JP2025080308A - Power Conversion Equipment - Google Patents

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

This disclosure relates to power conversion devices such as inverters and converters in the power electronics field.

The power conversion device is equipped with switching elements such as an IGBT (Insulated Gate Bipolar Transistor) and a MOSFET (Metal Oxide Semiconductor Field Effect Transistor). In power conversion devices used in electric powertrains, 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.

However, due to differences in characteristics between switch elements or variations in inductance in the main circuit or control circuit of the power conversion device, a shift in switching timing may occur between the switch elements. If such a timing shift occurs, a current imbalance occurs due to the timing shift. For example, current may concentrate in the switch element that switched the earliest, increasing losses and causing the switch element to break down.

In addition, in a power conversion device, if a difference occurs in the switching timing between switch elements, this difference causes a potential difference in the drain-source voltage. If there is a potential difference between switch elements, a resonance phenomenon occurs due to the inductance between the switch 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 the switch element). If such a resonance phenomenon occurs, an excessive voltage may be applied to the control unit (for example, a gate drive circuit that outputs a switching control signal to turn the switch element on or off), which may cause it to be destroyed. This problem is particularly noticeable when the switch elements are switched at high speed.

To solve the above-mentioned problems, a power conversion device has been proposed that suppresses the timing discrepancy of switching between switch elements, which is the source of the resonance phenomenon between switch elements. For example, the power conversion device of Patent Document 1 includes multiple semiconductor modules connected in parallel, a gate drive circuit that drives these semiconductor modules, and gate wiring that is provided in each semiconductor module and connects the semiconductor module to the gate drive circuit or other semiconductor modules. In this power conversion device, the impedance of the gate wiring is lowered for semiconductor modules with lower gate threshold voltages, so that the gate current values supplied to each semiconductor module during off operation are the same.

JP 2020-156304 A

However, in a power conversion device, even if the switching timing between switch elements is aligned, if there is variation in the impedance of the main circuit of each switch element, the timing at which the recovery current is generated by the internal diode of each switch element will differ. This causes a voltage difference in the drain-source voltage Vds of, for example, a transistor, which is a switch element. The resonance phenomenon that occurs between switch elements due to this voltage difference in the drain-source voltage Vds may cause the control unit for driving the switch element to break down.

This disclosure has been made in consideration of the above circumstances, and aims to provide a power conversion device that can prevent failure of the control unit due to resonance of the switching element.

In order to solve the above problem, a power conversion device according to one aspect of the present disclosure includes 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 turns 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 turns 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 the path from the first output terminal to the first impedance conversion unit or the path from the first output terminal to the second impedance conversion unit and a potential regulation unit that regulates the potential of the second control signal.

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. As a result, the power conversion device according to the present disclosure can prevent failure of the control unit due to the resonance phenomenon between the switch elements.

1 is a circuit section illustrating a schematic configuration of a power conversion device according to a first embodiment of the present disclosure. 1 is a circuit diagram showing a configuration of a switch element group included in a power conversion device according to a first embodiment of the present disclosure. 3 is a circuit diagram showing a more detailed configuration of a switch element group shown in FIG. 2. 3 is a waveform diagram showing changes over time in voltage and current in the switch element group shown in FIG. 2. 4 is an equivalent circuit of the control unit and the switch element group shown in FIG. 3. 4 is a waveform diagram showing changes over time in voltage applied to a switch element provided in a switch element group and an output terminal of a control unit in the first embodiment. FIG. 11 is a circuit diagram illustrating a portion of a configuration of a power conversion device according to a second embodiment of the present disclosure. 13 is a waveform diagram showing changes over time in voltage applied to a switch element provided in a switch element group and in current flowing through a diode and a protection function unit in the second embodiment. FIG. FIG. 11 is a diagram illustrating a portion of a configuration according to a modified example of a power conversion device according to embodiment 2 of the present disclosure. 13 is a circuit diagram showing a portion of a 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 the power converter according to the first to third embodiments of the present disclosure. FIG. 11 is a circuit diagram illustrating a second modified example of the 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 the power converter according to the first to third embodiments of the present disclosure.

The power conversion device according to the embodiment of the present disclosure will be described in detail below with reference to the drawings.

[First embodiment]
Fig. 1 is a circuit diagram showing a schematic configuration of a power conversion device according to a first embodiment of the present disclosure. The power conversion device 1 shown in Fig. 1 is an inverter circuit. A DC power source 2 is connected to an input stage of the power conversion device 1, and a motor 3, which is a load, is connected to an output stage of the power conversion device 1. The DC power source 2 is a DC storage battery, which 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, a secondary battery, such as a nickel-metal hydride battery or a lithium-ion battery, which outputs a voltage of 100 V or more, is used as the DC power source 2.

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 12-17, a voltage sensor circuit 20, and current sensor circuits 21a-21c. The power conversion device 1 converts the DC voltage output from the DC power source 2 into three-phase AC and outputs it to three-phase 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 provided in a generator or an electric motor.

The smoothing capacitor 11 is connected in parallel to the DC power source 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. The switch element groups 12 to 17 each perform a switching operation based on a control signal from the control unit 10 input via control lines 32a to 32f.

Switch element groups 12 and 13 are connected in series, switch element groups 14 and 15 are connected in series, and switch element groups 16 and 17 are connected in series. The circuit consisting of switch element groups 12 and 13 connected in series, the circuit consisting of switch element groups 14 and 15 connected in series, and the circuit consisting of switch element groups 16 and 17 connected in series are connected in parallel to smoothing capacitor 11. Connection point P1 of switch element groups 12 and 13, connection point P2 of switch element groups 14 and 15, and connection point P3 of switch element groups 16 and 17 are connected to output terminals Vu, Vv, and Vw, respectively. Switch element groups 12, 14, and 16 are arranged on the upper arm side, and switch element groups 13, 15, and 17 are arranged on the lower arm side.

Although details 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 the switch elements may also be configured with an IGBT and a diode. In the following, it is assumed that the switch elements included in the switch element groups 12 to 17 are MOSFETs.

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 multiple switch elements in the switch element groups 12 to 17 to switch between an on state that provides conduction between the terminal pairs of the multiple switch elements and an off state that provides non-conduction. For example, it is the operation of applying a control voltage to the gate terminals (control terminals) of the multiple MOSFETs in the switch element group 12 to switch between an on state that provides conduction between the source terminals and drain terminals (between the terminal pairs) of the multiple MOSFETs and an off state that provides non-conduction.

FIG. 2 is a circuit diagram showing the configuration of a switch element group included in a power conversion device according to embodiment 1 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.

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

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

Switch elements 12a and 12b provided in switch element group 12 are upper arm switch elements, and switch elements 13a and 13b provided in switch element group 13 are lower arm switch elements. As shown in FIG. 2, parasitic capacitances exist between the drain and source, between the drain and gate, and between the gate and source of switch elements 12a, 12b and switch elements 13a, 13b.

Figure 3 is a circuit diagram showing a more detailed configuration of the switch element group shown in Figure 2. Note that in Figure 3, the switch element group 13 in Figure 2 is omitted, and only the switch element group 12 is shown. Also, Figure 3 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.

In addition, FIG. 3 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. Similarly, the drain-source parasitic capacitance Cds2, the drain-gate parasitic capacitance Cdg2, and the gate-source parasitic capacitance Cgs2 of the switch element 12b are also shown.

As shown in FIG. 3, the switch element group 12 includes, in addition to the switch elements 12a and 12b connected in parallel, resistive elements 121a and 121b, resistive elements 122a and 122b, impedance conversion units 123a and 123b, and a protection function unit 50. The impedance conversion units 123a and 123b are described as diodes. The resistive element 121a is connected in series with the impedance conversion unit 123a, and the resistive element 121b is connected in series with the impedance conversion unit 123b. The resistive element 121a and the impedance conversion unit 123a form a first circuit, and the resistive element 121b and the impedance conversion unit 123b form a second circuit.

The circuit consisting of the series-connected resistor element 121a and impedance conversion unit 123a is connected between the output terminal 10cc of the control unit 10 and the gate terminal 12ag of the switch element 12a. The circuit consisting of the series-connected resistor element 121b and impedance conversion unit 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 conversion unit 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 conversion unit 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.

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 a potential regulation 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 the control unit 10 from failing when a resonance phenomenon occurs due to a potential difference generated between the switch element 12a and the switch element 12b. 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.

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

The resistive elements 121a, 121b, resistive elements 122a, 122b, impedance conversion units 123a, 123b, and protection function unit 50 shown in FIG. 3 are for the switch element group 12. The resistive elements 121a, 121b, resistive elements 122a, 122b, impedance conversion units 123a, 123b, and protection function unit 50 shown in FIG. 3 are also provided in each of the switch element groups 13 to 17.

Figure 4 is a waveform diagram showing the change over time in voltage and current in the switch element group shown in Figure 2. The characteristics of the switch element group shown in Figure 2 will be explained using Figure 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.

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

Next, consider the case where the upper arm switch elements 12a, 12b and the lower arm switch elements 13a, 13b are all turned off, and then the lower arm switch elements 13a, 13b 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 switch element 13a is greater than the drain current I13b flowing into the drain terminal of switch element 13b.

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

Then, the parasitic capacitance between the drain and source of switch element 12a is charged, and the drain-source voltage Vds1 rises. In contrast, the internal diode of switch element 12b is in a conductive state, so the drain-source voltage Vds2 is approximately 0 V. For example, at time t2, the drain-source voltage Vds1 is not 0 V, and the drain-source voltage Vds2 is approximately 0 V, so a potential difference occurs between switch element 12a and switch element 12b.

As described above, the switch element group shown in FIG. 2 has a characteristic that a difference in parasitic inductance of the wiring causes a potential difference between switch element 12a and switch element 12b. With such a characteristic, there is a risk that the control unit 10 for driving switch elements 12a and 12b may fail due to the resonance phenomenon that occurs between switch elements 12a and 12b. To prevent such a failure, a protection function unit 50 shown in FIG. 3 is provided.

Figure 5 is an equivalent circuit of the control unit and switch element group shown in Figure 3. The operation of the control unit and switch element group shown in Figure 3 will be described using Figure 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 in a state of 0V.

The voltage applied across the impedance conversion unit 123b is V1a, the voltage applied across the resistance element 121b is V1b, the voltage applied across the resistance element 121a is V1c, and the voltage applied across the impedance conversion unit 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 x α = V1a + V1b + V1c + V1d. In other words, a part of the drain-source voltage Vds1 is applied to the impedance conversion units 123a and 123b and the resistance elements 121a and 121b. Note that α is a voltage division coefficient.

The voltage applied between the output terminal 10cc of the control unit 10 and the gate terminal 12bg of the switch element 12b is V1. The relationship between this voltage V1, the voltage V1a applied across the impedance conversion unit 123b, and the voltage V1b applied across the resistance 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 becomes 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. Here, if the voltage V2 applied across the switch element 101 is sufficiently larger than the gate-on potential Vcc, the voltages V1 and V2 are almost equal.

Since the impedance conversion unit 123a is subjected to a forward voltage, it is turned on and enters a low impedance state of a few ohms or less. In contrast, a reverse voltage is applied to the impedance conversion unit 123b, which enters the off state, so the impedance between both terminals of the impedance conversion unit 123b becomes a few kΩ or more. In other words, the impedance of the impedance conversion unit 123b becomes sufficiently higher than that of the impedance conversion unit 123a and the resistance elements 121a and 121b.

Therefore, the relationship between the voltages V1a, V1b, V1c, and V1d applied to the impedance conversion unit 123b, the resistance element 121b, the resistance element 121a, and the impedance conversion unit 123a, respectively, 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 resistance elements 121a and 121b, but due to the relationship described above, Vds1 x α ≒ V1a ≒ V1 ≒ V2, and the reference potential terminal 10s has a higher potential than the output terminal 10cc.

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 a breakdown of the control unit 10 can be prevented.

Figure 6 is a waveform diagram showing the change over time in the voltage applied to the output terminal of the switch element and control unit provided in the switch element group in embodiment 1. Note that in Figure 6, the "embodiment" shows the waveform when the protection function unit 50 is provided, and the "comparison 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 0V, and the drain-source voltage Vds2 of the switch element 12b is 0V.

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. In contrast, in the "Embodiment," the voltage applied to the output terminal 10cc of the control unit 10 is suppressed at time t10. Thus, in this 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 failure of the control unit 10 is prevented.

[Embodiment 2]
FIG. 7 is a circuit diagram showing a part 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 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 the second embodiment is different 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 circuit, for example, when the control unit 10 is an IC (Integrated Circuit).

Figure 8 is a waveform diagram showing the change over time in the voltage applied to the switch element provided in the switch element group and the current flowing through the diode and the protection function unit in the second embodiment. In Figure 8, the "embodiment" shows the waveform when the protection function unit 50 is provided, and the "comparison 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 0V, and the drain-source voltage Vds2 of the switch element 12b is 0V.

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, so that the current I103 flowing through the diode 103 becomes excessive, and there is a risk of the control unit 10 failing. 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, so that the control unit 10 can be prevented from failing.

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 making the diode of the protection function unit 50 a Schottky barrier diode, 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. This makes it possible to more effectively prevent failure of the control unit 10.

FIG. 9 is a diagram showing a part of the configuration of a modified example of a power conversion device according to the second embodiment of the present disclosure. As shown in FIG. 9, in this modified example, 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 an on state when the switch elements 12a and 12b are in an off state. In general, a switch element has a smaller 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, even more current flows through the protection function unit 50, which has a small 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.

Third Embodiment
Fig. 10 is a circuit diagram showing a part 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 that 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.

The switch element 124a is provided between the gate terminal 12ag of the switch element 12a and the gate-off potential Vee, and the switch element 124b is provided between the gate terminal 12bg of the switch element 12b and the gate-off potential Vee. These 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.

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, the 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 into the protection function unit 50, so 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.

The resonance phenomenon caused by the potential difference between the switch elements 12a and 12b occurs more significantly as the potential difference becomes larger. For example, even if the timing difference between the switching and recovery can be suppressed, if the switching speed (dV/dt) is fast, even a slight timing difference will cause a potential difference between the switch elements 12a and 12b. For this reason, the power conversion device 1 according to the first to third embodiments is significantly more effective when applied to a power conversion device equipped with a switch element that switches at high speed, i.e., is prone to generating a potential difference. For example, the wider the bandgap semiconductor (e.g., SiC element) the switch elements 12a and 12b are, the more likely the resonance will occur. Therefore, by providing the switch element groups 12 to 17 of the power conversion device 1 with elements generated using wide bandgap semiconductors, the failure of the control unit 10 can be prevented.

[Modifications of the embodiment]
FIG. 11 is a circuit diagram showing a first modified example of the power converter according to the first to third embodiments of the present disclosure. FIG. 11 is a diagram corresponding to FIG. 3. As shown in FIG. 11, the first modified example of the power converter has impedance conversion units 123a and 123b connected in series to the resistance elements 122a and 122b, respectively. Specifically, the impedance conversion unit 123a has an anode side connected to the gate terminal 12ag and a cathode side connected to the resistance element 1211. The impedance conversion unit 123b has an anode side connected to the gate terminal 12bg and a cathode side connected to the resistance element 122b. The resistance element 122a and the impedance conversion unit 123a form a first circuit, and the resistance element 122b and the impedance conversion unit 123b form a second circuit. Even if the impedance conversion units 123a and 123b are connected in series to the resistance elements 122a and 122b, the same effect as in the first embodiment can be obtained. The circuits shown in FIGS. 7, 9 and 10 can also be configured in a similar manner.

Figure 12 is a circuit diagram showing a second modified example of the power converter according to the first to third embodiments of the present disclosure. Note that Figure 12 is a diagram equivalent to Figure 3. As shown in Figure 12, in the second modified example of the power converter, the gate-off potential Vee as the potential regulating section is set to 0V, and is set to the same potential as the potential of the reference potential terminal 10s. In other words, in this modified example, the reference potential terminal 10s is used as the potential regulating section. With this configuration, the same effect as in the first embodiment can be achieved. Note that the circuits shown in Figures 7, 9, and 10 can also be configured in a similar manner.

Figure 13 is a circuit diagram showing a third modified example of the power converter according to the first to third embodiments of the present disclosure. Note that Figure 13 is a diagram equivalent to Figure 3. As shown in Figure 13, the third modified example of the power converter has a protection function unit 50 provided between the connection point between the resistance element 121a and the impedance conversion unit 123a and the gate-off potential Vee. Specifically, the diode of the protection function unit 50 has an anode side connected to the gate-off potential Vee and a cathode side connected to the connection point between the resistance element 121a and the impedance conversion unit 123a.

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 between the resistive element 121a and the impedance conversion unit 123a, but this is not limited to this. The cathode side of the diode in the protection function unit 50 may be connected to either the path from the output terminal 10cc to the impedance conversion unit 123a or the path from the output terminal 10cc to the impedance conversion unit 123b.

The power conversion device according to the embodiment of the present disclosure has been described above, but the present disclosure is not limited to the above embodiment and can be freely modified within the scope of the present disclosure. For example, the power conversion device 1 according to embodiments 1 to 3 is not limited to an inverter circuit, and may be a converter circuit.

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, but may have a configuration in which three or more switch elements are connected in parallel. The impedance conversion units 123a and 123b provided in the power conversion device 1 according to the first to third embodiments may be switch elements such as MOSFETs, or inductors. Although the first to third embodiments have been described with a focus on the switch element group 12, the other switch element groups 13 to 17 may also have a similar configuration.

The above-described embodiments and modifications may be combined as appropriate. In addition, any of the components of each of the above-described embodiments may be modified, or any of the components may be omitted from each of the embodiments.

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

Claims (6)

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 for turning on the first switch element and the second switch element is output, and a second output terminal from which a second control signal for turning off the first switch element and the second switch element 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;
A power conversion device comprising: The power conversion device according to claim 1, wherein the control unit includes a first diode connected between the potential regulation unit and the first output terminal. The power conversion device according to claim 2, wherein the protection function unit is a diode whose forward voltage is smaller than the forward voltage of the first diode. 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. 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 comprising:
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 converter according to claim 2. 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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