasks and features of various aspects of the present invention are clarified by the following description with reference to the accompanying drawings. Brief description of the drawings Fig. 1 is a circuit view showing a motor driver device according to a first embodiment of the present invention. Fig. 2 is a circuit view showing a motor driver device according to a second embodiment of the present invention. Fig. 3 is a circuit view showing a motor driver device according to a third embodiment of the present invention. Fig. 4 is a circuit view showing a first modification of the motor driver device of Fig. 3. Fig. 5 is a circuit view showing a second modification of the motor driver device of Fig. 3. Fig. 6 is a schematic view showing a design example of an EPS system with a power steering motor to which the motor driver device according to an embodiment of the present invention is applied. Description of preferred embodiments Fig. 1 is a circuit diagram showing a motor driver device according to a first embodiment of the present invention. This motor driver device comprises an inverter circuit 1 for driving an electric motor (a three-phase motor in this example) M, an inverter driver circuit 2 for controlling the inverter circuit 1, phase relays 3U, 3V and 3W, Zener diodes 4U, 4V and 4W for overvoltage protection, a power supply relay 5, a power supply IC 6, a microcomputer 7 serving as a control unit, a driver circuit 8 with a discrete structure, an amplification circuit 9, a switch 10, etc. Inverter circuit 1 contains three sets of switching elements, each for driving the U, V, and W phases of the electric motor M via driver lines 11U, 11V, and 11W, respectively. In this example, the switching elements are formed by N-channel MOSFETs 1UH, 1UL, 1VH, 1VL, 1WH, and 1WL. MOSFETs 1UH and 1UL are connected in series between a power supply line 13, which supplies current from a power source such as a battery 14, and a ground point, so that their drain-source current paths are connected in series, with their junction point also connected to one end of a driver line 11U. MOSFETs 1VH and 1VL are connected in series between the power supply line 13 and a ground point, so that their drain-source current paths are connected in series, with their junction point also connected to one end of a driver line 11V.The MOSFETs 1WH and 1WL are connected in series between the power supply line 13 and an earth point, so that their drain-source current paths are connected in series, with their connection point still connected to one end of a driver line 11W. The inverter driver circuit 2 comprises high-side (H-side) drivers 2UH, 2VH, and 2WH, each corresponding to the power-side MOSFETs 1UH, 1VH, and 1WH, and low-side (N-side) drivers 2UL, 2VL, and 2WL, each corresponding to the ground-side MOSFETs 1UL, 1VL, and 1WL. The H-side drivers 2UH, 2VH, and 2WH and the N-side drivers 2UL, 2VL, and 2WL are supplied with an amplified voltage generated by a gain amplifier circuit 9. The output terminals of the H-side drivers 2UH, 2VH, and 2WH are each connected to the gates of the MOSFETs 1UH, 1VH, and 1WH, respectively, so that these MOSFETs are selectively switched ON / OFF. The output terminals of the N-side drivers 2UL, 2VL and 2WL are each connected to the gates of the MOSFETs 1UL, 1VL and 1WL, so that these MOSFETs can be selectively controlled ON / OFF. Phase relays 3U, 3V, and 3W are each connected to driver lines 11U, 11V, and 11W, respectively, to drive the electric motor M. These phase relays 3U, 3V, and 3W are solid-state relays and, in this example, N-channel MOSFETs. A control signal CS from the driver circuit 8 is supplied to the gates of these MOSFETs via a first control line 15. Between the first control line 15 and the motor-side sections of the driver lines 11U, 11V, and 11W, which connect phases of the electric motor M to the phase relays 3U, 3V, and 3W, the cathodes and anodes of Zener diodes (first overvoltage protection devices) 4U, 4V, and 4W for the corresponding phases are connected, thus serving as overvoltage protection circuits.The Zener diodes 4U, 4V and 4W are provided at a position between the first connection terminals of the MOSFETs of the phase relays 3U, 3V and 3W, which are connected to the driver circuit 8, and the second terminals of the MOSFETs, which are connected to the electric motor M. In accordance with the control of the microcomputer 7, the driver circuit 8 supplies a control signal CS with a voltage level amplified by the amplifier circuit 9 via a first control line 15 to the phase relays 3U, 3V, and 3W to simultaneously control the phase relays ON / OFF. Furthermore, the driver circuit 8 is configured to supply the control signal CS to the power supply relay 5 (mechanical relay) via a second control line 16 to control the power supply relay 5 (opening / closing) and thereby supply current (operating power) from the battery 14 to the inverter circuit 1. The power supply IC 6 supplies operating power to the microcomputer 7 based on a supply voltage provided by the battery 14 via a switch 10, such as an ignition switch. The supply voltage is also supplied by the battery 14 via the switch 10 to the amplification circuit 9, which amplifies the supply voltage to generate a boosted voltage. In the MOSFETs 1UH, 1UL, 1VH, 1VL, 1WH, 1WL and the MOSFETs of the phase relays 3U, 3V and 3W, the diodes D1 to D9 between the drains and sources are parasitic diodes. When switch 10 is turned on in the above-mentioned setup, the operating power is supplied from the power supply IC 6 to the microcomputer 7, and the supply voltage is amplified by the gain circuit 9 and fed to the inverter driver circuit 2. The microcomputer 7 controls the driver circuit 8, which then outputs, for example, a pulse width modulation (PWM) signal to the inverter driver circuit 2. In the inverter driver circuit 2, H-side drivers 2UH, 2VH, and 2WH and L-side drivers 2UL, 2VL, and 2WL feed driver signals based on the PWM signals to the gates of the MOSFETs 1UH, 1VH, 1WH, 1UL, 1VL, and 1WL in the inverter circuit 1, in order to selectively switch the MOSFETs ON / OFF. Furthermore, the driver circuit 8 supplies a control signal CS to the phase relays 3U, 3V and 3W via the first control line 15 to control the phase relays ON / OFF simultaneously, and supplies the control signal CS to the power supply relay 5 via the second control line 16 to control the power supply relay 5 ON / OFF. Then, while the electric motor M is being driven, the MOSFETs of the phase relays 3U, 3V, and 3W are switched on, and the power supply relay 5 is closed. In this state, the MOSFETs 1UH, 1VH, 1WH, 1UL, 1VL, and 1WL of the inverter circuit 1 are selectively switched ON / OFF to enable three-phase driving of the electric motor M via the driver lines 11U, 11V, and 11W. The duty cycles of the PWM signals are changed as needed to control the rotational speed of the electric motor M. If, for example, an abnormality occurs during this process, the MOSFETs of the phase relays 3U, 3V, and 3W are switched off by the driver circuit 8 to interrupt the power supply from the inverter circuit 1 to the electric motor M, and the power supply relay 5 is opened to interrupt the power supply from the battery 14. In this way, a stop of the electric motor M can be forced to perform a failsafe function or similar. In the configuration described above, the phase relays 3U, 3V, and 3W and the power supply relay 5 can share the driver circuit 8 to control the phase relays and the power supply relay simultaneously. Accordingly, the circuit design of the driver circuit can be simplified and the number of components reduced, resulting in cost reduction, size reduction, a lower failure rate, and consequently, improved reliability, etc. Furthermore, the power supply line 13 from the battery 14 to the inverter circuit 1 is interrupted, and the driver lines 11U, 11V and 11W of the electric motor M are interrupted in order to interrupt the power supply to the inverter circuit 1 and also the operating voltage for the electric motor M, so that the electric motor M can be stopped even if the power supply line 13 or one of the driver lines 11U, 11V and 11W cannot be interrupted. [Second embodiment] Fig. 2 is a circuit diagram showing a motor driver device according to a second embodiment of the present invention. The motor driver device corresponds to the circuit shown in Fig. 1, except that the power supply relay 5 is not a mechanical relay but a solid-state relay. In this embodiment, an N-channel MOSFET is used as a solid-state switching element of the power supply relay 17. The MOSFET is provided on a power supply line 13, with its drain connected to a power supply such as a battery 14 and its source connected to a power supply terminal of the inverter circuit 1. A control signal CS from the driver circuit 8 is supplied to the gate of the MOSFET via a second control line 16. An anode and a cathode of a Zener diode (second overvoltage protection device) 18 are connected between the source and the gate of the MOSFET, serving as an overvoltage protection circuit. In this case, diode D10 between the drain and the source of the MOSFET is a parasitic diode. Because Fig. 2 corresponds to Fig. 1 with regard to the other basic circuit configurations, identical components in Fig. 2 and Fig. 1 are indicated by the same reference numerals, and a repeated explanation of these is omitted here. Because in the second embodiment mentioned above the power supply relay 17 is not a mechanical relay but a semiconductor relay, the failure rate can be reduced to improve reliability, and a reduction in size can be achieved by reducing the volume. [Third embodiment] Fig. 3 is a circuit view showing a motor driver device according to a third embodiment of the present invention. This motor driver device comprises high-resistance resistors 19 and 20 (first and second current reduction devices), which are provided on the first control line 15 and the second control line 16 of the circuit of Fig. 2, respectively. Furthermore, the motor driver device comprises a charge accumulation element, which is a smoothing capacitor (accumulation device) 21, provided at a position between a grounding point and an inverter-side section of the power supply line 13 between the power supply relay 17 and the inverter circuit 1. Because Fig. 3 corresponds to Fig. 2 with regard to the other basic circuit configurations, identical components in Fig. 3 and Fig. 2 are indicated by the same reference numerals, and a repeated explanation of these is omitted here. In such a setup, when the phase relays 3U, 3V, and 3W are in an OFF state, the high-resistance resistors 19 and 20 prevent a current caused by a counter-electromotive force in a coil of the electric motor M from flowing through the Zener diodes 4U, 4V, and 4W, the first control line 15, and the second control line 16 into the power supply relay 17 (as a leakage current). Accordingly, a voltage rise between the gate and source of the MOSFET, which serves as the power supply relay 17, and thus a faulty turn-on, can be prevented. And because a smoothing capacitor 21 is provided on the power supply line 13 for the inverter circuit 1, a power supply capacitance of the inverter circuit 1 can be maintained. And when the electric motor M stops, high-resistance resistors 20, 19 prevent a current caused by an electrical charge accumulated in the smoothing capacitor 21 of this embodiment from flowing through a Zener diode 18, the second control line 16, and the first control line 15 into the phase relays 3U, 3V, and 3W (as a leakage current). Accordingly, a voltage increase between the gate and source of the MOSFETs serving as the phase relays 3U, 3V, and 3W, which would cause a faulty turn-on, can be prevented. Therefore, because in the third embodiment the leakage current caused by the joint use of the driver circuit 18 by the phase relays 3U, 3V and 3W and the power supply relay 17 can be reduced, faulty switching on of the phase relays 3U, 3V and 3W and the power supply relay 17 can be prevented. (First modification) Fig. 4 is a circuit diagram showing a first modification of the motor driver device of Fig. 3. This motor driver device corresponds to the circuit of Fig. 3, except that instead of the high-resistance resistor 19, high-resistance resistors 19U, 19V and 19W, which serve as current reduction circuits (first current reduction devices), are provided at a position between the gates of the MOSFETs that form the phase relays 3U, 3V and 3W, and the first control line 15 for supplying a control signal CS from the driver circuit 8. In other words, while the circuit shown in Fig. 3 has the high-resistance resistor 19 on the first control line 15, the circuit shown in Fig. 4 has high-resistance resistors 19U, 19V and 19W that are provided at positions branching off from the first control line 15, so that the high-resistance resistors 19U, 19V and 19W are in series with the Zener diodes 4U, 4V and 4W. Because Fig. 4 corresponds to Fig. 3 with regard to the other basic circuit configurations, identical components in Fig. 4 and Fig. 3 are indicated by the same reference numerals, and a repeated explanation of these is omitted here. When the phase relays 3U, 3V, and 3W are in the OFF state in this setup, the high-resistance resistors 19U, 19V, 19W, and 20 prevent a current caused by a counter-electromotive force in a coil of the electric motor M from flowing through the Zener diodes 4U, 4V, and 4W, the first control line 15, and the second control line 16 into the power supply relay 17 (as a leakage current). Accordingly, this prevents the MOSFET forming the power supply relay 17 from causing a faulty switch-on. And when the electric motor M stops, the high-resistance resistors 19U, 19V, 19W, and 20 prevent a current caused by an electrical charge accumulated in the smoothing capacitor 21 of this embodiment from flowing through a Zener diode 18, the second control line 16, and the first control line 15 into the phase relays 3U, 3V, and 3W (as a leakage current). Accordingly, this prevents the MOSFETs forming the phase relays 3U, 3V, and 3W from causing a faulty turn-on. (Second modification) Fig. 5 is a circuit diagram showing a second modification of the motor driver device from Fig. 3. This motor driver device uses Zener diodes as the first and second current reduction circuits (first and second current reduction devices) instead of resistors. In addition to the Zener diodes 4Ua, 4Va, and 4Wa for overvoltage protection of the phase relays 3U, 3V, and 3W, Zener diodes 4Ub, 4Vb, and 4Wb are provided to create back-to-back connections and prevent leakage current. Furthermore, in addition to a Zener diode 18a for overvoltage protection of the power supply relay 17, a Zener diode 18 is provided to create a back-to-back connection and prevent leakage current. The Zener diodes 4Ub, 4Vb, and 4Wb function as the second current reduction circuits, or in other words, as second current reduction devices. Because Fig. 5 corresponds to Fig. 3 with regard to the other basic circuit configurations, identical components in Fig. 5 and Fig. 3 are indicated by the same reference numerals, and a repeated explanation of these is omitted here. When the phase relays 3U, 3V, and 3W are in the OFF state in this setup, the Zener diodes 4Ub, 4Vb, and 4Wb, connected in the reverse direction, prevent a current caused by a counter-electromotive force in a coil of the electric motor M from flowing through the Zener diodes 4Ua, 4Va, and 4Wa, the first control line 15, and the second control line 16 into the power supply relay 17. Accordingly, a malfunction of the power supply relay 17 can be prevented. And when the electric motor M stops, the Zener diode 18b can prevent a current caused by an electrical charge accumulated in the smoothing capacitor 21 of this embodiment from flowing through the Zener diode 18a, the second control line 16 and the first control line 15 into the phase relays 3U, 3V and 3W. This prevents a malfunction of the phase relays 3U, 3V and 3W. In the first three examples and in the first and second modifications, the output of the amplification circuit 9 is routed to the inverter circuit 2 and the driver circuit 8. However, the output can also be routed to the inverter circuit 1, so that an amplified voltage is supplied to the power supply relay 17, the phase relays 3U, 3V and 3W, and the inverter circuit 1 from the same amplification circuit. Examples were described in which Zener diodes are used for overvoltage protection. However, diodes can also be used, and if necessary, multiple stages of diodes can be connected in series. Furthermore, examples were described in which resistors or Zener diodes were used to reduce leakage currents. However, diodes, other load elements, or a combination thereof can also be used. (Application example) Fig. 6 is a schematic view showing a design example of a power steering system (EPS system) comprising a power steering motor to which a motor driver device according to an embodiment of the present invention is applied. The EPS system includes a steering wheel 30, a steering torque sensing sensor 31, an auxiliary motor 32, a control unit 33, etc. A steering torque sensing sensor 31 and a reduction gear unit 36 ​​are provided in a steering column 35 surrounding a steering shaft 34. When a driver operates the steering wheel 30, a steering torque generated in the steering shaft 34 is detected by the steering torque sensor 31. In accordance with this steering torque signal S1 and a vehicle speed signal S2 or similar, the control unit 33 drives the auxiliary motor 32, so that the auxiliary motor 32 generates a steering assistance force suitable for the driving conditions. When a gear 37 provided at a tip end of the steering shaft 34 is rotated in this process, a rack 38 moves horizontally in the left-right direction with respect to the direction of travel of the vehicle, thereby transmitting the driver's operation of the steering wheel 30 to the tires 39 for cornering. In this configuration, the auxiliary motor 32 corresponds to the electric motor M, the control unit 33 corresponds to the microcomputer 7, and a steering torque signal S1 and a vehicle speed signal S2 are fed to the microcomputer 7 to control the driver circuit 8. The auxiliary motor 32 is then driven by the inverter driver circuit 2 and the inverter circuit 1 to generate a steering assistance force suitable for the driving conditions. Thus, an EPS system is provided that exhibits the functions and effects described in the embodiments and their modifications described above. (Test result) The costs for a conventional electronic control unit (ECU) with a design in which driver circuits are provided for each relay and for the circuit designs according to the embodiments of the present invention were estimated, and it was found that a cost reduction of 25% was possible. Of course, the motor driver device of the present invention can be applied not only to the above-mentioned auxiliary motor for power steering, but also to various other types of electric motors.

Claims

Motor driver device comprising: an inverter circuit (1) for supplying current to an electric motor (M), a power supply relay (5, 17) provided on a power supply line (13) for supplying current from a power supply (14) to the inverter circuit (1), a phase relay (3U, 3V, 3W) provided on a driver line (11U, 11V, 11W) between the inverter circuit (1) and the electric motor (M) and formed by a semiconductor switching element, a driver circuit (8) connected to the phase relay (3U, 3V, 3W) and the power supply relay (5, 17) to drive the phase relay (3U, 3V, 3W) and the power supply relay (5, 17), a first control line (15) connecting the driver circuit (8) to the phase relay (3U, 3V, 3W), a first overvoltage protection device (4U, 4V, 4W, 4Ua, 4Va, 4Wa), which are located at a position between a motor-side conductor section of the driver line (11U, 11V,11W) between the electric motor (M) and the phase relay (3U, 3V, 3W) and the first control line (15) is provided and configured to protect the phase relay (3U, 3V, 3W) from overvoltage; a first current reduction device (19, 19U, 19V, 19W, 4Ub, 4Vb, 4Wb) to reduce leakage current flowing from the electric motor (M) into the first control line (15); a second control line (16) connecting the driver circuit (8) to the power supply relay (5, 17); a charge accumulation device (21) provided on an inverter-side line section of the power supply line (13) between the inverter circuit (1) and the power supply relay (5, 17); a second overvoltage protection device (18) connected to a position between the second control line (16) and the is connected to the inverter-side line section, and a second current reduction device (20) for reducing a leakage current,which flows from the charge accumulation device (21) into the second control line (16). Motor driver device according to claim 1, characterized in that the first current reduction device (19, 19U, 19V, 19W, 4Ub, 4Vb, 4Wb) is provided on the first control line (15). Motor driver device according to claim 1, characterized in that the first current reduction device (19, 19U, 19V, 19W, 4Ub, 4Vb, 4Wb) is provided at a position branching off from the first control line (15) so that it is in series with the first overvoltage protection device (4U, 4V, 4W, 4Ua, 4Va, 4Wa). Motor driver device according to one of claims 1 to 3, characterized in that: the first overvoltage protection device (4U, 4V, 4W, 4Ua, 4Va, 4Wa) contains a Zener diode and / or a diode, and the first current reduction device (19, 19U, 19V, 19W, 4Ub, 4Vb, 4Wb) contains a Zener diode, a diode, a resistor and / or a load element. Motor driver device according to one of claims 1 to 4, characterized in that the power supply relay (5, 17) is formed by a semiconductor switching element. Motor driver device according to one of claims 1 to 5, characterized in that the charge accumulation device (21) is a smoothing capacitor which is provided at a position between the power supply line (13) and an earthing point. Motor driver device according to one of claims 1 to 5, characterized in that the second current reduction device (20) includes a Zener diode, a diode, a resistor and / or a load element, which are provided on the second control line (16). Motor driver device according to one of claims 1 to 4, characterized in that the second current reduction device (20) contains a Zener diode or a diode which is connected in series with the second overvoltage protection device (18). Motor driver device according to one of claims 1 to 8, characterized in that the semiconductor switching element forming the phase relay (3U, 3V, 3W) contains an N-channel MOSFET. Motor driver device according to one of claims 1 to 9, characterized in that the electric motor (M) is a three-phase motor. Motor driver device according to claim 10, characterized in that the inverter circuit (1) includes an upstream driver element (1UH, 1VH, 1WH) and a downstream driver element (1UL, 1VL, 1WL) for each of the driver lines (11U, 11V, 11W) of the three-phase motor corresponding to each phase. Motor driver device according to claim 11, further characterized by an inverter driver circuit (2) which is supplied with an amplified supply voltage and controls the inverter circuit (1). Motor driver device according to claim 12, characterized in that the inverter driver circuit (2) includes for each phase a high-side driver (2UH, 2VH, 2WH) for controlling the upstream driver element (1UH, 1VH, 1WH) of the inverter circuit (1) and a low-side driver (2UL, 2VL, 2WL) for controlling the downstream driver element (1UL, 1VL, 1WL) of the inverter circuit (1). Motor driver device according to one of claims 1 to 13, further characterized by an amplification circuit (9) for amplifying the supply voltage and for supplying the amplified voltage to the driver circuit (8), such that the driver circuit (8) supplies a control signal based on the amplified voltage to the phase relay (3U, 3V, 3W) and the power supply relay (5, 17). Motor driver device according to one of claims 1 to 14, further characterized by: a microcomputer (7) for controlling the driver circuit (8), and a power supply IC (6) for supplying operating power to the microcomputer (7) based on the supply voltage.

Images