Power conversion device

Abstract

To provide a power conversion device in which a failure in a control unit caused by resonance of a switching element can be prevented.SOLUTION: A power conversion device includes: switching elements 12a, 12b connected in parallel with each other; a control unit 10 including an output terminal 10cc from which a first control signal for turning on the switching elements 12a, 12b is output and an output terminal 10ee from which a second control signal for turning off the switching elements 12a, 12b is output; an impedance conversion unit 123a disposed on a path between the output terminal 10cc and a gate terminal 12ag; an impedance conversion unit 123b disposed on a path between the output terminal 10cc and a gate terminal 12bg; and a protection function unit 50 connected between either one of a path from the output terminal 10cc to the impedance conversion unit 123a and a path from the output terminal 10cc to the impedance conversion unit 123b and a gate off potential Vee for defining the potential of the second control signal.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present disclosure relates to a power conversion device such as an inverter or a converter in the field of power electronics.

Background Art

[0002] Power conversion devices include switching elements such as IGBTs (Insulated Gate Bipolar Transistors) and MOSFETs (Metal Oxide Semiconductor Field Effect Transistors). In a power conversion device used in an electric power train, a plurality of switching elements are connected in parallel to one arm in order to increase the power capacity. The switching elements connected in parallel are switched simultaneously.

[0003] However, due to the characteristic differences between the switching elements, or the variations in the inductance of the main circuit or control circuit of the power conversion device, there may be a shift in the switching timing between the switching elements. With such a timing shift, a current imbalance caused by the timing shift occurs. For example, current concentrates on the switching element that switches earliest, increasing losses and risking damage to the switching element.

[0004] Also, in a power conversion device, when a shift occurs in the switching timing between the switching elements, a potential difference is generated in the drain-source voltage due to this shift. When there is a potential difference between the switching elements, a resonance phenomenon occurs due to the inductance between the switching element and its parasitic capacitance and the inductance component of the control line (for example, the gate line or source line of a transistor that is a switching element). When such a resonance phenomenon occurs, there is a risk that an excessive voltage is applied to the control unit (for example, a gate drive circuit that outputs a switching control signal for turning on or off the switching element) and it is damaged. In particular, this problem becomes prominent when the switching element is switched at high speed.

[0005] In order to solve the above problems, a power conversion device has been proposed that suppresses the deviation in the switching timing between switch elements, which is the origin of the resonance phenomenon between the switch elements. For example, the power conversion device of Patent Document 1 includes a plurality of semiconductor modules connected in parallel, a gate drive circuit that drives these semiconductor modules, and gate wirings provided in each semiconductor module to connect between the semiconductor module and the gate drive circuit or another semiconductor module. In this power conversion device, the lower the gate threshold voltage of the semiconductor module, the lower the impedance of the above gate wiring, so that the gate current value supplied to each semiconductor module becomes the same value during the off operation.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] However, in a power conversion device, even if the switching timings are aligned between switch elements, if there are variations in the impedance of the main circuits of each switch element, the timings at which recovery currents are generated by the internal diodes of each switch element will be different. For this reason, for example, a voltage difference occurs in the drain-source voltage Vds of a transistor, which is a switch element. Due to the resonance phenomenon that occurs between the switch elements caused by this voltage difference in the drain-source voltage Vds, there is a possibility that the control unit for driving the switch elements may malfunction.

[0008] The present disclosure has been made in view of the above circumstances, and an object thereof is to provide a power conversion device capable of preventing a failure of a control unit due to resonance of switch elements.

Means for Solving the Problems

[0009] To solve the above problems, a power conversion device according to one aspect of the present disclosure includes a first switch element having a first control terminal, a second switch element connected in parallel with the first switch element and having a second control terminal, a first output terminal to which a first control signal for turning on the first switch element and the second switch element is output, a second output terminal to which a second control signal for turning off the first switch element and the second switch element is output, a control unit having, a first impedance conversion unit provided on a path between the first output terminal or the second output terminal and the first control terminal, a second impedance conversion unit provided on a path between the first output terminal or the second output terminal and the second control terminal, and a protection function unit connected between either one of a path from the first output terminal to the first impedance conversion unit or a path from the first output terminal to the second impedance conversion unit and a potential defining unit that defines the potential of the second control signal.

Advantages of the Invention

[0010] According to the present disclosure, when a resonance phenomenon occurs, the protection function unit operates to suppress the resonance voltage applied to the control unit. Thereby, the power conversion device according to the present disclosure can prevent a failure of the control unit due to a resonance phenomenon between the switch elements.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Embodiments for Carrying Out the Invention

[0012] Hereinafter, with reference to the drawings, the power conversion device according to the embodiments of the present disclosure will be described in detail.

[0013] 〔Embodiment 1〕 FIG. 1 is a circuit section showing the schematic configuration of the power conversion device according to Embodiment 1 of the present disclosure. The power conversion device 1 shown in FIG. 1 is an inverter circuit. A DC power supply 2 is connected to the input stage of the power conversion device 1, and a motor 3 as a load is connected to the output stage of the power conversion device 1. The DC power supply 2 is a DC storage battery that is a battery and outputs a DC voltage. When the power conversion device 1 is an inverter circuit applied to an electric vehicle or a hybrid vehicle, as the DC power supply 2, for example, a secondary battery such as a nickel-metal hydride battery or a lithium-ion battery that outputs a voltage of 100 V or more is used.

[0014] As shown in FIG. 1, the power conversion device 1 is a three-phase inverter circuit including a control unit 10, a smoothing capacitor 11, six switch element groups 12 to 17, a voltage sensor circuit 20, and current sensor circuits 21a to 21c. The power conversion device 1 converts the DC voltage output from the DC power supply 2 into three-phase AC and outputs it to the three output terminals Vu, Vv, and Vw. The three-phase AC is supplied from the output terminals Vu, Vv, and Vw to the motor 3. The motor 3 is, for example, a motor included in a generator or an electric motor.

[0015] The smoothing capacitor 11 is provided so as to be connected in parallel to the DC power supply 2 at the input stage of the power conversion device 1, and removes voltage ripple and noise from the three-phase AC converted by the power conversion device 1. Each of the switch element groups 12 to 17 performs a switching operation based on the control signal of the control unit 10 input via the control lines 32a to 32f.

[0016] The switch element groups 12 and 13 are connected in series, the switch element groups 14 and 15 are connected in series, and the switch element groups 16 and 17 are connected in series. The circuits composed of the series-connected switch element groups 12 and 13, the circuits composed of the series-connected switch element groups 14 and 15, and the circuits composed of the series-connected switch element groups 16 and 17 are connected in parallel to the smoothing capacitor 11. The connection point P1 of the switch element groups 12 and 13, the connection point P2 of the switch element groups 14 and 15, and the connection point P3 of the switch element groups 16 and 17 are connected to the output terminals Vu, Vv, and Vw, respectively. Note that the switch element groups 12, 14, and 16 are arranged on the upper arm side, and the switch element groups 13, 15, and 17 are arranged on the lower arm side.

[0017] As will be described later, each of the switch element groups 12 to 17 includes a plurality of switch elements. The plurality of switch elements included in the switch element groups 12 to 17 are semiconductor switch elements, and for example, MOSFETs are used. Note that as the switch element, one constituted by an IGBT and a diode may be used. Hereinafter, it is assumed that the switch elements included in the switch element groups 12 to 17 are MOSFETs.

[0018] Here, the switching of the switch element groups 12 to 17 is an operation of applying a control voltage to the control terminals of the plurality of switch elements included in the switch element groups 12 to 17 and switching between an on state in which the terminals of the plurality of switch elements are made conductive and an off state in which they are made non-conductive. For example, it is an operation of applying a control voltage to the gate terminals (control terminals) of the plurality of MOSFETs included in the switch element group 12 and switching between an on state in which the source terminals and drain terminals of the plurality of MOSFETs are made conductive and an off state in which they are made non-conductive.

[0019] FIG. 2 is a circuit diagram showing the configuration of the switch element group included in the power conversion device according to Embodiment 1 of the present disclosure. In FIG. 2, only the switch element groups 12 and 13 out of the six switch element groups 12 to 17 shown in FIG. 1 are illustrated. Note that the other switch element groups 14 to 17 also have the same configuration as the switch element groups 12 and 13.

[0020] As shown in FIG. 2, the switch element group 12 includes a switch element 12a and a switch element 12b connected in parallel. The switch elements 12a and 12b have a drain terminal and a source terminal which are a terminal pair. The drain terminals of the switch elements 12a and 12b are connected to each other via the parasitic inductances L12a and L12b of the wiring, and the source terminals of the switch elements 12a and 12b are connected to each other. Note that there is also a parasitic inductance of the wiring between the source terminals, but it is omitted in the present embodiment for simplicity of explanation.

[0021] Further, the switch element group 13 includes switch elements 13a and 13b connected in parallel. The switch elements 13a and 13b, similar to the switch elements 12a and 12b, have a drain terminal and a source terminal which are a terminal pair. The drain terminals of the switch elements 13a and 13b are connected to each other, and the source terminals of the switch elements 13a and 13b are connected to each other via the parasitic inductances L13a and L13b of the wiring. Note that there is also parasitic inductance of the wiring between the drain terminals, but it is omitted in this embodiment for simplicity of explanation.

[0022] The switch elements 12a and 12b provided in the switch element group 12 are upper-arm-side switch elements, and the switch elements 13a and 13b provided in the switch element group 13 are lower-arm-side switch elements. As shown in FIG. 2, there are parasitic capacitances between the drain-source, drain-gate, and gate-source of the switch elements 12a, 12b and the switch elements 13a, 13b.

[0023] FIG. 3 is a circuit diagram showing a more detailed configuration of the switch element group shown in FIG. 2. Note that in FIG. 3, the switch element group 13 in FIG. 2 is omitted, and only the switch element group 12 is shown. Further, in FIG. 3, the drain terminal 12ad, source terminal 12as, and gate terminal 12ag of the switch element 12a, and the drain terminal 12bd, source terminal 12bs, and gate terminal 12bg of the switch element 12b are clearly shown.

[0024] In addition, in FIG. 3, the parasitic capacitance Cds1 between the drain-source, the parasitic capacitance Cdg1 between the drain-gate, and the parasitic capacitance Cgs1 between the gate-source in the switch element 12a are clearly shown. Similarly, the parasitic capacitance Cds2 between the drain-source, the parasitic capacitance Cdg2 between the drain-gate, and the parasitic capacitance Cgs2 between the gate-source in the switch element 12b are also clearly shown.

[0025] As shown in FIG. 3, the switch element group 12 includes, in addition to the switch elements 12a and 12b connected in parallel, resistor elements 121a and 121b, resistor elements 122a and 122b, impedance conversion units 123a and 123b, and a protection function unit 50. Note that the impedance conversion units 123a and 123b will be described as diodes. The resistor element 121a is connected in series with the impedance conversion unit 123a, and the resistor element 121b is connected in series with the impedance conversion unit 123b. The resistor element 121a and the impedance conversion unit 123a constitute a first circuit, and the resistor element 121b and the impedance conversion unit 123b constitute a second circuit.

[0026] The circuit composed of the resistor element 121a and the impedance conversion unit 123a connected in series is connected between the output terminal 10cc of the control unit 10 and the gate terminal 12ag of the switch element 12a. Also, the circuit composed of the resistor element 121b and the impedance conversion unit 123b connected in series is connected between the output terminal 10cc of the control unit 10 and the gate terminal 12bg of the switch element 12b. Note that for the impedance conversion unit 123a, the anode side is connected to the resistor element 121a, and the cathode side is connected to the gate terminal 12ag. Also, for the impedance conversion unit 123b, the anode side is connected to the resistor element 121b, and the cathode side is connected to the gate terminal 12bg. The resistor element 122a is connected between the output terminal 10ee of the control unit 10 and the gate terminal 12ag of the switch element 12a. Also, the resistor element 122b is connected between the output terminal 10ee of the control unit 10 and the gate terminal 12bg of the switch element 12b.

[0027] Also, as shown in FIG. 3, the protection function unit 50 is connected to the output terminal 10cc of the control unit 10 and the gate-off potential Vee as the potential defining unit. When a resonance phenomenon occurs due to the potential difference generated between the switch elements 12a and 12b, the protection function unit 50 is provided to suppress the voltage applied to the output terminal 10cc of the control unit 10 and prevent a failure of the control unit 10. Note that the protection function unit 50 is, for example, a diode, with the anode side connected to the gate-off potential Vee and the cathode side connected to the output terminal 10cc.

[0028] In addition to the output terminals 10cc and 10ee, the control unit 10 includes switch elements 101 and 102. The switch element 101 is connected to the output terminal 10cc and the gate-on potential Vcc, and the switch element 102 is connected to the output terminal 10ee and the gate-off potential Vee. When the switch element 101 is in the on state and the switch element 102 is in the off state, the gate-on potential Vcc is output from the output terminal 10cc. On the other hand, when the switch element 101 is in the off state and the switch element 102 is in the on state, the gate-off potential Vee is output from the output terminal 10ee. Note that the gate-on potential Vcc and the gate-off potential Vee are potentials based on the potential of the reference potential terminal 10s.

[0029] Note that the resistance elements 121a and 121b, the resistance elements 122a and 122b, the impedance conversion units 123a and 123b, and the protection function unit 50 shown in FIG. 3 are for the switch element group 12. The same components as the resistance elements 121a and 121b, the resistance elements 122a and 122b, the impedance conversion units 123a and 123b, and the protection function unit 50 shown in FIG. 3 are also provided for each of the switch element groups 13 to 17.

[0030] FIG. 4 is a waveform diagram showing the changes over time of the voltage and current in the switch element group shown in FIG. 2. The characteristics of the switch element group shown in FIG. 2 will be described with reference to FIG. 4. Note that the parasitic inductances L12a and L12b of the wiring are different in magnitude, and similarly, the parasitic inductances L13a and L13b of the wiring are different in magnitude.

[0031] First, consider the case where all of the switch elements 12a and 12b on the upper arm side and the switch elements 13a and 13b on the lower arm side are in the OFF state (time t0). In this state, currents I12a and I12b flow into the switch elements 12a and 12b from the motor 3 side. These currents I12a and I12b flow from the source terminal side to the drain terminal side through the internal diodes of the switch elements 12a and 12b, respectively. Therefore, the internal diodes of the switch elements 12a and 12b are in the conducting state, and the drain-source voltages Vds1 and Vds2 of the switch elements 12a and 12b are 0V. Since the switch elements 13a and 13b are in the OFF state, the drain currents I13a and I13b are 0A.

[0032] Next, consider the case where all of the switch elements 12a and 12b on the upper arm side and the switch elements 13a and 13b on the lower arm side change from the OFF state to the ON state of the switch elements 13a and 13b on the lower arm side. In this state, as shown in FIG. 3, the drain currents I13a and I13b increase. However, even when the timing at which the switch elements 13a and 13b become ON is the same, the current is biased due to the difference in the parasitic inductance of the wiring. For example, at time t1, the drain current I13a flowing into the drain terminal of the switch element 13a becomes larger than the drain current I13b flowing into the drain terminal of the switch element 13b.

[0033] On the other hand, at time t1, the current I12a flowing through the internal diode of the switch element 12a becomes smaller than the current I12b flowing through the internal diode of the switch element 12b. Therefore, the current flowing through the internal diode of the switch element 12a becomes 0A first, and reverse recovery (recovery) occurs in the internal diode.

[0034] Thereafter, the parasitic capacitance between the drain and source of the switch element 12a is charged, and the drain-source voltage Vds1 increases. On the other hand, since the internal diode of the switch element 12b is in the conducting state, the drain-source voltage Vds2 is approximately 0V. For example, at time t2, since the drain-source voltage Vds1 is not 0V and the drain-source voltage Vds2 is approximately 0V, a potential difference occurs between the switch element 12a and the switch element 12b.

[0035] Thus, in the switch element group shown in FIG. 2, if there is a difference in the parasitic inductance of the wiring, there is a characteristic that a potential difference occurs between the switch element 12a and the switch element 12b. If such a characteristic is present, there is a possibility that the control unit 10 for driving the switch elements 12a and 12b may malfunction due to the resonance phenomenon occurring between the switch elements 12a and 12b. To prevent such a malfunction, the protection function unit 50 shown in FIG. 3 is provided.

[0036] FIG. 5 is an equivalent circuit of the control unit and the switch element group shown in FIG. 3. Using FIG. 5, the operations of the control unit and the switch element group shown in FIG. 3 will be described. Now, assume that the drain-source voltage Vds1 of the switch element 12a rises earlier than the drain-source voltage Vds2 of the switch element 12b. That is, assume that the drain-source voltage Vds1 of the switch element 12a becomes a voltage greater than 0V and the drain-source voltage Vds2 of the switch element 12b is in a state of 0V.

[0037] Let the voltage applied across both ends of the impedance conversion unit 123b be V1a, the voltage applied across both ends of the resistor element 121b be V1b, the voltage applied across both ends of the resistor element 121a be V1c, and the voltage V1d applied across both ends of the impedance conversion unit 123a. The relationship between these voltages V1a, V1b, V1c, V1d and the drain-source voltage Vds1 of the switch element 12a is Vds1×α = V1a + V1b + V1c + V1d. That is, a part of the drain-source voltage Vds1 is applied to the impedance conversion units 123a, 123b and the resistor elements 121a, 121b. Here, α is the voltage division coefficient.

[0038] Let the voltage applied between the output terminal 10cc of the control unit 10 and the gate terminal 12bg of the switch element 12b be V1. The relationship between this voltage V1, the voltage V1a applied across both ends of the impedance conversion unit 123b, and the voltage V1b applied across both ends of the resistor element 121b is V1 = V1a + V1b. Also, when the switch element group 12 is in the off state, the switch element 101 of the control unit 10 is also in the off state, and the terminal pair of the switch element 101 has a high impedance. Therefore, the relationship between the voltage V2 applied across both ends of the switch element 101 and the voltage V1 applied between the output terminal 10cc of the control unit 10 and the gate terminal 12bg of the switch element 12b is V1 = V2 - Vcc. Here, assuming that the voltage V2 applied across both ends of the switch element 101 is much larger than the gate-on potential Vcc, the voltage V1 and the voltage V2 are almost equal.

[0039] Here, due to the forward voltage, the impedance conversion unit 123a is in the on state and has a low impedance state of several Ω or less. In contrast, since a reverse voltage is applied to the impedance conversion unit 123b and it is in the off state, the impedance between both terminals of the impedance conversion unit 123b is in a state of several kΩ or more. That is, the impedance of the impedance conversion unit 123b is much higher than that of the impedance conversion unit 123a and the resistor elements 121a, 121b.

[0040] Therefore, the relationship between the voltages V1a, V1b, V1c, and V1d applied to the impedance conversion unit 123b, the resistor element 121b, the resistor element 121a, and the impedance conversion unit 123a is V1a ≫ V1b + V1c + V1d. As described above, a part of the drain-source voltage Vds1 is applied to the impedance conversion units 123a and 123b and the resistor elements 121a and 121b. Due to the above-described relationship, Vds1×α ≒ V1a ≒ V1 ≒ V2, and the reference potential terminal 10s has a higher potential than the output terminal 10cc.

[0041] At this time, a forward voltage is applied to the protection function unit 50 via the gate-off potential Vee, so that the protection function unit 50 is turned on, and the potential of the output terminal 10cc becomes Vee. As a result, when a resonance phenomenon occurs due to the potential difference between the switch element 12a and the switch element 12b, the voltage applied to the output terminal 10cc of the control unit 10 can be suppressed, and a failure of the control unit 10 can be prevented.

[0042] FIG. 6 is a waveform diagram showing the change over time of the voltage applied to the output terminal of the switch element provided in the switch element group and the control unit in the first embodiment. In FIG. 6, “Embodiment” is the waveform when the protection function unit 50 is provided, and “Comparative Example” is the waveform when the protection function unit 50 is not provided. Here, it is assumed that the drain-source voltage Vds1 of the switch element 12a rises earlier than the drain-source voltage Vds2 of the switch element 12b. That is, it is assumed that the drain-source voltage Vds1 of the switch element 12a becomes a voltage greater than 0 V, and the drain-source voltage Vds2 of the switch element 12b is 0 V.

[0043] As shown in FIG. 6, in the "comparative example", an excessive voltage is applied to the output terminal 10cc of the control unit 10 at time t10. On the other hand, in the "embodiment", the voltage applied to the output terminal 10cc of the control unit 10 is suppressed at time t10. Thus, in the present embodiment, even if a resonance phenomenon occurs due to the potential difference between the switch element 12a and the switch element 12b, the voltage applied to the output terminal 10cc of the control unit 10 is suppressed by the protection function unit 50. As a result, a failure of the control unit 10 is prevented.

[0044] 〔Embodiment 2〕 FIG. 7 is a circuit section showing a part of the configuration of the power conversion device according to Embodiment 2 of the present disclosure. The overall configuration of the power conversion device according to Embodiment 2 is the same as that shown in FIG. 1. FIG. 7 is a diagram corresponding to FIG. 3. As shown in FIG. 7, the power conversion device according to Embodiment 2 is different from the power conversion device according to Embodiment 1 in that a diode 103 is provided between the output terminal 10cc of the control unit 10 and the gate-off potential Vee. The diode 103 has its anode side connected to the gate-off potential Vee and its cathode side connected to the output terminal 10cc. This diode 103 is provided, for example, when the control unit 10 is an IC (Integrated Circuit) to protect the internal circuit.

[0045] FIG. 8 is a waveform diagram showing the change over time of the voltage applied to the switch element provided in the switch element group, as well as the current flowing through the diode and the protection function unit, in Embodiment 2. In FIG. 8, "Embodiment" is the waveform when the protection function unit 50 is provided, and "Comparative Example" is the waveform when the protection function unit 50 is not provided. Similar to Embodiment 1, it is assumed that the drain-source voltage Vds1 of the switch element 12a rises earlier than the drain-source voltage Vds2 of the switch element 12b. That is, it is assumed that the drain-source voltage Vds1 of the switch element 12a becomes a voltage greater than 0V and the drain-source voltage Vds2 of the switch element 12b is 0V.

[0046] As shown in Fig. 8, in the "comparative example", when the drain-source voltage Vds1 of the switch element 12a rises, a voltage is applied to the output terminal 10cc of the control unit 10. At this time, since a forward voltage is applied to the diode 103 and it becomes in the on state, the current I103 flowing through the diode 103 becomes excessive, and there is a risk that the control unit 10 may malfunction. On the other hand, in the "embodiment", when the drain-source voltage Vds1 of the switch element 12a rises, a forward voltage is applied to the diode 103 and the protection function unit 50, and they become in the on state. At this time, the current I50 flows through the protection function unit 50, and the current I103 flowing through the diode 103 is reduced, so that a malfunction of the control unit 10 can be prevented.

[0047] Here, it is desirable that the forward voltage Vf of the protection function unit 50 is smaller than the forward voltage Vf of the diode 103 provided in the control unit 10. For example, by using a Schottky barrier diode as the diode of the protection function unit 50, the forward voltage Vf of the protection function unit 50 can be made smaller than the forward voltage Vf of the diode 103 provided in the control unit 10. By making the forward voltage Vf of the protection function unit 50 smaller than the forward voltage Vf of the diode 103 provided in the control unit 10, the current I50 flowing through the protection function unit 50 becomes larger, and the current I103 flowing through the diode 103 is further reduced. Thereby, a malfunction of the control unit 10 can be prevented more effectively.

[0048] Fig. 9 is a diagram showing a part of the configuration according to a modification of the power conversion device according to Embodiment 2 of the present disclosure. As shown in Fig. 9, in this modification, the protection function unit 50 is a switch element. The switch element of the protection function unit 50 is controlled by the control unit 10 so as to be in the on state when the switch elements 12a and 12b are in the off state. Generally, a switch element has a smaller conduction resistance in the on state than a diode. For example, by using a MOSFET as the switch element of the protection function unit 50, more current flows through the protection function unit 50 with a small conduction resistance, and the current flowing through the diode 103 is further reduced. Thereby, a malfunction of the control unit 10 can be prevented more effectively.

[0049] 〔Embodiment 3〕 FIG. 10 is a circuit section showing a part of the configuration of the power conversion device according to Embodiment 3 of the present disclosure. Note that the overall configuration of the power conversion device according to Embodiment 3 is the same as that shown in FIG. 1. FIG. 10 corresponds to FIGS. 3 and 7. As shown in FIG. 10, the power conversion device according to Embodiment 3 is different from the power conversion device according to Embodiment 2 in that switch elements 124a and 124b are provided.

[0050] Switch element 124a is provided between the gate terminal 12ag of switch element 12a and the gate-off potential Vee, and switch element 124b is provided between the gate terminal 12bg of switch element 12b and the gate-off potential Vee. These switch elements 12a and 12b are controlled by the control unit 10 so as to be in the on state when the switch elements 12a and 12b are in the off state.

[0051] Switch elements 124a and 124b are connected to the gate-off potential Vee. Therefore, when switch element 124a or switch element 124b is turned on, the resonance current generated by the resonance phenomenon flows toward the gate-off potential Vee through the gate terminal 12ag of switch element 12a or the gate terminal 12bg of switch element 12b. Since this resonance current flows to the protection function unit 50, the current flowing through diode 103 is reduced. Thus, it is possible to prevent a failure of the control unit 10 due to the resonance current.

[0052] Furthermore, the resonance phenomenon due to the potential difference between the switching elements 12a and 12b occurs more prominently as the potential difference increases. For example, even if the deviation in switching timing and recovery timing can be suppressed, if the switching speed (dV / dt) is high, even a slight deviation in timing will cause a potential difference to occur between the switching elements 12a and 12b. Therefore, the power conversion device 1 according to Embodiments 1 to 3 exhibits remarkable effects when applied to a power conversion device that switches at high speed, that is, a power conversion device provided with switching elements that are prone to generating potential differences. For example, the wider the bandgap semiconductor (e.g., SiC element) of the switching elements 12a and 12b, the more likely resonance is to occur. Thus, by providing the switching element group 12 to 17 included in the power conversion device 1 with elements generated using a wide bandgap semiconductor, a failure of the control unit 10 can be prevented.

[0053] 〔Modification Example of Embodiment〕 FIG. 11 is a circuit diagram showing a first modification example of the power converter according to Embodiments 1 to 3 of the present disclosure. Note that FIG. 11 corresponds to FIG. 3. As shown in FIG. 11, in the first modification example of the power converter, impedance conversion units 123a and 123b are respectively connected in series to resistor elements 122a and 122b. Specifically, for the impedance conversion unit 123a, the anode side is connected to the gate terminal 12ag, and the cathode side is connected to the resistor element 1211. Also, for the impedance conversion unit 123b, the anode side is connected to the gate terminal 12bg, and the cathode side is connected to the resistor element 122b. The resistor element 122a and the impedance conversion unit 123a constitute a first circuit, and the resistor element 122b and the impedance conversion unit 123b constitute a second circuit. Even if the impedance conversion units 123a and 123b are connected in series to the resistor elements 122a and 122b, the same effects as those in Embodiment 1 can be obtained. Note that the circuits shown in FIGS. 7, 9, and 10 can also have the same configuration.

[0054] FIG. 12 is a circuit diagram showing a second modified example of the power converter according to Embodiments 1 to 3 of the present disclosure. Note that FIG. 12 corresponds to FIG. 3. As shown in FIG. 12, in the second modified example of the power converter, the gate-off potential Vee as the potential defining unit is set to 0 V, which is the same potential as the potential of the reference potential terminal 10s. That is, in this modified example, the reference potential terminal 10s serves as the potential defining unit. Even with such a configuration, the same effects as those in Embodiment 1 can be achieved. Note that the circuits shown in FIGS. 7, 9, and 10 can also have the same configuration.

[0055] FIG. 13 is a circuit diagram showing a third modified example of the power converter according to Embodiments 1 to 3 of the present disclosure. Note that FIG. 13 corresponds to FIG. 3. As shown in FIG. 13, in the third modified example of the power converter, a protection function unit 50 is provided between the connection point of the resistance element 121a and the impedance conversion unit 123a and the gate-off potential Vee. Specifically, the anode side of the diode of the protection function unit 50 is connected to the gate-off potential Vee, and the cathode side is connected to the connection point of the resistance element 121a and the impedance conversion unit 123a.

[0056] Note that FIG. 13 shows an example in which the cathode side of the diode in the protection function unit 50 is connected to the connection point of the resistance element 121a and the impedance conversion unit 123a, but the present invention is not limited to this. The cathode side of the diode in the protection function unit 50 may be connected to either one of the path from the output terminal 10cc to the impedance conversion unit 123a and the path from the output terminal 10cc to the impedance conversion unit 123b.

[0057] As described above, the power conversion device according to the embodiment of the present disclosure has been described. However, the present disclosure is not limited to the above embodiment and can be freely changed within the scope of the present disclosure. For example, the power conversion device 1 according to Embodiments 1 to 3 is not limited to the inverter circuit and may be a converter circuit.

[0058] Moreover, the power conversion device 1 according to Embodiments 1 to 3 is not limited to a configuration in which two switching elements are connected in parallel in the switching element groups 12 to 17, and a configuration in which three or more switching elements are connected in parallel may be used. Further, the impedance conversion units 123a and 123b included in the power conversion device 1 according to Embodiments 1 to 3 may be switching elements such as MOSFETs or inductors. In Embodiments 1 to 3, the switching element group 12 has been described as an example, but the other switching element groups 13 to 17 may have the same configuration.

[0059] It should be noted that it is also possible to appropriately combine the above-described embodiments and modification examples. Further, it is possible to modify any component of the above-described embodiments or omit any component in each of the above-described embodiments.

Description of Reference Numerals

[0060] 1... Power conversion device, 10... Control unit, 10cc, 10ee... Output terminals, 12 to 17... Switching element groups, 12a, 12b, 13a, 13b... Switching elements, 12ag, 12bg... Gate terminals, 50... Protection function unit, 103... Diode, 123a, 123b... Impedance conversion units, 124a, 124b... Switching elements, Vcc... Gate-on potential, Vee... Gate-off potential.

Claims

1. a first switch element having a first control terminal; a second switch element connected in parallel to the first switch element and having a second control terminal; a control unit having a first output terminal from which a first control signal that turns the first switch element and the second switch element on is output, and a second output terminal from which a second control signal that turns the first switch element and the second switch element off is output; a first impedance transformation unit provided on a path between the first output terminal or the second output terminal and the first control terminal; a second impedance transformation unit provided on a path between the first output terminal or the second output terminal and the second control terminal; a protection function unit connected between a path from the first output terminal to the first impedance transformation unit or a path from the first output terminal to the second impedance transformation unit and a potential regulating unit that regulates a potential of the second control signal; Equipped with the control unit includes a first diode connected between the potential regulating unit and the first output terminal; Power conversion device.

2. The power conversion device according to claim 1 , wherein the protection function unit is a diode having a forward voltage smaller than a forward voltage of the first diode.

3. The power conversion device according to claim 1 , wherein the protection function unit is a switch element that is turned on when the first switch element and the second switch element are turned off.

4. a third switch element provided between the potential regulating unit and the first control terminal; a fourth switch element provided between the potential regulating unit and the second control terminal; Further provided with the third switch element and the fourth switch element are turned on when the first switch element and the second switch element are turned off; The power conversion device according to claim 1 .

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