WO2021124453A1

WO2021124453A1 - Inverter circuit

Info

Publication number: WO2021124453A1
Application number: PCT/JP2019/049446
Authority: WO
Inventors: 歩生小石
Original assignee: 株式会社デンソー
Priority date: 2019-12-17
Filing date: 2019-12-17
Publication date: 2021-06-24
Also published as: JPWO2021124453A1

Abstract

Disclosed is an inverter circuit that supplies power to a traveling motor. This inverter circuit is provided with: a high-potential wire; a low-potential wire; an intermediate wire connected to the traveling motor; a first switching element connected to one of a part between the high-potential wire and the intermediate wire and a part between the intermediate wire and the low-potential wire; a second switching element connected to the other of the part between the high-potential wire and the intermediate wire and the part between the intermediate wire and the low-potential wire; and a gate driving circuit connected to a gate of the second switching element. In a first state where the inverter circuit supplies power to the traveling motor, the gate driving circuit changes a potential to be applied to the gate between a negative potential and a gate-on potential higher than a gate threshold value of the second switching element. In a second state where the inverter circuit does not supply power to the traveling motor, the gate driving circuit applies, to the gate, a potential higher than the negative potential but lower than the gate threshold value.

Description

Inverter circuit

The technology disclosed herein relates to an inverter circuit.

Japanese Patent Publication No. 2013-243877 discloses an inverter circuit including two MOSFETs connected in series. A gate drive circuit is connected to the gate of each MOSFET. Each gate drive circuit applies a negative potential to the gate of the MOSFET when controlling the MOSFET to the off state.

The MOSFET may turn on unintentionally (hereinafter referred to as erroneous turning on). For example, when the MOSFET of the upper arm turns on, the drain potential of the MOSFET of the lower arm rises. Then, the gate potential of the MOSFET of the lower arm rises momentarily due to the capacitive coupling between the drain and the gate of the MOSFET of the lower arm. Due to this increase in the gate potential, the MOSFET of the lower arm may be erroneously turned on. In addition, false on may occur in the MOSFET of the upper arm. That is, when the MOSFET of the lower arm is turned on, the source potential of the MOSFET of the upper arm is lowered, and the gate potential of the MOSFET of the upper arm is lowered accordingly. Therefore, the drain potential of the MOSFET of the upper arm rises relative to the gate potential. Then, the gate potential of the upper arm rises momentarily due to the capacitive coupling between the drain and the gate of the MOSFET of the upper arm. Due to this increase in the gate potential, the MOSFET of the upper arm may be erroneously turned on. In this way, the MOSFET of the own arm (that is, the MOSFET that is kept in the off state) may be erroneously turned on by the turn-on of the MOSFET of the opposite arm (that is, the MOSFET that is not the MOSFET of the own arm).

As described above, in the inverter circuit of Japanese Patent Application Laid-Open No. 2013-243877, a negative potential is applied to the gate when each MOSFET is controlled to the off state. That is, even if the gate potential rises momentarily, the gate potential of each MOSFET is controlled so that the gate potential does not exceed the gate threshold value. This suppresses erroneous ON of the MOSFET.

If a negative potential is applied to the gate of the MOSFET while the MOSFET is in the off state, there arises a problem that the gate threshold of the MOSFET decreases with time. This specification proposes a technique for suppressing erroneous ON of a switching element in an inverter circuit and suppressing a decrease in a gate threshold value.

This specification discloses an inverter circuit that supplies electric power to a traveling motor. The inverter circuit includes high-potential wiring, low-potential wiring, intermediate wiring connected to the traveling motor, between the high-potential wiring and the intermediate wiring, and between the intermediate wiring and the low-potential wiring. The first switching element connected to one side, the second switching element connected to the other between the high-potential wiring and the intermediate wiring, and the other between the intermediate wiring and the low-potential wiring, and the second switching. It has a gate drive circuit connected to the gate of the element. In the first state in which the inverter circuit supplies electric power to the traveling motor, the gate drive circuit sets the potential applied to the gate to a gate-on potential and a negative potential higher than the gate threshold of the second switching element. In the second state in which the inverter circuit does not supply electric power to the traveling motor, a potential higher than the negative potential and lower than the gate threshold is applied to the gate.

The value of the potential applied to the gate of the second switching element in the second state may be higher than the negative potential and lower than the gate threshold value, and may be negative or positive. , May be zero.

In the above inverter circuit, the gate drive circuit changes the potential applied to the gate between the gate-on potential and the negative potential in the first state, and in the second state, the potential is higher than the negative potential and lower than the gate threshold. Is applied to the gate. That is, in the first state in which the inverter circuit is operating, the above-mentioned erroneous on can occur, so that the gate drive circuit applies a negative potential to the gate in order to maintain the second switching element in the off state. On the other hand, in the second state in which the inverter circuit is not operating, both the first switching element and the second switching element do not switch (that is, they are maintained in the off state), so that the above-mentioned increase in the gate potential does not occur. In such a case, the gate drive circuit applies a potential higher than the negative potential to the gate of the second switching element. As a result, it is possible to suppress a decrease in the gate threshold value of the switching element as compared with a configuration in which a negative potential is always applied to the gate when the switching element is in the off state. As described above, in the above-mentioned inverter circuit, by changing the potential applied to the gate according to the operating condition of the inverter circuit, it is possible to suppress the occurrence of erroneous ON and suppress the decrease of the gate threshold value.

The circuit diagram of the inverter circuit 10. The circuit diagram which shows the series circuit of the

switching element

22a, 22d. The graph which shows the change of each value when the switching element 22a is switched in the 1st state. The graph which shows each value in the 2nd state. The graph which shows the change of each value when the switching element 22d is switched in the 1st state. The flowchart of the state determination process of the inverter circuit 10.

The technical elements disclosed in this specification are listed below. The following technical elements are useful independently.

In the configuration of one example disclosed in the present specification, a control device connected to the gate drive circuit may be further provided. The inverter circuit may be mounted on a vehicle. The control device may determine that it is in the first state when the vehicle is traveling, and may determine that it is in the second state when the vehicle is stopped.

In the configuration of an example disclosed in the present specification, the first switching element and the second switching element may be FETs (Field Effect Transistors) provided on a SiC substrate.

Since the switching element provided with the SiC substrate has a low gate threshold value, the above-mentioned erroneous on is likely to occur. For this reason, the techniques disclosed herein are particularly useful for inverter circuits that include FETs on SiC substrates.

(Example)
Hereinafter, the inverter circuit 10 of this embodiment will be described with reference to the drawings. The inverter circuit 10 is mounted on an electric vehicle (including a hybrid vehicle and a fuel cell vehicle). The inverter circuit 10 shown in FIG. 1 converts the DC power supplied from the DC power supply 20 into three-phase AC power, and supplies the three-phase AC power to the traveling motor (hereinafter, simply referred to as a motor) 18. The inverter circuit 10 has a high-potential wiring 12, a low-potential wiring 14, and three intermediate wirings 16a to 16c. The positive electrode of the DC power supply 20 is connected to the high potential wiring 12. The negative electrode of the DC power supply 20 is connected to the low potential wiring 14. Therefore, a higher potential is applied to the high-potential wiring 12 than to the low-potential wiring 14. The intermediate wirings 16a to 16c are connected to the motor 18.

The inverter circuit 10 has six switching elements 22a to 22f and six gate drive circuits 30a to 30f. The switching elements 22a to 22f are insulated gate type switching elements, respectively, and are MOSFETs in this embodiment. The switching elements 22a to 22f include a SiC substrate. Current switching is performed inside the SiC substrate. Since the switching elements 22a to 22f provided with the SiC substrate have a low gate threshold value, erroneous ON is likely to occur. Instead of the SiC substrate, another semiconductor substrate such as a Si substrate or a GaN substrate may be used.

The drain of the switching element 22a is connected to the high potential wiring 12. The source of the switching element 22a is connected to the intermediate wiring 16a. The gate of the switching element 22a is connected to the gate drive circuit 30a. The gate drive circuit 30a controls the potential of the gate of the switching element 22a. When the switching element 22a is turned on, a current flows from the high potential wiring 12 to the intermediate wiring 16a. The drain of the switching element 22b is connected to the high potential wiring 12. The source of the switching element 22b is connected to the intermediate wiring 16b. The gate of the switching element 22b is connected to the gate drive circuit 30b. The gate drive circuit 30b controls the potential of the gate of the switching element 22b. When the switching element 22b is turned on, a current flows from the high potential wiring 12 to the intermediate wiring 16b. The drain of the switching element 22c is connected to the high potential wiring 12. The source of the switching element 22c is connected to the intermediate wiring 16c. The gate of the switching element 22c is connected to the gate drive circuit 30c. The gate drive circuit 30c controls the potential of the gate of the switching element 22c. When the switching element 22c is turned on, a current flows from the high potential wiring 12 to the intermediate wiring 16c. In the following, each of the switching elements 22a to 22c may be referred to as an upper arm switching element.

The drain of the switching element 22d is connected to the intermediate wiring 16a. The source of the switching element 22d is connected to the low potential wiring 14. The gate of the switching element 22d is connected to the gate drive circuit 30d. The gate drive circuit 30d controls the potential of the gate of the switching element 22d. When the switching element 22d is turned on, a current flows from the intermediate wiring 16a to the low potential wiring 14. The drain of the switching element 22e is connected to the intermediate wiring 16b. The source of the switching element 22e is connected to the low potential wiring 14. The gate of the switching element 22e is connected to the gate drive circuit 30e. The gate drive circuit 30e controls the potential of the gate of the switching element 22e. When the switching element 22e is turned on, a current flows from the intermediate wiring 16b to the low potential wiring 14. The drain of the switching element 22f is connected to the intermediate wiring 16c. The source of the switching element 22f is connected to the low potential wiring 14. The gate of the switching element 22f is connected to the gate drive circuit 30f. The gate drive circuit 30f controls the potential of the gate of the switching element 22f. When the switching element 22f is turned on, a current flows from the intermediate wiring 16c to the low potential wiring 14. In the following, each of the switching elements 22d to 22f may be referred to as a lower arm switching element.

Diodes 24a to 24f are connected in parallel to each of the switching elements 22a to 22f. Each of the anodes of the diodes 24a-24f is connected to the source of the corresponding switching elements 22a-22f. Each of the cathodes of the diodes 24a to 24f is connected to the drain of the corresponding switching elements 22a to 22f. By switching each of the switching elements 22a to 22f, DC power is converted into three-phase AC power.

The gate drive circuits 30a to 30f are connected to the control device 40. The control device 40 outputs a gate drive signal for controlling the potential of the gate of each of the switching elements 22a to 22f to each of the gate drive circuits 30a to 30f.

Hereinafter, the operation of the series circuit of the switching element 22a and the switching element 22d will be described as an example, but the same operation will be performed on the series circuit of the switching element 22b and the switching element 22e and the series circuit of the switching element 22c and the switching element 22f. To do.

FIG. 2 shows a series circuit of the switching element 22a and the switching element 22d. As shown in FIG. 2, signals are input from the control device 40 to the

gate drive circuits

30a and 30d. As will be described in detail later, the control device 40 determines whether or not the vehicle is traveling. That is, the control device 40 determines whether or not power is being supplied from the inverter circuit 10 to the motor 18. The control device 40 inputs signals to the

gate drive circuits

30a and 30d according to the determination result.

In a state where power is being supplied from the inverter circuit 10 to the motor 18 (hereinafter referred to as the first state), the gate drive signal Sa1 is input from the control device 40 to the gate drive circuit 30a. In the first state, the gate drive circuit 30a switches the switching element 22a based on the gate drive signal Sa1. Further, in the first state, the gate drive signal Sd1 is input from the control device 40 to the gate drive circuit 30d. The gate drive circuit 30d switches the switching element 22d based on the gate drive signal Sd1. As described above, in the first state, the

gate drive circuits

30a and 30d switch the

switching elements

22a and 22d based on the gate drive signals Sa1 and Sd1, so that the motor 18 is supplied with electric power. In the first state, the

gate drive circuits

30a and 30d control the potential of each gate so that the switching element 22a and the switching element 22d do not turn on at the same time.

Further, in a state where power is not supplied from the inverter circuit 10 to the motor 18 (hereinafter referred to as a second state), the gate drive signal Sa2 is input from the control device 40 to the gate drive circuit 30a. In the second state, the gate drive circuit 30a controls the potential of the gate of the switching element 22a so as to keep the switching element 22a in the off state based on the gate drive signal Sa2. Further, in the second state, the gate drive signal Sd2 is input from the control device 40 to the gate drive circuit 30d. The gate drive circuit 30d controls the potential of the gate of the switching element 22d so as to keep the switching element 22d in the off state based on the gate drive signal Sd2.

FIG. 3 shows the operation in the first state. That is, the gate drive signal Sa1 is input from the control device 40 to the gate drive circuit 30a, and the gate drive signal Sd1 is input from the control device 40 to the gate drive circuit 30d. Further, FIG. 3 shows changes in each value when switching the switching element 22a of the upper arm while keeping the switching element 22d of the lower arm in the off state in the first state. In FIGS. 3 and 4 to 5, which will be described later, reference numeral Vga indicates the gate potential of the switching element 22a of the upper arm, and reference numeral Vdsa indicates the drain-source voltage of the switching element 22a of the upper arm. , Reference symbol Vgd indicates the gate potential of the switching element 22d of the lower arm, and reference numeral Vdsd indicates the drain-source voltage of the switching element 22d of the lower arm. The gate potential VGA is shown as the potential of the switching element 22a with respect to the source, and the gate potential Vgd is shown as the potential of the switching element 22d with respect to the source.

In the initial state shown in FIG. 3, the gate drive circuit 30a controls the gate potential VGA of the switching element 22a to the gate-off potential Voffa1. The gate-off potential Voffa1 is lower than the gate threshold value Vtha of the switching element 22a. The gate-off potential Voffa1 is a negative potential (that is, a potential lower than the source of the switching element 22a). Since the gate-off potential Voffa1 is lower than the gate threshold value Vtha, the switching element 22a is turned off. Further, in the initial state, the gate drive circuit 30d controls the gate potential Vgd of the switching element 22d to the gate-off potential Voffd1. The gate-off potential Voffd1 is lower than the gate threshold value Vthd of the switching element 22d. The gate-off potential Voffd1 is a negative potential (that is, a potential lower than the source of the switching element 22d). Since the gate-off potential Voffd1 is lower than the gate threshold value Vthd, the switching element 22d is off. In this state, since the motor 18 is driven, the potential of the intermediate wiring 16a is lower than the potential of the low potential wiring 14. Therefore, as shown by the arrow 100 in FIG. 2, a current flows from the low potential wiring 14 to the intermediate wiring 16a via the diode 24d. Since the diode 24d is on, the drain-source voltage Vdsd of the switching element 22d is approximately 0V. Further, since the potential difference between the high potential wiring 12 and the intermediate wiring 16a is applied to the switching element 22a, the drain-source voltage Vdsa of the switching element 22a becomes a high voltage.

After that, at the timing t1, the gate drive circuit 30a raises the gate potential VGA of the switching element 22a from the gate-off potential Voffa1 to the gate-on potential Vona. The gate-on potential Vona is higher than the gate threshold Vza. Therefore, immediately after the timing t1, the switching element 22a turns on. Then, the current indicated by the arrow 100 in FIG. 2 is stopped, and as shown by the arrow 102, the current flows from the high potential wiring 12 to the intermediate wiring 16a via the switching element 22a. Since the switching element 22a turns on, the drain-source voltage Vdsa of the switching element 22a drops to approximately 0V immediately after the timing t1. Therefore, the potential of the drain of the switching element 22d rises to a high potential. That is, the drain-source voltage Vdsd of the switching element 22d rises to a high voltage. Here, the gate drive circuit 30d continues to apply the gate-off potential Voffd1 (that is, the negative potential) to the gate of the switching element 22d. When the potential of the drain of the switching element 22d rises sharply immediately after the timing t1, the gate of the switching element 22d is momentarily coupled by the capacitance via the parasitic capacitance (Cd in FIG. 2) between the drain and the gate of the switching element 22d. A surge voltage 90 is applied to the. Therefore, immediately after the timing t1, the gate potential Vgd rises momentarily. However, in the first state, the gate drive circuit 30d applies a gate-off potential Voffd1 (that is, a negative potential) to the gate of the switching element 22d. Therefore, even if the surge voltage 90 is applied, the gate potential Vgd does not reach the gate threshold value Vthd. As a result, erroneous ON of the switching element 22d is suppressed.

FIG. 4 shows the operation of the second state. That is, the gate drive signal Sa2 is input from the control device 40 to the gate drive circuit 30a, and the gate drive signal Sd2 is input from the control device 40 to the gate drive circuit 30d. In the second state, since the inverter circuit 10 does not supply electric power to the motor 18, both the switching element 22a and the switching element 22d are maintained in the off state. That is, the switching element 22a and the switching element 22d do not switch.

In the second state shown in FIG. 4, the gate drive circuit 30a controls the gate potential VGA of the switching element 22a to the gate-off potential Voffa2. The gate-off potential Voffa2 is lower than the gate threshold value Vtha of the switching element 22a. Therefore, the switching element 22a is turned off. Further, the gate-off potential Voffa2 is higher than the gate-off potential Voffa1 in the first state shown in FIG. In this embodiment, the gate-off potential Voffa2 is higher than 0V and lower than the gate threshold Vthd. Further, the gate drive circuit 30d controls the gate potential Vgd of the switching element 22d to the gate-off potential Voffd2. The gate-off potential Voffd2 is lower than the gate threshold value Vthd of the switching element 22d. Therefore, the switching element 22d is turned off. Further, the gate-off potential Voffd2 is higher than the gate-off potential Voffd1 in the first state shown in FIG. In this embodiment, the gate-off potential Voffd2 is higher than 0V. In this state, since no current flows through the inverter circuit 10, the potential of the intermediate wiring 16a is floating, and the potential difference between the high potential wiring 12 and the low potential wiring 14 is applied to the series circuit of the switching element 22a and the switching element 22d. To. Therefore, the drain-source voltage Vdsd of the switching element 22a and the drain-source voltage Vdsd of the switching element 22d are substantially equal. In the second state, the gate drive circuit 30a continues to apply the gate-off potential Voffa2 to the gate of the switching element 22a. Further, the gate drive circuit 30d continues to apply the gate-off potential Voffd2 to the gate of the switching element 22d.

As described above, in the second state, neither the switching element 22a nor the switching element 22d is switched. Therefore, the surge voltage 90 described in the first state is not applied to the gate of the switching element 22d. Therefore, in the second state, even if the potential applied to the gate (that is, the gate-off potential Voltage2) for maintaining the switching element 22d in the off state is set to a value higher than the gate-off potential Voltage1 in the first state, The switching element 22d is not erroneously turned on due to the surge voltage 90. Further, in the second state, by applying the gate-off potential Voffd2 (that is, a potential higher than the gate-off potential Voffd1) to the gate of the switching element 22d, it is possible to suppress a decrease in the gate threshold value of the switching element 22d.

FIG. 5 shows the operation in the first state. That is, the gate drive signal Sa1 is input from the control device 40 to the gate drive circuit 30a, and the gate drive signal Sd1 is input from the control device 40 to the gate drive circuit 30d. FIG. 5 shows changes in each value when switching the switching element 22d of the lower arm while maintaining the switching element 22a of the upper arm in the off state in the first state, unlike FIG.

The initial states of the gate potentials VGA and Vda of the

switching elements

22a and 22d shown in FIG. 5 are the same as the initial states of FIG. That is, both the switching element 22a and the switching element 22d are off. In this state, since the motor 18 is driven, the potential of the intermediate wiring 16a is higher than the potential of the high potential wiring 12. Therefore, as shown by the arrow 104 in FIG. 2, a current flows from the intermediate wiring 16a to the high potential wiring 12 via the diode 24a. Since the diode 24a is on, the drain-source voltage Vdsa of the switching element 22a is approximately 0V. Further, since the potential difference between the intermediate wiring 16a and the low potential wiring 14 is applied to the switching element 22d, the drain-source voltage Vdsd of the switching element 22d becomes a high voltage.

After that, at the timing t2, the gate drive circuit 30d raises the gate potential Vgd of the switching element 22d from the gate-off potential Voffd1 to the gate-on potential Vondo. The gate-on potential Bond is higher than the gate threshold Vthd. Therefore, immediately after the timing t2, the switching element 22d turns on. Then, the current indicated by the arrow 104 in FIG. 2 is stopped, and as shown by the arrow 106, the current flows from the intermediate wiring 16a to the low potential wiring 14 via the switching element 22d. Since the switching element 22d turns on, the drain-source voltage Vdsd of the switching element 22d drops to approximately 0V immediately after the timing t2. Therefore, the potential of the source of the switching element 22a drops to a low potential. That is, the potential of the drain of the switching element 22a is relatively high with respect to the potential of the source. Therefore, the drain-source voltage Vdsa of the switching element 22a rises to a high voltage. Here, the gate drive circuit 30a continues to apply the gate-off potential Voffa1 (that is, the negative potential) to the gate of the switching element 22a. When the potential of the drain of the switching element 22a rises sharply immediately after the timing t2, the gate of the switching element 22a is momentarily connected by the capacitance coupling via the parasitic capacitance (Ca in FIG. 2) between the drain and the gate of the switching element 22a. A surge voltage 92 is applied to the. Therefore, immediately after the timing t2, the gate potential Vga rises momentarily. However, in the first state, the gate drive circuit 30a applies a gate-off potential Voffa1 (that is, a negative potential) to the gate of the switching element 22a. Therefore, even if the surge voltage 92 is applied, the gate potential VGA does not reach the gate threshold value Vtha. As a result, erroneous ON of the switching element 22a is suppressed.

As described above, according to the inverter circuit 10 of the present embodiment, the potentials applied to the gates of the

switching elements

22a and 22d (specifically, the

switching elements

22a and 22d are set according to the operating condition of the inverter circuit 10). By changing the potential (off state), it is possible to suppress the occurrence of erroneous on and suppress the decrease of the gate threshold with time.

Next, the process of determining the state of the inverter circuit 10 will be described with reference to FIG. In this state determination process, the control device 40 determines whether the inverter circuit 10 is in the first state or the second state. The state determination process is repeatedly executed while the main switch of the vehicle is on. In S10 of FIG. 6, the control device 40 determines whether or not the vehicle is traveling. When the control device 40 determines that the vehicle is traveling (YES in S10), the control device 40 proceeds to S12. It can be determined that the vehicle is running, for example, by detecting that the D (drive) range is selected in the shift lever of the vehicle and the vehicle speed is not zero.

In S12, the control device 40 determines that the vehicle is traveling and is in the first state (that is, the state in which the inverter circuit 10 is supplying electric power to the motor 18). Then, the control device 40 outputs the gate drive signals Sa1 and Sd1 for commanding the target output to the

gate drive circuits

30a and 30d, respectively. As a result, the gate drive circuit 30a applies a potential that changes between the gate-on potential Vona and the gate-off potential Voffa1 (that is, a negative potential) described above to the gate of the switching element 22a. Further, the gate drive circuit 30d applies a potential that changes between the gate-on potential Bond and the gate-off potential Voffd1 (that is, a negative potential) described above to the gate of the switching element 22d. As a result, the

switching elements

22a and 22d are switched, and electric power is supplied to the motor 18.

On the other hand, when the control device 40 determines in S10 that the vehicle is stopped (NO in S10), the control device 40 proceeds to S14. The fact that the vehicle is stopped means that, for example, the P (parking) range or the N (neutral) range is selected in the shift lever of the vehicle, the vehicle speed is zero and the brake pedal is depressed, and the vehicle speed. It can be determined by detecting that the state in which is zero continues for a predetermined period of time.

In S14, the control device 40 determines that the vehicle is in the second state (that is, the state in which the power is not supplied from the inverter circuit 10 to the motor 18) because the vehicle is stopped. Then, the control device 40 outputs the gate drive signals Sa2 and Sd2 to the

gate drive circuits

30a and 30d, respectively. As a result, the gate drive circuit 30a applies the above-mentioned gate-off potential Voffa2 (that is, a potential higher than 0V and lower than the gate threshold value Vtha) to the gate of the switching element 22a. Further, the gate drive circuit 30d applies the above-mentioned gate-off potential Voffad (that is, a potential higher than 0V and lower than the gate threshold value Vthd) to the gate of the switching element 22d. That is, the

switching elements

22a and 22d are maintained in the off state.

In the above-described embodiment, the gate-off potentials Voffa2 and Voffd2 had values higher than 0V. However, the gate-off potential Voffa2 may be higher than the gate-off potential Vofa1 and lower than the gate threshold value Vtha. Further, the gate-off potential Voffd2 may be higher than the gate-off potential Voffd1 and lower than the gate threshold value Vthd. That is, the values of the gate-off potentials Voffa2 and Voffd2 may be negative, positive, or zero.

(Correspondence)
The switching element 22a or the switching element 22d of the embodiment is an example of the "first switching element" of the claim, and the switching element 22d or the switching element 22a of the embodiment is an example of the "second switching element" of the claim. is there. The gate-off potentials Voffa1 and Voffd1 of the embodiment are examples of the "negative potential" of the claim. The gate-off potentials Voffa2 and Voffd2 of the embodiment are an example of the claim "potential higher than negative potential and lower than gate threshold value".

Although the embodiments have been described in detail above, these are merely examples and do not limit the scope of claims. The techniques described in the claims include various modifications and modifications of the specific examples illustrated above. The technical elements described in the present specification or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the techniques illustrated in this specification or drawings achieve a plurality of objectives at the same time, and achieving one of the objectives itself has technical usefulness.

Claims

An inverter circuit that supplies electric power to a traction motor.
With high potential wiring
With low potential wiring
The intermediate wiring connected to the traveling motor and
A first switching element connected between the high-potential wiring and the intermediate wiring and between the intermediate wiring and the low-potential wiring.
A second switching element connected to the other between the high-potential wiring and the intermediate wiring and between the intermediate wiring and the low-potential wiring.
A gate drive circuit connected to the gate of the second switching element,
Is equipped with
The gate drive circuit
In the first state in which the inverter circuit supplies electric power to the traveling motor, the potential applied to the gate changes between a gate-on potential higher than the gate threshold of the second switching element and a negative potential. Let me
In the second state in which the inverter circuit does not supply electric power to the traveling motor, a potential higher than the negative potential and lower than the gate threshold value is applied to the gate.
Inverter circuit.
It further includes a control device connected to the gate drive circuit.
The inverter circuit is mounted on the vehicle and
The control device is
When the vehicle is traveling, it is determined that the vehicle is in the first state, and the vehicle is determined to be in the first state.
The inverter circuit according to claim 1, wherein when the vehicle is stopped, it is determined that the vehicle is in the second state.
The inverter circuit according to claim 1 or 2, wherein the first switching element and the second switching element are FETs (Field Effect Transistors) provided on a SiC substrate.