Semiconductor switch drive circuit and electric power conversion apparatus
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- IHI CORP
- Filing Date
- 2025-11-06
- Publication Date
- 2026-07-30
Smart Images
Figure JP2025038982_30072026_PF_FP_ABST
Abstract
Description
Semiconductor Switch Drive Circuit and Power Conversion Device
[0001] The present disclosure relates to a semiconductor switch drive circuit and a power conversion device.
[0002] An inverter, which is a power conversion device that supplies power to a motor, includes a power conversion circuit composed of a plurality of semiconductor switches. These semiconductor switches are mainly transistors such as MOSFETs, and their operations are controlled by gate voltages applied to their gates. Patent Documents 1 to 3 disclose technologies related to semiconductor switch drive circuits for gate voltages that control semiconductor switches.
[0003] Japanese Unexamined Patent Application Publication No. 2019-75887, Japanese Unexamined Patent Application Publication No. 11-146640, Japanese Unexamined Patent Application Publication No. 2009-182743
[0004] A semiconductor switch drive circuit is provided for each semiconductor switch. And a drive power source for generating positive and negative voltages as gate voltages is connected to the semiconductor switch drive circuit. As the number of semiconductor switches constituting the inverter increases, the number of semiconductor switch drive circuits also increases. Therefore, in this technical field, it has been desired to simplify the configuration of the semiconductor switch drive circuit.
[0005] The present disclosure describes a semiconductor switch drive circuit capable of simplifying the circuit configuration and a power conversion device including the semiconductor switch drive circuit.
[0006] One embodiment of the present disclosure is a semiconductor switch drive circuit for a power conversion device that uses a first semiconductor switch and a second semiconductor switch to convert power supplied by a power source into a form of power required by a load device. The semiconductor switch drive circuit includes a drive power supply unit including a positive voltage power supply for a positive voltage and a negative voltage power supply for a negative voltage; a first semiconductor switch drive unit that selectively connects to a first semiconductor switch a first positive voltage capacitor that generates a positive voltage to turn on a first semiconductor switch by charging power from the positive voltage power supply and a first negative voltage capacitor that generates a negative voltage to turn off a first semiconductor switch by charging power from the negative voltage power supply; a second semiconductor switch drive unit that selectively connects to a second semiconductor switch a second positive voltage capacitor that generates a positive voltage to turn on a second semiconductor switch by charging power from the positive voltage power supply and a second negative voltage capacitor that generates a negative voltage to turn off a second semiconductor switch by charging power from the negative voltage power supply; and a negative voltage charging circuit unit that selectively performs a configuration of connecting the first negative voltage capacitor to the negative voltage power supply and a configuration of disconnecting the first negative voltage capacitor from the negative voltage power supply.
[0007] This power converter includes a negative voltage charging circuit, which selectively performs two configurations: connecting the first negative voltage capacitor to a negative voltage power supply and disconnecting the first negative voltage capacitor from the negative voltage power supply. With this negative voltage charging circuit, the first negative voltage capacitor can be charged using the drive power supply. Therefore, since it is not necessary to provide a power supply for negative voltage in each of the first semiconductor switch drive unit and the second semiconductor switch drive unit, the circuit configuration can be simplified.
[0008] In the power conversion device described above, the first semiconductor switch drive unit further includes a first connection switching unit that selectively connects a first positive voltage capacitor and a first negative voltage capacitor to the first semiconductor switch, the second semiconductor switch drive unit further includes a second connection switching unit that selectively connects a second positive voltage capacitor and a second negative voltage capacitor to the second semiconductor switch, and the negative voltage charging circuit unit may include charging wiring that connects the wiring connecting the first negative voltage capacitor to the first connection switching unit to the wiring connecting the second negative voltage capacitor to the second connection switching unit.
[0009] In the power conversion device described above, the negative voltage charging circuit may further include a charging switch element provided on the wiring that includes a charging wire connecting the first negative voltage capacitor to the second negative voltage capacitor. With this configuration, a configuration in which the first negative voltage capacitor is connected to a negative voltage power supply and a configuration in which the first negative voltage capacitor is disconnected from the negative voltage power supply can be realized in a simple configuration.
[0010] In the power conversion device described above, a closed circuit including a charging switch element and a second semiconductor switch may be formed when the first negative voltage capacitor is charged by a negative voltage power supply. With this configuration, a closed circuit for charging the first negative voltage capacitor can be formed.
[0011] In the power conversion device described above, the negative voltage charging circuit is provided on wiring that includes charging wiring connecting the first negative voltage capacitor to the second negative voltage capacitor, and may further include a diode element to prevent current from flowing from the second negative voltage capacitor side to the first negative voltage capacitor side. This configuration makes it possible to prevent malfunctions caused by reverse current flow.
[0012] The power conversion device described above further includes a controller that controls the second connection switching unit and the charging switch element, and the controller may control the second connection switching unit and the charging switch element so that the charging switch element is in the ON state when the second semiconductor switch is in the ON state. With this configuration as well, a configuration in which the first negative voltage capacitor is connected to a negative voltage power supply and a configuration in which the first negative voltage capacitor is disconnected from a negative voltage power supply can be realized in a simple configuration.
[0013] The controller of the power converter described above may switch the charging switch element from the off state to the on state after switching the second semiconductor switch from the off state to the on state. This operation can suppress the occurrence of circuit malfunctions.
[0014] The controller of the power converter described above may switch the charging switch element from the on state to the off state before switching the second semiconductor switch from the on state to the off state. This operation can also suppress the occurrence of circuit malfunctions.
[0015] The negative voltage charging circuit section of the power converter described above may further include a status signal generating section that generates a connection status signal indicating whether the second semiconductor switch is in the ON state or the OFF state, and a switching signal generating section that switches the charging switch element to the ON state when it receives a connection status signal indicating that the second semiconductor switch is in the ON state and a control signal for switching the charging switch element from the OFF state to the ON state. This configuration also helps to suppress the occurrence of circuit malfunctions.
[0016] Another form of this disclosure is a power converter that converts a form of power provided by a power source to a form of power required by a load device. The power converter includes a first semiconductor switch electrically connected between a power source and a load device, a second semiconductor switch electrically connected between a power source and a load device, a drive power supply unit including a positive voltage power supply for a positive voltage and a negative voltage power supply for a negative voltage, a first semiconductor switch drive unit that selectively connects to the first semiconductor switch a first positive voltage capacitor that generates a positive voltage to turn on the first semiconductor switch by charging power from the positive voltage power supply and a first negative voltage capacitor that generates a negative voltage to turn off the first semiconductor switch by charging power from the negative voltage power supply, a second semiconductor switch drive unit that selectively connects to the second semiconductor switch a second positive voltage capacitor that generates a positive voltage to turn on the second semiconductor switch by charging power from the positive voltage power supply and a second negative voltage capacitor that generates a negative voltage to turn off the second semiconductor switch by charging power from the negative voltage power supply, and a negative voltage charging circuit unit that selectively performs a configuration of connecting the first negative voltage capacitor to the negative voltage power supply and a configuration of disconnecting the first negative voltage capacitor from the negative voltage power supply.
[0017] This power converter is equipped with the semiconductor switch drive circuit described above. Therefore, the circuit configuration can be simplified.
[0018] According to the semiconductor switch drive circuit and the power conversion device equipped with the semiconductor switch drive circuit of this disclosure, the circuit configuration can be simplified.
[0019] Figure 1 is a circuit diagram of a power converter equipped with a semiconductor switch drive circuit according to the first embodiment. Figure 2 is a schematic circuit diagram illustrating the positive voltage charging closed circuit and the negative voltage charging closed circuit in the semiconductor switch drive circuit shown in Figure 1. Figures 3(a), 3(b), 3(c), 3(d), 3(e), and 3(f) are timing charts illustrating the operation of the semiconductor switch drive circuit shown in Figure 1. Figure 4 is a circuit diagram of a power converter equipped with a semiconductor switch drive circuit according to the second embodiment. Figures 5(a), 5(b), 5(c), 5(d), and 5(e) are timing charts illustrating the operation of the semiconductor switch drive circuit shown in Figure 4.
[0020] The semiconductor switch drive circuit and the power conversion device equipped with the semiconductor switch drive circuit described herein will be described in detail below with reference to the attached drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant descriptions are omitted.
[0021] Referring to Figure 1, a power converter 1 according to the first embodiment will be described. The power converter 1 converts the form of power received from the power source 4 into the form of power required by the load device M. The power source 4 is a power source for driving the load device M. The load device M may be, for example, a three-phase AC motor used as a power source to rotate an impeller. Therefore, the power converter 1 may be used as an electrical component of an electric compressor or electric blower. The power converter 1 according to the first embodiment is, for example, an inverter that converts DC power to AC power. The power converter 1 may also be a converter that converts AC power to DC power. The power converter may convert DC power of the first embodiment to DC power of the second embodiment.
[0022] As shown in Figure 1, the power conversion device 1 includes, for example, a semiconductor switch 2, a semiconductor switch 3, a semiconductor switch drive circuit 6, a power supply 4, and a controller 7.
[0023] The semiconductor switches 2 and 3 are connected in series with each other between the power supply 4 and GND (ground), forming a switch leg. Semiconductor switch 2 constitutes the so-called upper arm in the semiconductor switch drive circuit 6. Semiconductor switch 3 constitutes the so-called lower arm in the semiconductor switch drive circuit 6. Semiconductor switches 2 and 3 are each, for example, n-type MOSFETs (metal-oxide-semiconductor field-effect transistors). Semiconductor switches 2 and 3 may each be IGBTs (Insulated Gate Bipolar Transistors), or they may be switches made of wide-bandgap semiconductors such as SiC (silicon carbide) or GaN (gallium nitride).
[0024] The drain 2a (input terminal) of semiconductor switch 2 is connected to power supply 4. The source 2b (output terminal) of semiconductor switch 2 is connected to the drain 3a (input terminal) of semiconductor switch 3. The source 3b (output terminal) of semiconductor switch 3 is connected to GND. The gate 2c (control terminal) of semiconductor switch 2 and the gate 3c (control terminal) of semiconductor switch 3 are connected to semiconductor switch drive circuit 6. Furthermore, a diode 21 is connected between the drain 2a of semiconductor switch 2 and the source 2b of semiconductor switch 2. Also, a diode 31 is connected between the drain 3a of semiconductor switch 3 and the source 3b of semiconductor switch 3.
[0025] In the following explanation, when an element is said to be “connected” to another element, unless otherwise specified, it means that the element is “electrically connected” to the other element. “Electrically connected” means that the two elements are connected in such a way that control signals can be transmitted and power can be supplied between them. Therefore, “electrically connected” includes both cases where the two elements are directly connected to each other by wiring and cases where the two elements are indirectly connected through other electrical components.
[0026] The semiconductor switch drive circuit 6 drives semiconductor switches 2 and 3. The controller 7 controls the semiconductor switch drive circuit 6 by providing control signals D1a and D1b to the semiconductor switch drive circuit 6. The controller 7 is composed of a computer including, for example, a CPU, ROM, and RAM. The controller 7 controls the semiconductor switch drive circuit 6 so that semiconductor switches 2 and 3 are alternately turned on. As a result, the input voltage Vin provided from the power supply 4 is converted to an AC voltage and supplied to the load device M.
[0027] The semiconductor switch drive circuit 6 includes, for example, a semiconductor switch drive unit 6a (first semiconductor switch drive circuit), a semiconductor switch drive unit 6b (second semiconductor switch drive circuit), and a drive power supply unit 5.
[0028] The semiconductor switch drive unit 6a is a drive circuit for the upper arm that drives the semiconductor switch 2. The positive voltage generation unit of the semiconductor switch drive unit 6a is a so-called bootstrap circuit. The semiconductor switch drive unit 6a switches the semiconductor switch 2 on or off using the voltage VDD. The semiconductor switch drive unit 6b is a drive circuit for the lower arm that drives the semiconductor switch 3. The semiconductor switch drive unit 6b switches the semiconductor switch 3 on or off using the voltage VDD.
[0029] As shown in the circuit diagram in Figure 1, the semiconductor switch drive unit 6a does not include a power supply element as a component, but the semiconductor switch drive unit 6b does. The power supply element is the drive power supply unit 5. In other words, the semiconductor switch drive unit 6b generates the gate voltage supplied to the semiconductor switch 3 using the power generated by the drive power supply unit 5.
[0030] In contrast, the semiconductor switch drive unit 6a does not include the drive power supply unit 5, so it receives power from the drive power supply unit 5 of the semiconductor switch drive unit 6b and generates the gate voltage supplied to the semiconductor switch 2.
[0031] Controller 7 is electrically connected to semiconductor switch drive unit 6a and outputs a control signal D1a to semiconductor switch drive unit 6a to control the driving of semiconductor switch drive unit 6a. Similarly, controller 7 is electrically connected to semiconductor switch drive unit 6b and outputs a control signal D1b to semiconductor switch drive unit 6b to control the driving of semiconductor switch drive unit 6b. Control signals D1a and D1b are, for example, PWM (Pulse Width Modulation) signals.
[0032] The controller 7 controls the switching of the semiconductor switch 2 to the on or off state by outputting a control signal D1a to the semiconductor switch drive unit 6a that instructs the semiconductor switch 2 to be turned on or off. When the semiconductor switch drive unit 6a receives a control signal D1a that instructs the semiconductor switch 2 to be turned on, it generates a positive voltage using the voltage VDD to sufficiently turn on the semiconductor switch 2 and applies the generated positive voltage to the gate 2c of the semiconductor switch 2. As a result, the semiconductor switch 2 becomes ON. When the semiconductor switch drive unit 6a receives a control signal D1a that instructs the semiconductor switch 2 to be turned off, it generates a negative voltage using the voltage VDD to sufficiently turn off the semiconductor switch 2 and applies the generated negative voltage to the gate 2c of the semiconductor switch 2. As a result, the semiconductor switch 2 becomes OFF.
[0033] The controller 7 controls the switching of the semiconductor switch 3 on or off by outputting a control signal D1b to the semiconductor switch drive unit 6b that instructs the semiconductor switch 3 to be turned on or off. The operation of the semiconductor switch drive unit 6b upon receiving the control signal D1b is the same as the operation of the semiconductor switch drive unit 6a upon receiving the control signal D1a, so a detailed explanation is omitted.
[0034] Furthermore, the controller 7 also controls the operation of generating a negative voltage in the semiconductor switch drive unit 6a using the power supply unit 5 of the semiconductor switch drive unit 6b. Details of this control will be described later.
[0035] The configurations of the semiconductor switch drive unit 6a and the semiconductor switch drive unit 6b will be described in more detail below.
[0036] The semiconductor switch drive unit 6a includes, for example, a connection switching unit 13a, a capacitor 11a (first positive voltage capacitor), a capacitor 16a (first negative voltage capacitor), and a diode 21a.
[0037] Capacitor 11a is connected between the positive voltage power supply 51 and the connection switching unit 13a. Capacitor 11a is a positive power supply capacitor that generates a positive voltage. The positive terminal 111a (one end) of capacitor 11a is connected to the drive power supply unit 5 and the connection switching unit 13a. The negative terminal 211a (the other end) of capacitor 11a is connected to the source 2b of the semiconductor switch 2 via wiring L4a. More specifically, the positive terminal 51p of the positive voltage power supply 51 is connected to wiring L2a, and wiring L2a is connected to the positive terminal 111a of capacitor 11a at connection point P2a. Furthermore, wiring L2a is connected to wiring L3a at connection point P2a, and wiring L3a is connected to the gate 2c of the semiconductor switch 2 via the connection switching unit 13a. In addition, wiring L2a is connected to the drive power supply unit 5 of the semiconductor switch drive unit 6b.
[0038] Capacitor 16a is a negative power supply capacitor that receives power from the drive power supply unit 5 of the semiconductor switch drive unit 6b and generates a negative voltage. The positive terminal 116a (one end) of capacitor 16a is connected to wiring L4a, and via wiring L4a it is connected to the source 2b of the semiconductor switch 2. The negative terminal 216a (the other end) of capacitor 16a is connected to wiring L7a, and wiring L7a is connected to the first connection switching unit 13a.
[0039] Diode 21a is connected in series between the drive power supply unit 5 of the semiconductor switch drive unit 6b and the capacitor 11a. Diode 21a is a diode for preventing reverse current. Diode 21a is connected in the wiring L2a with the direction from the drive power supply unit 5 to the connection point P2a being the forward direction. Therefore, the anode of diode 21a is connected to the positive terminal 51p of the positive voltage power supply 51, and the cathode of diode 21a is connected to the positive terminal 111a of the capacitor 11a.
[0040] The connection switching unit 13a, which is a push-pull circuit, functions as a buffer. The connection switching unit 13a includes bipolar transistors 131a and 132a connected in series with each other. Bipolar transistors 131a and 132a constitute a so-called push-pull circuit. The collector terminal of bipolar transistor 131a is connected to the positive terminal 111a of capacitor 11a. The emitter terminal of bipolar transistor 131a is connected to the emitter terminal of bipolar transistor 132a. The connection point between the emitter terminals of bipolar transistor 131a and bipolar transistor 132a is connected to the gate 2c of semiconductor switch 2. The collector terminal of bipolar transistor 132a is connected to the negative terminal 216a of capacitor 16a. The base terminals of bipolar transistor 131a and bipolar transistor 132a are connected to controller 7 and receive control signal D1a from controller 7.
[0041] The semiconductor switch drive unit 6b has circuit elements common to the semiconductor switch drive unit 6a, as well as circuit elements not present in the semiconductor switch drive unit 6a. The semiconductor switch drive unit 6b has circuit elements common to the semiconductor switch drive unit 6a, including capacitors 11b and 16b, a diode 21b, and a connection switching unit 13b. Detailed explanations of these will not be repeated.
[0042] The semiconductor switch drive unit 6b has a drive power supply unit 5, which is a circuit element not present in the semiconductor switch drive unit 6a. The drive power supply unit 5 has a positive voltage power supply 51 and a negative voltage power supply 52. These power supplies generate a predetermined potential difference between the positive and negative electrodes.
[0043] The positive voltage power supply 51 has its negative electrode 51n connected to the reference potential GND. If the reference potential GND is 0V, the voltage of the negative electrode 51n of the positive voltage power supply 51 connected to the reference potential GND is 0V. In contrast, the voltage of the positive electrode 51p of the positive voltage power supply 51 is +20V. And the positive electrode 51p of the positive voltage power supply 51 is connected to the positive electrode 111b of the capacitor 11b. The negative electrode 51n of the positive voltage power supply 51 is connected to the negative electrode 211b of the capacitor 11b. The charge stored in the capacitor 11b by such a connection configuration can generate a positive gate voltage (+20V) for the semiconductor switch 3.
[0044] The negative voltage power supply 52 has its positive electrode 52p connected to the reference potential GND. If the reference potential GND is 0V, the voltage of the positive electrode 52p of the negative voltage power supply 52 connected to the reference potential GND is 0V. In contrast, the voltage of the negative electrode 52n of the negative voltage power supply 52 is -5V. And the positive electrode 52p of the negative voltage power supply 52 is connected to the positive electrode 116b of the capacitor 16b. The negative electrode 52n of the negative voltage power supply 52 is connected to the negative electrode 216b of the capacitor 16b. The charge stored in the capacitor 16b by such a connection configuration can generate a negative gate voltage (-5V) for the semiconductor switch 3.
[0045] Further, as circuit elements that the semiconductor switch driving unit 6b does not have in the semiconductor switch driving unit 6a, it has a wiring L8, a diode 82b, and a switch element 81b. The switch element 81b and the diode 82b constitute a negative voltage charging circuit unit 80b.
[0046] One end of the wiring L8 is connected to the wiring L7a of the semiconductor switch driving unit 6a. The other end of the wiring L8 is connected to the wiring L7b of the semiconductor switch driving unit 6b via the switch element 81b. That is, the wiring L8 connects the wiring L7b of the semiconductor switch driving unit 6b to the wiring L7a of the semiconductor switch driving unit 6a.
[0047] The wiring L8 has a diode 83b and a switch element 81b arranged thereon. The diode 83b prevents current from flowing from the wiring L7b of the semiconductor switch driving unit 6b to the wiring L7a of the semiconductor switch driving unit 6a.
[0048] The switch element 81b mutually switches between a configuration in which the wiring L7b of the semiconductor switch driving unit 6b is connected to the wiring L7a of the semiconductor switch driving unit 6a and a configuration in which the wiring L7b of the semiconductor switch driving unit 6b is disconnected from the wiring L7a of the semiconductor switch driving unit 6a. The switch element 81b receives a control signal D1b and switches between an on state and an off state. This control signal D1b is common with the control signal D1b given to the connection switching unit 13b. The drain 81b1 of the switch element 81b is connected to the cathode of the diode 83b. The source 81b2 of the switch element 81b is connected to the wiring L7b. The gate 81b3 of the switch element 81b is connected to the controller 7 and receives the control signal D1b. In the present embodiment, it will be described that the control signal D1b output from the controller 7 is given to each of the connection switching unit 13b and the negative voltage charging circuit unit 80b. For example, the control signal given to the negative voltage charging circuit unit 80b may be a signal generated separately from the control signal D1b and may be another control signal adjusted so that the on / off timing is the same as that of the control signal D1b.
[0049] As previously mentioned, the semiconductor switch drive unit 6b has a drive power supply unit 5, which charges the capacitors 11b and 16b. This drive power supply unit 5 is also used to charge the capacitors 11a and 16a of the semiconductor switch drive unit 6a. Below, the circuit configuration for charging the capacitors 11a and 16a of the semiconductor switch drive unit 6a using the drive power supply unit 5 of the semiconductor switch drive unit 6b will be explained with reference to Figure 2. In Figure 2, circuit elements such as capacitors are simplified in order to clearly show the closed circuits for charging the capacitors 11a and 16a. Circuit elements that can take on or off states are shown with solid lines to indicate the on state and with dashed lines to indicate the off state. Furthermore, closed circuits for positive voltage (+20V) are shown with thick solid lines. Closed circuits for negative voltage (-5V) are shown with thick dashed lines.
[0050] As shown in Figure 2, the positive voltage charging closed circuit W11a charges the capacitor 11a that supplies a positive voltage to the semiconductor switch 2. The positive voltage charging closed circuit W11a passes through the positive voltage power supply 51, the capacitor 11a, and the semiconductor switch 3. More specifically, the positive voltage charging closed circuit W11a passes through wiring L2a, wiring L4a, and wiring L4b. In other words, when forming the positive voltage charging closed circuit W11a, the semiconductor switch 3 must be in the ON state. Therefore, when forming the positive voltage charging closed circuit W11a, the semiconductor switch drive unit 6b connects the capacitor 11b to the gate 3c of the semiconductor switch 3 in order to turn on the semiconductor switch 3. Specifically, by turning on the bipolar transistor 131b of the connection switching unit 13b and turning off the bipolar transistor 132b, the closed circuit W11b is formed which connects the capacitor 11b to the gate 3c of the semiconductor switch 3. Since the bipolar transistor 132b is in the off state, the capacitor 16b for the negative voltage of the semiconductor switch drive unit 6b is not connected to the semiconductor switch 3. At this time, the capacitor 16b, together with the negative voltage power supply 52, forms a closed circuit W16b. In addition, in the connection switching unit 13a of the semiconductor switch drive unit 6a, the bipolar transistor 131a is in the off state and the bipolar transistor 132a is in the on state.
[0051] The negative voltage charging closed circuit W16a charges the capacitor 16a that supplies a negative voltage to the semiconductor switch 2. The negative voltage charging closed circuit W16a passes through the negative voltage power supply 52, the capacitor 16b, and the switch element 81b. More specifically, the negative voltage charging closed circuit W16a passes through wiring L4b, wiring L4a, wiring L7a, wiring L8, and wiring L7b. The aforementioned negative voltage charging circuit section 80b can also be described as connecting the negative terminal 52n of the negative voltage power supply 52 to the negative terminal 216a of the capacitor 16a. Similar to when forming the positive voltage charging closed circuit W11a, when forming the negative voltage charging closed circuit W16a, the semiconductor switch 3 must be in the ON state. In other words, the periods during which the positive voltage charging closed circuit W11a and the negative voltage charging closed circuit W16a are formed overlap with the period during which the semiconductor switch 3 is in the ON state.
[0052] Next, the relationship between the operation of the semiconductor switch 3 and the operation of the switch element 81b will be further explained with reference to several timing charts shown in Figure 3. In Figure 3, Figure 3(a) shows the control signal D1b applied to the connection switching unit 13b of the semiconductor switch drive unit 6b. Figure 3(b) shows the control signal D1b applied to the switch element 81b of the semiconductor switch drive unit 6b. As is clear from Figures 3(a) and 3(b), the period during which the control signal D1b applied to the connection switching unit 13b is high coincides with the period during which the control signal D1b applied to the switch element 81b is high. Figure 3(c) shows the negative voltage in the semiconductor switch drive unit 6a.
[0053] Figures 3(d), (e), and (f) are magnified views of part E3 of Figures 3(a) to (c) in the time axis. Figure 3(d) shows the gate voltage of semiconductor switch 3. Figure 3(e) shows the drain voltage of semiconductor switch 3. Figure 3(f) shows the drain voltage of the added switch element 81b. The period when the drain voltage is at a predetermined value (Vin) indicates that the drain and source are isolated, that is, each element is in the off state. The period when the drain voltage is 0V indicates that the drain and source are conducting, that is, each element is in the on state.
[0054] In an ideal state where the delay of the switching element is not considered, the semiconductor switch 3 switches from the off state to the on state at the same time that the control signal D1b switches to high (HI). Since the same control signal D1b is also applied to the switching element 81b, the switching element 81b also switches from the off state to the on state at the same time that the control signal D1b switches to high (HI). In other words, ideally, the timing of the semiconductor switch 3 switching from the off state to the on state coincides with the timing of the switching element 81b switching from the off state to the on state.
[0055] However, when forming a negative voltage charging closed circuit W16a, the timing at which the semiconductor switch 3 switches from the off state to the on state is earlier than the timing at which the switch element 81b switches from the off state to the on state. Also, when disconnecting the negative voltage charging closed circuit W16a, the timing at which the semiconductor switch 3 switches from the on state to the off state is later than the timing at which the switch element 81b switches from the on state to the off state.
[0056] We focus on the period P31 during which the semiconductor switch 3 and switch element 81b switch from the off state to the on state. Period P31 includes times t1, t2, t3, and t4. First, at time t1, the gate signal G3d switches from low (LO) to high (HI). Next, at time t2, the semiconductor switch 3 begins to switch from the off state (Vin) to the on state (0V). Then, at time t3, the drain voltage of the semiconductor switch 3 converges to 0V, and the switch to the on state is completed. At this time t3, the switch element 81b begins to switch from the off state (Vin) to the on state (0V). During the period when the drain voltage of the switch element 81b is transitioning from Vin to 0V, the drain voltage of the semiconductor switch 3 is 0V. Then, at time t4, the drain voltage of the switch element 81b converges to 0V, and the switch to the on state is completed.
[0057] Next, we focus on the period P32 during which the semiconductor switch 3 and the switch element 81b switch from the ON state to the OFF state. Period P32 includes times t5, t6, t7, and t8. First, at time t5, the gate signal G3d switches from high (HI) to low (LO). Next, at time t6, the switch element 81b begins to switch from the ON state (0V) to the OFF state (Vin). Then, at time t7, the drain voltage of the switch element 81b converges to Vin, and the switch to the OFF state is completed. At this time t7, the semiconductor switch 3 begins to switch from the ON state (0V) to the OFF state (Vin). During the period when the drain voltage of the semiconductor switch 3 is transitioning from 0V to Vin, the drain voltage of the switch element 81b is Vin. Then, at time t8, the drain voltage of the semiconductor switch 3 converges to Vin, and the switch to the OFF state is completed.
[0058] In other words, when the switch element 81b is in the ON state, the semiconductor switch 3 is always in the ON state.
[0059] <Effects of the First Embodiment>
[0060] The power converter 1 includes a semiconductor switch 2 electrically connected between the power supply and the load device M, a semiconductor switch 3 electrically connected between ground (GND) and the load device M, a drive power supply unit 5 including a positive voltage power supply 51 for positive voltage and a negative voltage power supply 52 for negative voltage, a capacitor 11a that generates a positive voltage to turn on the semiconductor switch 2 by charging power from the positive voltage power supply 51, and a capacitor 16a that generates a negative voltage to turn off the semiconductor switch 2 by charging power from the negative voltage power supply 52, which are selected for the semiconductor switch 2. The semiconductor switch drive unit 6b selectively connects to the semiconductor switch 3 a semiconductor switch drive unit 6a, a capacitor 11b that generates a positive voltage to turn on the semiconductor switch 3 by charging power from a positive voltage power supply 51, and a capacitor 16b that generates a negative voltage to turn off the semiconductor switch 3 by charging power from a negative voltage power supply 52, and a negative voltage charging circuit unit 80b that selectively executes a configuration in which capacitor 16a is connected to the negative voltage power supply 52 and a configuration in which capacitor 16a is disconnected from the negative voltage power supply 52.
[0061] The semiconductor switch drive circuit includes a drive power supply unit 5 including a positive voltage power supply 51 for a positive voltage and a negative voltage power supply 52 for a negative voltage; a semiconductor switch drive unit 6a that selectively connects a capacitor 11a, which generates a positive voltage to turn on the semiconductor switch 2 by charging power from the positive voltage power supply 51, and a capacitor 16a, which generates a negative voltage to turn off the semiconductor switch 2 by charging power from the negative voltage power supply 52, to the semiconductor switch 2; a semiconductor switch drive unit 6b that selectively connects a capacitor 11b, which generates a positive voltage to turn on the semiconductor switch 3 by charging power from the positive voltage power supply 51, and a capacitor 16b, which generates a negative voltage to turn off the semiconductor switch 3 by charging power from the negative voltage power supply 52, to the semiconductor switch 3; and a negative voltage charging circuit unit 80b that selectively performs a configuration of connecting capacitor 16a to the negative voltage power supply 52 and a configuration of disconnecting capacitor 16a from the negative voltage power supply 52.
[0062] The power converter 1 includes a negative voltage charging circuit section 80b. The negative voltage charging circuit section 80b selectively performs a configuration in which the capacitor 16a is connected to the negative voltage power supply 52 and a configuration in which the capacitor 16a is disconnected from the negative voltage power supply 52. With this negative voltage charging circuit section 80b, the capacitor 16a can be charged using the drive power supply section 5. Therefore, since it is not necessary to provide a power supply for negative voltage in each of the semiconductor switch drive units 6a and 6b, the circuit configuration can be simplified.
[0063] The semiconductor switch drive unit 6a further includes a connection switching unit 13a that selectively connects capacitors 11a and 16a to the semiconductor switch 2. The semiconductor switch drive unit 6b further includes a connection switching unit 13b that selectively connects capacitors 11b and 16b to the semiconductor switch 3. The negative voltage charging circuit unit 80b includes wiring L8 that connects the wiring that connects capacitor 16a to the connection switching unit 13a to the wiring that connects capacitor 16b to the connection switching unit 13b.
[0064] The negative voltage charging circuit section 80b includes a switch element 81b provided on the wiring that includes the wiring L8 connecting capacitor 16a to capacitor 16b. With this configuration, a configuration in which capacitor 16a is connected to the negative voltage power supply 52 and a configuration in which capacitor 16a is disconnected from the negative voltage power supply 52 can be realized in a simple configuration.
[0065] When the capacitor 16a is charged by the negative voltage power supply 52, the power converter 1 forms a negative voltage charging closed circuit W16a including a switching element 81b and a semiconductor switch 3. With this configuration, a negative voltage charging closed circuit W16a for charging the capacitor 16a can be formed.
[0066] The negative voltage charging circuit section 80b is provided on the wiring including the charging wiring connecting capacitor 16a to capacitor 16b, and further includes a diode 83b to prevent current from flowing from capacitor 16b to capacitor 16a. This configuration prevents malfunctions caused by reverse current flow.
[0067] The power converter 1 further includes a controller 7 that controls the connection switching unit 13b and the switch element 81b. The controller 7 controls the connection switching unit 13b and the switch element 81b so that the switch element 81b is in the ON state when the semiconductor switch 3 is in the ON state. With this configuration, it is possible to easily realize a configuration in which the capacitor 16a is connected to the negative voltage power supply 52 and a configuration in which the capacitor 16a is disconnected from the negative voltage power supply 52.
[0068] The controller 7 of the power converter 1 switches the semiconductor switch 3 from the off state to the on state, and then switches the switch element 81b from the off state to the on state. This operation suppresses the occurrence of circuit malfunctions.
[0069] The controller 7 of the power converter 1 switches the switch element 81b from the on state to the off state before switching the semiconductor switch 3 from the on state to the off state. This operation also helps to suppress the occurrence of circuit malfunctions.
[0070] <Second Embodiment> Referring to Figure 4, the semiconductor switch drive circuit 6S provided in the power converter 1S of the second embodiment will be described. The semiconductor switch drive circuit 6S of the second embodiment has additional circuit elements compared to the semiconductor switch drive circuit 6 of the first embodiment. Therefore, in Figure 4, the same reference numerals are used for circuit elements common to the semiconductor switch drive circuit 6 of the first embodiment, and detailed explanations are omitted. Also, the positive voltage charging closed circuit W11a that charges the capacitor 11a is the same as in the first embodiment. The negative voltage charging closed circuit W16a that charges the capacitor 16a is also the same as in the first embodiment. Therefore, detailed explanations of these positive voltage charging closed circuits W11a and negative voltage charging closed circuits W16a are also omitted.
[0071] The semiconductor switch driving circuit 6S of the second embodiment further includes a comparator 86b, an arithmetic unit 85b, a Zener diode 84b, resistors 87b, 881b, and 882b, and wiring L9. These circuit elements detect when the semiconductor switch 3 is in the ON state. In the second embodiment, when both the condition that the control signal D1b is high (HI) and the condition that the semiconductor switch 3 is in the ON state are met, the switch element 81b is switched from the OFF state to the ON state.
[0072] The ON state of the semiconductor switch 3 is detected by a detection circuit 89b consisting of a comparator 86b, a Zener diode 84b, and a resistor 87b. The comparator 86b has a non-inverting input 86b2, an inverting input 86b1, and a comparator output 86b3. The non-inverting input 86b2 is connected to a circuit formed by resistors 881b and 882b. Resistor 881b is connected to the drive power supply unit 5 via connection point P9b and wiring L3b and receives a positive voltage. Resistor 882b is connected to the reference potential GND via connection point P10b. With this configuration, a voltage of about 2V is generated at the connection point P8c of resistors 881b and 882b, which is a voltage division between the positive voltage and the reference potential GND. Therefore, the non-inverting input 86b2 receives a voltage of about 2V. The inverting input 86b1 is connected to the Zener diode 84b and the resistor 87b via connection point P8b. The Zener diode 84b and the resistor 87b constitute a so-called constant voltage circuit. The anode of the Zener diode 84b is connected to wiring L7b. The cathode of the Zener diode 84b is connected to connection point P8b. The resistor 87b is connected to wiring L4a and connection point P8b. The constant voltage circuit generates a voltage at connection point P8b corresponding to the potential difference between wiring L4a and wiring L7b. In other words, the inverting input 86b1 receives a voltage corresponding to the potential difference between wiring L4a and wiring L7b.
[0073] The detection circuit 89b outputs a signal high (HI) when the value obtained by subtracting the voltage applied to the inverting input 86b1 from the voltage applied to the non-inverting input 86b2 of the comparator 86b is positive. Conversely, the detection circuit 89b outputs a signal low (LO) when the value obtained by subtracting the voltage applied to the inverting input 86b1 from the voltage applied to the non-inverting input 86b2 of the comparator 86b is negative.
[0074] The arithmetic unit 85b has a first input 85b2, a second input 85b1, and an arithmetic unit output 85b3. The first input 85b2 is connected to the comparator output 86b3. The second input 85b1 is connected to the controller 7, which receives the control signal D1b. The arithmetic unit output 85b3 is connected to the gate 81b3 of the switch element 81b. The arithmetic unit 85b outputs a high result when the first input 85b2 is high and the input to the second input 85b1 is also high. In other words, if the control signal D1b is high but the output of the comparator 86b is low, the calculation result is low, and therefore the switch element 81b does not switch to the ON state.
[0075] Next, the relationship between the operation of the semiconductor switch 3 and the operation of the switch element 81b will be further explained with reference to several timing charts shown in Figure 5. Figure 5(a) is the control signal D1b applied to the connection switching unit 13b. Figure 5(b) is the drain voltage of the semiconductor switch 3. Figure 5(c) is the output of the comparator 86b. Figure 5(d) is the gate voltage applied to the switch element 81b. In other words, Figure 5(d) is the output of the arithmetic unit 85b. Figure 5(e) is the drain voltage of the switch element 81b.
[0076] First, at time t1 in period P51, the control signal D1b switches from low (LO) to high (HI). Then, at time t2, the drain voltage of semiconductor switch 3 begins to change from Vin towards 0V, and converges to 0V at time t3. During this period from time t1 to time t3, the output of comparator 86b is low (LO). Therefore, the result of arithmetic unit 85b is also low (LO), and the switch element 81b remains in the off state.
[0077] When the drain voltage of semiconductor switch 3 becomes 0V, the output of comparator 86b switches from low (LO) to high (HI). At this time, the control signal D1b is already high (HI), so the first input 85b2 and the second input 85b1 of arithmetic unit 85b are both supplied with high (HI). As a result, arithmetic unit 85b outputs high (HI). Then, upon receiving the control signal (HI), the switch element 81b begins to change its drain voltage from Vin to 0V at time t4. Then, at time t5, the switch element 81b switches to the ON state.
[0078] Next, at time t6 in period P52, the control signal D1b switches from high (HI) to low (LO). Then, at time t7, the drain voltage of semiconductor switch 3 begins to change from 0V toward Vin, and converges to Vin at time t8. During this period from time t6 to time t7, the output of comparator 86b is high (HI). However, since the control signal D1b switches from high (HI) to low (LO), the result of arithmetic unit 85b is low (LO). As a result, the switch element 81b begins to switch to the off state.
[0079] As described above, the semiconductor switch driving circuit 6S of the second embodiment, which has a detection circuit section 89b, can ensure that the semiconductor switch 3 is always in the ON state when the switch element 81b is in the ON state, regardless of the characteristics of the semiconductor switch 3 and the switch element 81b.
[0080] Furthermore, in the semiconductor switch drive circuit 6S of the second embodiment having a detection circuit section 89b, the switch element 81b will not switch to the ON state even if an unintended noise component N5a is superimposed on the control signal D1b. Similarly, the switch element 81b will not switch to the ON state even if an unintended noise component N5b is superimposed on the output of the comparator 86b. Therefore, malfunctions of the switch element 81b caused by noise components can be prevented.
[0081] <Effects of the Second Embodiment> The negative voltage charging circuit section 80b includes a comparator 86b that generates a connection status signal indicating whether the semiconductor switch 3 is in an ON state or an OFF state, and a calculator 85b that switches the switch element to an ON state when it receives a connection status signal indicating that the semiconductor switch 3 is in an ON state and a control signal D1b for switching the switch element 81b from an OFF state to an ON state. This configuration also suppresses the occurrence of circuit malfunctions.
[0082] <Modifications> The present disclosure is not limited to the embodiments described above, and various modifications are possible without departing from the spirit of the claims.
[0083] <Additional Note> This disclosure includes the following components:
[0084] This disclosure relates to "1" a semiconductor switch drive circuit for a power conversion device that uses a first semiconductor switch and a second semiconductor switch to convert power provided by a power source into a form of power required by a load device, comprising: a drive power supply unit including a positive voltage power supply for a positive voltage and a negative voltage power supply for a negative voltage; a first semiconductor switch drive unit selectively connecting to the first semiconductor switch a first positive voltage capacitor that generates a positive voltage to turn on the first semiconductor switch by charging the power from the positive voltage power supply and a first negative voltage capacitor that generates a negative voltage to turn off the first semiconductor switch by charging the power from the negative voltage power supply; and a second semiconductor switch drive unit selectively connecting to the second semiconductor switch a second positive voltage capacitor that generates a positive voltage to turn on the second semiconductor switch by charging the power from the positive voltage power supply and a second negative voltage capacitor that generates a negative voltage to turn off the second semiconductor switch by charging the power from the negative voltage power supply. A semiconductor switch drive circuit comprising: a negative voltage charging circuit section that selectively performs a configuration in which the first negative voltage capacitor is connected to the negative voltage power supply and a configuration in which the first negative voltage capacitor is disconnected from the negative voltage power supply.
[0085] This disclosure is "2" "the semiconductor switch drive circuit described in [1] above, wherein the first semiconductor switch drive unit further includes a first connection switching unit that selectively connects the first positive voltage capacitor and the first negative voltage capacitor to the first semiconductor switch, the second semiconductor switch drive unit further includes a second connection switching unit that selectively connects the second positive voltage capacitor and the second negative voltage capacitor to the second semiconductor switch, and the negative voltage charging circuit unit includes a charging wiring that connects the wiring that connects the first negative voltage capacitor to the first connection switching unit to the wiring that connects the second negative voltage capacitor to the second connection switching unit."
[0086] This disclosure is "3" "The semiconductor switch drive circuit according to [2] above, wherein the negative voltage charging circuit further includes a charging switch element provided on wiring including the charging wiring that connects the first negative voltage capacitor to the second negative voltage capacitor."
[0087] This disclosure relates to "4" "the semiconductor switch driving circuit according to [3] above, wherein a closed circuit including the charging switch element and the second semiconductor switch is formed when the first negative voltage capacitor is charged by the negative voltage power supply."
[0088] This disclosure is "5" "The semiconductor switch driving circuit according to [3] or [4] above, wherein the negative voltage charging circuit is provided on wiring including the charging wiring that connects the first negative voltage capacitor to the second negative voltage capacitor, and further includes a diode element for preventing current from flowing from the second negative voltage capacitor side to the first negative voltage capacitor side."
[0089] This disclosure is "6" "a semiconductor switch driving circuit according to any one of the above [3] to [5], further comprising a controller for controlling the second connection switching unit and the charging switch element, wherein the controller controls the second connection switching unit and the charging switch element so that the charging switch element is in the ON state when the second semiconductor switch is in the ON state."
[0090] This disclosure includes "7" "the semiconductor switch driving circuit described in [6] above, wherein the controller switches the second semiconductor switch from the off state to the on state, and then switches the charging switch element from the off state to the on state."
[0091] This disclosure includes "8" "the semiconductor switch driving circuit according to [6] or [7] above, wherein the controller switches the charging switch element from the ON state to the OFF state before switching the second semiconductor switch from the ON state to the OFF state."
[0092] This disclosure is "9" "The negative voltage charging circuit further includes a status signal generating unit that generates a connection status signal indicating whether the second semiconductor switch is in an ON state or an OFF state, and a switching signal generating unit that switches the charging switch element to an ON state when it receives the connection status signal indicating that the second semiconductor switch is in an ON state and a control signal for switching the charging switch element from an OFF state to an ON state, the semiconductor switch driving circuit according to any one of the above [6] to [8]."
[0093] This disclosure relates to "10" a power conversion device that converts a power source to a power source required by a load device, comprising: a first semiconductor switch electrically connected between the power source and the load device; a second semiconductor switch electrically connected between the power source and the load device; a drive power supply unit including a positive voltage power supply for a positive voltage and a negative voltage power supply for a negative voltage; a first semiconductor switch drive unit selectively connecting to the first semiconductor switch a first positive voltage capacitor that generates a positive voltage to turn on the first semiconductor switch by charging the power from the positive voltage power supply and a first negative voltage capacitor that generates a negative voltage to turn off the first semiconductor switch by charging the power from the negative voltage power supply; a second semiconductor switch drive unit selectively connecting to the second semiconductor switch a second positive voltage capacitor that generates a positive voltage to turn on the second semiconductor switch by charging the power from the positive voltage power supply and a second negative voltage capacitor that generates a negative voltage to turn off the second semiconductor switch by charging the power from the negative voltage power supply. A power conversion device comprising a negative voltage charging circuit section that selectively performs a configuration in which the first negative voltage capacitor is connected to the negative voltage power supply and a configuration in which the first negative voltage capacitor is disconnected from the negative voltage power supply.
[0094] 1, 1S Power converter 2, 3 Semiconductor switch 4 Power supply 5 Drive power supply unit 6, 6S Semiconductor switch drive circuit 6a Semiconductor switch drive unit (first semiconductor switch drive circuit) 6b Semiconductor switch drive unit (second semiconductor switch drive circuit) 7 Controller 11a Capacitor (first positive voltage capacitor) 11b Capacitor (second positive voltage capacitor) 13a, 13b Connection switching unit 16a Capacitor (first negative voltage capacitor) 16b Capacitor (second negative voltage capacitor) 21a, 21b Diode 51 Power supply for positive voltage 52 Power supply for negative voltage 80b Negative voltage charging circuit unit 81b Switch element 82b, 83b Diode 84b Zener diode 85b Calculator 86b Comparator 87b, 881b, 882b Resistor element 89b Detection circuit unit 131a, 132a, 131b, 132b Bipolar transistor GND Reference potential M Load device W11a Positive voltage charging closed circuit W11b Closed circuit W16a Negative voltage charging closed circuit W16b Closed circuit
Claims
1. A semiconductor switch drive circuit for a power conversion device that uses a first semiconductor switch and a second semiconductor switch to convert power supplied by a power source into a form of power required by a load device, comprising: a drive power supply unit including a positive voltage power supply for a positive voltage and a negative voltage power supply for a negative voltage; a first semiconductor switch drive unit selectively connecting to the first semiconductor switch a first positive voltage capacitor that generates a positive voltage to turn on the first semiconductor switch by charging the power from the positive voltage power supply and a first negative voltage capacitor that generates a negative voltage to turn off the first semiconductor switch by charging the power from the negative voltage power supply; a second semiconductor switch drive unit selectively connecting to the second semiconductor switch a second positive voltage capacitor that generates a positive voltage to turn on the second semiconductor switch by charging the power from the positive voltage power supply and a second negative voltage capacitor that generates a negative voltage to turn off the second semiconductor switch by charging the power from the negative voltage power supply; A semiconductor switch drive circuit comprising: a negative voltage charging circuit section that selectively performs a configuration of connecting the first negative voltage capacitor to the negative voltage power supply and a configuration of disconnecting the first negative voltage capacitor from the negative voltage power supply.
2. The semiconductor switch drive circuit according to claim 1, wherein the first semiconductor switch drive unit further includes a first connection switching unit that selectively connects the first positive voltage capacitor and the first negative voltage capacitor to the first semiconductor switch, the second semiconductor switch drive unit further includes a second connection switching unit that selectively connects the second positive voltage capacitor and the second negative voltage capacitor to the second semiconductor switch, and the negative voltage charging circuit unit includes a charging wiring that connects the wiring that connects the first negative voltage capacitor to the first connection switching unit to the wiring that connects the second negative voltage capacitor to the second connection switching unit.
3. The semiconductor switch drive circuit according to claim 2, wherein the negative voltage charging circuit further includes a charging switch element provided on wiring including the charging wiring that connects the first negative voltage capacitor to the second negative voltage capacitor.
4. The semiconductor switch driving circuit according to claim 3, wherein a closed circuit including the charging switch element and the second semiconductor switch is formed when the first negative voltage capacitor is charged by the negative voltage power supply.
5. The semiconductor switch drive circuit according to claim 3, wherein the negative voltage charging circuit is provided on wiring including the charging wiring that connects the first negative voltage capacitor to the second negative voltage capacitor, and further includes a diode element for preventing current from flowing from the second negative voltage capacitor side to the first negative voltage capacitor side.
6. The semiconductor switch drive circuit according to claim 3, further comprising a controller for controlling the second connection switching unit and the charging switch element, wherein the controller controls the second connection switching unit and the charging switch element so that the charging switch element is in the ON state when the second semiconductor switch is in the ON state.
7. The semiconductor switch driving circuit according to claim 6, wherein the controller switches the second semiconductor switch from the off state to the on state, and then switches the charging switch element from the off state to the on state.
8. The semiconductor switch driving circuit according to claim 6 or 7, wherein the controller switches the charging switch element from the ON state to the OFF state before switching the second semiconductor switch from the ON state to the OFF state.
9. The semiconductor switch drive circuit according to claim 6, further comprising: a status signal generating unit that generates a connection status signal indicating whether the second semiconductor switch is in an ON state or an OFF state; and a switching signal generating unit that, upon receiving the connection status signal indicating that the second semiconductor switch is in an ON state and a control signal for switching the charging switch element from an OFF state to an ON state, switches the charging switch element to an ON state.
10. A power conversion device that converts the power provided by a power source to the power required by a load device, comprising: a first semiconductor switch electrically connected between the power source and the load device; a second semiconductor switch electrically connected between the power source and the load device; a drive power supply unit including a positive voltage power supply for a positive voltage and a negative voltage power supply for a negative voltage; a first semiconductor switch drive unit selectively connecting to the first semiconductor switch a first positive voltage capacitor that generates a positive voltage to turn on the first semiconductor switch by charging the power from the positive voltage power supply and a first negative voltage capacitor that generates a negative voltage to turn off the first semiconductor switch by charging the power from the negative voltage power supply; a second semiconductor switch drive unit selectively connecting to the second semiconductor switch a second positive voltage capacitor that generates a positive voltage to turn on the second semiconductor switch by charging the power from the positive voltage power supply and a second negative voltage capacitor that generates a negative voltage to turn off the second semiconductor switch by charging the power from the negative voltage power supply; A power conversion device comprising a negative voltage charging circuit section that selectively performs a configuration in which the first negative voltage capacitor is connected to the negative voltage power supply and a configuration in which the first negative voltage capacitor is disconnected from the negative voltage power supply.