阅读说明：本技术 电动机驱动装置以及电动机驱动方法 (Motor driving device and motor driving method ) 是由 平形政树 于 2020-08-28 设计创作，主要内容包括：本发明提供一种电动机驱动装置,即使在故障时也能够检测电动机的速度并且能够决定是否解除故障安全控制。该电动机驱动装置包括：上臂栅极驱动电路；下臂栅极驱动电路；接收来自第1电源的供电的第1旋转检测部；接收来自第2电源的供电的第2旋转检测部；使用来自第1旋转检测部的检测信号,来对上臂栅极驱动电路和下臂栅极驱动电路中的至少接收来自第1电源的供电的栅极驱动电路进行故障安全控制的第1故障安全电路；以及使用来自第2旋转检测部的检测信号,来对上臂栅极驱动电路和下臂栅极驱动电路中的至少接收来自第2电源的供电的栅极驱动电路进行故障安全控制的第2故障安全控制部。(The invention provides a motor driving device, which can detect the speed of a motor even in failure and determine whether to cancel fail-safe control. The motor drive device includes: an upper arm gate drive circuit; a lower arm gate drive circuit; a 1 st rotation detecting unit that receives power supply from a 1 st power supply; a 2 nd rotation detecting unit that receives power supply from a 2 nd power supply; a 1 st fail-safe circuit for performing fail-safe control of at least a gate drive circuit that receives power supply from a 1 st power supply, out of the upper arm gate drive circuit and the lower arm gate drive circuit, using a detection signal from the 1 st rotation detecting section; and a 2 nd fail-safe control unit that performs fail-safe control on at least the gate drive circuit that receives power supply from the 2 nd power supply, from among the upper arm gate drive circuit and the lower arm gate drive circuit, using the detection signal from the 2 nd rotation detection unit.)

1. A motor drive device characterized by comprising:

an upper arm gate drive circuit that drives a gate of an upper arm-side switching element included in an inverter for driving a motor;

a lower arm gate drive circuit that drives a gate of a lower arm-side switching element included in the inverter;

a 1 st rotation detecting unit that receives power supply from a 1 st power supply and detects rotation of the motor;

a 2 nd rotation detecting section that receives power supply from a 2 nd power supply and detects rotation of the motor;

a 1 st fail-safe circuit that performs fail-safe control of at least one of the upper arm gate drive circuit and the lower arm gate drive circuit that receives power supply from the 1 st power supply, using a detection signal from the 1 st rotation detecting section; and

and a 2 nd fail-safe circuit that performs fail-safe control of at least the gate drive circuit that receives power supply from the 2 nd power supply, of the upper arm gate drive circuit and the lower arm gate drive circuit, using the detection signal from the 2 nd rotation detecting unit.

2. The motor drive device according to claim 1,

the 2 nd power supply is insulated from the 1 st power supply.

3. The motor drive device according to claim 1 or 2,

in the inverter, a dc bus is connected to the 2 nd power source.

4. The motor drive device according to claim 3,

the 1 st fail-safe circuit receives at least power from the 1 st power source,

the 2 nd fail-safe circuit receives at least power from the 2 nd power source.

5. The motor drive device according to claim 4,

when the power supply from the 1 st power supply is lost, the 2 nd fail-safe circuit receives the power supply from the 2 nd power supply, and performs fail-safe control on at least the gate drive circuit, which receives the power supply from the 2 nd power supply, of the upper arm gate drive circuit and the lower arm gate drive circuit.

6. The motor drive device according to claim 4 or 5,

the 2 nd rotation detecting unit detects rotation of the motor based on a current detection signal from a current detection terminal of the upper arm side switching element or the lower arm side switching element.

7. The motor drive device according to claim 6,

the 2 nd rotation detecting unit detects rotation of the motor based on the current detection signal from the current detection terminal of the lower arm side switching element,

the 2 nd fail-safe circuit in the fail-safe control,

a plurality of the lower arm side switching elements are alternately turned on or off all over, and

a period during which all of the lower arm side switching elements are turned on when the 2 nd rotation detecting unit senses the current detection signal is longer than a period during which all of the lower arm side switching elements are turned on when the 2 nd rotation detecting unit does not sense the current detection signal.

8. The motor drive device according to claim 6,

the 2 nd rotation detecting unit detects rotation of the motor based on the current detection signal from the current detection terminal of the lower arm side switching element,

at least one of the 1 st fail-safe circuit and the 2 nd fail-safe circuit is in the fail-safe control,

a plurality of the upper arm side switching elements and a plurality of the lower arm side switching elements are alternately turned on all over, and

a period during which all of the lower arm-side switching elements are turned on when the 2 nd rotation detecting unit senses the current detection signal is longer than a period during which all of the upper arm-side switching elements are turned on.

9. The motor drive device according to claim 6,

at least one of the 1 st fail-safe circuit and the 2 nd fail-safe circuit is in the fail-safe control,

a plurality of the upper arm side switching elements and a plurality of the lower arm side switching elements are alternately turned on all over,

when the rotation speed of the motor detected by the 1 st rotation detecting unit or the 2 nd rotation detecting unit decreases, a frequency at which all of the plurality of upper arm side switching elements and the plurality of lower arm side switching elements are alternately turned on decreases.

10. A method for driving a motor, characterized in that,

a 1 st rotation detecting unit that receives power supply from a 1 st power supply and detects rotation of the motor;

a 2 nd rotation detecting section that receives power supply from a 2 nd power supply detects rotation of the motor;

a 1 st fail-safe circuit for performing fail-safe control of at least a gate drive circuit that receives power supply from the 1 st power supply, among an upper arm gate drive circuit that drives a gate of an upper arm-side switching element included in an inverter that drives the motor and a lower arm gate drive circuit that drives a gate of a lower arm-side switching element included in the inverter, using a detection signal from the 1 st rotation detection unit; and

the 2 nd fail-safe circuit performs fail-safe control of at least the gate drive circuit that receives power supply from the 2 nd power supply, of the upper arm gate drive circuit and the lower arm gate drive circuit, using the detection signal from the 2 nd rotation detecting section.

Technical Field

The present invention relates to a motor driving device and a motor driving method.

Background

Electric motors and motor systems having inverters for driving the electric motors are used in electric vehicles such as hybrid cars and electric cars, for example. In such motor systems, the inverter control circuit typically receives a low voltage (e.g., 12V) supply from the vehicle. Patent document 1 discloses a technique of supplying a dc voltage converted from a high-voltage power supply for driving a motor to a motor controller device in order to control or regulate the motor even when a low-voltage power supply is lost due to a fault. Patent documents 1 and 2 disclose a technique in which the motor controller device turns on all upper-arm-side switching elements or all lower-arm-side switching elements in the inverter to short-circuit the motor. Patent document 3 discloses a power conversion device in which all upper arm side switching elements and all lower arm side switching elements are alternately turned on. Further, patent document 4 discloses a technique of detecting a current flowing through a motor using a current flowing through a current detection terminal of a power semiconductor element.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open No. 2000-14184

Patent document 2: japanese patent laid-open publication No. 2017-147806

Patent document 3: international publication No. 2016/136815

Patent document 4: japanese patent laid-open No. 2014-138538

Disclosure of Invention

Technical problem to be solved by the invention

When a failure occurs, if the motor is short-circuited by turning on all the upper arm side switching elements or all the lower arm side switching elements, for example, regenerative torque may be generated when the vehicle is towed, for example, and towing may be hindered. In addition, the inverter or the motor may generate excessive heat due to the short-circuit current.

Technical scheme for solving technical problem

In order to solve the above problem, according to the 1 st aspect of the present invention, a motor drive device is provided. The motor driving device may include: an upper arm gate drive circuit that drives a gate of an upper arm-side switching element included in an inverter for driving a motor; and a lower arm gate drive circuit that drives a gate of a lower arm side switching element included in the inverter. The motor driving device may include a 1 st rotation detecting portion that receives power supply from the 1 st power supply and detects rotation of the motor. The motor driving device may include a 2 nd rotation detecting portion that receives power supply from the 2 nd power supply and detects rotation of the motor. The motor driving device may include a 1 st fail-safe circuit that performs fail-safe control of at least a gate driving circuit that receives power supply from the 1 st power supply, of the upper arm gate driving circuit and the lower arm gate driving circuit, using a detection signal from the 1 st rotation detecting section. The motor driving device may include a 2 nd fail-safe circuit that performs fail-safe control of at least a gate driving circuit that receives power supply from the 2 nd power supply, of the upper arm gate driving circuit and the lower arm gate driving circuit, using the detection signal from the 2 nd rotation detecting section.

The 2 nd power supply may be insulated from the 1 st power supply.

In the inverter, the dc bus may be connected to the 2 nd power source.

The 1 st fail-safe circuit may receive at least power from the 1 st power source and the 2 nd fail-safe circuit may receive at least power from the 2 nd power source.

The 2 nd fail-safe circuit may receive power supply from the 2 nd power supply and perform fail-safe control of at least the gate drive circuit, which receives power supply from the 2 nd power supply, of the upper arm gate drive circuit and the lower arm gate drive circuit, when power supply from the 1 st power supply is lost.

The 2 nd rotation detecting section may detect rotation of the motor based on a current detection signal from a current detection terminal of the upper arm side switching element or the lower arm side switching element.

The 2 nd rotation detecting unit may detect rotation of the motor based on a current detection signal from a current detection terminal of the lower arm side switching element. The 2 nd fail-safe circuit may alternately turn all of the plurality of lower arm side switching elements on or off in the fail-safe control. The 2 nd fail-safe circuit may be configured such that, in the fail-safe control, a period during which all of the plurality of lower arm side switching elements are turned on when the 2 nd rotation detecting unit senses the current detection signal is longer than a period during which all of the plurality of lower arm side switching elements are turned on when the 2 nd rotation detecting unit does not sense the current detection signal.

The 2 nd rotation detecting section may detect rotation of the motor based on a current detection signal from a current detection terminal of the lower arm side switching element. At least one of the 1 st fail-safe circuit and the 2 nd fail-safe circuit may alternately turn on all of the plurality of upper arm side switching elements and the plurality of lower arm side switching elements in fail-safe control. At least one of the 1 st fail-safe circuit and the 2 nd fail-safe circuit may be configured such that, in the fail-safe control, a period during which all of the plurality of lower arm-side switching elements are turned on when the 2 nd rotation detecting unit senses the current detection signal is longer than a period during which all of the plurality of upper arm-side switching elements are turned on.

At least one of the 1 st fail-safe circuit and the 2 nd fail-safe circuit may alternately turn on all of the plurality of upper arm side switching elements and the plurality of lower arm side switching elements in fail-safe control. At least one of the 1 st fail-safe circuit and the 2 nd fail-safe circuit may decrease a frequency of turning on all of the plurality of upper arm side switching elements and the plurality of lower arm side switching elements alternately when the rotation speed of the motor detected by the 1 st rotation detecting unit or the 2 nd rotation detecting unit decreases in the fail-safe control.

In the 2 nd aspect of the present invention, a motor driving method is provided. In the motor driving method, the 1 st rotation detecting portion that receives power supply from the 1 st power supply may detect rotation of the motor. In the motor driving method, the 2 nd rotation detecting portion that receives the power supply from the 2 nd power supply may detect the rotation of the motor. In the motor driving method, the 1 st fail-safe circuit may perform fail-safe control on at least one of an upper arm gate drive circuit that drives a gate of an upper arm-side switching element included in an inverter that drives the motor and a lower arm gate drive circuit that drives a gate of a lower arm-side switching element included in the inverter, the gate drive circuit receiving power supply from the 1 st power supply, using a detection signal from the 1 st rotation detecting unit. In the motor driving method, the 2 nd fail-safe circuit may perform fail-safe control of at least the gate drive circuit that receives power supply from the 2 nd power supply, of the upper arm gate drive circuit and the lower arm gate drive circuit, using the detection signal from the 2 nd rotation detecting section.

In addition, the above summary of the invention does not list all necessary features of the present invention. Furthermore, sub-combinations of these feature sets are also contemplated by the present invention.

Drawings

Fig. 1 shows a configuration of a motor system according to the present embodiment.

Fig. 2 shows an example of the configuration of the speed detection unit according to the present embodiment.

Fig. 3 shows one example of the output characteristics of the current detection terminal in the on state of the switching element.

Fig. 4 shows one example of a speed detection method in the on state of the switching element.

Fig. 5 shows one example of the output characteristics of the current detection terminal in the off state of the switching element.

Fig. 6 shows one example of a speed detection method in an off state of the switching element.

Fig. 7 shows an example of the 2 nd fail-safe circuit according to the present embodiment.

Fig. 8 shows an example of a gate driver circuit according to the present embodiment.

Fig. 9 shows an example of an operation waveform of the motor system according to the present embodiment.

Fig. 10 shows a motor system according to a modification of the present embodiment.

Fig. 11 shows a 1 st example of an operation waveform of a motor system according to a modification of the present embodiment.

Fig. 12 shows an example 2 of an operation waveform of a motor system according to a modification of the present embodiment.

Fig. 13 shows a 3 rd example of an operation waveform of a motor system according to a modification of the present embodiment.

Detailed Description

The present invention will be described below with reference to embodiments thereof, but the following embodiments do not limit the invention according to the claims. In addition, not all combinations of all the features described in the embodiments are essential to the solution of the technical problem of the present invention.

Fig. 1 shows a configuration of a motor system 200 according to the present embodiment. Motor system 200 can detect the rotation speed of motor PM even at the time of failure, and can determine whether or not to cancel the short circuit of the motor based on the rotation speed. Thus, the motor system 200 can suppress unnecessary continuation of the short circuit of the motor, unnecessary actuation due to regenerative torque, and generation of unnecessary heat generation of the inverter or the motor.

The motor system 200 includes: main battery 1, switch 2, dc bus capacitor 3, auxiliary battery 6, motor PM, one or more current sensors 100, speed sensor 101, inverter 210, and motor drive 220. The main battery 1 is a power supply of, for example, 400V, is connected between the positive side and the negative side of the dc bus of the inverter 210, and generates electric power to be supplied to the motor PM.

The switch 2 is provided between the main battery 1 and the dc bus capacitor 3 and the inverter 210, and switches whether or not to connect the main battery 1 to the capacitor 3 and the inverter 210. As an example, the switch 2 may be switched to the on state in response to a start of the motor system 200 or a vehicle mounting the motor system 200, or the like, and may be switched to the off state in response to a failure or an abnormality of the motor system 200 or the vehicle mounting the motor system 200, or a voltage between the dc buses exceeding an upper limit voltage in accordance with regeneration from the motor PM side, or the like. The switch 2 may be switched to the off state in response to a situation where the power supply from the auxiliary battery 6 is cut off, that is, for example, a situation where the voltage supplied from the auxiliary battery 6 becomes equal to or lower than a predetermined lower limit voltage.

Dc bus capacitor 3 is connected between the positive and negative dc buses on the inverter 210 side of switch 2. Here, the main battery 1 and the dc bus capacitor 3 are one example of the 2 nd power supply. The dc bus capacitor 3 stabilizes the dc bus voltage and absorbs the fluctuation of the current supplied to the inverter 210.

Auxiliary battery 6 is a power supply of, for example, 12V, and generates electric power to be supplied to motor drive device 220. Here, the auxiliary battery 6 is an example of the 1 st power supply. The auxiliary battery 6 may be connected to other devices (a starter, an electric device, and the like) provided in a vehicle or the like on which the motor system 200 is mounted, and may supply electric power to these devices. The negative side of the auxiliary battery 6, i.e., the ground GND _ N1, may be grounded to the main body of the vehicle, insulated from the main battery 1 and the dc bus capacitor 3.

The power supply circuit 13 is connected between the dc buses, receives power supply from the dc bus capacitor 3, and outputs a power supply voltage VHV _2 obtained by dropping the voltage of the positive side dc bus. Here, the power supply voltage VHV _2 may have a potential of +12V, which is a potential of the ground GND _ N2, for example, while setting a potential of the negative-side dc bus (i.e., a potential of the ground GND _ N2 in the drawing) as a reference potential. The power supply circuit 13 may be, for example, a direct-current voltage converter such as a DC/DC converter, and is not insulated from the main battery 1 and the direct-current bus capacitor 3.

As one example, the motor PM is a 3-phase Permanent Magnet (PM) motor. Alternatively, motor PM may have a different number of phases, or may be another type of motor that receives the supply of electric power and rotates. In the present embodiment, the electric motor PM rotates the wheels of the vehicle on which the motor system 200 is mounted.

One or more current sensors 100 are provided in a part or all of one or more wires connected to the motor PM, and detect a current flowing through the corresponding wire. The Current sensor 100 may be a Current sensor that measures a Current in a non-contact manner with a wiring to be measured, such as a CT (Current Transformer) type. Speed sensor 101 is an example of the 1 st rotation detecting portion, receives power supply from auxiliary battery 6, and detects rotation of motor PM. The speed sensor 101 may be a rotation speed sensor or a rotation angle sensor or the like that detects a rotation angle of the motor PM.

The inverter 210 is connected between the dc bus lines, converts a dc bus voltage into an ac voltage (in the present embodiment, a 3-phase ac voltage) for driving the motor PM, and supplies the ac voltage to the motor PM. The inverter 210 includes a plurality of upper-arm-side switching elements 4a to 4c (hereinafter also referred to as "upper-arm-side switching elements 4") and a plurality of lower-arm-side switching elements 5a to 5c (hereinafter also referred to as "lower-arm-side switching elements 5") corresponding to the respective motors PM. Each upper-arm-side switching element 4 and each lower-arm-side switching element 5 may be a power semiconductor switch, and as an example, is an IGBT (insulated gate bipolar transistor) having a collector and an emitter as main terminals and a gate as a control terminal. Alternatively, each upper arm side switching element 4 and each lower arm side switching element 5 may be a MOSFET having a drain and a source as main terminals, and a gate as a control terminal.

Main terminals of the upper arm-side switching element 4a and the lower arm-side switching element 5a are connected in parallel with the dc bus capacitor 3 in this order between the positive-side dc bus and the negative-side dc bus, and a phase 1 terminal (U-phase terminal) of the motor PM is connected between the upper arm-side switching element 4a and the lower arm-side switching element 5 a. Main terminals of the upper arm side switching element 4b and the lower arm side switching element 5b, and the upper arm side switching element 4c and the lower arm side switching element 5c are connected between dc busbars in the same manner as the upper arm side switching element 4a and the lower arm side switching element 5a, a phase 2 terminal (phase V terminal) of the motor PM is connected between the upper arm side switching element 4b and the lower arm side switching element 5b, and a phase 3 terminal (phase W terminal) of the motor PM is connected between the upper arm side switching element 4c and the lower arm side switching element 5 c.

Each of the upper-arm-side switching elements 4 and each of the lower-arm-side switching elements 5 may have a freewheeling diode reversely connected to the switching element body. Here, when each upper arm side switching element 4 and each lower arm side switching element 5 are MOSFETs, the free wheel diode is a parasitic diode.

At least one of each of the upper arm side switching element 4 and the lower arm side switching element 5 has a current detection terminal. In the present embodiment, one of the lower arm side switching elements (for example, the lower arm side switching element 5a) has a current detection terminal. The current detection terminal allows a small current for current detection corresponding to the current flowing between the main terminals to flow therethrough. For example, in the case of an IGBT, in order to detect a current flowing through the IGBT, there is a sense emitter terminal. Such a sense emitter terminal may be utilized as a current detection terminal.

Here, when the switching element is off, the lower-arm switching element 5a to be a target of current detection does not allow current to flow through the switching element main body, but allows current to flow from the negative-side dc bus to the motor PM via the freewheeling diode. Therefore, in the present embodiment, the lower arm-side switching element 5a has a small current detection diode connected in parallel to the flywheel diode, and has a terminal, as a current detection terminal, to which the sense emitter terminal and the anode of the current detection diode are connected. In such a current detection terminal, a current obtained by combining a current flowing through the sense emitter terminal of the lower arm-side switching element 5a and a current flowing through the current detection diode, that is, a sense current corresponding to a current flowing through the entire lower arm-side switching element 5a including the flywheel diode flows. In addition, the sense current may be proportional to a current flowing through the entire lower arm-side switching element 5a to some extent in the steady state, but is not necessarily proportional in the transient state. The inverter 210 supplies a current detection signal corresponding to such a sensed current to the motor drive device 220. As one example, the current detection signal is a signal having a voltage of a magnitude corresponding to the sense current obtained by flowing the sense current through a sense resistor having a predetermined resistance value. In addition, the lower arm side switching element 5a may be designed such that the ratio between the magnitude of the freewheeling diode current and the magnitude of the current flowing through the current detection diode and the ratio between the magnitude of the current flowing through the emitter in the switching element body and the magnitude of the current flowing through the sense emitter are substantially the same.

Motor drive device 220 is connected to inverter 210, receives power supply from power supply circuit 13 and auxiliary battery 6, and controls inverter 210. Motor drive device 220 includes: the control circuit 7, the 1 st fail-safe circuit 8, the failure detection circuit 15, the plurality of upper arm power supply circuits 9a to 9c, the plurality of upper arm gate drive circuits 12a to 12c, the lower arm power supply circuit 10, the power supply circuit 13, the speed detection section 22, the 2 nd fail-safe circuit 14, and the plurality of gate drive circuits 21a to 21 c.

The control circuit 7 sets the potential of the ground GND _ N1 on the negative side of the auxiliary battery 6 as a reference potential, and receives power supply from the auxiliary battery 6. The control circuit 7 may be implemented by a CPU such as a microcontroller or a processor for controlling the motor, or a computer including the CPU. Alternatively, the control circuit 7 may be implemented by a hardware circuit. The Control circuit 7 receives a torque command τ designating the torque of the drive motor PM from a computer (not shown) such as an ECU (Electric Control Unit) of the vehicle, and generates and outputs gate drive commands Gu _ LV1, Gv _ LV1, Gw _ LV1, Gx _ LV1, Gy _ LV1, and Gz _ LV1 for driving the motor PM so as to generate a torque corresponding to the torque command τ. Gu _ LV1, Gv _ LV1, Gw _ LV1, Gx _ LV1, Gy _ LV1, and Gz _ LV1 are gate drive commands corresponding to the upper arm side switching element 4a, the upper arm side switching element 4b, the upper arm side switching element 4c, the lower arm side switching element 5a, the lower arm side switching element 5b, and the lower arm side switching element 5c in this order. In the present embodiment, the control circuit 7 outputs a gate drive command that instructs the inverter 210 to generate a 3-phase alternating current for rotating the motor PM at a torque specified by the torque command τ ×.

The 1 st fail-safe circuit 8 sets the potential of the ground GND _ N1 to a reference potential, and receives power supply from at least the auxiliary battery 6. In the present embodiment, the 1 st fail-safe circuit 8 receives the electric power supplied from the auxiliary battery 6, but does not receive the electric power supplied from the main battery 1 and the dc bus capacitor 3. The 1 st fail-safe circuit 8 performs fail-safe control of at least the gate drive circuit that receives power supply from the auxiliary battery 6, of the upper arm gate drive circuits 12a to 12c and the lower arm gate drive circuits 21a to 21c, using the detection signal from the speed sensor 101. In the present embodiment, the 1 st fail-safe circuit 8 performs fail-safe control of the upper arm gate drive circuits 12a to 12c that receive power supply from the speed sensor 101. In the present embodiment, since the gate drive circuits 21a to 21c also receive power supply from the speed sensor 101, the 1 st fail-safe circuit 8 also performs fail-safe control of the gate drive circuits 21a to 21 c.

Specifically, the 1 st fail-safe circuit 8 receives the gate drive commands Gu _ LV1, Gv _ LV1, Gw _ LV1, Gx _ LV1, Gy _ LV1, and Gz _ LV1 from the control circuit 7, and outputs the gate drive commands Gu _ LV1, Gv _ LV1, Gw _ LV1, Gx _ LV1, Gy _ LV1, and Gz _ LV1 as the gate drive commands Gu _ LV2, Gv _ LV2, Gw _ LV2, Gx _ LV2, Gy _ LV2, and Gz _ LV2 without changing the values of the gate drive commands Gu _ LV1, Gv _ LV1, Gw _ LV1, Gx _ LV1, Gy _ LV1 during the normal operation. Thereby, inverter 210 drives motor PM according to the control of control circuit 7. In the fail-safe operation, the 1 st fail-safe circuit 8 may perform fail-safe control on the inverter 210, the fail-safe control including at least one of setting all of the upper arm-side switching elements 4a to 4c in an on state and setting all of the lower arm-side switching elements 5a to 5c in an on state, when the rotation speed of the motor PM is equal to or greater than the threshold value.

The failure detection circuit 15 is connected to the control circuit 7 and receives power supply from the auxiliary battery 6. The failure detection circuit 15 monitors the control circuit 7 and detects a failure or abnormality of the control circuit 7, and resets and restarts the control circuit 7 according to the kind of the failure or abnormality. Further, the failure detection circuit 15 instructs the 1 st fail-safe circuit 8 to perform fail-safe control according to the type of failure or abnormality.

The upper arm power supply circuits 9a to 9c respectively receive power supply from the auxiliary battery 6, and convert a power supply voltage from the auxiliary battery 6 into a power supply voltage for controlling each of the upper arm side switching elements 4a to 4 c. Here, the upper arm side power supply circuit 9a outputs a voltage in which the main terminal of the upper arm side switching element 4a on the lower arm side switching element 5a side (in the present embodiment, the emitter terminal of the upper arm side switching element 4 a) is set to a reference potential (ground GND _ U) as a power supply voltage (for example, a potential +12V of GND _ U) for controlling the upper arm side switching element 4 a. The upper arm power supply circuit 9b outputs a voltage having the ground GND _ V set as a reference potential as a power supply voltage for controlling the upper arm side switching element 4 b. The upper arm power supply circuit 9c outputs a voltage having the ground GND _ W as a reference potential as a power supply voltage for controlling the upper arm switch element 4 c. As one example, the upper arm power supply circuits 9a to 9c may be insulation type DC/DC converters including insulation transformers, respectively.

The upper arm gate drive circuits 12a to 12c are connected to the 1 st fail-safe circuit 8, and receive power supply from the auxiliary battery 6 and the upper arm power supply circuits 9a to 9 c. The upper arm gate drive circuits 12a to 12c drive the gates of the upper arm side switching elements 4a to 4c based on the gate drive command from the 1 st fail-safe circuit 8. More specifically, the upper arm gate drive circuit 12a includes an insulating element such as an optocoupler which is electrically insulated and transmits a signal, boosts the gate drive command Gu _ LV2 having the reference potential (ground GND _ N1) of the auxiliary battery 6 as the reference potential to the gate drive command GuO _ HV having the ground GND _ U as the reference potential, and outputs the gate drive command to the gate of the upper arm side switching element 4 a. The upper arm gate drive circuit 12b and the upper arm gate drive circuit 12c are also the same.

The lower arm power supply circuit 10 receives power supply from the auxiliary battery 6, and converts the power supply voltage of the auxiliary battery 6 with the ground GND _ N1 set as the reference potential into the power supply voltage VHV _1 with the ground GND _ N2 set as the reference potential (e.g., the potential +12V of the ground GND _ N2). The lower arm power supply circuit 10 may be an insulation type DC/DC converter including an insulation transformer.

The power supply voltage VHV _1 from the lower arm power supply circuit 10 and the power supply voltage VHV _2 from the power supply circuit 13 are merged into a power supply voltage VHV via a rectifier element such as a rectifier diode, for example. Thus, the power supply voltage VHV is made redundant so that even if any one of the power supply voltage VHV _1 and the power supply voltage VHV _2 is lost, the power supply voltage VHV is not lost.

The speed detection portion 22 is an example of a 2 nd rotation detection portion, receives at least power supply from the 2 nd power supply, and detects rotation of the motor PM. Speed detecting unit 22 receives power supplied from power supply voltage VHV, and detects rotation of motor PM based on a current detection signal from a current detection terminal of upper arm-side switching element 4 or lower arm-side switching element 5. In the present embodiment, the speed detector 22 outputs a detection signal N _ det corresponding to the rotation speed of the motor based on a current detection signal from a current detection terminal of the lower arm-side switching element 5 a.

The 2 nd fail-safe circuit 14 is connected to the speed detection section 22 and receives at least power supply from the 2 nd power supply. In the present embodiment, the 2 nd fail-safe circuit 14 receives power supply from the power supply voltage VHV. The 2 nd fail-safe circuit 14 performs fail-safe control of at least the gate drive circuits (in the present embodiment, the gate drive circuits 21a to 21c) that receive power supply from the power supply circuit 13, of the upper arm gate drive circuits 12a to 12c and the lower arm gate drive circuits 21a to 21c, using the detection signal N _ det from the speed detection section 22.

In the present embodiment, the 2 nd fail-safe circuit 14 detects that the power supply from the auxiliary battery 6 is lost, based on the fact that the power supply voltage VHV _1 is input from the lower arm power supply circuit 10 and the power supply voltage VHV _1 becomes equal to or lower than the lower limit voltage. When the power supply from the auxiliary battery 6 is lost, the 2 nd fail-safe circuit 14 performs fail-safe control on the gate drive circuits 21a to 21c that receive the power supply from the dc bus capacitor 3 via the power supply circuit 13. In the present embodiment, the 2 nd fail-safe circuit 14 sets the gate drive command Gxyz _ HV to logic L (low) in the normal operation. In the fail-safe control, when the rotation speed of the motor PM is equal to or greater than the threshold value, the 2 nd fail-safe circuit 14 sets the gate drive command Gxyz _ HV to logic H (high), and turns on all the lower arm-side switching elements 5a to 5 c.

The gate drive circuits 21a to 21c are connected to the 1 st fail-safe circuit 8 and the 2 nd fail-safe circuit 14, and receive power supply from the auxiliary battery 6 and the power supply voltage VHV. The gate drive circuits 21a to 21c function as lower arm gate drive circuits, and drive the gates of the lower arm side switching elements 5a to 5c based on gate drive commands from the 1 st fail-safe circuit 8 and the 2 nd fail-safe circuit 14. When the gate drive command Gxyz _ HV from the 2 nd fail-safe circuit 14 is logic L, the gate drive circuit 21a switches the lower arm side switching element 5a on or off based on the gate drive command Gx _ LV2 from the 1 st fail-safe circuit 8, and when the gate drive command Gxyz _ HV is logic H, outputs a gate drive command GxO _ HV for turning the lower arm side switching element 5a on to the lower arm side switching element 5 a. Here, the gate drive command GxO _ HV is a signal for setting the reference potential (ground GND _ N2) of the main battery 1 and the dc bus capacitor 3 to the reference potential. The speed detection unit 22b and the speed detection unit 22c also have the same function.

According to the motor system 200 described above, the upper arm gate drive circuits 12a to 12c and the speed sensor 101 receive power supply from the auxiliary battery 6, but do not receive power supply from the power supply circuit 13. On the other hand, the speed detection unit 22, the No. 2 fail-safe circuit 14, and the gate drive circuits 21a to 21c receive power supply from the power supply circuit 13. Thus, even when the auxiliary battery 6 is lost, the upper arm gate drive circuits 12a to 12c are not operated, and the rotation speed cannot be detected by the speed sensor 101, the motor system 200 can perform the fail-safe control by the speed detection unit 22 receiving the power supply from the power supply circuit 13 and the No. 2 fail-safe circuit 14.

Further, the lower arm power supply circuit 10 and the power supply circuit 13 supply power to the speed detection unit 22, the 2 nd failsafe circuit 14, and the gate drive circuits 21a to 21c, but do not supply power to the control circuit 7, the 1 st failsafe circuit 8, the upper arm gate drive circuits 12a to 12c, and the failure detection circuit 15, so that the maximum output power of the lower arm power supply circuit 10 and the power supply circuit 13 can be suppressed, and the lower arm power supply circuit 10 and the power supply circuit 13 can be downsized.

In the present embodiment, the power supply of the circuit portion that controls the lower arm side switching elements 5a to 5c is made redundant by the power supply circuit 13 and the auxiliary battery 6. Alternatively, the circuit portion for controlling the lower arm side switching elements 5a to 5c may be configured not to supply electric power from the auxiliary battery 6. In this case, the motor system 200 performs fail-safe control on the upper arm-side switching elements 4a to 4c when the power supply from the auxiliary battery 6 is lost, and performs fail-safe control on the lower arm-side switching elements 5a to 5c when the power supply from the main battery 1 and the dc bus capacitor 3 is lost. Instead of making the power supply of the circuit portion that controls the lower arm side switching elements 5a to 5c redundant, the power supply of the circuit portion that controls the upper arm side switching elements 4a to 4c may be made redundant, and the speed detection section 22 and the No. 2 fail-safe circuit 14 may be used for the upper arm gate drive circuits 12a to 12 c.

Fig. 2 shows an example of the configuration of the speed detection unit 22 according to the present embodiment. The speed detection section 22 includes a reference voltage source 26, a converter CMP1, a monostable 24, and a low-pass filter 25. The reference voltage source 26 generates a reference voltage to be compared with a voltage value of the current detection signal Ix from the current detection terminal of the lower arm side switching element 5 a. In the present embodiment, current detection signal Ix has a voltage value corresponding to the sum of currents flowing through the switching element main body of lower arm-side switching element 5a and the flywheel diode, and is a sinusoidal signal having a period corresponding to the rotation period of motor PM. The frequency of such a signal should be detected, and as an example, the reference voltage source 26 generates 0V or a voltage obtained by subtracting a predetermined minute redundancy from 0V.

The converter CMP1 compares the current detection signal Ix with a reference voltage generated by the reference voltage source 26 and outputs a logic signal corresponding to the comparison result. Since current detection signal Ix has a period corresponding to the rotation period of motor PM, converter CMP1 outputs a logic signal including a period of logic H and a period of logic L every 1 cycle of the rotation period of motor PM. In addition, the converter CMP1 may also have hysteresis.

The monostable 24 generates a pulse signal having a pulse with a width determined according to the design of the monostable 24, using the logic signal output by the converter CMP1 as a trigger. In the present embodiment, the monostable 24 generates a pulse signal by triggering a falling edge (change from logic H to logic L) of the logic signal output from the converter CMP 1.

The low-pass filter 25 generates a detection signal N _ det corresponding to the pulse density (i.e., the ratio of the period of logic H) in the pulse signal output from the monostable 24. Specifically, the pulse signal output by the monostable circuit 24 has a pulse having a width predetermined for each period corresponding to the rotation period of the motor PM, and therefore, in the case where the rotation period of the motor PM is smaller (i.e., the rotation speed of the motor PM is larger), the proportion of the period of the logic H becomes higher, and in the case where the rotation period of the motor PM is larger (i.e., the rotation speed of the motor PM is smaller), the proportion of the period of the logic H becomes smaller. By smoothing such a pulse signal, the low-pass filter 25 can output the detection signal N _ det having a larger value (voltage value, as an example) when the rotation speed of the motor PM is larger, and can output the detection signal N _ det having a smaller value when the rotation speed of the motor PM is smaller.

Fig. 3 shows one example of the output characteristics of the current detection terminal in the on state of the switching element. When the lower-arm switching device 5a is on, the lower-arm switching device 5a may be configured to flow a current in any one of a direction from the negative-side dc bus to the motor PM and a direction from the motor PM to the negative-side dc bus. Therefore, the current detection signal (current sense signal in the figure) takes a positive value or a negative value depending on the positive or negative of the current Ic flowing through the lower arm side switching element 5 a.

Fig. 4 shows one example of a speed detection method in the on state of the switching element. When lower arm-side switching element 5a is on, current detection signal Ix changes between positive and negative as shown in the upper graph of fig. 4, and a sinusoidal signal waveform having a period corresponding to the rotation speed of motor PM is obtained. When the reference voltage source 26 generates a reference voltage of 0V, the converter CMP1 outputs a logic signal of logic H when the current detection signal Ix is positive (when it exceeds 0V), and outputs a logic signal of logic L when the current detection signal Ix is negative or 0 (when it is 0V or less). As shown in the lower graph of fig. 4, the monostable 24 generates a pulse of a fixed width at the falling edge of the logic signal (i.e., the timing at which the current detection signal Ix changes from positive to negative). The low-pass filter 25 may generate the detection signal N _ det corresponding to the rotation speed of the motor PM by smoothing a pulse signal including such pulses.

Fig. 5 shows one example of the output characteristics of the current detection terminal in the off state of the switching element. When lower arm side switching element 5a is off, a current in the direction from the negative side dc bus to motor PM flows through the freewheeling diode and the current detection diode in lower arm side switching element 5a, but a current in the direction from motor PM to the negative side dc bus is cut off. Therefore, the current detection signal (current sense signal in the figure) takes a negative value, but does not take a positive value, when the current Ic flowing through the lower arm side switching element 5a is negative.

Fig. 6 shows one example of a speed detection method in an off state of the switching element. When the lower arm-side switching element 5a is off, as shown in the upper graph of fig. 6, the current detection signal Ix is not positive, and a signal waveform whose upper limit is 0 is obtained among sinusoidal signal waveforms having a period corresponding to the rotation speed of the motor PM. When the reference voltage source 26 generates a reference voltage obtained by subtracting the redundancy from 0V, the converter CMP1 outputs a logic signal of logic H when the current detection signal Ix is substantially 0V, and outputs a logic signal of logic L when the current detection signal Ix is negative. As shown in the lower graph of fig. 6, the monostable 24 generates a pulse of a fixed width at the falling edge of the logic signal (i.e., at the timing when the current detection signal Ix changes from 0 to negative exceeding the redundancy). The low-pass filter 25 may generate the detection signal N _ det corresponding to the rotation speed of the motor PM by smoothing a pulse signal including such pulses. Further, when the reference voltage source 26 generates a reference voltage obtained by subtracting the redundancy from 0V, the speed detection unit 22 may detect the rotation speed of the motor PM when the lower arm side switching element 5a is on or off.

As the lower arm-side switching element 5a, an element not having a current detection small diode connected in parallel with a flywheel diode may be used. In such a configuration, when the lower arm side switching element 5a is off, the current flowing through the lower arm side switching element 5a cannot be detected. When lower arm-side switching element 5a is on, although a current (positive current Ic) flowing from motor PM to the negative dc bus can be detected, a partial current flowing through the flywheel diode cannot be detected out of a current (negative current Ic) flowing from the negative dc bus to motor PM. Therefore, the speed detection unit 22 may be configured such that, for example, the reference voltage source 26 is set to a voltage obtained by adding a positive redundancy to 0V, and the monostable circuit 24 generates a pulse signal based on a signal waveform of a portion equal to or greater than 0 in the signal waveform of the current detection signal Ix. In addition, when the positive or negative of the current flowing through the lower arm side switching element 5a can be accurately detected even if the partial current flowing through the flywheel diode cannot be detected, the speed detection unit 22 may be configured such that the monostable circuit 24 generates a pulse signal at a timing when the current detection signal Ix changes from negative to positive.

Fig. 7 shows an example of the 2 nd fail-safe circuit 14 according to the present embodiment. Fail-safe circuit 2 14 includes reference voltage source 23, converter CMP2, reference voltage source 19, converter CMP3, AND logical AND element AND 1.

The reference voltage source 23 generates a reference voltage. In the present embodiment, the reference voltage source 23 generates the threshold voltage Vth of the detection signal N _ det set according to the rotation speed of the motor PM being the lower limit rotation speed Vsafe at which the fail-safe control is performed. In the converter CMP2, the speed detector 22 is connected to a positive input terminal (non-inverting input terminal) to receive the detection signal N _ det, and the reference voltage of the reference voltage source 23 of the converter CMP2 is input to a negative input terminal (inverting input terminal). Thus, the converter CMP2 outputs logic L when the detection signal N _ det is equal to or less than the threshold voltage Vth, and outputs logic H when the detection signal N _ det exceeds the threshold voltage Vth. In addition, the converter CMP2 may also have hysteresis.

The reference voltage source 19 generates a reference voltage. In the present embodiment, the reference voltage source 19 generates a threshold voltage with reference to whether or not the auxiliary battery 6 is normal. In the converter CMP3, the power supply voltage VHV _1 from the lower arm power supply circuit 10 is input to the negative input terminal (inverting input terminal), and the reference voltage of the reference voltage source 19 is input to the positive input terminal (non-inverting input terminal). Thus, converter CMP3 outputs logic L when power supply voltage VHV _1 is higher than the threshold voltage, and outputs logic H when power supply voltage VHV _1 is equal to or lower than the threshold voltage (that is, when it is determined that auxiliary battery 6 is lost). In addition, the converter CMP3 may also have hysteresis.

The AND element AND1 outputs the gate drive signal Gxyz _ HV of logic H when both the output of the converter CMP2 AND the output of the converter CMP3 are logic H (that is, when the threshold value for determining logic H is exceeded). Thus, the 2 nd fail-safe circuit 14 sets the drive signal Gxyz _ HV for performing fail-safe control for turning on all the lower arm-side switching elements 5a to 5c to logic H, in response to the loss of the auxiliary battery 6 and the fact that the rotation speed of the motor PM exceeds the predetermined threshold lower limit value.

Fig. 8 shows an example of the gate driver circuit 21 according to the present embodiment. In this figure, the configuration of the gate drive circuit 21a among the gate drive circuits 21a to 21c is described as a representative example, but the gate drive circuit 21b and the gate drive circuit 21c may have the same configuration. The gate drive circuit 21a includes an insulation circuit 18, a buffer BUF1, a buffer BUF2, and an OR logic element OR 1.

The isolation circuit 18 includes an isolation transformer, an optocoupler, or the like. The insulation circuit 18 receives the power supply voltage VLV and the power supply voltage VHV, and converts the gate drive command Gx _ LV2 set to the reference potential with the ground GND _ N1 into a gate drive command set to the reference potential with the ground GND _ N2.

The buffer BUF1 shapes and outputs the gate drive command Gxyz _ HV set to the reference potential with the ground GND _ N2. The buffer BUF2 shapes and outputs the gate drive command obtained by converting the gate drive command Gx _ LV 2. The logical OR element OR1 outputs a logical OR of the output of the buffer BUF1 and the output of the buffer BUF 2. Thus, when at least one of the gate drive command Gxyz _ HV from the 2 nd fail-safe circuit 14 and the gate drive command Gx _ LV2 from the 1 st fail-safe circuit 8 is logic H, the OR element 1 outputs the gate drive command GxO _ HV having the ground GND _ N2 as logic H as the reference potential, and when both are logic L, outputs the gate drive command GxO _ HV having the ground GND _ N2 as logic L as the reference potential. Thus, during the normal operation, the isolation circuit 18 can supply a gate drive command corresponding to the gate drive command Gx _ LV1 from the control circuit 7 to the lower arm side switching element 5a, and supply the gate drive command Gxyz _ HV from the 2 nd fail-safe circuit 14 to the lower arm side switching element 5a when the auxiliary battery 6 is lost.

Fig. 9 shows an example of an operation waveform of the motor system according to the present embodiment. In this figure, the following are shown in order from top to bottom: the actual motor speed (rpm), the state of the contactor (switch 2), the motor speed detection value obtained by the speed detection unit 22 (i.e., the voltage of the detection signal N _ det), the gate drive command Gxyz _ HV output by the 2 nd fail-safe circuit 14, the states of the upper arm-side switching elements 4a to 4c, the states of the lower arm-side switching elements 5a to 5c, and the temporal changes in the state of the normal power supply (auxiliary battery 6).

At time t1, if the auxiliary battery 6 is lost due to an accident, a failure, or the like, the motor system 200 detects this and switches the switch 2 from the on state to the off state. In addition, in accordance with the loss of the auxiliary battery 6, the power supply voltage VHV _1 becomes equal to or lower than the threshold voltage. Therefore, in the 2 nd fail-safe circuit 14 shown in fig. 7, the converter CMP3 outputs logic H, AND the AND element AND1 outputs the gate drive command Gxyz _ HV of logic H while the detection signal N _ det exceeds the threshold voltage Vth. Even when switch 2 is turned off, power supply circuit 13 can continue to supply power supply voltage VHV _2 using the power charged in dc bus capacitor 3.

The upper arm gate drive circuits 12a to 12c receive power supply from the auxiliary battery 6, and become unable to drive the upper arm switching elements 4a to 4c with the loss of the auxiliary battery 6. Therefore, the upper arm side switching elements 4a to 4c are turned off. The gate drive circuits 21a to 21c receive the redundant power supply voltage VHV, and perform fail-safe control to turn all the lower arm-side switching elements 5a to 5c on in response to the gate drive command Gxyz _ HV becoming a logic H. If all of the lower arm-side switching elements 5a to 5c are turned on and the motor PM is in a winding short-circuited state, braking force acts on the motor PM and the rotation speed of the motor decreases.

At time t2, if the rotation speed of the motor PM becomes equal to or less than the lower limit rotation speed Vsafe at which the fail-safe control is performed, the detection signal N _ det becomes equal to or less than the threshold voltage Vth which is set in advance in accordance with the rotation speed Vsafe. Therefore, the output of the converter CMP2 changes from logic H to logic L, AND the gate drive signal Gxyz _ HV output by the AND element AND1 changes from logic H to logic L. Upon receiving the signals, the gate drive circuits 21a to 21c set the gate drive commands GxO _ HV, GyO _ HV, and GzO _ HV to logic L, thereby turning off the lower arm-side switching elements 5a to 5 c.

In this way, even when the auxiliary battery 6 is lost, the No. 2 fail-safe circuit 14 can perform fail-safe control of the gate drive circuits 21a to 21c receiving power supply from the power supply circuit 13 by using the detection signal N _ det of the speed detection unit 22 that detects rotation of the motor PM by receiving power supply from the power supply circuit 13. Even when the electric power supplied from the main battery 1 and the dc bus capacitor 3 is lost, the 1 st fail-safe circuit 8 receives the electric power supplied from the auxiliary battery and performs the same fail-safe control on the upper arm gate drive circuits 12a to 12c receiving the electric power supplied from the auxiliary battery 6 by using the speed sensor 101 that detects the rotation of the motor PM.

Fig. 10 shows a motor system 300 according to a modification of the present embodiment. The motor system 300 is a modification of the motor system 200 shown in fig. 1, and therefore, the description thereof is omitted except for the following points.

The motor system 300 employs the gate drive circuits 21d to 21f that are redundantly powered so that the gates of the upper arm-side switching elements 4a to 4c can be driven even if the auxiliary battery 6 is lost. Thus, the motor system 300 can perform fail-safe control in which the upper-arm-side switching elements 4a to 4c and the lower-arm-side switching elements 5a to 5c are all alternately turned on when the auxiliary battery 6 is lost.

The motor system 300 includes: main battery 1, switch 2, dc bus capacitor 3, auxiliary battery 6, power supply circuit 313, motor PM, one or more current sensors 100, speed sensor 101, inverter 210, and motor drive device 320. Here, the main battery 1, the switch 2, the dc bus capacitor 3, the auxiliary battery 6, the motor PM, the one or more current sensors 100, the speed sensor 101, and the inverter 210 are the same as those denoted by the same reference numerals in the motor system 200 shown in fig. 1, and therefore, description thereof is omitted.

The power supply circuit 313 is connected between the dc buses in the same manner as the power supply circuit 13, and outputs a voltage VHV _2 obtained by reducing the voltage of the dc bus on the positive side. The power supply circuit 313 outputs a power supply voltage VH _ U having a ground GND _ U as a reference potential, a power supply voltage VH _ V having a ground GND _ V as a reference potential, and a power supply voltage VH _ W having a ground GND _ W as a reference potential. In order to generate the power supply voltages VH _ U, VH _ V and VH _ W, respectively, as one example, the power supply circuit 313 may have an insulation type DC/DC converter including an insulation transformer.

Motor drive device 320 is connected to inverter 210, receives power supply from power supply circuit 313 and auxiliary battery 6, and controls inverter 210, as with motor drive device 220. The motor drive device 320 includes: the control circuit 7, the 1 st fail-safe circuit 8, the failure detection circuit 15, the plurality of upper arm power supply circuits 9a to 9c, the lower arm power supply circuit 10, the speed detection section 22, the 2 nd fail-safe circuit 314, the plurality of insulation circuits 27a to 27c, the plurality of gate drive circuits 21a to 21c, and the plurality of gate drive circuits 21d to 21 f. Here, the control circuit 7, the 1 st fail-safe circuit 8, the failure detection circuit 15, the plurality of upper arm power supply circuits 9a to 9c, the lower arm power supply circuit 10, the speed detection section 22, and the plurality of gate drive circuits 21a to 21c are the same as those denoted by the same reference numerals in the motor drive device 220 shown in fig. 1, and therefore, the description thereof is omitted.

The 2 nd fail-safe circuit 314 is connected to the speed detection section 22 and receives at least power supply from the 2 nd power supply. In the present modification, the 2 nd fail-safe circuit 314 receives power supply from the power supply voltage VHV. The 2 nd fail-safe circuit 314 performs fail-safe control on the gate drive circuits 21a to 21f that receive at least power supply from the power supply circuit 13, using the detection signal N _ det from the speed detection section 22.

In the present modification, the 2 nd fail-safe circuit 314 detects that the power supply from the auxiliary battery 6 is lost, based on the fact that the power supply voltage VHV _1 is input from the lower arm power supply circuit 10 and the power supply voltage VHV _1 becomes the lower limit voltage or less. The 2 nd fail-safe circuit 314 performs fail-safe control on the gate drive circuits 21a to 21c when the power supply from the auxiliary battery 6 is lost. The No. 2 fail-safe circuit 314 sets the gate drive command Gxyz _ HV to logic L in the normal operation. In the fail-safe control, the 2 nd fail-safe circuit 314 switches the gate drive command Gxyz _ HV alternately to logic H or logic L when the rotation speed of the motor PM is equal to or greater than the threshold value, thereby alternately turning on or off all of the lower arm-side switching elements 5a to 5 c.

As shown in fig. 10, the 2 nd fail-safe circuit 314 may further output a gate drive command Guvw _ HV to perform fail-safe control of the gate drive circuits 21d to 21 f. In the normal operation, the No. 2 fail-safe circuit 314 sets the gate drive command Gxyz _ HV and the gate drive command Guvw _ HV to logic L. In the fail-safe control, when the rotation speed of the motor PM is equal to or greater than the threshold value, the 2 nd fail-safe circuit 314 switches the gate drive command Gxyz _ HV alternately to logic H or logic L and sets the gate drive command Guvw _ HV to logic negation of the gate drive command Gxyz _ HV, thereby alternately turning on all of the upper-arm-side switching elements 4a to 4c and the lower-arm-side switching elements 5a to 5 c. As one example, the No. 2 fail-safe circuit 314 may include: the 2 nd fail-safe circuit 14; AND a control circuit that sets the gate drive command Gxyz _ HV AND the gate drive command Guvw _ HV to logic L when the AND-logic element AND1 of the 2 nd fail-safe circuit 14 outputs logic L, AND alternately sets the gate drive command Gxyz _ HV AND the gate drive command Guvw _ HV to logic H when the AND-logic element AND1 of the 2 nd fail-safe circuit 14 outputs logic H.

The insulating circuits 27a to 27c receive the gate drive signal Guvw _ HV with the ground GND _ N2 set to the reference potential, and convert the gate drive signal Guvw _ HV into a signal with the ground GND _ U set to the reference potential, a signal with the ground GND _ V set to the reference potential, and a signal with the ground GND _ W set to the reference potential, respectively. The insulating circuits 27a to 27c transmit the gate drive signal Guvw _ HV while insulating the ground GND _ N2 side from the grounds GND _ U, GND _ V, and GND _ W, respectively, by insulating elements such as photo couplers.

The gate drive circuits 21d to 21f function as upper arm gate drive circuits. The gate drive circuits 21d to 21f may have the same configuration as the gate drive circuit 21a shown in fig. 8. The gate drive circuit 21d is connected to the 1 st fail-safe circuit 8 and the insulation circuit 27a, and receives the power supply voltage VLV (with the ground GND _ N1 set to the reference potential) from the auxiliary battery 6 and receives the power supply voltage VH _ U (with the ground GND _ U set to the reference potential) from the power supply circuit 313 and the upper arm power supply circuit 9 a. Here, the power supply voltage from the power supply circuit 313 and the power supply voltage from the upper arm power supply circuit 9a are merged together via a rectifier element such as a rectifier diode, for example, to become the power supply voltage VH _ U. Thus, power supply voltage VH _ U is made redundant so that even if any one of the power supply voltage from power supply circuit 313 and the power supply voltage from upper arm power supply circuit 9a is lost, power supply voltage VH _ U is not lost.

The gate drive circuit 21d switches the upper arm side switching element 4a on or off based on the gate drive command Gu _ LV2 from the 1 st fail-safe circuit 8 when the gate drive command Guvm _ HV from the isolation circuit 27a is logic L, and outputs a gate drive command GuO _ HV for turning the upper arm side switching element 4a on to the upper arm side switching element 4a when the gate drive command Guvw _ HV is logic H. Here, the gate drive command GuO _ HV is a signal for setting the ground GND _ U to the reference potential. The gate drive circuits 21e to 21f also have the same function.

According to the present modification, in the motor system 300, the upper arm gate drive circuits 21a to 21c and the lower arm gate drive circuits 21d to 21f receive power supply from the auxiliary battery 6, the main battery 1, and the dc bus capacitor 3. Thus, even when the auxiliary battery 6 is lost, the motor system 300 can perform fail-safe control for alternately turning on all of the upper-arm-side switching elements 4a to 4c and the lower-arm-side switching elements 5a to 5c using the gate drive circuits 21a to 21f, and can increase the consumption of the power stored in the dc bus capacitor 3.

Fig. 11 shows a 1 st example of the operation waveform of the motor system 300. In this figure, the following are shown in order from top to bottom: the actual motor speed (rpm), the state of the contactor (switch 2), the motor speed detection value obtained by the speed detection unit 22 (i.e., the voltage of the detection signal N _ det), the gate drive command Gxyz _ HV output by the 2 nd fail-safe circuit 314, the states of the upper arm-side switching elements 4a to 4c, the states of the lower arm-side switching elements 5a to 5c, and the temporal changes in the state of the normal power supply (auxiliary battery 6).

At time t1, if the auxiliary battery 6 is lost due to an accident, a failure, or the like, the motor system 300 detects this and switches the switch 2 from the on state to the off state. In addition, in accordance with the loss of the auxiliary battery 6, the power supply voltage VHV _1 becomes equal to or lower than the threshold voltage. Therefore, the No. 2 fail-safe circuit 314 performs fail-safe control for alternately turning on all of the gate drive command Guvw _ HV and the gate drive command Gxyz _ HV on the condition that the detection signal N _ det exceeds the threshold voltage Vth.

In the present example, in the fail-safe control, the speed detection unit 22 senses the current detection signal from the lower arm side switching element 5a while the lower arm side switching element 5a is on every predetermined cycle or irregularly. Here, the 2 nd fail-safe circuit 314 may be configured such that a period during which all of the lower arm side switching elements 5a to 5c are turned on when the speed detection unit 22 senses the current detection signal is longer than a period during which all of the lower arm side switching elements 5a to 5c are turned on when the speed detection unit 22 does not sense the current detection signal.

For example, at time t2, speed detector 22 senses the current detection signal while gate drive command Gxyz _ HV is logic H. For this reason, the 2 nd fail-safe circuit 314 may be configured to make the lower arm side switching elements 5a to 5c all conductive at time t2 longer than a period in which the lower arm side switching elements 5a to 5c all are conductive when the current detection signal is not sensed, in a period from time t2 to time t3 when the current detection signal is sensed next. Here, the 2 nd fail-safe circuit 314 may be configured such that the period during which all of the lower arm side switching elements 5a to 5c are turned on when the speed detection unit 22 senses the current detection signal is longer than the period during which all of the lower arm side switching elements 5a to 5c are turned on when the speed detection unit 22 does not sense the current detection signal, or may be configured such that the period is longer than at least one period during which all of the lower arm side switching elements 5a to 5c are turned on when the speed detection unit 22 does not sense the current detection signal, as shown in fig. 11. As shown in the drawing, the 2 nd fail-safe circuit 314 may be configured such that the frequency of alternately turning on all of the upper-arm-side switching elements 4a to 4c and the lower-arm-side switching elements 5a to 5c during a period including the timing of sensing the current detection signal is lower than the frequency of alternately turning on all of the upper-arm-side switching elements 4a to 4c and the lower-arm-side switching elements 5a to 5c during a period not including the timing of sensing the current detection signal. At times t3 and t4, the speed detector 22 senses the current detection signal from the lower arm side switching element 5a while the lower arm side switching element 5a is on, as at time t 2.

At time t5, if the rotation speed of the motor PM becomes equal to or less than the lower limit rotation speed Vsafe at which the fail-safe control is performed, the detection signal N _ det becomes equal to or less than the threshold voltage Vth that is set in advance in accordance with the rotation speed Vsafe. Therefore, the 2 nd fail-safe circuit 314 ends fail-safe control for alternately turning on all of the upper arm-side switching elements 4a to 4c and the lower arm-side switching elements 5a to 5 c.

Thus, the 2 nd fail-safe circuit 314 can secure a longer time from when all the lower arm side switching elements 5a to 5c are turned on until the speed detection unit 22 senses the current detection signal, and can sense the current detection signal after the current detection signal is further stabilized after the switching of the lower arm side switching elements 5a to 5 c. Thus, even when all of the upper arm side switching elements 4a to 4c and the lower arm side switching elements 5a to 5c to be rapidly discharged from the dc bus capacitor 3 are turned on alternately, the speed detection unit 22 can sense the current detection signal after the noise associated with the switching is reduced. In the case where the speed detector 22 detects a current flowing through at least one of the upper arm side switching elements 4a to 4c, the No. 2 fail-safe circuit 314 may make a period during which all of the upper arm side switching elements 4a to 4c are turned on when the speed detector 22 senses a current detection signal longer than a period during which all of the upper arm side switching elements 4a to 4c are turned on when the speed detector 22 does not sense a current detection signal in the fail-safe control.

Fig. 12 shows a 2 nd example of the action waveform of the motor system 300. In the example of the present figure, the gate drive command Gxyz _ HV output by the 2 nd fail-safe circuit 314, the states of the upper arm-side switching elements 4a to 4c, and the temporal changes in the states of the lower arm-side switching elements 5a to 5c are different from those in fig. 11, and therefore the following description will be given mainly on these points.

In this example, the 2 nd fail-safe circuit 314 may make a period during which all the lower arm side switching elements 5a to 5c are turned on when the speed detection unit 22 senses the current detection signal longer than a period during which all the lower arm side switching elements 5a to 5c are turned on when the speed detection unit 22 does not sense the current detection signal, in the fail-safe control. In the example of the present figure, at times t2, t3, and t4, the period during which all of the lower arm side switching elements 5a to 5c are turned on when the speed detector 22 senses the current detection signal is maintained longer than the other period during which all of the lower arm side switching elements 5a to 5c are turned on and the respective periods during which all of the upper arm side switching elements 4a to 4c are turned on.

Thus, the 2 nd fail-safe circuit 314 can secure a longer time from when all the lower arm side switching elements 5a to 5c are turned on until the speed detector 22 senses the current detection signal, as in fig. 11, and can sense the current detection signal after the switched current detection signals of the lower arm side switching elements 5a to 5c are further stabilized. In the case where the speed detector 22 detects a current flowing through at least one of the upper arm side switching elements 4a to 4c, the No. 2 fail-safe circuit 314 may make a period during which all of the upper arm side switching elements 4a to 4c are turned on when the speed detector 22 senses a current detection signal longer than a period during which all of the upper arm side switching elements 4a to 4c are turned on when the speed detector 22 does not sense a current detection signal in the fail-safe control.

Fig. 13 shows a 3 rd example of the action waveform of the motor system 300. In the example of the present figure, the gate drive command Gxyz _ HV output by the 2 nd fail-safe circuit 314, the states of the upper arm-side switching elements 4a to 4c, and the temporal changes in the states of the lower arm-side switching elements 5a to 5c are different from those in fig. 11 and 12, and therefore, the following description will be given mainly of these contents.

In this example, the 2 nd fail-safe circuit 314 may make a period during which all of the lower arm-side switching elements 5a to 5c are turned on longer than a period during which all of the upper arm-side switching elements 4a to 4c are turned on when the speed detection unit 22 senses the current detection signal in the fail-safe control. In the example of the present figure, in the fail-safe control, the time length of each period for turning on all the upper arm side switching elements 4a to 4c is substantially the same as one example, and the time length of each period for turning on all the lower arm side switching elements 5a to 5c is substantially the same as one example, and is larger than each period for turning on all the upper arm side switching elements 4a to 4 c.

Thus, the 2 nd fail-safe circuit 314 can secure a longer time from turning on all the lower arm side switching elements 5a to 5c until the speed detector 22 senses the current detection signal, as in fig. 11 and 12, and can sense the current detection signal after the switched current detection signals of the lower arm side switching elements 5a to 5c are further stabilized. In the case where the speed detector 22 detects a current flowing through at least one of the upper arm side switching elements 4a to 4c, the No. 2 fail-safe circuit 314 may make a period during which all of the lower arm side switching elements 5a to 5c are turned on longer than a period during which all of the upper arm side switching elements 4a to 4c are turned on when the speed detector 22 senses a current detection signal in the fail-safe control.

Separately from the fail-safe control of fig. 11 to 13 or in common with the fail-safe control of fig. 11 to 13, when the power supply from the main battery 1, the dc bus capacitor 3, or the power supply current 313 is lost or is lost, the motor system 300 may perform the fail-safe control of alternately turning on all the upper arm side switching elements 4a to 4c and the lower arm side switching elements 5a to 5c by the 1 st fail-safe circuit 8 in the same manner as the 2 nd fail-safe circuit 314.

As described with reference to fig. 5 and 6, the speed detector 22 may detect the rotation of the motor PM while the lower arm side switching element 5a is on, based on the current detection signal from the lower arm side switching element 5 a. In this case, instead of making the period during which all the lower arm side switching elements 5a to 5c are turned on when the speed detection unit 22 senses the current detection signal longer in fig. 11 and 13, the 2 nd fail-safe circuit 314 may make the period during which all the lower arm side switching elements 5a to 5c are turned on when the speed detection unit 22 senses the current detection signal longer.

The present invention has been described above with reference to the embodiments, but the technical scope of the present invention is not limited to the scope described in the above embodiments. It will be apparent to those skilled in the art that various changes or modifications may be made to the above embodiments. It is clear from the description of the scope of the claims that the embodiment to which such a change or improvement is applied is also included in the technical scope of the present invention.

It should be noted that the execution order of the respective processes of the actions, the sequence, the steps, the stages, and the like in the apparatus, the system, the program, and the method shown in the claims, the description, and the drawings may be realized in any order as long as the execution order is not specifically explicitly shown as "before", and the like, and further, as long as the output of the previous process is not used in the subsequent process. In the operation flows in the claims, the specification, and the drawings, the terms "first", "next", and the like are used for convenience of description, but the terms do not necessarily mean that the operations are performed in this order.