JP5892868B2 - Electric power steering device, power converter - Google Patents

Description

  The present invention relates to an electric power steering apparatus.

  An electric power steering device that assists the steering device of a vehicle with the rotational force of the motor transmits the driving force of the motor to a transmission mechanism such as a gear or a belt via a reduction gear, and finally assists the operation of the steering shaft or the rack shaft. Is configured to do. In addition, an inverter for converting DC power into AC power and supplying it to the motor is provided between the battery as a power source and the motor.

  When a failure occurs in the electric power steering device, the electromagnetic brake is prevented from being generated by unintended auxiliary force from the motor by turning off the switch provided on the wiring that electrically connects the inverter and the motor. doing. As a conventional technique related to a switch, there is an electromagnetic (mechanical contact) type switch that is a part that mechanically turns on / off an electric circuit by controlling a spring using an electromagnetic coil.

  In Patent Document 1 below, a first compound semiconductor MOSFET and a second compound semiconductor MOSFET are prepared as a semiconductor switch using a semiconductor element such as an FET, and the respective source electrodes are internally connected to have the same potential. A configuration is described in which the drain electrode of the semiconductor MOSFET and the drain electrode of the second compound semiconductor MOSFET are used as output terminals.

  In the following Patent Document 2, one semiconductor switch (MOSFET) is arranged for each wiring that electrically connects the inverter and the motor, and when an abnormality occurs, the power semiconductor device in the inverter and the semiconductor between the inverter and the motor are arranged. An operation example in which all the switches are turned off is described.

JP 2011-254387 A JP 2009-274686 A

  Consider turning on / off the connection between an inverter and a motor using an electromagnetic switch. When the motor is configured as a three-phase motor, it is only necessary to provide a switch for only two of the three wires connecting the inverter and the motor. However, there are various problems such as chattering, operating noise, melting / welding of contacts due to overcurrent, contact icing due to temperature change, and deterioration of reliability due to contact wear. Moreover, the electromagnetic coil for operating the spring is large, and becomes a bottleneck for downsizing the inverter.

  As an alternative to the electromagnetic switch, a semiconductor switch using a MOSFET may be used. Since the MOSFET has a body diode, it operates as a unidirectional switch in which a current flows unidirectionally even when the gate signal is turned off. Therefore, if the electromagnetic switch is simply replaced with a MOSFET, a closed loop through the body diode is created between the motor coils, and an electromagnetic brake is generated by an unintended auxiliary force from the motor.

  In Patent Document 1, one electromagnetic relay is replaced with two MOSFETs, and a bidirectional switch is realized by setting the source electrode of the MOSFET to the same potential so that a current closed loop via a body diode is not created. . Further, in Patent Document 2, when an abnormality occurs, the MOSFET provided between the inverter and the motor and the MOSFET inside the inverter are all shut off so that a current closed loop is not created and electromagnetic braking by the motor is avoided. .

  However, in the techniques described in Patent Documents 1 and 2, the control for avoiding the electromagnetic brake that has been conventionally realized by two electromagnetic switches is realized by three or more semiconductor switches. There is a problem that leads to an increase in mounting area and cost.

  The present invention has been made in view of the above-described problems, and an object thereof is to provide an electric power steering device that can suppress an electromagnetic brake generated by a motor with a small mounting area and cost.

  An electric power steering apparatus according to the present invention includes a semiconductor switch formed using a normally-off GaN-FET on a wiring connecting a motor and a power supply apparatus.

  The electric power steering apparatus according to the present invention can separate the FET electrode and the diode electrode by using the GaN-FET having no body diode. Thereby, since the connection between the motor and the power supply device can be turned on / off with only two semiconductor elements, the electromagnetic brake generated by the motor can be suppressed while suppressing the mounting area and cost.

1 is a diagram illustrating a configuration of an electric power steering apparatus 101 according to a first embodiment. It is a block diagram of the electric power steering apparatus 101 which concerns on Embodiment 2. FIG. 2 is a diagram showing a specific configuration of a circuit for driving gates of semiconductor switches 102 and 103. FIG. It is a block diagram of the electric power steering apparatus 101 which concerns on Embodiment 3. FIG. 2 is a side sectional view of a semiconductor switch 102. FIG. FIG. 6 is a side sectional view showing a state in which the GaN device shown in FIG. It is a sectional side view of a GaN device in which some electrodes are configured in common. FIG. 8 is a connection diagram when the GaN device shown in FIG. 7 is used as the semiconductor switch 102. FIG. 10 is a configuration diagram of an electric power steering apparatus 101 according to a fifth embodiment. It is a block diagram of the electric power steering apparatus 101 which concerns on Embodiment 6. FIG. 2 is a side sectional view of semiconductor switches 102 and 103 according to Embodiment 1. FIG. FIG. 10 is an excerpt of the periphery of semiconductor switches 102 and 103 in the seventh embodiment.

<Embodiment 1>
FIG. 1 is a diagram showing a configuration of an electric power steering apparatus 101 according to Embodiment 1 of the present invention. The electric power steering apparatus 101 includes an inverter 130 (power supply apparatus), semiconductor switches 102 and 103, and a three-phase motor 110.

  The three-phase motor 110 is a motor that assists the operation of the steering device, and the power of the battery 105 is supplied via the inverter 130. The inverter 130 includes a capacitor 104 for smoothing power and a power converter 150 that converts DC power supplied from the battery 105 into AC power. The power semiconductor devices in the power conversion unit 150 are alternately switched to convert DC power into AC power. As power semiconductor devices, MOSFETs, GaN-FETs, and the like are conceivable.

  Although not shown in FIG. 1, the rotating shaft of the motor 110 is connected to an assisting gear, and the motor 110 is configured to assist the driver's steering operation. The inverter 130 also includes a gate drive circuit for controlling ON / OFF of the power semiconductor device.

  In the electric power steering apparatus, it is assumed that the power semiconductor device of the inverter 130, the coil of the motor 110, and the like are short-circuited. When these failures occur, the motor 110 cannot generate torque for assisting the steering operation. On the other hand, if the motor 110 and the inverter 130 remain electrically connected even if these failures occur, a short circuit between the coils of the motor 110 and the body diode of the MOSFET of the power conversion unit 150 are interposed. A closed current loop is formed. Therefore, there is a possibility that the electromagnetic brake due to the back electromotive voltage of the motor 110 hinders the driver's steering and the steering wheel does not move.

  In order to avoid the above situation, the semiconductor switches 102 and 103 are arranged in two of the three wires connecting the motor 110 and the inverter 130. These semiconductor switches are formed using normally-off GaN-FETs 106 and 108. Since a GaN-FET is a lateral semiconductor using a two-dimensional electron gas, it has a feature that does not have a body diode like a MOSFET, and a bidirectional switch can be realized by itself.

  When the power semiconductor device of the inverter 130 or the coil of the motor 110 is short-circuited, the GaN-FETs 106 and 108 are turned off, and the current closed loop caused by the back electromotive voltage of the motor 110 is cut off to avoid electromagnetic braking. it can.

<Embodiment 1: Summary>
As described above, in the electric power steering apparatus 101 according to the first embodiment, the semiconductor switches 102 and 103 formed using the normally-off GaN-FETs 106 and 108 are arranged between the inverter 130 and the motor 110. ing. As a result, the minimum number of semiconductor switches can be two, which is the minimum necessary, and the electromagnetic brake by the motor 110 can be suppressed while reducing the mounting area and cost of the circuit board.

  Moreover, according to the electric power steering apparatus 101 according to the first embodiment, by using a GaN-FET having a smaller on-resistance than the MOSFET, the circuit loss can be reduced and the operation efficiency can be increased.

  In the first embodiment, when one phase of the power conversion unit 150 fails, only the target phase GaN-FET is turned off, and the steering operation assist by the motor 110 is realized using the remaining two phases. You can also.

<Embodiment 2>
In the first embodiment, the operations required for the semiconductor switches 102 and 103 are not constantly switched during operation as in the case of the power semiconductor device of the power converter 150, but are turned on / off when the driver starts and stops the engine. Only the operation to turn off and the operation to turn off in an emergency. In other words, a circuit for controlling the semiconductor switches 102 and 103 only needs to have a stable constant voltage power supply and a small power switch such as a transistor for turning on and off the circuit.

  In practice, however, the source electrodes 111 and 116 of the GaN-FETs 106 and 108 are connected between the upper and lower arms of the power converter 150. Therefore, each time the power semiconductor device of the power conversion unit 150 is switched, the potential of the source electrodes 111 and 116 varies between the potential (Vb) of the battery 105 and the ground potential (0) of the inverter 130. Whether or not this potential variation is allowed depends on the characteristics of the GaN-FET.

  For the characteristics of the GaN-FET, for example, a data sheet of EPC, a semiconductor manufacturer, can be referred to (http://epc-co.com/epc/). As an example, looking at the data sheet of EPC2015, which is a 40V withstand voltage FET with a built-in diode, it can be confirmed that the upper limit of the gate voltage is 6V and the change of the on-resistance with respect to the variation of the gate voltage is large. In particular, since the loss must be kept low for use as a semiconductor switch, a very strict value of about 5.5V ± 0.5V is required as the control range of the gate voltage.

  In view of the above problems, in order to stably operate the semiconductor switches 102 and 103, it is conceivable that an insulating gate drive circuit is provided in each semiconductor switch so as not to be affected by the above-described potential fluctuation. However, in this case, there is a problem that the number of parts of the control circuit increases, and the mounting area and cost increase.

  Therefore, in the second embodiment of the present invention, a filter circuit is provided that reduces potential fluctuations at the source electrodes of the semiconductor switches 102 and 103, respectively. Since the other configuration is the same as that of the first embodiment, the following description will focus on the differences relating to the filter circuit.

  FIG. 2 is a configuration diagram of the electric power steering apparatus 101 according to the second embodiment. In FIG. 2, resistors 401 and 403 for controlling the switching speed of the gate signal are connected to the gate electrodes 112 and 117 of the GaN-FETs 106 and 108, respectively. Similarly, capacitors 402 and 404 for controlling the switching speed are connected between the gate electrode 112 and the source electrode 111 and between the gate electrode 117 and the source electrode 116, respectively. Resistor 401 and capacitor 402, and resistor 403 and capacitor 404 form an RC low-pass filter circuit, respectively.

  The time constant of each RC low-pass filter circuit is set to one or more periods of the carrier frequency of the PWM control signal that controls the power semiconductor device of the power converter 150. Thereby, the potential fluctuations of the source electrodes 111 and 116 that have been changed each time the power semiconductor device of the power conversion unit 150 is switched can be suppressed by the RC filter. That is, the gate voltage fluctuation of the semiconductor switches 102 and 103 can be suppressed and controlled within the target range.

  FIG. 3 is a diagram showing a specific configuration of a circuit that drives the gates of the semiconductor switches 102 and 103. The power source for driving the upper arm of the inverter 130 is constituted by a booster circuit 501 such as a charge pump, and the ground wiring is common to the ground wiring of the inverter 130. Switches 502 and 503 for controlling ON / OFF of the semiconductor switches 102 and 103 are provided between the booster circuit 501 and the gate electrodes 112 and 117 of the semiconductor switches 102 and 103, respectively.

  By adopting the circuit configuration shown in FIG. 3, the boosted power supply Vpp can be used as the gate power supply for driving the semiconductor switches 102 and 103. As a result, it is not necessary to prepare a separate power source for driving the semiconductor switches 102 and 103, and in addition to the effect of the RC low-pass filter circuit described above, the number of parts of the gate drive circuit can be reduced.

  In the circuit configuration described in FIGS. 2 to 3, if the time constant of the RC filter circuit is excessively increased, the speed at which the semiconductor switches 102 and 103 are turned off when an abnormality occurs may be reduced, and a desired operation may not be realized. There is. Therefore, a circuit for increasing the OFF switching speed can be connected in parallel with the RC filter circuit described above. For example, a circuit in which a diode and a resistor are connected in series can be considered.

  In the second embodiment, other filter circuits may be employed as long as the same effects as those of the RC low-pass filter circuit described with reference to FIGS. In other words, if the filter circuit has such characteristics that the gate voltage fluctuations of the semiconductor switches 102 and 103 are smaller than the maximum value of the voltage across the power semiconductor device that occurs in one switching cycle of the power semiconductor device of the power converter 150. Good.

<Embodiment 2: Summary>
As described above, according to the electric power steering apparatus 101 according to the second embodiment, there is no need to provide an insulated gate drive circuit as a gate drive circuit for controlling the semiconductor switches 102 and 103. The number of parts of the drive circuit can be greatly reduced, and further downsizing of the circuit configuration can be realized.

  Further, according to the electric power steering apparatus 101 according to the second embodiment, the semiconductor switches 102 and 103 can be driven by using the existing booster circuit 501 as a power source, which further reduces the number of parts and the cost of the gate drive circuit. Can be promoted.

<Embodiment 3>
In the first and second embodiments, the power semiconductor device included in the inverter 130 and the semiconductor switches 102 and 103 are different types of semiconductor switches. However, in actuality, it may be considered that the circuit may be mounted using the same type of semiconductor switches. Therefore, in the third embodiment of the present invention, a configuration example using the same GaN-FET as the semiconductor switches 102 and 103 as a power semiconductor device of the power conversion unit 150 will be described. Since other configurations are the same as those in the first and second embodiments, the following description will be made mainly on the differences based on the configuration described in the first embodiment. However, the third embodiment under the configuration described in the second embodiment is described below. The structure which concerns on can also be employ | adopted.

  FIG. 4 is a configuration diagram of the electric power steering apparatus 101 according to the third embodiment. Since the power semiconductor device included in the inverter 130 requires a body diode, when the semiconductor switches 102 and 103 are configured using the same type of semiconductor switch, the body diode is also provided to these. However, as will be described later with reference to FIGS. 5 to 6, this body diode can be electrically disconnected from the FET by being connected to the floating potential wiring. As a result, the same effects as those of the first and second embodiments are exhibited. be able to.

  In the circuit configuration shown in FIG. 4, the anode electrode 114 and the cathode electrode 115 of the GaN diode 107 included in the semiconductor switch 102 are connected to the floating potential wiring at the same potential, and the drain electrode 113 and the source electrode 111 of the GaN-FET 106 are respectively connected to the wiring. To the motor 110 and the inverter 130. Since the GaN diode 107 is connected to a floating potential wiring that is electrically disconnected from the GaN-FET 106, the GaN diode 107 is not used in the operation of the semiconductor switch 102. The same applies to the semiconductor switch 103.

  FIG. 5 is a side sectional view of the semiconductor switch 102. Since the semiconductor switch 103 has the same configuration, the description thereof is omitted.

  In FIG. 5, a GaN-FET 106 and a GaN diode 107 are formed on the same wafer. The GaN-FET 106 and the GaN diode 107 are devices that use a two-dimensional electron gas 204 generated at the heterojunction interface between AlGaN (aluminum gallium nitride) 205 and GaN (gallium nitride) 203. A plurality of elements are arranged in the horizontal direction. It is a horizontal type semiconductor device arranged side by side. Reference numeral 202 denotes a buffer layer. In recent years, technology using the Si substrate 201 as a growth substrate for a GaN-based semiconductor crystal has progressed, and the possibility of cost reduction of semiconductor devices using GaN has increased.

  Since a pn junction is not formed between the GaN diode 107 and the GaN-FET 106 unlike the MOSFET, the GaN diode 107 is placed on the same wafer as the GaN-FET 106 in order to be used as a power semiconductor device of the power conversion unit 150. Must be placed. As a result, the drain electrode 113 and source electrode 111 of the GaN-FET 106 and the cathode electrode 115 and anode electrode 114 of the GaN diode 107 can be separate electrodes. That is, the GaN-FET 106 and the GaN diode 107 can be electrically independent from each other.

  FIG. 6 is a side sectional view showing a state in which the GaN device shown in FIG. The semiconductor switches 102 and 103 are connected to the substrate 310 via an electrical bonding member 311. As the joining member 311, for example, lead-free solder or silver paste can be considered. As the substrate 310, for example, a printed circuit board, an insulating metal substrate, a ceramic substrate, or the like can be considered.

  The GaN-FETs 106 and 108 are arranged on the wiring connecting the motor 110 and the inverter 130 as in the first and second embodiments. The cathode electrodes 115 and 120 and the anode electrodes 114 and 119 of the GaN diodes 107 and 109 are not connected to the wiring electrically connected to the inverter 130 and the motor 110 in order to avoid electromagnetic braking by the motor 110. Specifically, it is connected to the floating potential wirings 304 and 305. Since the wirings 304 and 305 are separated from the wiring 301 that connects the GaN-FETs 106 and 108, a current closed loop is not formed even when the potential is the same as that of the ground wiring of the inverter 130. Therefore, the wirings 304 and 305 may be connected to the ground wiring of the inverter 130.

<Embodiment 3: Summary>
As described above, according to the electric power steering apparatus 101 according to the third embodiment, the power semiconductor device used in the power conversion unit 150 and the semiconductor switches 102 and 103 for avoiding the electromagnetic brake by the motor 110 are shared. Can be in specification. Thereby, apparatus design can be simplified.

  Moreover, according to the electric power steering apparatus 101 according to the third embodiment, the GaN diode is formed between the coils of the motor 110 by connecting the electrode of the GaN diode formed on the same wafer as the GaN-FET to the floating potential wiring. Since no current closed loop is created via, electromagnetic braking by the motor 110 can be suppressed as in the first and second embodiments.

  In addition, according to the electric power steering apparatus 101 according to the third embodiment, the GaN diodes built in the semiconductor switches 102 and 103 are connected to the floating potential wiring, so that the Joule heat generated on the GaN-FETs 106 and 108 is floated. It can effectively escape to the potential wiring, leading to improved reliability.

<Embodiment 4>
In a semiconductor switch incorporating a GaN-FET and a GaN diode, the drain electrode of the GaN-FET and the cathode electrode of the GaN diode are configured in common, and the source electrode of the GaN-FET and the anode electrode of the GaN diode are commonly used. There is something configured. In the fourth embodiment of the present invention, an example in which the semiconductor switch described in the third embodiment is configured as described above will be described. Other configurations are the same as those of the third embodiment.

  FIG. 7 is a side sectional view of a GaN device in which some electrodes are commonly configured. The drain electrode 113 of the GaN-FET 106 and the cathode electrode 115 of the GaN diode 107 are connected by a wiring 501, and these electrodes are configured as a common electrode. Similarly, the source electrode 111 ′ of the GaN-FET 106 ′ and the anode electrode 114 of the GaN diode 107 are connected by a wiring 502, and these electrodes are configured as a common electrode. As shown in FIG. 8 described later, the same number of GaN-FETs and GaN diodes are provided on the substrate, and are alternately connected in series.

  FIG. 8 is a connection diagram when the GaN device shown in FIG. 7 is used as the semiconductor switch 102. As described above, the GaN-FET 106 and the GaN diode 107 are alternately connected in series. The source electrodes and drain electrodes of all the GaN-FETs 106 are connected not to the motor 110 and the inverter 130 but to every other GaN-FET 106 and 106 ″. The reason for this will be described below.

  If the drain electrodes and source electrodes of all the GaN-FETs 106 are connected to the inverter 130 and the motor 110, a closed current loop through the GaN diode 107 is formed. However, as shown in FIG. 8, when every other drain electrode and source electrode are connected to the inverter 130 and the motor 110 and each GaN-FET 106 is connected in parallel, a current closed loop via the GaN diode 107 is formed. A circuit configuration that is not formed can be obtained.

<Embodiment 4: Summary>
As described above, in the electric power steering apparatus 101 according to the fourth embodiment, as the semiconductor switches 102 and 103, the drain electrode 113 of the GaN-FET 106 and the cathode electrode 115 of the GaN diode 107 are formed as the same electrode. A GaN device in which the source electrode 111 and the anode electrode 114 of the GaN diode 107 are formed as the same electrode can be used.

  In the fourth embodiment, since the on-resistance of the GaN-FET 106 is smaller than the on-resistance of the MOSFET, even when there is a GaN-FET 106 that is idle without using all the GaN-FETs 106 connected in parallel in FIG. Performance equivalent to that of a MOSFET can be realized.

<Embodiment 5>
In the first to fourth embodiments, the source electrodes 111 and 119 of the GaN-FETs 106 and 108 are connected to the inverter 130 via wiring, and the drain electrodes 113 and 118 of the GaN-FETs 106 and 108 are connected to the motor 110 via the wiring. Although connected, the connection relationship is not limited to this. In the fifth embodiment of the present invention, a modified example in which these connection relationships are changed will be described. Other configurations are the same as those in the first to fourth embodiments.

  FIG. 9 is a configuration diagram of the electric power steering apparatus 101 according to the fifth embodiment. In FIG. 9, the source electrodes 111 and 119 of the GaN-FETs 106 and 108 are connected to the motor 110 via wiring, and the drain electrodes 113 and 118 of the GaN-FETs 106 and 108 are connected to the inverter 130 via wiring. Yes. Also in the circuit configuration shown in FIG. 9, the same effects as those of the first to fourth embodiments can be exhibited.

<Embodiment 6>
In the first to fifth embodiments, when the semiconductor switches 102 and 103 having GaN diodes are employed, the GaN diodes 107 and 109 are connected to different wirings 301 and 302, respectively, but this is not restrictive. In the sixth embodiment of the present invention, a configuration example in which the GaN diodes 107 and 109 are connected to the same wiring will be described. Other configurations are the same as those of the first to fifth embodiments.

  FIG. 10 is a configuration diagram of the electric power steering apparatus 101 according to the sixth embodiment. The cathode electrodes 115 and 120 and the anode electrodes 114 and 119 of the GaN diodes 107 and 109, respectively, are connected to the floating potential wiring 306. The wiring 306 may be connected to the ground wiring of the inverter 130.

  FIG. 11 is a sectional side view of the semiconductor switches 102 and 103 in the first embodiment. The cathode electrodes 115 and 120 and the anode electrodes 114 and 119 are connected to the floating potential wiring 306. Since the floating potential wiring 306 is separated from the wiring connected to the motor 110 and the wiring connected to the inverter 130, the same effect as in the third embodiment can be exhibited.

  According to the configuration of the sixth embodiment, the area of the floating potential wiring 306 can be made larger than that of the other embodiments. Thereby, the heat generated in the GaN-FETs 106 and 108 can be released more effectively. As a result, the reliability is further improved.

<Embodiment 7>
In the first to sixth embodiments, the semiconductor switches 102 and 103 are arranged at independent positions, but the wiring length can be kept short by arranging them in the vicinity. In the seventh embodiment of the present invention, a circuit example in which wirings for driving the semiconductor switches 102 and 103 are configured in common will be described. Other configurations are the same as those of the first to sixth embodiments.

  FIG. 12 is an excerpt of the periphery of the semiconductor switches 102 and 103 in the seventh embodiment. In FIG. 12, the gate electrodes 112 and 117 of the semiconductor switches 102 and 103 are arranged so as to face each other with the gate wiring interposed therebetween. As a result, the gate wiring length can be made common and the wiring length can be kept short.

  The present invention is not limited to the embodiments described above, and includes various modifications. The above embodiment has been described in detail for easy understanding of the present invention, and is not necessarily limited to the one having all the configurations described. A part of the configuration of one embodiment can be replaced with the configuration of another embodiment. The configuration of another embodiment can be added to the configuration of a certain embodiment. Further, with respect to a part of the configuration of each embodiment, another configuration can be added, deleted, or replaced. For example, the following modifications can be considered.

(Modification 1)
The power semiconductor devices of the semiconductor switches 102 and 103 and the power conversion unit 150 can also be mounted on the same substrate. Thereby, the freedom degree of the mounting layout of the inverter 130 is improved, and the whole apparatus can be reduced in size.

(Modification 2)
The power semiconductor device of the power conversion unit 150 is not limited to a GaN device except for the configuration example described in the third embodiment, and a MOSFET or an IGBT can also be adopted.

(Modification 3)
The motor 110 is not limited to a three-phase motor, and, for example, a DC motor can be adopted. In this case, instead of the inverter 130, for example, a DC-DC converter or the like can be provided as the power supply device. Also in this configuration, the functions of the semiconductor switches 102 and 103 for turning on / off the connection between the power supply device and the motor 110 are the same as in the other configuration examples.

(Modification 4)
The semiconductor switches 102 and 103 can also be used for purposes other than avoiding electromagnetic braking by the motor 110. For example, it can be utilized as a power switch provided on a wiring connecting the battery 105 and the inverter 130. A GaN semiconductor is a device that can be put to practical use up to a withstand voltage of several kV, has a wide range of voltages to be used, and can be used in various applications such as in-vehicle and power systems.

(Modification 5)
The configuration and time constant of using the filter circuit using the resistor and the capacitor described in the second embodiment for driving the gate and the time constant thereof can be adopted without being limited to the GaN semiconductor. For example, even when MOSFETs are employed as the semiconductor switches 102 and 103, the problem that the gate voltage fluctuates similarly occurs, and this can be suppressed using the same filter circuit as in the second embodiment.

  Each of the above-described configurations, functions, processing units, processing means, and the like may be realized in hardware by designing a part or all of them, for example, with an integrated circuit. Each of the above-described configurations, functions, and the like may be realized by software by interpreting and executing a program that realizes each function by the processor. Information such as programs, tables, and files for realizing each function can be stored in a recording device such as a memory, a hard disk, an SSD (Solid State Drive), or a recording medium such as an IC card, an SD card, or a DVD.

  101: Electric power steering device, 102 and 103: Semiconductor switch, 106 and 108: GaN-FET, 107 and 109: GaN diode, 110: Motor, 130: Inverter, 150: Power converter.

Claims (9)

A motor for assisting the operation of the steering device;
A power supply device for supplying power to the motor;
A semiconductor switch that is installed on a wiring that electrically connects the motor and the power supply device, and that switches whether to electrically connect the motor and the power supply device;
An electric power steering apparatus comprising:
The semiconductor switch is formed using a normally-off GaN-FET ,
The power supply apparatus includes a power semiconductor device for converting power,
The electric power steering device is
A filter circuit is provided between the gate electrode and the source electrode of the semiconductor switch to reduce a voltage variation applied between the gate electrode and the source electrode of the semiconductor switch in accordance with the operation of the power semiconductor device. An electric power steering device. The filtering characteristics of the filter circuit are:
The voltage applied between the gate electrode and the source electrode of the semiconductor switch in accordance with the operation of the power semiconductor device is configured to be equal to or lower than the maximum voltage generated at both ends of the power semiconductor device. The electric power steering apparatus according to claim 1 . The filter circuit is
Wherein a resistor connected to the gate electrode of the semiconductor switch, the electric power according to claim 1, characterized by being constructed using a capacitor connected between the gate electrode and the source electrode of the semiconductor switch Steering device. 4. The electric power steering apparatus according to claim 3 , wherein a time constant of the filter circuit configured using the resistor and the capacitor is set to a value equal to or greater than a switching period of the power semiconductor device. A motor,
A power supply device for supplying power to the motor;
A semiconductor switch that is installed on a wiring that electrically connects the motor and the power supply device, and that switches whether to electrically connect the motor and the power supply device;
A power conversion device comprising:
The semiconductor switch is formed using a normally-off type MOSFET,
The power supply apparatus includes a power semiconductor device for converting power,
The power converter is
A filter circuit is provided between the gate electrode and the source electrode of the semiconductor switch to reduce a voltage fluctuation applied between the gate electrode and the source electrode of the semiconductor switch in accordance with the operation of the power semiconductor device.
The power converter characterized by the above-mentioned. The filtering characteristics of the filter circuit are:
The voltage applied between the gate electrode and the source electrode of the semiconductor switch in accordance with the operation of the power semiconductor device is configured to be equal to or lower than the maximum voltage generated at both ends of the power semiconductor device.
The power conversion device according to claim 5. The filter circuit is
The resistor is connected to the gate electrode of the semiconductor switch, and the capacitor is connected between the gate electrode and the source electrode of the semiconductor switch.
The power conversion device according to claim 5. The time constant of the filter circuit configured using the resistor and the capacitor is set to a value equal to or greater than the switching period of the power semiconductor device.
The power conversion device according to claim 7. The power conversion device according to any one of claims 5 to 8,
A steering device whose operation is assisted by the motor;
An electric power steering apparatus comprising:

Images