Power conversion device

Abstract

This power conversion device has a first switch element, a second switch element, a control unit, a first impedance conversion unit, a second impedance conversion unit, and a protection function unit. The control unit has a first output terminal and a second output terminal. A first control signal is output to the first output terminal. A second control signal is output to the second output terminal. The protection function unit is connected between either a first path from the first output terminal to the first impedance conversion unit or a second path from the first output terminal to the second impedance conversion unit and a voltage-level defining unit that defines the voltage-level of the second control signal.

Description

Power Conversion Device

[0001] This disclosure relates to a power conversion device such as an inverter or converter in the field of power electronics. This application claims priority to Japanese Patent Application No. 2023-193383, filed on November 14, 2023, the contents of which are incorporated herein by reference.

[0002] A power conversion device includes switching elements such as an insulated gate bipolar transistor (IGBT) or a metal oxide semiconductor field effect transistor (MOSFET). In a power conversion device used in an electric powertrain, multiple 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 differences in characteristics among multiple switch elements, variations in inductance of the main circuit of the power conversion device, or variations in inductance of the control circuit, there may be a difference in the switching timing among multiple switch elements. When such a difference in timing occurs, a current imbalance occurs due to the difference in switching timing. For example, current may concentrate in the switch element that switched first, increasing loss and potentially damaging the switch element.

[0004] Furthermore, in a power conversion device, if a difference in switching timing occurs between multiple switch elements, this difference causes a potential difference in the drain-source voltage. When a potential difference occurs between multiple switch elements, a resonance phenomenon occurs due to the inductance between the switch elements and their parasitic capacitance, and the inductance component of a control line (e.g., a gate line or source line of a transistor that is a switch element). When this resonance phenomenon occurs, an excessive voltage may be applied to a control unit (e.g., a gate drive circuit that outputs a switching control signal to turn the switch elements on or off), potentially causing damage. This problem is particularly noticeable when the switch elements are switched at high speed.

[0005] To solve the above-mentioned problems, a power conversion device has been proposed that suppresses the mismatch in switching timing between multiple switch elements, which can cause resonance between multiple switch elements. For example, the power conversion device disclosed in Patent Document 1 includes multiple semiconductor modules connected in parallel, a gate drive circuit that drives the semiconductor modules, and gate wiring. The gate wiring is provided in each of the multiple semiconductor modules. The gate wiring connects the semiconductor module to the gate drive circuit or another semiconductor module. In this power conversion device, the impedance of the gate wiring is lowered for semiconductor modules with lower gate threshold voltages, thereby ensuring that the gate current values ​​supplied to each of the multiple semiconductor modules are the same during off operation.

[0006] Japanese Patent Application Publication No. 2020-156304

[0007] However, even if the switching timing of multiple switch elements in a power conversion device is synchronized, if there is variation in the impedance of the main circuits of the multiple switch elements, the timing at which recovery currents are generated by the internal diodes of the multiple switch elements will differ. This can result in, for example, a voltage difference in the drain-source voltage Vds of the transistors that serve as switch elements. This voltage difference in the drain-source voltage Vds can cause a resonance phenomenon between the multiple switch elements, potentially causing a malfunction in the control unit that drives the switch elements.

[0008] The present disclosure has been made in consideration of the above circumstances, and has an object to provide a power conversion device that can prevent failure of a control unit due to resonance of a switching element.

[0009] In order to solve the above problem, a power conversion device according to an aspect of the present disclosure includes: a control unit including: 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 first output terminal from which a first control signal that switches the first switch element and the second switch element to an on state is output; and a second output terminal from which a second control signal that switches the first switch element and the second switch element to an off state is output; 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 a first path from the first output terminal to the first impedance conversion unit or a second path from the first output terminal to the second impedance conversion unit and a potential regulating unit that regulates a potential of the second control signal.

[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 making it possible for the power conversion device according to the present disclosure to prevent failure of the control unit due to the resonance phenomenon between the switch elements.

[0011] 1 is a circuit diagram illustrating a schematic configuration of a power conversion device according to a first embodiment of the present disclosure. FIG. 2 is a circuit diagram illustrating a configuration of a switch element group included in the power conversion device according to the first embodiment of the present disclosure. FIG. 3 is a circuit diagram illustrating a more detailed configuration of the switch element group shown in FIG. 2. FIG. 4 is a waveform diagram illustrating changes over time in voltage and current in the switch element group shown in FIG. 2. FIG. 5 is an equivalent circuit of the control unit and the switch element group shown in FIG. 3. FIG. 6 is a waveform diagram illustrating changes over time in voltage across switch elements provided in the switch element group and across output terminals of the control unit. FIG. 7 is a circuit diagram illustrating a portion of the configuration of a power conversion device according to a second embodiment of the present disclosure. FIG. 8 is a waveform diagram illustrating changes over time in voltage across switch elements provided in the switch element group and in current flowing through a diode and a protection function unit. FIG. 9 is a diagram illustrating a portion of the configuration of a modified example of the power conversion device according to the second embodiment of the present disclosure. FIG. 10 is a circuit diagram illustrating a portion of the configuration of a power conversion device according to a third embodiment of the present disclosure. FIG. 11 is a circuit diagram illustrating a first modified example of a power converter according to the first to third embodiments of the present disclosure. FIG. 12 is a circuit diagram illustrating a second modified example of a power converter according to the first to third embodiments of the present disclosure. FIG. 13 is a circuit diagram illustrating a third modified example of a power converter according to the first to third embodiments of the present disclosure.

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

[0013] First Embodiment. Fig. 1 is a circuit diagram illustrating a schematic configuration of a power conversion device according to a first embodiment of the present disclosure. The power conversion device 1 illustrated in Fig. 1 is an inverter circuit. A DC power supply 2 is connected to an input stage of the power conversion device 1. A motor 3, which is a load, is connected to an output stage of the power conversion device 1. The DC power supply 2 is a DC storage battery, which is a battery. The DC storage battery outputs a DC voltage. The power conversion device 1 may be an inverter circuit applied to an electric vehicle or a hybrid vehicle. In this case, 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 as the DC power supply 2.

[0014] 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 a DC voltage output from a DC power supply 2 into three-phase AC and outputs the three-phase AC to three-phase output terminals Vu, Vv, and Vw. The three-phase AC is supplied from the output terminals Vu, Vv, and Vw to a 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 in the input stage of the power conversion device 1 so as to be connected in parallel to the DC power supply 2. The smoothing capacitor 11 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 a control signal from the control unit 10 input via 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. The switch element groups 16 and 17 are connected in series. A circuit consisting of the series-connected switch element groups 12 and 13, a circuit consisting of the series-connected switch element groups 14 and 15, and a circuit consisting of the series-connected switch element groups 16 and 17 are connected in parallel to the smoothing capacitor 11. A connection point P1 between the switch element groups 12 and 13, a connection point P2 between the switch element groups 14 and 15, and a connection point P3 between the switch element groups 16 and 17 are connected to output terminals Vu, Vv, and Vw, respectively. The switch element groups 12, 14, and 16 are arranged on the upper arm side. The switch element groups 13, 15, and 17 are arranged on the lower arm side.

[0017] As will be described in detail 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. For example, MOSFETs are used as the semiconductor switch elements. Note that elements configured by IGBTs and diodes may also be used as the switch elements. The following describes the case where the switch elements included in the switch element groups 12 to 17 are MOSFETs.

[0018] Here, switching of the switch element groups 12 to 17 refers to the 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 to switch between an ON state in which the terminal pairs of the plurality of switch elements are conductive and an OFF state in which the terminal pairs of the plurality of switch elements are non-conductive. For example, switching refers to the operation of applying a control voltage to the gate terminals (control terminals) of the plurality of MOSFETs included in the switch element group 12 to switch between an ON state in which the source terminals and drain terminals (between terminal pairs) of the plurality of MOSFETs are conductive and an OFF state in which the terminal pairs are non-conductive.

[0019] Fig. 2 is a circuit diagram showing the configuration of a switch element group included in a power conversion device according to the first embodiment of the present disclosure. Note that Fig. 2 shows only switch element groups 12 and 13 out of the six switch element groups 12 to 17 shown in Fig. 1. Note that the other switch element groups 14 to 17 have the same configuration as switch element groups 12 and 13.

[0020] 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 terminal pair consisting of a drain terminal and a source terminal. The drain terminals of the switch elements 12a and 12b are connected to each other via parasitic inductances L12a and L12b of wiring. The source terminals of the switch elements 12a and 12b are connected to each other. Note that parasitic inductance of wiring also exists between the source terminals, but this is omitted in this embodiment for simplicity of explanation.

[0021] The switch element group 13 includes a switch element 13a and a switch element 13b connected in parallel. Like the switch elements 12a and 12b, the switch elements 13a and 13b have a terminal pair consisting of a drain terminal and a source terminal. The drain terminals of the switch elements 13a and 13b are connected to each other. The source terminals of the switch elements 13a and 13b are connected to each other via parasitic inductances L13a and L13b of the wiring. While parasitic inductances of the wiring also exist between the drain terminals, they are not described in this embodiment for simplicity.

[0022] The switch elements 12a and 12b provided in the switch element group 12 are switch elements located on the upper arm side. The switch elements 13a and 13b provided in the switch element group 13 are switch elements located on the lower arm side. As shown in Figure 2, parasitic capacitances exist between the drain and source, between the drain and gate, and between the gate and 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 Fig. 3 omits the switch element group 13 in Fig. 2 and shows only the switch element group 12. Fig. 3 also clearly shows 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.

[0024] 3 also shows the drain-source parasitic capacitance Cds1, the drain-gate parasitic capacitance Cdg1, and the gate-source parasitic capacitance Cgs1 of the switch element 12a, as well as the drain-source parasitic capacitance Cds2, the drain-gate parasitic capacitance Cdg2, and the gate-source parasitic capacitance Cgs2 of the switch element 12b.

[0025] 3, the switch element group 12 includes, in addition to switch elements 12a and 12b connected in parallel, resistive elements 121a and 121b, resistive elements 122a and 122b, impedance converters 123a and 123b, and a protection function unit 50. The following description will be given of a case where the impedance converters 123a and 123b are diodes. The resistive element 121a is connected in series with the impedance converter 123a. The resistive element 121b is connected in series with the impedance converter 123b. The resistive element 121a and the impedance converter 123a form a first circuit. The resistive element 121b and the impedance converter 123b form a second circuit.

[0026] A circuit including a series-connected resistor element 121a and an impedance converter 123a is connected between the output terminal 10cc of the control unit 10 and the gate terminal 12ag of the switch element 12a. A circuit including a series-connected resistor element 121b and an impedance converter 123b is connected between the output terminal 10cc of the control unit 10 and the gate terminal 12bg of the switch element 12b. The anode side of the impedance converter 123a is connected to the resistor element 121a, and the cathode side is connected to the gate terminal 12ag. The anode side of the impedance converter 123b 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. 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] 3, the protection function unit 50 is connected to the output terminal 10cc of the control unit 10 and to a gate-off potential Vee as a potential regulating unit. This protection function unit 50 is provided to suppress the voltage applied to the output terminal 10cc of the control unit 10 and prevent a breakdown of the control unit 10 when a resonance phenomenon occurs due to a potential difference generated between the switch elements 12a and 12b. The protection function unit 50 is, for example, a diode. In this diode, the anode side is connected to the gate-off potential Vee and the cathode side is connected to the output terminal 10cc.

[0028] The control unit 10 includes switch elements 101 and 102 in addition to output terminals 10cc and 10ee. The switch element 101 is connected to the output terminal 10cc and a gate-on potential Vcc. The switch element 102 is connected to the output terminal 10ee and a 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. The gate-on potential Vcc and the gate-off potential Vee are potentials based on the potential of the reference potential terminal 10s.

[0029] 3 constitute the switch element group 12. As with the switch element group 12, the resistive elements 121a and 121b, the resistive elements 122a and 122b, the impedance conversion units 123a and 123b, and the protection function unit 50 constitute each of the switch element groups 13 to 17.

[0030] Fig. 4 is a waveform diagram showing changes over time in 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 using Fig. 4. In the following, it is assumed that the magnitudes of the parasitic inductances L12a and L12b of the wiring are different, and similarly, the magnitudes of the parasitic inductances L13a and L13b of the wiring are different.

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

[0032] Next, consider a case where the switch elements 12a and 12b located on the upper arm and the switch elements 13a and 13b located on the lower arm are all turned off, and then the switch elements 13a and 13b located on the lower arm are turned on. In this state, as shown in FIG. 3, the drain currents I13a and I13b increase. However, even if the switch elements 13a and 13b are turned on at the same time, the currents are biased due to differences 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 is 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 reaches 0 A first, and reverse recovery occurs in the internal diode.

[0034] Thereafter, the parasitic capacitance between the drain and source of the switch element 12a is charged, causing the drain-source voltage Vds1 to rise. In contrast, the internal diode of the switch element 12b is in a conductive state. Therefore, the drain-source voltage Vds2 is approximately 0 V. For example, at time t2, the drain-source voltage Vds1 is not 0 V, but the drain-source voltage Vds2 is approximately 0 V. Therefore, a potential difference occurs between the switch elements 12a and 12b.

[0035] 2, a difference in parasitic inductance between the wirings causes a potential difference between switch element 12a and switch element 12b. This characteristic may cause a resonance phenomenon between switch elements 12a and 12b, potentially resulting in a malfunction of control unit 10, which drives switch elements 12a and 12b. To prevent this malfunction, a protection function unit 50, shown in FIG. 3, is provided.

[0036] Fig. 5 is an equivalent circuit of the control unit and switch element group shown in Fig. 3. The operation of the control unit and switch element group shown in Fig. 3 will be described using Fig. 5. Now, assume that the drain-source voltage Vds1 of switch element 12a rises before the drain-source voltage Vds2 of switch element 12b. In other words, assume that the drain-source voltage Vds1 of switch element 12a becomes a voltage greater than 0V, and the drain-source voltage Vds2 of switch element 12b is 0V.

[0037] The voltage applied across the impedance converter 123b is V1a, the voltage applied across the resistor element 121b is V1b, the voltage applied across the resistor element 121a is V1c, and the voltage applied across the impedance converter 123a is V1d. The relationship between these voltages V1a, V1b, V1c, and V1d and the drain-source voltage Vds1 of the switch element 12a is Vds1×α=V1a+V1b+V1c+V1d. In other words, a portion of the drain-source voltage Vds1 is applied to the impedance converters 123a and 123b and the resistor elements 121a and 121b. α is a voltage division coefficient.

[0038] The voltage applied between the output terminal 10cc of the control unit 10 and the gate terminal 12bg of the switch element 12b is defined as V1. The relationship between this voltage V1, the voltage V1a applied across the impedance conversion unit 123b, and the voltage V1b applied across the resistor element 121b is V1 = V1a + V1b. 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 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. If the voltage V2 applied across the switch element 101 is sufficiently greater than the gate-on potential Vcc, the voltages V1 and V2 are approximately equal.

[0039] Here, the impedance transformation unit 123a is turned on due to the forward voltage and is in a low impedance state of several ohms or less. In contrast, the impedance transformation unit 123b is turned off due to the reverse voltage being applied, and the impedance between both terminals of the impedance transformation unit 123b is in a state of several kΩ or more. In other words, the impedance of the impedance transformation unit 123b is sufficiently higher than that of the impedance transformation unit 123a and the resistance elements 121a and 121b.

[0040] Therefore, the relationship between the voltages V1a, V1b, V1c, and V1d applied to the impedance converter 123b, the resistor element 121b, the resistor element 121a, and the impedance converter 123a, respectively, is V1a >> V1b + V1c + V1d. As described above, part of the drain-source voltage Vds1 is applied to the impedance converters 123a and 123b and the resistor elements 121a and 121b, but due to the relationship described above, 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 is suppressed, and it is possible to prevent a breakdown of the control unit 10.

[0042] 6 is a waveform diagram showing the time-dependent change in voltage applied to the output terminals of the switch elements and the control unit provided in the switch element group in the first embodiment. In FIG. 6, "Embodiment" shows the waveform when the protection function unit 50 is provided, and "Comparative Example" shows 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 before the drain-source voltage Vds2 of the switch element 12b. In other words, 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] 6 , in the "Comparative Example," an excessive voltage is applied to the output terminal 10cc of the control unit 10 at time t10. In contrast, in the "Embodiment," the voltage applied to the output terminal 10cc of the control unit 10 is suppressed at time t10. As such, in the embodiment, even if a resonance phenomenon occurs due to the potential difference between the switch elements 12a and 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 breakdown of the control unit 10 is prevented.

[0044] Second Embodiment. Fig. 7 is a circuit diagram illustrating a portion of the configuration of a power conversion device according to a second embodiment of the present disclosure. The overall configuration of the power conversion device according to the second embodiment is similar to the overall configuration shown in Fig. 1. Fig. 7 is a diagram corresponding to Fig. 3. As shown in Fig. 7, the power conversion device according to the second embodiment differs from the power conversion device according to the first embodiment in that a diode 103 is provided between the output terminal 10cc of the control unit 10 and the gate-off potential Vee. The anode side of the diode 103 is connected to the gate-off potential Vee, and the cathode side is connected to the output terminal 10cc. This diode 103 is provided to protect the internal circuitry, for example, when the control unit 10 is an integrated circuit (IC).

[0045] 8 is a waveform diagram showing the time-dependent changes in the voltage applied to the switch elements provided in the switch element group and the current flowing through the diode and the protection function unit in the second embodiment. In FIG. 8, "Embodiment" shows the waveform when the protection function unit 50 is provided, and "Comparative Example" shows the waveform when the protection function unit 50 is not provided. As in the first embodiment, it is assumed that the drain-source voltage Vds1 of the switch element 12a rises before the drain-source voltage Vds2 of the switch element 12b. In other words, 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.

[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, a forward voltage is applied to the diode 103, turning it on, and the current I103 flowing through the diode 103 becomes excessive, which may cause the control unit 10 to malfunction. In contrast, 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, turning them on. At this time, the current I50 flows through the protection function unit 50, and the current I103 flowing through the diode 103 is reduced, thereby preventing the control unit 10 from malfunctioning.

[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 increases, and the current I103 flowing through the diode 103 is further reduced. This makes it possible to more effectively prevent failure of the control unit 10.

[0048] FIG. 9 is a diagram illustrating a portion of a configuration according to a modified example of a power conversion apparatus according to the second embodiment of the present disclosure. As shown in FIG. 9 , in this modified example, the protection function unit 50 includes a switch element. The switch element of the protection function unit 50 is controlled by the control unit 10 to be in an on state when the switch elements 12 a and 12 b are in an off state. In general, a switch element has a lower conduction resistance in an 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, which has a lower conduction resistance, and the current flowing through the diode 103 is further reduced. This makes it possible to more effectively prevent failure of the control unit 10.

[0049] Third Embodiment Fig. 10 is a circuit diagram illustrating a portion of the configuration of a power conversion device according to a third embodiment of the present disclosure. The overall configuration of the power conversion device according to the third embodiment is similar to the configuration shown in Fig. 1. Fig. 10 is a diagram corresponding to Figs. 3 and 7. As shown in Fig. 10, the power conversion device according to the third embodiment differs from the power conversion device according to the second embodiment in that switch elements 124a and 124b are provided.

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

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

[0052] The resonance phenomenon caused by the potential difference between the switch elements 12a and 12b occurs more significantly as the potential difference increases. For example, even if the deviation in the switching timing and recovery timing can be suppressed, if the switching speed (dV / dt) is fast, even a slight deviation in timing can cause a potential difference between the switch elements 12a and 12b. Therefore, applying the power conversion device 1 according to embodiments 1 to 3 to a power conversion device that switches at high speed, i.e., includes switch elements that are prone to generating a potential difference, provides significant benefits. For example, the more wide-bandgap semiconductors (e.g., SiC elements) the switch elements 12a and 12b are, the more likely they are to generate resonance. Therefore, by including elements made of wide-bandgap semiconductors in the switch element groups 12 to 17 included in the power conversion device 1, failure of the control unit 10 can be prevented.

[0053] Modifications of the Embodiments FIG. 11 is a circuit diagram illustrating a first modification of the power converter according to the first to third embodiments of the present disclosure. Note that FIG. 11 corresponds to FIG. 3. As shown in FIG. 11, in the first modification of the power converter, the impedance conversion units 123a and 123b are connected in series to the resistance elements 122a and 122b, respectively. Specifically, in the impedance conversion unit 123a, the anode side is connected to the gate terminal 12ag and the cathode side is connected to the resistance element 1211. In addition, in the impedance conversion unit 123b, the anode side is connected to the gate terminal 12bg and the cathode side is connected to the resistance element 122b. The resistance element 122a and the impedance conversion unit 123a form a first circuit. The resistance element 122b and the impedance conversion unit 123b form a second circuit. Even when the impedance conversion units 123a and 123b are connected in series to the resistance elements 122a and 122b, the same effects as those of the first embodiment can be achieved. The circuits shown in FIGS. 7, 9 and 10 can also be configured in a similar manner.

[0054] FIG. 12 is a circuit diagram illustrating a second modified example of the power converter according to the first to third embodiments 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 serving as the potential regulating unit is set to 0 V, which is the same potential as the potential of the reference potential terminal 10s. In other words, in this modified example, the reference potential terminal 10s serves as the potential regulating unit. This configuration also achieves the same effects as the first embodiment. Note that the circuits shown in FIGS. 7, 9, and 10 can also have a similar configuration.

[0055] FIG. 13 is a circuit diagram illustrating a third modified example of the power converter according to the first to third embodiments of the present disclosure. 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 between 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 between the resistance element 121a and the impedance conversion unit 123a.

[0056] 13 shows an example in which the cathode side of the diode in the protection function unit 50 is connected to the connection point between the resistive element 121a and the impedance conversion unit 123a. The present disclosure is not limited to this example. The cathode side of the diode in the protection function unit 50 may be connected to either a first path from the output terminal 10cc to the impedance conversion unit 123a or a second path from the output terminal 10cc to the impedance conversion unit 123b. Here, the impedance conversion unit 123a is an example of a first impedance conversion unit. The impedance conversion unit 123b is an example of a second impedance conversion unit.

[0057] Although the power conversion device according to the embodiment of the present disclosure has been described above, the present disclosure is not limited to the above-described embodiment and can be freely modified within the scope of the present disclosure. For example, the power conversion device 1 according to the first to third embodiments is not limited to an inverter circuit and may be a converter circuit.

[0058] Furthermore, the configuration of the power conversion device 1 according to the first to third embodiments is not limited to a configuration in which two switch elements are connected in parallel in the switch element groups 12 to 17. The power conversion device 1 may have a configuration in which three or more switch elements are connected in parallel. Furthermore, the impedance conversion units 123a and 123b included in the power conversion device 1 according to the first to third embodiments may be switch elements such as MOSFETs or inductors. Furthermore, although the first to third embodiments have been described focusing on the switch element group 12, the other switch element groups 13 to 17 may also have a similar configuration.

[0059] It is also possible to combine the above-described embodiments and modifications as appropriate. In addition, any of the components of the above-described embodiments can be modified, or any of the components can be omitted from the embodiments.

[0060] 1...power conversion device, 10...control unit, 10cc, 10ee...output terminals, 12 to 17...switch element group, 12a, 12b, 13a, 13b...switch elements, 12ag, 12bg...gate terminals, 50...protection function unit, 103...diode, 123a, 123b...impedance conversion unit, 124a, 124b...switch elements, Vcc...gate on potential, Vee...gate off potential.

Claims

a control unit having 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 first output terminal from which a first control signal that switches the first switch element and the second switch element to an on state is output, and a second output terminal from which a second control signal that switches the first switch element and the second switch element to an off state is output; 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 a first path from the first output terminal to the first impedance conversion unit or a second path from the first output terminal to the second impedance conversion unit, and a potential regulating unit that regulates a potential of the second control signal.

2. The power conversion device according to claim 1, wherein the control unit includes a first diode connected between the potential regulating unit and the first output terminal.

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

4. The power conversion device according to claim 2, 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.

5. The power conversion device according to claim 2, further comprising: a third switch element provided between the potential regulating unit and the first control terminal; and a fourth switch element provided between the potential regulating unit and the second control terminal, wherein 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.

6. The power conversion device according to any one of claims 1 to 5, wherein the first switch element and the second switch element are elements produced using a wide band gap semiconductor.

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