Semiconductor switch driver circuit and power converter

Abstract

This semiconductor switch drive circuit comprises a drive power source and a semiconductor switch drive unit. The semiconductor switch drive unit comprises: a connection switching unit; a capacitor that generates a positive voltage; a capacitor for power charging; and a capacitor that generates a negative voltage. The connection switching unit alternately switches between: a first connection state, in which a positive voltage application closed circuit is formed to apply a positive voltage to a gate terminal of the semiconductor switch; and a second connection state, in which a negative voltage application closed circuit is formed to apply a negative voltage to the gate terminal of the semiconductor switch. Between the drive power source and the semiconductor switch, a movement restriction unit is provided which restricts movement of an electric charge from a path through the positive voltage application closed circuit to another path that passes through a positive terminal of the capacitor without passing through the gate terminal of the semiconductor switch.

Description

Technical Field

[0001] The present disclosure relates to a semiconductor switch drive circuit and a power converter.

Background Art

[0002] Patent Documents 1 to 3 disclose a semiconductor switch drive circuit for driving a semiconductor switch. Such a semiconductor switch drive circuit is used, for example, in a power converter such as an inverter. As the semiconductor switch, for example, a normally-off type semiconductor switch can be employed. In this case, in order to surely control the semiconductor switch to the off state, it is required to supply a negative voltage to the semiconductor switch. Patent Document 1 discloses a configuration in which, in addition to a drive power source that generates a positive voltage, a drive power source that generates a negative voltage is added. However, among the components constituting the semiconductor switch drive circuit, the size and weight of such a drive power source are relatively large. Therefore, this drive power source can cause an increase in the size and weight of the device.

[0003] Patent Document 2 discloses a circuit configuration capable of generating both a positive voltage and a negative voltage using one drive power source. In this circuit configuration, a positive power supply capacitor that charges power from the drive power source to generate a positive voltage and a negative power supply capacitor that charges power from the positive power supply capacitor to generate a negative voltage are provided. These positive and negative voltages are alternately applied to the semiconductor switch. In this circuit configuration, since a drive power source for generating a negative voltage does not need to be provided separately, an increase in the size and weight of the device is suppressed. Patent Document 3 discloses a circuit configuration in which, in addition to the circuit configuration described in Patent Document 2, a negative power supply buffer capacitor for charging power for negative voltage generation is added. In this circuit configuration, the negative power supply capacitor is not directly charged by the positive power supply capacitor but is charged via the negative power supply buffer capacitor.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

[0005] In the semiconductor switch drive circuit disclosed in Patent Document 3, when a positive voltage is applied to the semiconductor switch, the charge transfer path between the positive power supply capacitor and the semiconductor switch does not pass through the third capacitor. In this case, when a positive voltage is applied to the semiconductor switch, the situation in which the positive voltage of the positive power supply capacitor is divided between the semiconductor switch and the negative power supply capacitor is avoided. This suppresses the decrease in the positive voltage of the positive power supply capacitor. However, in a semiconductor switch drive circuit, there may be factors other than the division of the positive voltage by the negative power supply capacitor that cause the positive voltage of the positive power supply capacitor to decrease. Therefore, there is room for improvement from the viewpoint of suppressing the decrease in the positive voltage to the semiconductor switch.

[0006] This disclosure describes a semiconductor switch driving circuit and a power converter that can effectively suppress a situation in which the positive voltage to the semiconductor switch decreases. [Means for solving the problem]

[0007] A semiconductor switch drive circuit according to one embodiment of the present disclosure comprises a drive power supply and a semiconductor switch drive unit electrically connected to the drive power supply and driving a semiconductor switch using power from the drive power supply. The semiconductor switch drive unit comprises a connection switching unit electrically connected between the drive power supply and the semiconductor switch and switching the connection state of the semiconductor switch, a first capacitor electrically connected between the drive power supply and the connection switching unit and generating a positive voltage to turn on the semiconductor switch by charging power from the drive power supply, a second capacitor electrically connected in parallel with the first capacitor to the drive power supply and charging power from the drive power supply, and a third capacitor electrically connected between the second capacitor and the connection switching unit and generating a negative voltage to turn off the semiconductor switch by charging power discharged from the second capacitor in a charged state. The connection switching unit alternately switches between a first connection state in which a positive voltage application closed circuit is formed by electrically connecting the positive terminal of the first capacitor with the control terminal of the semiconductor switch to apply a positive voltage to the control terminal of the semiconductor switch, and a second connection state in which a negative voltage application closed circuit is formed by electrically connecting the negative terminal of the third capacitor with the control terminal of the semiconductor switch to apply a negative voltage to the control terminal of the semiconductor switch. Between the first capacitor and the semiconductor switch, a movement restricting unit is provided to restrict the movement of charge from the path through the positive voltage application closed circuit to another path that passes through the positive terminal of the first capacitor but does not pass through the control terminal of the semiconductor switch. [Effects of the Invention]

[0008] According to this disclosure, a semiconductor switch driving circuit and a power converter are provided that can effectively suppress the situation in which the positive voltage to the semiconductor switch decreases. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a circuit diagram showing a power converter according to the first embodiment. [Figure 2] Figure 2 illustrates the operation of the semiconductor switch drive circuit included in the power converter shown in Figure 1. [Figure 3]Figure 3 is a diagram illustrating the operation of the semiconductor switch drive circuit included in the power converter shown in Figure 1. [Figure 4] Figure 4 is a diagram illustrating the operation of the semiconductor switch drive circuit included in the power converter shown in Figure 1. [Figure 5] Figure 5 is a diagram illustrating the operation of the semiconductor switch drive circuit included in the power converter shown in Figure 1. [Figure 6] Figure 6 is a circuit diagram showing a modified version of the power converter in Figure 1. [Figure 7] Figure 7 is a circuit diagram showing a power converter according to the second embodiment. [Figure 8] Figure 8 is a diagram illustrating the operation of the semiconductor switch drive circuit included in the power converter shown in Figure 7. [Figure 9] Figure 9 is a diagram illustrating the operation of the semiconductor switch drive circuit included in the power converter shown in Figure 7. [Figure 10] Figure 10 is a diagram illustrating the operation of the semiconductor switch drive circuit included in the power converter shown in Figure 7. [Figure 11] Figure 11 is a diagram illustrating the operation of the semiconductor switch drive circuit included in the power converter shown in Figure 7. [Figure 12] Figure 12 illustrates the problems of the power converter in the comparative example. [Modes for carrying out the invention]

[0010] Embodiments of this disclosure will be described below with reference to the drawings. In the description of the drawings, the same elements will be denoted by the same reference numerals, and redundant descriptions will be omitted.

[0011] A semiconductor switch drive circuit according to one embodiment of the present disclosure comprises a drive power supply and a semiconductor switch drive unit electrically connected to the drive power supply and driving a semiconductor switch using power from the drive power supply. The semiconductor switch drive unit comprises a connection switching unit electrically connected between the drive power supply and the semiconductor switch and switching the connection state of the semiconductor switch, a first capacitor electrically connected between the drive power supply and the connection switching unit and generating a positive voltage to turn on the semiconductor switch by charging power from the drive power supply, a second capacitor electrically connected in parallel with the first capacitor to the drive power supply and charging power from the drive power supply, and a third capacitor electrically connected between the second capacitor and the connection switching unit and generating a negative voltage to turn off the semiconductor switch by charging power discharged from the second capacitor in a charged state. The connection switching unit alternately switches between a first connection state in which a positive voltage application closed circuit is formed by electrically connecting the positive terminal of the first capacitor with the control terminal of the semiconductor switch to apply a positive voltage to the control terminal of the semiconductor switch, and a second connection state in which a negative voltage application closed circuit is formed by electrically connecting the negative terminal of the third capacitor with the control terminal of the semiconductor switch to apply a negative voltage to the control terminal of the semiconductor switch. Between the first capacitor and the semiconductor switch, a movement restricting unit is provided to restrict the movement of charge from the path through the positive voltage application closed circuit to another path that passes through the positive terminal of the first capacitor but does not pass through the control terminal of the semiconductor switch.

[0012] In the semiconductor switch drive circuit described above, a positive voltage is generated in the first capacitor by power from the drive power supply, and a negative voltage is generated in the third capacitor by power discharged from the second capacitor, which is in a charged state. In other words, both a positive and negative voltage are generated using a single drive power supply. The connection switching unit alternately switches between a first connection state in which a positive voltage application closed circuit is formed by applying the positive voltage of the first capacitor to the control terminal of the semiconductor switch, and a second connection state in which a negative voltage application closed circuit is formed by applying the negative voltage of the third capacitor to the control terminal of the semiconductor switch, thereby alternately switching the semiconductor switch on or off. In the semiconductor switch drive circuit described above, a second capacitor is provided for charging the third capacitor. This eliminates the need to place the third capacitor on a positive voltage application closed circuit in which the positive voltage of the first capacitor is applied to the control terminal of the semiconductor switch for charging the third capacitor. This avoids the situation in which the positive voltage of the first capacitor is divided between the semiconductor switch and the third capacitor. Furthermore, the semiconductor switch drive circuit described above is provided with a movement restriction unit that restricts the movement of charge from the path flowing through the positive voltage application closed circuit to other paths that pass through the positive terminal of the first capacitor but do not pass through the control terminal of the semiconductor switch. This makes it possible to avoid a situation in which the positive voltage of the first capacitor is divided by circuit elements on other paths. Therefore, the semiconductor switch drive circuit described above can effectively suppress a situation in which the positive voltage from the first capacitor to the semiconductor switch decreases.

[0013] In some embodiments, the movement restriction unit may include a first connection point between the positive terminal of the first capacitor and the control terminal of the semiconductor switch, a second connection point between the positive terminal of the second capacitor and the input terminal of the semiconductor switch, a third connection point disposed between the first connection point and the positive terminal of the drive power source and electrically connected to the positive terminal of the drive power source, a first wiring connecting the first connection point and the third connection point, and a second wiring connecting the second connection point and the third connection point. Thus, when the third connection point is provided between the first connection point and the drive power source, while allowing charge to move from the drive power source to the first capacitor via the third connection point and the first connection point, it is possible to avoid the charge released from the first capacitor from moving to the second connection point via the first connection point and the third connection point. Thereby, it is possible to avoid the charge of the first capacitor moving in the positive voltage application closed circuit from moving from the first connection point to other paths via the second connection point. As a result, it is possible to more effectively suppress the situation where the positive voltage from the first capacitor to the semiconductor switch decreases.

[0014] In some embodiments, the movement restriction unit may further include a first diode connected in the forward direction with the direction from the third connection point to the first connection point in the first wiring, and a second diode connected in the forward direction with the direction from the third connection point to the second connection point in the second wiring. By providing the first diode and the second diode in this way, it is possible to avoid the situation where the charge flows back from the first capacitor and the second capacitor to the drive power source. Furthermore, by providing the first diode between the third connection point and the first connection point, it is possible to avoid the situation where the charge of the first capacitor moves from the first connection point to the second connection point via the third connection point. Thereby, since it is possible to avoid the charge of the first capacitor from moving to other paths via the second connection point, it is possible to more effectively suppress the situation where the positive voltage from the first capacitor to the semiconductor switch decreases.

[0015] In some embodiments, the movement control unit may further include a first resistor element connected in series with the first diode in the first wiring, and a second resistor element connected in series with the second diode in the second wiring and having a higher resistance value than the first resistor element. The negative voltage for turning off the semiconductor switch tends to be smaller than the positive voltage for turning on the semiconductor switch. When the negative voltage is small in this way, the charge amount of the second capacitor that charges the power for generating the negative voltage may be made smaller than the charge amount of the first capacitor that charges the power for generating the positive voltage. Therefore, in the above-described configuration, the second resistor element provided on the movement path of the charge flowing from the drive power source to the second capacitor has a higher resistance value than the resistance value of the first resistor element provided on the movement path of the charge flowing from the drive power source to the first capacitor. Thereby, the charging current supplied from the drive power source to the second capacitor can be suppressed to be small. As a result, it is possible to suppress an increase in the capacity of the drive power source that provides power to the second capacitor.

[0016] In some embodiments, the positive electrode terminal of the first capacitor may be electrically connected to the positive electrode terminal of the drive power source and the control terminal of the semiconductor switch. The positive electrode terminal of the second capacitor may be electrically connected to the positive electrode terminal of the drive power source. The negative electrode terminal of the third capacitor may be electrically connected to the negative electrode terminal of the second capacitor. The positive electrode terminal of the third capacitor may be electrically connected to the control terminal of the semiconductor switch. In this case, a configuration for generating a positive voltage and a negative voltage using one drive power source can be easily realized.

[0017] In some embodiments, the semiconductor switch drive circuit may include a first semiconductor switch drive unit and a second semiconductor switch drive unit, which are semiconductor switch drive units. The first semiconductor switch drive unit and the second semiconductor switch drive unit may drive a first semiconductor switch and a second semiconductor switch, respectively. The first semiconductor switch may constitute the upper arm in the semiconductor switch drive circuit. The second semiconductor switch may constitute the lower arm in the semiconductor switch drive circuit and may be electrically connected in series with the first semiconductor switch. In this case, a decrease in the positive voltage from the first capacitor to the semiconductor switch can be effectively suppressed in both the upper and lower arms.

[0018] In some embodiments, the movement restricting section of the first semiconductor switch drive unit and the second semiconductor switch drive unit may have a first connection point between the positive terminal of the first capacitor and the control terminal of the semiconductor switch, a second connection point between the positive terminal of the second capacitor and the input terminal of the semiconductor switch, a third connection point positioned between the first connection point and the positive terminal of the drive power supply and electrically connected to the positive terminal of the drive power supply, a first wiring connecting the first connection point and the third connection point, and a second wiring connecting the second connection point and the third connection point. Of the first and second semiconductor switch drive units, only the movement restricting section of the second semiconductor switch drive unit may further have a first diode connected in the first wiring with the forward direction from the third connection point toward the first connection point, and a second diode connected in the second wiring with the forward direction from the third connection point toward the second connection point. In the upper arm, due to the circuit configuration, reverse charge flow to the drive power supply is likely to occur depending on whether the semiconductor switch is turned on or off. On the other hand, in the lower arm, it is unlikely that charge will flow back into the drive power supply regardless of whether the semiconductor switch is on or off. Therefore, in the above configuration, the first and second diodes for preventing reverse current are provided only in the first semiconductor switch drive unit that constitutes the upper arm. This simplifies the circuit configuration of the second semiconductor switch drive unit and reduces the number of components that make up the second semiconductor switch drive unit.

[0019] In some embodiments, the semiconductor switch drive unit may include a first semiconductor switch drive unit that drives a first semiconductor switch, which is a semiconductor switch, and a second semiconductor switch drive unit that is electrically connected to a drive power supply and drives a second semiconductor switch electrically connected in series with the first semiconductor switch using power from the drive power supply. The first semiconductor switch may constitute the upper arm in the semiconductor switch drive circuit. The second semiconductor switch may constitute the lower arm in the semiconductor switch drive circuit. The second semiconductor switch drive unit may include another connection switching unit electrically connected between the drive power supply and the second semiconductor switch and switching the connection state of the second semiconductor switch, a fourth capacitor electrically connected between the drive power supply and the other connection switching unit and generating a positive voltage to turn on the second semiconductor switch by charging power from the drive power supply, and a fifth capacitor electrically connected in series between the fourth capacitor and the other connection switching unit and generating a negative voltage to turn off the second semiconductor switch by charging power discharged from the fourth capacitor in a charged state. Another connection switching unit may alternately switch between a third connection state, which forms another positive voltage application closed circuit by electrically connecting the positive terminal of the fourth capacitor with the control terminal of the second semiconductor switch to apply a positive voltage to the control terminal of the second semiconductor switch, and a fourth connection state, which forms another negative voltage application closed circuit by electrically connecting the negative terminal of the fifth capacitor with the control terminal of the second semiconductor switch to apply a negative voltage to the control terminal of the second semiconductor switch. In the upper arm, the charge state of the first capacitor switches according to whether the semiconductor switch is on or off, so the voltage of the first capacitor is prone to fluctuations. On the other hand, in the lower arm, the fourth capacitor can be kept in a constantly charged state, making it easier to maintain a constant voltage of the fourth capacitor. Therefore, in the lower arm, by adopting a simplified circuit configuration without providing a configuration equivalent to the second capacitor in the upper arm, the number of components constituting the second semiconductor switch drive unit can be reduced.

[0020] A power converter according to one embodiment of the present disclosure is a power converter that converts the form of power provided by a power source to the form of power required by a load device. This power converter comprises a semiconductor switch electrically connected between the power source and the load device, and one of the above-described semiconductor switch driving circuits electrically connected to the semiconductor switch and driving the semiconductor switch. Because this power converter includes one of the above-described semiconductor switch driving circuits, it is possible to more effectively suppress the situation in which the positive voltage from the first capacitor to the semiconductor switch decreases.

[0021] [First Embodiment] 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 this 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 converter 1 includes, for example, a semiconductor switch 2 (an example of a "first semiconductor switch"), a semiconductor switch 3 (an example of a "second semiconductor switch"), a semiconductor switch drive circuit 6, a power supply 4, and a control device 7.

[0023] Semiconductor switches 2 and 3 are connected in series with respect to each other between the power supply 4 and GND (ground), forming a switching 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 also be IGBTs (Insulated Gate Bipolar Transistors), or wide-bandgap semiconductor switches such as SiC (silicon carbide) or GaN (gallium nitride).

[0024] The drain terminal 2a of semiconductor switch 2 (an example of an "input terminal") is connected to power supply 4. The source terminal 2b of semiconductor switch 2 (an example of an "output terminal") is connected to the drain terminal 3a of semiconductor switch 3 (an example of an "input terminal"). The source terminal 3b of semiconductor switch 3 (an example of an "output terminal") is connected to GND. The gate terminal 2c of semiconductor switch 2 (an example of a "control terminal") and the gate terminal 3c of semiconductor switch 3 (an example of a "control terminal") are connected to semiconductor switch drive circuit 6.

[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 a manner that allows for the transmission of signals and the supply of power 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 control device 7 is electrically connected to the semiconductor switch drive circuit 6 and controls it. The control device 7 is composed of a computer, for example, a CPU, ROM, and RAM. The control device 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 driving circuit 6 includes, for example, a semiconductor switch driving unit 6a (an example of the "first semiconductor switch driving circuit"), a semiconductor switch driving unit 6b (an example of the "second semiconductor switch driving circuit"), and a driving power supply 5.

[0028] The semiconductor switch drive unit 6a is a drive circuit for the upper arm that drives the semiconductor switch 2. The semiconductor switch drive unit 6b is a drive circuit for the lower arm that drives the semiconductor switch 3. The drive power supply 5 is, for example, a DC power supply that outputs a DC voltage VDD having positive polarity. The drive power supply 5 is electrically connected to the semiconductor switch drive units 6a and 6b and provides the voltage VDD to the semiconductor switch drive units 6a and 6b. The semiconductor switch drive unit 6a switches the semiconductor switch 2 on or off using the voltage VDD. The semiconductor switch drive unit 6b switches the semiconductor switch 3 on or off using the voltage VDD.

[0029] The control device 7 is electrically connected to the semiconductor switch drive unit 6a and the semiconductor switch drive unit 6b. The control device 7 outputs control signals to the semiconductor switch drive unit 6a and the semiconductor switch drive unit 6b, respectively, to control the driving of the semiconductor switch drive unit 6a and the semiconductor switch drive unit 6b. The control signals are, for example, PWM (Pulse Width Modulation) signals. The control device 7 controls the switching of the semiconductor switch 2 on or off by outputting a control signal 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 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 terminal 2c of the semiconductor switch 2. This turns on the semiconductor switch 2. When the semiconductor switch drive unit 6a receives a control signal 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 terminal 2c of the semiconductor switch 2. This causes semiconductor switch 2 to turn off.

[0030] The control device 7 controls the switching of the semiconductor switch 3 to the on or off state by outputting a control signal to the semiconductor switch drive unit 6b that instructs the semiconductor switch 3 to be turned on or off. When the semiconductor switch drive unit 6b receives a control signal that instructs the semiconductor switch 3 to be turned on, it generates a positive voltage using the voltage VDD to sufficiently turn on the semiconductor switch 3 and applies the generated positive voltage to the gate terminal 3c of the semiconductor switch 3. As a result, the semiconductor switch 3 is turned on. When the semiconductor switch drive unit 6b receives a control signal that instructs the semiconductor switch 3 to be turned off, it generates a negative voltage using the voltage VDD to sufficiently turn off the semiconductor switch 3 and applies the generated negative voltage to the gate terminal 3c of the semiconductor switch 3. As a result, the semiconductor switch 3 is turned off.

[0031] The configurations of the semiconductor switch drive unit 6a and the semiconductor switch drive unit 6b will be described in more detail below.

[0032] The semiconductor switch drive unit 6a includes, for example, a connection switching unit 13a, a capacitor 11a (an example of a "first capacitor"), a capacitor 12a (an example of a "second capacitor"), a capacitor 16a (an example of a "third capacitor"), a diode 21a, a diode 22a, a diode 10a, a diode 14a, a diode 15a, a resistive element 31a, a resistive element 32a, a resistive element 33a, a resistive element 34a, a resistive element 35a, and a resistive element 36a.

[0033] The connection switching unit 13a is connected between the drive power supply 5 and the semiconductor switch 2. The capacitor 11a is connected between the drive power supply 5 and the connection switching unit 13a. The capacitor 11a is, for example, a positive power supply capacitor that generates a positive voltage. The positive terminal 111a (one end) of the capacitor 11a is connected to the positive terminal 5a of the drive power supply 5 and the connection switching unit 13a. More specifically, the positive terminal 5a of the drive power supply 5 is connected to wiring L2a at connection point P1a, and wiring L2a is connected to the positive terminal 111a of the capacitor 11a at connection point P2a. Wiring L2a is connected to wiring L3a at connection point P2a, and wiring L3a is connected to the gate terminal 2c of the semiconductor switch 2 via the connection switching unit 13a. The negative terminal 211a (the other end) of the capacitor 11a is connected to the source terminal 2b of the semiconductor switch 2 via wiring L4a.

[0034] Capacitor 12a is a negative power buffer capacitor that temporarily charges power to generate a negative voltage, for example. Capacitor 12a is connected between the drive power supply 5 and the semiconductor switch 2. Capacitor 12a is connected in parallel with capacitor 11a to the drive power supply 5. One positive terminal 112a of capacitor 12a is connected to the positive terminal 5a of the drive power supply 5 and the drain terminal 2a of the semiconductor switch 2. More specifically, the positive terminal 5a of the drive power supply 5 is connected to wiring L5a, which extends in parallel with wiring L2a at connection point P1a. Wiring L5a is connected to the positive terminal 112a of capacitor 12a at connection point P3a. Wiring L5a is connected to wiring L6a at connection point P3a, and wiring L6a is connected to the drain terminal 2a of the semiconductor switch 2. The other negative terminal 212a of capacitor 12a is connected to the drain terminal 2a of the semiconductor switch 2 via wiring L4a.

[0035] Capacitor 16a is, for example, a negative power supply capacitor that receives power from the charged capacitor 12a to generate a negative voltage. Capacitor 16a is connected between capacitor 12a and connection switching unit 13a. The negative terminal 216a (other end) of capacitor 16a is connected to wiring L7a at connection point P5a, and wiring L7a is connected to the negative terminal 212a of capacitor 12a via connection point P6a. The positive terminal 116a (one end) of capacitor 16a is connected to wiring L4a at connection point P4a, and is connected to the source terminal 2b of semiconductor switch 2 via wiring L4a.

[0036] Diode 21a is connected in series between the drive power supply 5 and the capacitor 11a. Diode 21a is, for example, a reverse current prevention diode. Diode 21a is connected in the wiring L2a that connects connection point P1a, which is connected to the positive terminal 5a of the drive power supply 5, and connection point P2a, which is connected to the positive terminal 111a of the capacitor 11a, with the direction from connection point P1a to connection point P2a being forward. Therefore, the anode of diode 21a is connected to the positive terminal 5a of the drive power supply 5, and the cathode of diode 21a is connected to the positive terminal 111a of the capacitor 11a.

[0037] The resistive element 31a is, for example, a limiting resistor that restricts the current from the drive power supply 5 to the capacitor 11a. The resistive element 31a is connected in series between the diode 21a and the capacitor 11a. More specifically, the resistive element 31a is connected in series between the diode 21a and the connection point P2a in the wiring L2a. One end of the resistive element 31a is connected to the positive terminal 5a of the drive power supply 5 via the diode 21a. The other end of the resistive element 31a is connected to the positive terminal 111a of the capacitor 11a.

[0038] Diode 22a is connected in series between the drive power supply 5 and the capacitor 12a. Diode 22a is, for example, a reverse current prevention diode. Diode 22a is connected in the wiring L3a that connects connection point P1a to connection point P3a, which is connected to the positive terminal 112a of capacitor 12a, with the direction from connection point P1a to connection point P3a being the forward direction. Therefore, the anode of diode 22a is connected to the positive terminal 5a of the drive power supply 5. The cathode of diode 22a is connected to the positive terminal 112a of capacitor 12a.

[0039] The resistor 32a is, for example, a limiting resistor that restricts the current from the drive power supply 5 to the capacitor 12a. The resistor 32a is connected in series between the diode 22a and the capacitor 12a. More specifically, the resistor 32a is connected in series between the diode 22a and the connection point P3a in the wiring L3a. One end of the resistor 32a is connected to the positive terminal 5a of the drive power supply 5 via the diode 22a. The other end of the resistor 32a is connected to the positive terminal 112a of the capacitor 12a. The resistor 32a has a resistance value different from that of the resistor 31a, for example. The resistance value of the resistor 32a may be higher than that of the resistor 31a.

[0040] The resistor 33a is connected in series between the positive terminal 112a of the capacitor 12a and the connection point P3a. The resistor 33a is a limiting resistor that limits the current from the drive power supply 5 to the capacitor 12a and the current from the capacitor 12a to the capacitor 16a. One end of the resistor 33a is connected to the positive terminal 5a of the drive power supply 5 via the resistor 32a and the diode 22a. One end of the resistor 33a is connected to the positive terminal 116a of the capacitor 16a via the semiconductor switch 2. The other end of the resistor 33a is connected to the positive terminal 112a of the capacitor 12a.

[0041] Diode 10a is connected in series between connection point P3a and the drain terminal 2a of semiconductor switch 2. Diode 10a is, for example, a reverse current prevention diode. Diode 10a is connected in the wiring L6a between connection point P3a and the drain terminal 2a of semiconductor switch 2 with the direction from connection point P3a to drain terminal 2a being the forward direction. As a result, diode 10a is connected in series with diode 22a and resistor element 32a. Diode 10a is connected in series with semiconductor switch 2 and capacitor 16a. Therefore, the anode of diode 10a is connected to the positive terminal 5a of the drive power supply 5 via diode 22a and resistor element 32a. The cathode of diode 10a is connected to the positive terminal 116a of capacitor 16a via semiconductor switch 2.

[0042] The resistor 34a is connected in series between the diode 10a and the drain terminal 2a of the semiconductor switch 2. The resistor 34a is, for example, a limiting resistor that restricts the current from capacitor 12a to capacitor 16a. One end of the resistor 34a is connected to the positive terminal 5a of the drive power supply 5 via diode 10a, resistor 32a, and diode 22a. The other end of the resistor 34a is connected to the positive terminal 116a of capacitor 16a via the semiconductor switch 2.

[0043] Diode 14a is connected in series between connection point P5a and connection point P6a. Diode 14a is, for example, a rectifier diode. Diode 14a is connected in the wiring L7a between connection point P5a and connection point P6a with the direction from connection point P5a to connection point P6a being the forward direction. The anode of diode 14a is connected to the connection switching unit 13a and the negative terminal 216a of capacitor 16a via connection point P5a. The cathode of diode 14a is connected to the negative terminal 212a of capacitor 12a via connection point P6a.

[0044] The resistor 35a is connected in series between the diode 14a and the connection point P6a. The resistor 35a is, for example, a limiting resistor that limits the current from capacitor 12a to capacitor 16a. One end of the resistor 35a is connected to the negative terminal 212a of capacitor 12a via the connection point P6a. The other end of the resistor 35a is connected to the negative terminal 216a of capacitor 16a via the diode 14a and the connection point P5a.

[0045] Diode 15a is directly connected between connection point P6a and wiring L4a, and is also connected in parallel with capacitor 16a. Diode 15a is connected with the forward direction from connection point P6a to wiring L4a. Diode 15a is, for example, a voltage limiting diode that limits the voltage across capacitor 16a to a predetermined voltage. The predetermined voltage is, for example, a negative voltage applied as a gate voltage to the gate terminal 2c of semiconductor switch 2. This voltage is set, for example, based on the breakdown voltage of the gate terminal 2c of semiconductor switch 2.

[0046] The resistor 36a is connected in series between the diode 10a and the wiring L4a. The resistor 36a is, for example, a limiting resistor that limits the current from the drive power supply 5 to the capacitor 12a. One end of the resistor 36a is connected to the negative terminal 211a of the capacitor 12a via the diode 15a. The other end of the resistor 36a is connected to the wiring L4a.

[0047] The connection switching unit 13a includes switches 131a and 132a connected in series with each other. For example, switch 131a is an NPN type IGBT, and switch 132a is a PNP type IGBT. Switches 131a and 132a constitute a so-called push-pull circuit. The collector terminal of switch 131a is connected to the positive terminal 111a of capacitor 11a. The emitter terminal of switch 131a is connected to the emitter terminal of switch 132a. The connection point between the emitter terminals of switch 131a and switch 132a is connected to the gate terminal 2c of semiconductor switch 2. The collector terminal of switch 132a is connected to the negative terminal 216a of capacitor 16a. The base terminals of switch 131a and switch 132a are connected to the control device 7 and receive control signals from the control device 7.

[0048] When the connection switching unit 13a receives a control signal instructing the semiconductor switch 2 to be turned on, it is controlled to a first connection state in which switch 131a is turned on and switch 132a is turned off. In the first connection state, a positive voltage application closed circuit C14 is formed which applies the positive voltage of capacitor 11a to the gate terminal 2c of semiconductor switch 2, and a negative voltage charging closed circuit C15 is formed which charges capacitor 16a with a negative voltage (see Figure 3).

[0049] The positive voltage application closed circuit C14 is a closed circuit that passes through the path W14 in Figure 3. The positive voltage application closed circuit C14 is formed by connecting the positive terminal 111a of capacitor 11a to the gate terminal 2c of semiconductor switch 2 via switch 131a, which is in the ON state. The positive voltage application closed circuit C14 includes, for example, capacitor 11a, switch 131a, and semiconductor switch 2. In the positive voltage application closed circuit C14, the charge stored in capacitor 11a is supplied to semiconductor switch 2 via switch 131a. As a result, the input capacitance of semiconductor switch 2 begins to charge with the charge discharged from capacitor 11a. Subsequently, when a certain amount of charge is stored in the input capacitance of semiconductor switch 2, semiconductor switch 2 turns ON. In this embodiment, the positive voltage application closed circuit C14 does not include a resistive element.

[0050] The negative voltage charging closed circuit C15 is a closed circuit that passes through the path W15 in Figure 3. The negative voltage charging closed circuit C15 is formed when the positive terminal 112a of capacitor 12a is connected to the positive terminal 116a of capacitor 16a via a switch 131a that is in the ON state. The negative voltage charging closed circuit C15 includes, for example, capacitor 12a, resistor 33a, diode 10a, resistor 34a, semiconductor switch 2, capacitor 16a, diode 14a, and resistor 35a. In the negative voltage charging closed circuit C15, the charge stored in capacitor 12a is supplied to capacitor 16a via resistor 33a, diode 10a, resistor 34a, and semiconductor switch 2. Capacitor 16a is charged by this charge from capacitor 12a. At this time, a positive charge is stored at the positive terminal 116a of capacitor 16a, and a negative charge is stored at the negative terminal 216a of capacitor 16a. This generates a negative voltage across capacitor 16a.

[0051] In the negative voltage charging closed circuit C15, the charge stored in capacitor 12a flows through resistors 33a, 34a, and 35a. Therefore, resistors 33a, 34a, and 35a have the function of limiting the charging current from capacitor 12a to capacitor 16a. Consequently, the charging current to capacitor 16a can be adjusted by adjusting the combined resistance value of resistors 33a, 34a, and 35a.

[0052] When the connection switching unit 13a receives a control signal instructing the semiconductor switch 2 to turn off, it is controlled to a second connection state in which switch 131a is turned off and switch 132a is turned on. In the second connection state, a negative voltage application closed circuit C13 is formed for applying the negative voltage of capacitor 16a to the gate terminal 2c of semiconductor switch 2, a positive voltage charging closed circuit C11 is formed for charging a positive voltage in capacitor 11a, and a temporary charging closed circuit C12 is formed for temporarily charging power for generating a negative voltage in capacitor 12a (see Figure 2).

[0053] The negative voltage application closed circuit C13 is a closed circuit that passes through the path W13 in Figure 2. The negative voltage application closed circuit C13 is formed when the negative terminal 216a of capacitor 16a is connected to the gate terminal 2c of semiconductor switch 2 via switch 132a, which is in the ON state. The negative voltage application closed circuit C13 includes, for example, capacitor 16a, switch 132a, and semiconductor switch 2. In the negative voltage application closed circuit C13, the charge stored in capacitor 16a is supplied to semiconductor switch 2 via switch 132a. This applies a positive voltage to semiconductor switch 2, turning semiconductor switch 2 into the ON state. In this case, the charge stored in the input capacitance of semiconductor switch 2 is discharged, causing semiconductor switch 2 to transition from the ON state to the OFF state. In other words, the negative charge stored in capacitor 16a is supplied to the gate terminal 2c of semiconductor switch 2, applying a negative voltage to the gate terminal 2c of semiconductor switch 2. This turns semiconductor switch 2 into the OFF state.

[0054] The positive voltage charging closed circuit C11 is a closed circuit that passes through the path W11 in Figure 2. It is formed when the negative terminal 211a of capacitor 11a is connected to the negative terminal 5b of the drive power supply 5 via an ON semiconductor switch 3. The positive voltage charging closed circuit C11 includes, for example, a drive power supply 5, a diode 21a, a resistor 31a, a capacitor 11a, and a semiconductor switch 3. In the positive voltage charging closed circuit C11, capacitor 11a is charged by the voltage VDD from the drive power supply 5. In the positive voltage charging closed circuit C11, the charge from the drive power supply 5 flows through the resistor 31a. Therefore, the resistor 31a has the function of limiting the charging current from the drive power supply 5 to capacitor 11a. Accordingly, it is possible to adjust the charging current to capacitor 11a by adjusting the resistance value of the resistor 31a.

[0055] The temporary charging closed circuit C12 is a closed circuit that passes through the path W12 in Figure 2. The temporary charging closed circuit C12 is formed by connecting the negative terminal 212a of capacitor 12a to the negative terminal 5b of the drive power supply 5 via a semiconductor switch 3 that is in the ON state. The temporary charging closed circuit C12 includes, for example, a drive power supply 5, a diode 22a, a resistor 32a, a capacitor 12a, and a semiconductor switch 3. In the temporary charging closed circuit C12, capacitor 12a is charged by the voltage VDD from the drive power supply 5. In the temporary charging closed circuit C12, the charge from the drive power supply 5 flows through resistors 32a, 33a, and 36a. Therefore, resistors 32a, 33a, and 36a have the function of limiting the charging current from the drive power supply 5 to capacitor 12a. Thus, it is possible to adjust the charging current to capacitor 12a by adjusting the combined resistance value of resistors 32a, 33a, and 36a. The resistor element 33a has both the function of adjusting the charging current to capacitor 12a and the function of adjusting the charging current to capacitor 16a as described above.

[0056] In this way, the connection switching unit 13a alternately switches between a first connection state in which a positive voltage application closed circuit C14 and a negative voltage charging closed circuit C15 are formed, and a second connection state in which a negative voltage application closed circuit C13, a positive voltage charging closed circuit C11, and a temporary charging closed circuit C12 are formed, according to the control signal. In the first connection state, a positive voltage to turn on the semiconductor switch 2 is applied to the gate terminal 2c of the semiconductor switch 2 by the positive voltage application closed circuit C14. In the second connection state, a negative voltage to turn off the semiconductor switch 2 is applied to the gate terminal 2c of the semiconductor switch 2 by the negative voltage application closed circuit C13. Therefore, by the connection switching unit 13a alternately switching between the first connection state and the second connection state, the semiconductor switch 2 can be alternately turned on or off.

[0057] In the semiconductor switch drive unit 6a according to this embodiment, a movement restricting unit 50a (see Figure 1) is provided to restrict the movement of charge from the path W14 passing through the positive voltage application closed circuit C14 to other paths that pass through the positive terminal 111a of the capacitor 11a but do not pass through the gate terminal 2c of the semiconductor switch 2. The movement restricting unit 50a is provided between the positive terminal 111a of the capacitor 11a and the drain terminal 2a of the semiconductor switch 2. The movement restricting unit 50a adjusts the charge movement path of the capacitor 11a so as to avoid the movement of charge from the path W14 passing through the positive voltage application closed circuit C14 to paths other than path W14. "Other paths" can be any path that passes through the positive terminal 111a of the capacitor 11a but does not pass through the gate terminal 2c of the semiconductor switch 2, and can be any path other than path W14 that passes through the positive terminal 111a of the capacitor 11a and the gate terminal 2c of the semiconductor switch 2. For example, the "other path" may be a path that goes from the positive terminal 111a of capacitor 11a through the drain terminal 2a of semiconductor switch 2 and returns to the positive terminal 111a of capacitor 11a.

[0058] The movement restricting section 50a includes, for example, a connection point P1a (an example of a "third connection point"), a connection point P2a (an example of a "first connection point"), a connection point P3a (an example of a "second connection point"), wiring L2a (an example of a "first wiring"), wiring L5a (an example of a "second wiring"), a diode 21a (an example of a "first diode"), a diode 22a (an example of a "second diode"), a resistive element 31a (an example of a "first resistive element"), and a resistive element 32a (an example of a "second resistive element"). Connection point P1a is a branching point where wiring connected to the positive terminal 5a of the drive power supply 5 branches off to wiring L2a and wiring L5a. Connection point P1a is located closer to the drive power supply 5 than connection point P2a on the wiring between the positive terminal 5a of the drive power supply 5 and the positive terminal 111a of the capacitor 11a. The wiring L2a connecting connection point P1a and connection point P2a is connected to the wiring L3a that constitutes the positive voltage application closed circuit C14 at connection point P2a.

[0059] Connection point P3a is located closer to the power supply 5 than connection point P5a on the wiring between the positive terminal 5a of the power supply 5 and the positive terminal 112a of the capacitor 12a. Wiring L5a connecting connection point P1a and connection point P3a is connected to wiring L6a at connection point P3a. Connection point P2a is not directly connected to either wiring L5a or wiring L6a. Therefore, beyond connection point P1a, which is the branching point between wiring L2a and wiring L5a, wiring L2a and wiring L3a are independent of wiring L5a and wiring L6a and do not have connection points with wiring L5a and wiring L6a.

[0060] In this case, the possible paths for charge to move in capacitor 11a in the first connection state are limited to two paths: one from the positive terminal 111a of capacitor 11a to wiring L3a via connection point P2a, and another from the positive terminal 111a of capacitor 11a to wiring L2a via connection point P2a. Here, since a diode 21a for preventing reverse current is provided in wiring L2a, the movement of charge from connection point P2a to connection point P1a is restricted. Therefore, the path for charge to move from connection point P2a to connection point P3a is eliminated.

[0061] As a result, in the first connection state, the movement of charge from the positive voltage application closed circuit C14's path W14 to other paths is avoided, such as the path through which the charge of capacitor 11a moves via connection point P3a and capacitor 12a, or the path through which the charge of capacitor 11a moves via connection point P3a and the drain terminal 2a of semiconductor switch 2. Therefore, in the first connection state, the charge of capacitor 11a moves only along the path W14 that passes through wiring L3a and the gate terminal 2c of semiconductor switch 2. Thus, in this embodiment, the movement restricting unit 50a prevents the charge of capacitor 11a from moving from the positive voltage application closed circuit C14's path W14 to other paths in the first connection state.

[0062] The semiconductor switch drive unit 6b has the same configuration as the semiconductor switch drive unit 6a, except that it does not have circuit elements corresponding to diodes 21a and 22a. When the part of the code attached to the configuration of the semiconductor switch drive unit 6b, excluding the last suffix b, is the same as the part of the code attached to the configuration of the semiconductor switch drive unit 6a, excluding the last suffix a, it indicates that the configurations indicated by those codes are identical. Therefore, a detailed explanation of each component of the semiconductor switch drive unit 6b is omitted as it would overlap with the explanation of each component of the semiconductor switch drive unit 6a.

[0063] Unlike the semiconductor switch drive unit 6a that constitutes the upper arm, in the semiconductor switch drive unit 6b that constitutes the lower arm, it is not expected that charge will flow back into the drive power supply 5 due to voltage balance considerations, so it is possible to omit the circuit elements corresponding to diodes 21a and 22a. Typically, the voltage VDD (e.g., 15V) of the drive power supply 5 for driving semiconductor switches 2 and 3 is lower than the input voltage Vin (e.g., 300V) of the power supply 4 for driving the load device M.

[0064] In the first connection state (i.e., when semiconductor switch 2 is ON and semiconductor switch 3 is OFF), the negative terminal 211a of capacitor 11a is connected to power supply 4 via semiconductor switch 2. Therefore, a relatively high input voltage Vin is applied to the negative terminal 211a of capacitor 11a. On the other hand, the positive terminal 111a of capacitor 11a is connected to the positive terminal 5a of drive power supply 5. Therefore, a relatively low voltage VDD is applied to the positive terminal 111a of capacitor 11a. In this case, in the upper arm, the voltage difference between these input voltages Vin and VDD may cause current to flow in reverse from power supply 4 to drive power supply 5. Therefore, it is necessary to provide diodes 21a and 22a to prevent such reverse current flow.

[0065] On the other hand, in the lower arm, reverse current flow from power supply 4 to drive power supply 5 is prevented by diode 10b, so that the voltage VDD of power supply 4 is not applied to capacitor 11a, etc. Furthermore, the negative terminal 5b of drive power supply 5 is always connected to GND potential. As a result, in the lower arm, the situation where current flows back from power supply 4 to drive power supply 5 due to the voltage difference between the input voltage Vin and voltage VDD does not occur. Therefore, it is not necessary to provide circuit elements corresponding to diodes 21a and 22a. However, the semiconductor switch drive unit 6b of the lower arm may be equipped with circuit elements corresponding to diodes 21a and 22a, similar to the semiconductor switch drive unit 6a of the upper arm. In this case, these circuit elements can function as backups in case diode 10b is damaged. The semiconductor switch drive unit 6b may have a different configuration from the semiconductor switch drive unit 6a, in addition to diodes 21a and 22a.

[0066] [Operation of semiconductor switch drive circuit] Next, the operation flow of the semiconductor switch drive circuit 6 will be described. In this embodiment, the semiconductor switch drive circuit 6 has a first operating mode in which the connection switching unit 13a of the semiconductor switch drive unit 6a is in a second connected state and the connection switching unit 13b of the semiconductor switch drive unit 6b is in a first connected state, and a second operating mode in which the connection switching unit 13a of the semiconductor switch drive unit 6a is in a first connected state and the connection switching unit 13b of the semiconductor switch drive unit 6b is in a second connected state. The semiconductor switch drive circuit 6 drives the semiconductor switch 2 and the semiconductor switch 3 to alternately turn on by alternately switching between the first operating mode and the second operating mode according to the control signal from the control device 7.

[0067] First, the operation of the semiconductor switch drive unit 6a, which switches semiconductor switch 2 on or off, will be explained with reference to Figures 2 and 3. In Figures 2 and 3, the dashed lines indicate that semiconductor switch 2, semiconductor switch 3, switch 131a, switch 132a, switch 131b, and switch 132b are off. The solid lines indicate that semiconductor switch 2, semiconductor switch 3, switch 131a, switch 132a, switch 131b, and switch 132b are on. Before the first operating mode is performed, the capacitor 16a is charged.

[0068] <First operating mode> In the first operating mode, the connection switching unit 13a enters the second connection state, and as shown in Figure 2, a negative voltage application closed circuit C13 is formed by the connection between the capacitor 16a and the semiconductor switch 2. In the negative voltage application closed circuit C13, the charge that was stored in the capacitor 16a returns to the capacitor 16a via the semiconductor switch 2 through a path W13. The negative voltage across the capacitor 16a is supplied to the gate terminal 2c of the semiconductor switch 2, causing the semiconductor switch 2 to turn off.

[0069] In the first operating mode, a positive voltage charging closed circuit C11 is formed by connecting capacitor 11a to the drive power supply 5. In the positive voltage charging closed circuit C11, current from the drive power supply 5 flows through a path W11 that returns to the drive power supply 5 via capacitor 11a and semiconductor switch 3. This current charges capacitor 11a. In the first operating mode, a temporary charging closed circuit C12 is formed by connecting capacitor 12a to the drive power supply 5. In the temporary charging closed circuit C12, current from the drive power supply 5 flows through a path W12 that returns to the drive power supply 5 via capacitor 12a and semiconductor switch 3. This current charges capacitor 12a.

[0070] <Second operating mode> In the second operating mode, the connection switching unit 13a enters the first connection state, and as shown in Figure 3, a positive voltage application closed circuit C14 is formed by the connection between the capacitor 11a and the semiconductor switch 2. In the positive voltage application closed circuit C14, the charge that was stored in the capacitor 11a returns to the capacitor 11a via the semiconductor switch 2 through a path W14. As the positive charge of the capacitor 11a is supplied to the gate terminal 2c of the semiconductor switch 2, the semiconductor switch 2 transitions from the off state to the on state.

[0071] In the second operating mode, a negative voltage charging closed circuit C15 is formed by connecting capacitor 12a and capacitor 16a. In the negative voltage charging closed circuit C15, the charge stored in capacitor 12a flows through a path W15 that returns to capacitor 12a via semiconductor switch 2 and capacitor 16a. As a result, capacitor 16a is charged.

[0072] Next, the operation of the semiconductor switch drive unit 6b, which switches the semiconductor switch 3 on or off, will be described with reference to Figures 4 and 5. In Figures 4 and 5, the dashed lines indicate that semiconductor switches 2, 3, 131a, 132a, 131b, and 132b are off, and the solid lines indicate that semiconductor switches 2, 3, 131a, 132a, 131b, and 132b are on. Before the first operating mode is performed, the capacitor 16a is charged.

[0073] <First operating mode> In the first operating mode, the connection switching unit 13b of the semiconductor switch drive unit 6b enters the first connection state, and as shown in Figure 4, a positive voltage application closed circuit C24 is formed by the connection between the capacitor 11b and the semiconductor switch 3. In the positive voltage application closed circuit C24, the charge that was stored in the capacitor 11b returns to the capacitor 11b via the semiconductor switch 3 through a path W24. The positive charge from the capacitor 11b is supplied to the gate terminal 2c of the semiconductor switch 3, causing the semiconductor switch 3 to turn on.

[0074] In the first operating mode, a negative voltage charging closed circuit C25 is formed by connecting capacitor 12b and capacitor 16b. In the negative voltage charging closed circuit C25, the charge stored in capacitor 12b flows through a path W25 that returns to capacitor 12b via the semiconductor switch 3 and capacitor 16b. As a result, capacitor 16b is charged.

[0075] <Second operating mode> In the second operating mode, the connection switching unit 13b of the semiconductor switch drive unit 6b enters the second connection state, and as shown in Figure 5, a negative voltage application closed circuit C23 is formed by the connection between the capacitor 16b and the semiconductor switch 3. In the negative voltage application closed circuit C23, the charge that was stored in the capacitor 16b returns to the capacitor 16b via the semiconductor switch 3 through a path W23. The negative charge of the capacitor 16b is supplied to the gate terminal 2c of the semiconductor switch 3, causing the semiconductor switch 3 to turn off.

[0076] In the second operating mode, a positive voltage charging closed circuit C21 is formed by connecting capacitor 11b to the drive power supply 5. In the positive voltage charging closed circuit C21, current from the drive power supply 5 flows through a path W21 that returns to the drive power supply 5 via capacitor 11b and semiconductor switch 3. This current charges capacitor 11b. In the first operating mode, a temporary charging closed circuit C22 is formed by connecting capacitor 12b to the drive power supply 5. In the temporary charging closed circuit C22, current from the drive power supply 5 flows through a path W22 that returns to the drive power supply 5 via capacitor 12b and semiconductor switch 3. This current charges capacitor 12b.

[0077] [Effects and Effects] Next, the effects and advantages of the semiconductor switch drive circuit 6 and power converter 1 according to this embodiment will be explained, along with the problems of the comparative example.

[0078] Figure 12 shows the drive circuit 206 for the upper arm of the power converter 100 according to the comparative example. Unlike the semiconductor switch drive unit 6a according to this embodiment, the drive circuit 206 does not have a movement restricting unit 50a. In this case, in the first connection state, the charge that was charged in the capacitor 101 passes through a path W110 that returns to the capacitor 101 via the gate terminal 2c of the semiconductor switch 2, as well as a path W120 that moves from connection point P101 to connection point P102 and through the capacitor 102, and a path W130 that moves from connection point P101 to connection point P102 and through the drain terminal 2a of the semiconductor switch 2.

[0079] As described above, the charge of capacitor 101 passes through path W120, which goes through the gate terminal 2c of semiconductor switch 2. Therefore, when the charge moves to another path W120 or path W130 that passes through capacitor 101 and the gate terminal 2c of semiconductor switch 2, the positive voltage of capacitor 101 is divided between semiconductor switch 2 and other circuit elements, resulting in a decrease in the positive voltage applied to semiconductor switch 2. For example, in path W120, the positive voltage of capacitor 101 is divided between resistor 105, capacitor 102, and semiconductor switch 2. In path W130, the positive voltage of capacitor 101 is divided between resistor 105 and semiconductor switch 2. In particular, in path W130, the charge of capacitor 101 does not contribute to the charging of capacitor 102, but is consumed by resistor 105 and returns to capacitor 101, resulting in wasted power in capacitor 101.

[0080] In contrast, in this embodiment, a movement restricting unit 50a is provided that restricts the movement of charge from the capacitor 11a from the path W14 of the positive voltage application closed circuit C14 to other paths. This prevents the charge of the capacitor 11a from passing through other paths such as the aforementioned paths W120 and W130, thus preventing the positive voltage of the capacitor 11a from being divided by circuit elements on other paths. This effectively suppresses the situation in which the positive voltage from the capacitor 11a to the semiconductor switch 2 decreases. As a result, the semiconductor switch driving circuit 6 can supply sufficient charge to the gate terminal 2c of the semiconductor switch 2 when turning on the semiconductor switch 2. In other words, the semiconductor switch driving circuit 6 can reliably control the semiconductor switch 2 to turn on.

[0081] In this embodiment, a capacitor 12a is provided for charging capacitor 16a. This eliminates the need to place capacitor 16a on the positive voltage application closed circuit C14, where the positive voltage of capacitor 11a is applied to the control terminal of semiconductor switch 2, for charging capacitor 16a. In other words, the path W14 through which the charge of capacitor 11a moves in the positive voltage application closed circuit C14 does not pass through capacitor 16a. This avoids the situation where the positive voltage of capacitor 11a is divided between semiconductor switch 2 and capacitor 16a. In this embodiment, the path W11 through which the charge of capacitor 11a moves in the positive voltage charging closed circuit C11, and the path W12 through which the charge of capacitor 12a moves in the temporary charging closed circuit C12, both do not pass through capacitor 16a. As a result, the voltage VDD of the drive power supply 5 is applied to capacitor 11a without being divided by capacitor 16a. Similarly, the voltage VDD of the drive power supply 5 is applied to capacitor 11a without being divided by capacitor 16a.

[0082] Therefore, in this embodiment, the situation in which the positive voltage to the semiconductor switch 2 decreases is effectively suppressed. In this embodiment, a positive voltage is generated at capacitor 11a by power from the drive power supply 5, and a negative voltage is generated at capacitor 16a by power discharged from the charged capacitor 12a. In other words, both positive and negative voltages are generated using a single drive power supply 5. As a result, there is no need to provide a separate drive power supply 5 for generating the negative voltage, thus suppressing an increase in the size and weight of the device configuration.

[0083] As in this embodiment, the movement restricting unit 50a may include a connection point P2a between the positive terminal 111a of capacitor 11a and the gate terminal 2c of semiconductor switch 2, a connection point P3a between the positive terminal 112a of capacitor 12a and the drain terminal 2a of semiconductor switch 2, a connection point P1a between connection point P2a and the positive terminal 5a of drive power supply 5, a wiring L2a connecting connection point P2a and connection point P1a, and a wiring L5a connecting connection point P3a and connection point P1a. In this way, when connection point P1a is provided between connection point P2a and drive power supply 5, it is possible to allow charge to move from drive power supply 5 to capacitor 11a via connection point P1a and connection point P2a, while preventing charge released from capacitor 11a from moving to connection point P3a via connection point P2a and connection point P1a. This prevents the charge of capacitor 11a moving along path W14 of the positive voltage applied closed circuit C14 from moving from connection point P2a through connection point P3a to another path. As a result, the situation in which the positive voltage of capacitor 11a is divided by other circuit elements can be more effectively suppressed, and the situation in which the positive voltage to semiconductor switch 2 decreases can be more effectively suppressed.

[0084] As in this embodiment, the movement restricting unit 50a may include a diode 21a connected in wiring L2a with the forward direction from connection point P1a to connection point P2a, and a diode 22a connected in wiring L5a with the forward direction from connection point P1a to connection point P3a. By providing diodes 21a and 22a in this way, it is possible to avoid a situation in which reverse charge flows from capacitors 11a and 12a to the drive power supply 5. Furthermore, by providing diode 21a between connection point P1a and connection point P2a, it is possible to avoid a situation in which the charge of capacitor 11a moves from connection point P2a to connection point P3a via connection point P1a. This makes it possible to more effectively suppress the situation in which the positive voltage of capacitor 11a is divided by other circuit elements. As a result, it is possible to more effectively suppress a situation in which the charge of capacitor 11a moves to other paths via connection point P3a, and thus it is possible to more effectively suppress a decrease in the positive voltage from capacitor 11a to semiconductor switch 2.

[0085] As in this embodiment, the movement restricting unit 50a may include a resistive element 31a connected in series with the diode 21a in the wiring L2a, and a resistive element 32a connected in series with the diode 22a in the wiring L5a, having a higher resistance value than the resistive element 31a. The negative voltage required to turn off the semiconductor switch 2 tends to be smaller than the positive voltage required to turn on the semiconductor switch 2. When the negative voltage is small in this way, the amount of charge in the capacitor 12a that charges the power for generating the negative voltage may be smaller than the amount of charge in the capacitor 11a that charges the power for generating the positive voltage. Therefore, in the above configuration, the resistive element 32a provided on the charge transfer path from the drive power supply 5 to the capacitor 12a has a higher resistance value than the resistive element 31a provided on the charge transfer path from the drive power supply 5 to the capacitor 11a. This makes it possible to keep the charging current supplied from the drive power supply 5 to the capacitor 12a small. As a result, it becomes possible to suppress an increase in the capacity of the drive power supply 5 that provides power to the capacitor 12a.

[0086] As in this embodiment, the positive terminal 111a of capacitor 11a may be connected to the positive terminal 5a of the drive power supply 5 and the gate terminal 2c of the semiconductor switch 2. The positive terminal 112a of capacitor 12a may be connected to the positive terminal 5a of the drive power supply 5. The negative terminal 216a of capacitor 16a may be connected to the negative terminal 212a of capacitor 12a. The positive terminal 116a of capacitor 16a may be connected to the gate terminal 2c of the semiconductor switch 2. In this case, a configuration in which a positive voltage and a negative voltage are generated using a single drive power supply 5 can be easily realized.

[0087] As in this embodiment, the semiconductor switch drive unit 6a and the semiconductor switch drive unit 6b may each be equipped with a movement restricting unit 50a and a movement restricting unit 50b. In this case, a decrease in the positive voltage to the semiconductor switch 2 and the semiconductor switch 3 can be effectively suppressed in both the upper arm and the lower arm.

[0088] As in this embodiment, the semiconductor switch drive unit 6b may have the same configuration as the semiconductor switch drive unit 6a, except that it does not have circuit elements corresponding to diodes 21a and 22a. As described above, in the upper arm, charge may flow back into the drive power supply 5 depending on whether the semiconductor switch 2 is turned on or off. On the other hand, in the lower arm, charge does not flow back into the drive power supply 5 regardless of whether the semiconductor switch 3 is turned on or off. Therefore, in this embodiment, diodes 21a and 22a are provided in the semiconductor switch drive unit 6a that constitutes the upper arm, and circuit elements corresponding to diodes 21a and 22a are not provided in the semiconductor switch drive unit 6b that constitutes the lower arm. This makes it possible to reduce the number of components that make up the semiconductor switch drive unit 6b.

[0089] The semiconductor switch drive circuit 6 is not limited to the circuit configuration described above and may have other circuit configurations. For example, as shown in Figure 6, the power converter 1A may have a semiconductor switch drive circuit 6A with a different arrangement of resistive elements instead of the semiconductor switch drive circuit 6. The semiconductor switch drive unit 6aa of the semiconductor switch drive circuit 6A (an example of the "first semiconductor switch drive unit") includes resistive elements 41a, 42a, 43a, and 44a instead of resistive elements 31a, 32a, 33a, 34a, 35a, and 36a.

[0090] Resistor element 41a is connected in series between the positive terminal 111a of capacitor 11a and connection point P2a. Resistor element 41a is a limiting resistor that, for example, limits the charging current from the drive power supply 5 to capacitor 11a and the gate current (positive voltage) from capacitor 11a to semiconductor switch 2. Resistor element 42a is connected in series between the negative terminal 211a of capacitor 11a and connection point P4a. Resistor element 42a is a limiting resistor that, for example, limits the charging current from the drive power supply 5 to capacitor 11a, the charging current from the drive power supply 5 to capacitor 12a, and the gate current (positive voltage) from capacitor 11a to semiconductor switch 2.

[0091] Resistor element 43a is connected in series between the positive terminal 116a of capacitor 16a and connection point P4a. Resistor element 43a is a limiting resistor that, for example, limits the charging current from capacitor 12a to capacitor 16a and the gate current (negative voltage) from capacitor 16a to semiconductor switch 2. Resistor element 44a is connected in series between connection point P4a and source terminal 2b of semiconductor switch 2. Resistor element 44a is a limiting resistor that, for example, limits the charging current from the drive power supply 5 to capacitor 11a, the charging current from the drive power supply 5 to capacitor 12a, the charging current from capacitor 12a to capacitor 16a, and the gate current (negative voltage) from capacitor 16a to semiconductor switch 2.

[0092] The semiconductor switch drive unit 6bb of the semiconductor switch drive circuit 6A (an example of the "second semiconductor switch drive unit") includes resistor elements 41b, 42b, 43b, and 44b, which correspond to resistor elements 41a, 42a, 43a, and 44a, respectively. Even with such a circuit configuration, the semiconductor switch drive circuit 6A will produce the same effects as described above.

[0093] [Second Embodiment] Next, the second embodiment will be described. In the following description of the second embodiment, explanations of parts that overlap with the first embodiment will be omitted as appropriate, and the parts that differ from the first embodiment will be mainly described.

[0094] As shown in Figure 7, the power converter 1B according to the second embodiment includes a semiconductor switch drive circuit 6B instead of the semiconductor switch drive circuit 6. The semiconductor switch drive circuit 6B differs from the semiconductor switch drive circuit 6 in that it has a semiconductor switch drive unit 6c instead of the semiconductor switch drive unit 6b. The semiconductor switch drive unit 6c includes, for example, a connection switching unit 13c (an example of "another connection switching unit"), a capacitor 11c (an example of "a fourth capacitor"), a capacitor 16c (an example of "a fifth capacitor"), and a resistive element 51c.

[0095] Capacitor 11c is connected between the drive power supply 5 and the connection switching unit 13c. Capacitor 11c is, for example, a positive power supply capacitor that generates a positive voltage. The positive terminal 111c (one end) of capacitor 11c is connected to the positive terminal 5a of the drive power supply 5 via wiring L2c. The positive terminal 111c of capacitor 11c is connected to the connection switching unit 13c via wiring L4c. The negative terminal 211c (the other end) of capacitor 11c is connected to the negative terminal 5b of the drive power supply 5 via wiring L3c. The negative terminal 211c of capacitor 11c is connected to the connection switching unit 13c via wiring L5c.

[0096] Capacitor 16c is a negative power supply capacitor that receives power from the charged capacitor 12c and generates a negative voltage. Capacitor 16c is connected in series with capacitor 11c between the connection point P2c between wiring L2c and wiring L4c, and between the connection point P3c between wiring L3c and wiring L5c. Capacitor 16c is connected between capacitor 11c and connection point P3c. The negative terminal 216c (other end) of capacitor 16c is connected to the negative terminal 211c of capacitor 11c. The positive terminal 116c (one end) of capacitor 16c is connected to connection point P3c. The connection point P4c between the negative terminal 216c of capacitor 16c and the negative terminal 211c of capacitor 11c is connected to the source terminal 3b of semiconductor switch 3 via wiring L6c. Resistor element 51c is, for example, a limiting resistor that limits the current from the drive power supply 5 to capacitor 11c. The resistor 51c is connected to the wiring L2c between connection point P1c, which is connected to the positive terminal 5a of the drive power supply 5, and connection point P2c. One end of the resistor 31c is connected to the positive terminal 5a of the drive power supply 5. The other end of the resistor 51c is connected to the positive terminal 111c of the capacitor 11c.

[0097] [Operation of semiconductor switch drive circuit] Next, the operation flow of the semiconductor switch drive circuit 6B will be described with reference to Figures 8 to 11. In this embodiment, the semiconductor switch drive circuit 6B has a first operating mode in which the connection switching unit 13a of the semiconductor switch drive unit 6a is in a second connected state and the connection switching unit 13c of the semiconductor switch drive unit 6c is in a first connected state, and a second operating mode in which the connection switching unit 13a of the semiconductor switch drive unit 6a is in a first connected state and the connection switching unit 13c of the semiconductor switch drive unit 6c is in a second connected state. The semiconductor switch drive circuit 6 drives the semiconductor switch 2 and the semiconductor switch 3 to alternately turn on by alternately switching between the first operating mode and the second operating mode according to the control signal from the control device 7.

[0098] First, with reference to Figures 8 and 9, the operation of the semiconductor switch drive unit 6a, which switches the semiconductor switch 2 on or off, will be explained.

[0099] <First operating mode> In the first operating mode, the connection switching unit 13a enters the second connection state, and as shown in Figure 8, a negative voltage application closed circuit C13 is formed by the connection between the capacitor 16a and the semiconductor switch 2. In the negative voltage application closed circuit C13, the charge that was stored in the capacitor 16a returns to the capacitor 16a via the semiconductor switch 2 through a path W13. The negative voltage across the capacitor 16a is supplied to the gate terminal 2c of the semiconductor switch 2, causing the semiconductor switch 2 to turn off.

[0100] In the first operating mode, a positive voltage charging closed circuit C11 is formed by connecting capacitor 11a to the drive power supply 5. In the positive voltage charging closed circuit C11, current from the drive power supply 5 flows through a path W11 that returns to the drive power supply 5 via capacitor 11a and semiconductor switch 3. This current charges capacitor 11a. In the first operating mode, a temporary charging closed circuit C12 is formed by connecting capacitor 12a to the drive power supply 5. In the temporary charging closed circuit C12, current from the drive power supply 5 flows through a path W12 that returns to the drive power supply 5 via capacitor 12a and semiconductor switch 3. This current charges capacitor 12a.

[0101] <Second operating mode> In the second operating mode, the connection switching unit 13a enters the first connection state, and as shown in Figure 9, a positive voltage application closed circuit C14 is formed by the connection between capacitor 11a and semiconductor switch 2. In the positive voltage application closed circuit C14, the charge stored in capacitor 11a returns to capacitor 11a via semiconductor switch 2 through path W14. As the positive charge of capacitor 11a is supplied to the gate terminal 2c of semiconductor switch 2, semiconductor switch 2 transitions from the off state to the on state. In the second operating mode, a negative voltage charging closed circuit C15 is formed by the connection between capacitor 12a and capacitor 16a. In the negative voltage charging closed circuit C15, the charge stored in capacitor 12a flows through path W15, returning to capacitor 12a via semiconductor switch 2 and capacitor 16a. As a result, capacitor 16a is charged.

[0102] Next, with reference to Figures 10 and 11, the operation of the semiconductor switch drive unit 6c, which switches the semiconductor switch 3 on or off, will be described.

[0103] <First operating mode> In the first operating mode, the connection switching unit 13c of the semiconductor switch drive unit 6c enters a first connection state (an example of a "third connection state"), and as shown in Figure 10, a positive voltage application closed circuit C34 (an example of another "positive voltage application closed circuit") is formed by the connection between the capacitor 11c and the semiconductor switch 3. In the positive voltage application closed circuit C34, the charge that was stored in the capacitor 11c returns to the capacitor 11c via the semiconductor switch 3 through a path W34. The positive charge of the capacitor 11c is supplied to the gate terminal 2c of the semiconductor switch 3, causing the semiconductor switch 3 to turn on. In the first operating mode, a negative voltage charging closed circuit C35 is formed by the connection between the capacitor 11c and the capacitor 16c. In the negative voltage charging closed circuit C35, the charge that was stored in the capacitor 11c and the charge of the drive power supply 5 flow through a path W35 that returns to the drive power supply 5 via the capacitor 16c. As a result, the capacitor 16c is charged.

[0104] <Second operating mode> In the second operating mode, the connection switching section 13c of the semiconductor switch drive unit 6c enters a second connection state (an example of a "fourth connection state"), and as shown in Figure 11, a negative voltage application closed circuit C33 (an example of another "negative voltage application closed circuit") is formed by the connection between capacitor 16c and semiconductor switch 3. In the negative voltage application closed circuit C33, the charge stored in capacitor 16c returns to capacitor 16c via the semiconductor switch 3 through a path W33. The negative charge of capacitor 16c is supplied to the gate terminal 2c of semiconductor switch 3, causing semiconductor switch 3 to turn off. In the second operating mode, a positive voltage charging closed circuit C31 is formed by the connection between capacitor 11c and drive power supply 5. In the positive voltage charging closed circuit C31, current from drive power supply 5 flows through a path W31 that returns to drive power supply 5 via capacitors 11c and 16c. This current charges capacitor 11c.

[0105] [Effects and Effects] Next, the effects of the semiconductor switch drive circuit 6B and power converter 1B according to this embodiment will be explained. The semiconductor switch drive circuit 6B according to this embodiment includes a semiconductor switch drive unit 6a similar to that of the first embodiment, and therefore the same effects as the first embodiment can be obtained. Furthermore, the semiconductor switch drive circuit 6B according to this embodiment includes a semiconductor switch drive unit 6c instead of a semiconductor switch drive unit 6b. In the semiconductor switch drive unit 6a that constitutes the upper arm, the charge state of the capacitor 11a switches according to whether the semiconductor switch 2 is on or off, so the voltage of the capacitor 11a tends to fluctuate. On the other hand, in the semiconductor switch drive unit 6c that constitutes the lower arm, the capacitor 11c can be kept in a constantly charged state, making it easier to maintain a constant voltage of the capacitor 11c. Therefore, in the lower arm, a simplified circuit configuration is adopted in which a configuration corresponding to the capacitor 12a cannot be provided, thereby reducing the number of components constituting the semiconductor switch drive unit 6c.

[0106] This disclosure is not limited to the embodiments and modifications described above, and various other modifications are possible. For example, the embodiments and modifications described above may be combined with each other depending on the required purpose and effect. In the first embodiment described above, the case in which the semiconductor switch drive unit 6a and the semiconductor switch drive unit 6b are provided with movement restricting units 50a and 50b, respectively, was described. However, the semiconductor switch drive unit 6a may be provided with a movement restricting unit 50a, and the semiconductor switch drive unit 6b may not be provided with a movement restricting unit 50b. The circuit configuration of the movement restricting unit 50a is not limited to the example described above, and other circuit configurations are possible as long as they can restrict the movement of charge from the path W14 of the positive voltage application closed circuit C14 to other paths.

[0107] The gist of this disclosure is as follows: [1] Power supply and A semiconductor switch drive unit is electrically connected to the aforementioned drive power supply and drives the semiconductor switch using power from the aforementioned drive power supply, Equipped with, The semiconductor switch drive unit is A connection switching unit is electrically connected between the drive power supply and the semiconductor switch, and switches the connection state of the semiconductor switch. A first capacitor is electrically connected between the drive power supply and the connection switching unit, and generates a positive voltage to turn on the semiconductor switch by charging the power from the drive power supply. A second capacitor is electrically connected in parallel with the first capacitor to the drive power supply and charges the power from the drive power supply, A third capacitor is electrically connected between the second capacitor and the connection switching unit, and generates a negative voltage to turn off the semiconductor switch by charging the power discharged from the second capacitor in a charged state. It has, The aforementioned connection switching unit is A first connection state in which a positive voltage application closed circuit is formed by the electrical connection between the positive terminal of the first capacitor and the control terminal of the semiconductor switch, thereby applying the positive voltage to the control terminal of the semiconductor switch, The system alternately switches between a second connection state, in which an electrical connection is made between the negative terminal of the third capacitor and the control terminal of the semiconductor switch to form a negative voltage application closed circuit that applies the negative voltage to the control terminal of the semiconductor switch, and a second connection state, in which the negative voltage is applied to the control terminal of the semiconductor switch. A semiconductor switch drive circuit is provided between the first capacitor and the semiconductor switch, wherein a movement restricting unit is provided to restrict the movement of charge from the path through the positive voltage application closed circuit to another path that passes through the positive terminal of the first capacitor but does not pass through the control terminal of the semiconductor switch. [2] The movement restriction unit is, The first connection point between the positive terminal of the first capacitor and the control terminal of the semiconductor switch, The second connection point between the positive terminal of the second capacitor and the input terminal of the semiconductor switch, A third connection point is positioned between the first connection point and the positive terminal of the drive power supply and is electrically connected to the positive terminal of the drive power supply, A first wiring that connects the first connection point and the third connection point, A second wiring that connects the second connection point and the third connection point, A semiconductor switch drive circuit according to [1], having the following features. [3] The movement restriction unit is, In the first wiring, a first diode is connected with the forward direction being from the third connection point toward the first connection point, In the second wiring, a second diode is connected with the direction from the third connection point toward the second connection point as the forward direction, The semiconductor switch driving circuit described in [2] further comprises the following: [4] The movement restriction unit is, In the first wiring, a first resistor element is connected in series with the first diode, In the second wiring, a second resistive element is connected in series with the second diode and has a higher resistance value than the first resistive element, The semiconductor switch driving circuit described in [3] further comprises the following: [5] The positive terminal of the first capacitor is electrically connected to the positive terminal of the drive power supply and the control terminal of the semiconductor switch. The positive terminal of the second capacitor is electrically connected to the positive terminal of the drive power supply. The negative terminal of the third capacitor is electrically connected to the negative terminal of the second capacitor. The positive terminal of the third capacitor is electrically connected to the control terminal of the semiconductor switch, as described in any of [1] to [4], for the semiconductor switch driving circuit. [6] comprising a first semiconductor switch drive unit and a second semiconductor switch drive unit, which are semiconductor switch drive units. The first semiconductor switch drive unit and the second semiconductor switch drive unit drive the first semiconductor switch and the second semiconductor switch, respectively. The first semiconductor switch constitutes the upper arm in the semiconductor switch drive circuit. The semiconductor switch drive circuit according to any one of [1] to [5], wherein the second semiconductor switch constitutes the lower arm in the semiconductor switch drive circuit and is electrically connected in series with the first semiconductor switch. [7] The movement restricting units of the first semiconductor switch drive unit and the second semiconductor switch drive unit are as follows: The first connection point between the positive terminal of the first capacitor and the control terminal of the semiconductor switch, The second connection point between the positive terminal of the second capacitor and the input terminal of the semiconductor switch, A third connection point is positioned between the first connection point and the positive terminal of the drive power supply and is electrically connected to the positive terminal of the drive power supply, A first wiring that connects the first connection point and the third connection point, A second wiring that connects the second connection point and the third connection point, It has, Of the first semiconductor switch drive unit and the second semiconductor switch drive unit, only the movement restricting unit of the second semiconductor switch drive unit is In the first wiring, a first diode is connected with the forward direction being from the third connection point toward the first connection point, In the second wiring, a second diode is connected with the direction from the third connection point toward the second connection point as the forward direction, The semiconductor switch driving circuit described in [6] further comprises the following: [8] A first semiconductor switch drive unit which drives the first semiconductor switch which is a semiconductor switch, The system includes a second semiconductor switch drive unit which is electrically connected to the drive power supply and drives a second semiconductor switch electrically connected in series with the first semiconductor switch using the power from the drive power supply, The first semiconductor switch constitutes the upper arm in the semiconductor switch drive circuit. The second semiconductor switch constitutes the lower arm in the semiconductor switch drive circuit, and the second semiconductor switch drive unit is A separate connection switching unit is electrically connected between the drive power supply and the second semiconductor switch, and switches the connection state of the second semiconductor switch. A fourth capacitor is electrically connected between the drive power supply and the other connection switching unit, and generates a positive voltage to turn on the second semiconductor switch by charging the power from the drive power supply. A fifth capacitor is electrically connected in series between the fourth capacitor and the other connection switching unit, and generates a negative voltage to turn off the second semiconductor switch by charging the power discharged from the fourth capacitor in a charged state. It has, The aforementioned other connection switching unit is A first connection state in which a positive voltage application closed circuit is formed by the electrical connection between the positive terminal of the fourth capacitor and the control terminal of the second semiconductor switch, thereby applying the positive voltage to the control terminal of the second semiconductor switch, A semiconductor switch driving circuit according to any one of [1] to [5], which alternately switches between a second connection state in which a negative voltage application closed circuit is formed by an electrical connection between the negative terminal of the fifth capacitor and the control terminal of the second semiconductor switch, thereby applying the negative voltage to the control terminal of the second semiconductor switch. [9] A power converter that converts from a power source to a power source required by a load device, A semiconductor switch electrically connected between the power supply and the load device, A semiconductor switch driving circuit according to any one of [1] to [8], which is electrically connected to a semiconductor switch and drives the semiconductor switch, A power converter equipped with the following features. [Explanation of Symbols]

[0108] 1,1A,1B Power Converter 2. Semiconductor switches (an example of a "first semiconductor switch") 3. Semiconductor switch ("second semiconductor switch") 2a, 3a Drain terminals (an example of "input terminals") 2c, 3c gate terminals (an example of "control terminals") 4 Power supply 5 Power supply 5a Positive terminal 5b Negative terminal 6, 6A, 6B Semiconductor Switch Driver Circuit 6a, 6aa Semiconductor switch drive unit (an example of the "first semiconductor switch drive unit") 6b, 6bb, 6c Semiconductor switch drive unit (an example of the "second semiconductor switch drive unit") 11a Capacitor (an example of a "first capacitor") 11c capacitor (an example of a "fourth capacitor") 12a Capacitor (an example of a "second capacitor") 13a, 13b Connection switching section 13c Connection switching section (an example of "another connection switching section") 16a Capacitor (an example of a "third capacitor") 16c capacitor (an example of a "fifth capacitor") 21a Diode (an example of a "first diode") 22a diode (an example of a "second diode") 31a Resistor element (an example of a "first resistor element") 32a Resistor element (an example of a "second resistor element") 50a, 50b Movement Restriction Section 111a,111c,112a,116a,116c Positive terminal 211a,211c,212a,216a,216c Negative terminal C13 Negative voltage applied closed circuit C14 Positive voltage applied closed circuit C33 Negative voltage applied closed circuit (an example of "another negative voltage applied closed circuit") C34 Positive voltage applied closed circuit (an example of "another positive voltage applied closed circuit") L2a wiring (an example of "first wiring") L5a Wiring (An example of "Second Wiring") M load device P1a Connection point (an example of a "third connection point") P2a connection point (an example of a "first connection point") P3a Connection point (an example of a "second connection point") W14 Route

Claims

1. Power supply and A semiconductor switch drive unit, electrically connected to the aforementioned drive power supply and using power from the drive power supply to drive a semiconductor switch, comprises a first semiconductor switch drive unit and a second semiconductor switch drive unit. The first semiconductor switch drive unit and the second semiconductor switch drive unit drive the first semiconductor switch and the second semiconductor switch, respectively. The first semiconductor switch constitutes the upper arm in the semiconductor switch drive circuit. The second semiconductor switch constitutes the lower arm in the semiconductor switch drive circuit and is electrically connected in series with the first semiconductor switch. Each of the first semiconductor switch drive unit and the second semiconductor switch drive unit is: A connection switching unit is electrically connected between the drive power supply and the semiconductor switch, and switches the connection state of the semiconductor switch. A first capacitor is electrically connected between the drive power supply and the connection switching unit, and generates a positive voltage to turn on the semiconductor switch by charging the power from the drive power supply. A second capacitor is electrically connected in parallel with the first capacitor to the drive power supply and charges the power from the drive power supply, The device comprises a third capacitor electrically connected between the second capacitor and the connection switching unit, which generates a negative voltage to turn off the semiconductor switch by charging the power discharged from the second capacitor in a charged state, The aforementioned connection switching unit is A first connection state in which a positive voltage application closed circuit is formed by the electrical connection between the positive terminal of the first capacitor and the control terminal of the semiconductor switch, thereby applying the positive voltage to the control terminal of the semiconductor switch, The system alternately switches between a second connection state, in which an electrical connection is made between the negative terminal of the third capacitor and the control terminal of the semiconductor switch to form a negative voltage application closed circuit that applies the negative voltage to the control terminal of the semiconductor switch, and a second connection state, in which the negative voltage is applied to the control terminal of the semiconductor switch. In each of the first semiconductor switch drive unit and the second semiconductor switch drive unit, a movement restricting unit is provided between the first capacitor and the semiconductor switch to restrict the movement of charge of the first capacitor from the path through the positive voltage application closed circuit to another path that passes through the positive terminal of the first capacitor but does not pass through the control terminal of the semiconductor switch. The movement restricting unit of the first semiconductor switch drive unit has a diode that prevents reverse current flow from the drive power supply to the first capacitor. The movement restricting unit of the second semiconductor switch drive unit is a semiconductor switch drive circuit that does not have the diode.

2. The movement restricting unit of the first semiconductor switch drive unit is The first connection point between the positive terminal of the first capacitor and the control terminal of the semiconductor switch, The second connection point between the positive terminal of the second capacitor and the input terminal of the semiconductor switch, A third connection point is positioned between the first connection point and the positive terminal of the drive power supply, and is electrically connected to the positive terminal of the drive power supply, A first wiring that connects the first connection point and the third connection point, A second wiring that connects the second connection point and the third connection point, A semiconductor switch driving circuit according to claim 1, having the following features.

3. The movement restricting unit of the first semiconductor switch drive unit is In the first wiring, a first diode is connected with the direction from the third connection point toward the first connection point being the forward direction, In the second wiring, a second diode is connected with the direction from the third connection point toward the second connection point as the forward direction, The semiconductor switch driving circuit according to claim 2, further comprising the above.

4. The movement restricting unit of the first semiconductor switch drive unit is In the first wiring, a first resistor element is connected in series with the first diode, In the second wiring, a second resistive element is connected in series with the second diode and has a higher resistance value than the first resistive element, The semiconductor switch driving circuit according to claim 3, further comprising the above.

5. The positive terminal of the first capacitor is electrically connected to the positive terminal of the drive power supply and the control terminal of the semiconductor switch. The positive terminal of the second capacitor is electrically connected to the positive terminal of the drive power supply. The negative terminal of the third capacitor is electrically connected to the negative terminal of the second capacitor. The semiconductor switch driving circuit according to claim 1, wherein the positive terminal of the third capacitor is electrically connected to the control terminal of the semiconductor switch.

6. A power supply and A first semiconductor switch drive unit is electrically connected to the aforementioned drive power supply and drives the first semiconductor switch using power from the aforementioned drive power supply, A second semiconductor switch drive unit is electrically connected to the drive power supply and drives a second semiconductor switch electrically connected in series with the first semiconductor switch using the power from the drive power supply. Equipped with, The first semiconductor switch constitutes the upper arm in the semiconductor switch drive circuit. The second semiconductor switch constitutes the lower arm in the semiconductor switch drive circuit and is electrically connected in series with the first semiconductor switch. The first semiconductor switch drive unit is A connection switching unit is electrically connected between the drive power supply and the first semiconductor switch, and switches the connection state of the first semiconductor switch. A first capacitor is electrically connected between the drive power supply and the connection switching unit, and generates a positive voltage to turn on the first semiconductor switch by charging the power from the drive power supply. A second capacitor is electrically connected in parallel with the first capacitor to the drive power supply and charges the power from the drive power supply, A third capacitor is electrically connected between the second capacitor and the connection switching unit, and generates a negative voltage to turn off the first semiconductor switch by charging the power discharged from the second capacitor in a charged state. It has, The aforementioned connection switching unit is A first connection state in which a positive voltage application closed circuit is formed by the electrical connection between the positive terminal of the first capacitor and the control terminal of the first semiconductor switch, thereby applying the positive voltage to the control terminal of the first semiconductor switch, The system alternately switches between a second connection state, in which an electrical connection is made between the negative terminal of the third capacitor and the control terminal of the first semiconductor switch to form a negative voltage application closed circuit that applies the negative voltage to the control terminal of the first semiconductor switch, and a second connection state, in which the negative voltage is applied to the control terminal of the first semiconductor switch. Between the first capacitor and the first semiconductor switch, there is a movement restricting unit that restricts the movement of charge from the path passing through the positive voltage application closed circuit to another path that passes through the positive terminal of the first capacitor but does not pass through the control terminal of the first semiconductor switch. The second semiconductor switch drive unit is, A separate connection switching unit is electrically connected between the drive power supply and the second semiconductor switch, and switches the connection state of the second semiconductor switch. A fourth capacitor is electrically connected between the drive power supply and the other connection switching unit, and generates a positive voltage to turn on the second semiconductor switch by charging the power from the drive power supply. A fifth capacitor is electrically connected in series between the fourth capacitor and the other connection switching unit, and generates a negative voltage to turn off the second semiconductor switch by charging the power discharged from the fourth capacitor in a charged state. It has, The aforementioned other connection switching unit is A third connection state in which the positive terminal of the fourth capacitor and the control terminal of the second semiconductor switch are electrically connected to form another positive voltage application closed circuit that applies the positive voltage to the control terminal of the second semiconductor switch, The system alternately switches between a fourth connection state, in which an electrical connection is made between the negative terminal of the fifth capacitor and the control terminal of the second semiconductor switch to form another negative voltage application closed circuit that applies the negative voltage to the control terminal of the second semiconductor switch, and a fourth connection state, in which the negative voltage is applied to the control terminal of the second semiconductor switch. The movement restricting unit of the first semiconductor switch drive unit has a diode that prevents reverse current flow from the drive power supply to the first capacitor. The movement restricting unit of the second semiconductor switch drive unit is a semiconductor switch drive circuit that does not have a diode to prevent reverse current flow from the drive power supply to the fourth capacitor.

7. A power converter that converts the form of power provided by a power source to the form of power required by a load device, The first semiconductor switch and the second semiconductor switch are electrically connected between the power supply and the load device, A semiconductor switch driving circuit according to any one of claims 1 to 6, which is electrically connected to the first semiconductor switch and the second semiconductor switch and drives the first semiconductor switch and the second semiconductor switch, A power converter equipped with the following features.

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