Semiconductor switch drive circuit and power conversion device
The semiconductor switch driving circuit addresses malfunctions by adjusting gate voltage through capacitive charging control, maintaining stability despite component variations, ensuring reliable switch operation.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- IHI CORP
- Filing Date
- 2025-09-03
- Publication Date
- 2026-07-02
Smart Images
Figure JP2025031170_02072026_PF_FP_ABST
Abstract
Description
Semiconductor Switch Driving Circuit and Power Conversion Device
[0001] This disclosure describes a semiconductor switch driving circuit and a power conversion device.
[0002] An inverter that supplies power to a motor includes a power conversion circuit composed of a plurality of semiconductor switches. These semiconductor switches are mainly transistors such as MOSFETs, and their operations are controlled by the gate voltage applied to the gates. Patent Documents 1 to 3 disclose technologies related to semiconductor switch driving circuits for the gate voltage that controls semiconductor switches.
[0003] Japanese Patent Application Laid-Open No. 2019-75887, Japanese Patent Application Laid-Open No. 11-146640, Japanese Patent Application Laid-Open No. 2009-182743
[0004] A semiconductor switch driving circuit is composed of a plurality of electrical components such as resistors, capacitors, and diodes. The characteristics of these electrical components have a certain degree of variation. The characteristics of electrical components may also change due to external factors such as temperature. Due to the variation and change of the characteristics of the electrical components that make up the semiconductor switch driving circuit, the gate voltage applied by the semiconductor switch driving circuit to the semiconductor switch may also change. The change in the gate voltage is one of the factors that cause the semiconductor switch to malfunction.
[0005] This disclosure describes a semiconductor switch driving circuit that can generate a desired gate voltage while tolerating variations and changes in the characteristics of the electrical components that make up the semiconductor switch driving circuit, and a power conversion device equipped with the semiconductor switch driving circuit.
[0006] A semiconductor switch drive circuit in one embodiment of the present disclosure includes 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 includes a connection switching unit electrically connected between the drive power supply and the semiconductor switch and switching the 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, 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, a switch element that permits or prohibits charging power from the drive power supply to the second capacitor, and a switch control unit that switches the switch element between a charge-permitted state that permits charging power from the drive power supply to the second capacitor and a charge-prohibited state that prohibits charging power from the drive power supply to the second capacitor.
[0007] The semiconductor switch drive circuit includes a switch element and a switch control unit for switching this switch element. This switch element has the function of allowing or prohibiting the charging of power from the drive power supply to the second capacitor. This makes it possible to connect or disconnect the drive power supply to the second capacitor, which temporarily stores the charge that will be stored in the third capacitor for generating a negative voltage. Therefore, it becomes possible to increase or decrease the amount of charge stored in the second capacitor in accordance with the control signal of the switch control unit. As a result, even if there are variations or changes in the electrical characteristics of the components constituting the semiconductor switch drive circuit, it becomes possible to apply the gate voltage necessary to switch the semiconductor switch to the desired operation to the semiconductor switch by increasing or decreasing the amount of charge stored in the second capacitor.
[0008] The switch control unit in the semiconductor switch drive circuit described above may use the negative voltage generated by the third capacitor to switch between a charge-enabled state and a charge-disabled state. With this configuration, the charge-enabled state and the charge-disabled state can be switched between each other in response to changes in the negative voltage generated by the third capacitor.
[0009] In the semiconductor switch drive circuit described above, the switch control unit may output a charge enable signal to allow the switch element to charge the second capacitor from the drive power supply when the negative voltage is higher than the threshold voltage, and a charge disable signal to prohibit the switch element from charging the second capacitor from the drive power supply when the negative voltage is lower than the threshold voltage. With this configuration, when the negative voltage is higher than the threshold voltage, it becomes possible to bring the negative voltage closer to a desired value. Furthermore, even when the negative voltage is lower than the threshold voltage, it becomes possible to bring the negative voltage closer to a desired value.
[0010] In the semiconductor switch drive circuit described above, the switch control unit may generate a threshold voltage based on the voltage output by the drive power supply. With this configuration, the threshold voltage can be obtained with a simple configuration.
[0011] The switch control unit in the semiconductor switch drive circuit described above includes a comparator, which accepts a voltage based on a negative voltage and a voltage based on a threshold voltage, compares the voltage based on the negative voltage and the voltage based on the threshold voltage, and may provide either a charge-enable signal or a charge-prohibition signal to the switch element based on the result of the comparison. This configuration makes it possible to select a charge-enable signal or a charge-prohibition signal based on the negative voltage and the threshold voltage.
[0012] The switch control unit in the semiconductor switch drive circuit described above may include a resistive voltage divider circuit that generates a threshold voltage based on the voltage output by the drive power supply. With this configuration, the desired threshold voltage can be obtained with a simple configuration.
[0013] In the semiconductor switch drive circuit described above, the switch element may be provided on a closed circuit where the drive power supply is connected to the second capacitor and charges the second capacitor. With this configuration, the switch element in the off state can prevent charging of the second capacitor from the drive power supply. The switch element in the on state can allow charging of the second capacitor from the drive power supply.
[0014] In the semiconductor switch drive circuit described above, the switch element may be placed between the second capacitor and the reference potential. Alternatively, the switch element may be placed between the drive power supply and the second capacitor. With these configurations, the switch element in the off state can prevent charging from the drive power supply to the second capacitor. The switch element in the on state can allow charging from the drive power supply to the second capacitor.
[0015] Another embodiment of the present disclosure is a power converter that converts a power source into a power source required by a load device. The power converter comprises a semiconductor switch electrically connected between the power source and the load device, and a semiconductor switch drive circuit electrically connected to the semiconductor switch and driving the semiconductor switch. The switch drive circuit comprises a drive power source and a semiconductor switch drive unit electrically connected to the drive power source and driving the semiconductor switch using power from the drive power source. The semiconductor switch drive unit includes: a connection switching unit electrically connected between a drive power supply and a semiconductor switch to switch the state of the semiconductor switch; a first capacitor electrically connected between the drive power supply and the connection switching unit to generate 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 to charge power from the drive power supply; a third capacitor electrically connected between the second capacitor and the connection switching unit to generate a negative voltage to turn off the semiconductor switch by charging power discharged from the second capacitor in a charged state; a switch element that permits or prohibits charging power from the drive power supply to the second capacitor; and a switch control unit that switches the switch element between a charge-permitted state, which permits charging power from the drive power supply to the second capacitor, and a charge-prohibited state, which prohibits charging power from the drive power supply to the second capacitor.
[0016] This power converter is equipped with the semiconductor switch drive circuit described above. Therefore, even if there are variations or changes in the electrical characteristics of the components constituting the semiconductor switch drive circuit, it is possible to apply the desired gate voltage to the semiconductor switch. As a result, it is possible to suppress the occurrence of malfunctions of the semiconductor switch while tolerating variations and changes in electrical characteristics.
[0017] According to the semiconductor switch drive circuit and power conversion device equipped with the semiconductor switch drive circuit of this disclosure, a desired gate voltage can be generated while tolerating variations in the characteristics and changes in the characteristics of the electrical components constituting the semiconductor switch drive circuit.
[0018] Figure 1 is a circuit diagram showing a power converter according to an embodiment. Figure 2 is a circuit diagram illustrating the operation of the first semiconductor switch drive unit when the power converter shown in Figure 1 is in the first operating mode and charging of the capacitor for the negative voltage buffer is permitted. Figure 3 is a circuit diagram illustrating the operation of the first semiconductor switch drive unit when the power converter shown in Figure 1 is in the first operating mode and charging of the capacitor for the negative voltage buffer is prohibited. Figure 4 is a circuit diagram illustrating the operation of the first semiconductor switch drive unit when the power converter shown in Figure 1 is in the second operating mode. Figure 5 is a circuit diagram illustrating the operation of the second semiconductor switch drive unit when the power converter shown in Figure 1 is in the first operating mode and charging of the capacitor for the negative voltage buffer is permitted. Figure 6 is a circuit diagram illustrating the operation of the second semiconductor switch drive unit when the power converter shown in Figure 1 is in the first operating mode and charging of the capacitor for the negative voltage buffer is prohibited. Figure 7 is a circuit diagram illustrating the operation of the second semiconductor switch drive unit when the power converter shown in Figure 1 is in the second operating mode. Figures 8(a), 8(b), 8(c), and 8(d) are several sequence diagrams showing examples of operation of a semiconductor switch drive circuit. Figure 9 is a circuit diagram showing a modified power converter.
[0019] The semiconductor switch drive circuit and the power conversion device equipped with the semiconductor switch drive circuit described herein will be described in detail below with reference to the attached drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant descriptions are omitted.
[0020] Referring to Figure 1, a power converter 1 according to the first embodiment will be described. The power converter 1 converts the form of power received from the power source 4 into the form of power required by the load device M. The power source 4 is a power source for driving the load device M. The load device M may be, for example, a three-phase AC motor used as a power source to rotate an impeller. Therefore, the power converter 1 may be used as an electrical component of an electric compressor or electric blower. The power converter 1 according to the first embodiment is, for example, an inverter that converts DC power to AC power. The power converter 1 may also be a converter that converts AC power to DC power. The power converter may convert DC power of the first embodiment to DC power of the second embodiment.
[0021] As shown in Figure 1, the power conversion device 1 includes, for example, a semiconductor switch 2, a semiconductor switch 3, a semiconductor switch drive circuit 6, a power supply 4, and a control device 7.
[0022] The semiconductor switches 2 and 3 are connected in series with each other between the power supply 4 and GND (ground), forming a switch leg. Semiconductor switch 2 constitutes the so-called upper arm in the semiconductor switch drive circuit 6. Semiconductor switch 3 constitutes the so-called lower arm in the semiconductor switch drive circuit 6. Semiconductor switches 2 and 3 are each, for example, n-type MOSFETs (metal-oxide-semiconductor field-effect transistors). Semiconductor switches 2 and 3 may each be IGBTs (Insulated Gate Bipolar Transistors), or they may be switches made of wide-bandgap semiconductors such as SiC (silicon carbide) or GaN (gallium nitride).
[0023] The drain 2a (input terminal) of semiconductor switch 2 is connected to power supply 4. The source 2b (output terminal) of semiconductor switch 2 is connected to the drain 3a (input terminal) of semiconductor switch 3. The source 3b (output terminal) of semiconductor switch 3 is connected to GND. The gate 2c (control terminal) of semiconductor switch 2 and the gate 3c (control terminal) of semiconductor switch 3 are connected to semiconductor switch drive circuit 6.
[0024] In the following explanation, when an element is said to be “connected” to another element, unless otherwise specified, it means that the element is “electrically connected” to the other element. “Electrically connected” means that the two elements are connected in such a way that control signals can be transmitted and power can be supplied between them. Therefore, “electrically connected” includes both cases where the two elements are directly connected to each other by wiring and cases where the two elements are indirectly connected through other electrical components.
[0025] The semiconductor switch drive circuit 6 drives semiconductor switches 2 and 3. The control device 7 controls the semiconductor switch drive circuit 6 by providing control signals D1a and D1b to the semiconductor switch drive circuit 6. The control device 7 is composed of a computer including, 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.
[0026] The semiconductor switch drive circuit 6 includes, for example, a semiconductor switch drive unit 6a (first semiconductor switch drive circuit), a semiconductor switch drive unit 6b (second semiconductor switch drive circuit), and a drive power supply 5.
[0027] 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 semiconductor switch drive units 6a and 6b are a so-called bootstrap circuit. The drive power supply 5 is, for example, a DC power supply that outputs a DC voltage VDD with positive polarity. The drive power supply 5 is electrically connected to the semiconductor switch drive units 6a and 6b and provides the semiconductor switch drive units 6a and 6b with the voltage VDD. 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.
[0028] The control device 7 is electrically connected to the semiconductor switch drive unit 6a and outputs a control signal D1a to the semiconductor switch drive unit 6a to control the driving of the semiconductor switch drive unit 6a. Similarly, the control device 7 is electrically connected to the semiconductor switch drive unit 6b and outputs a control signal D1b to the semiconductor switch drive unit 6b to control the driving of the semiconductor switch drive unit 6b. The control signals D1a and D1b are, for example, PWM (Pulse Width Modulation) signals.
[0029] The control device 7 controls the switching of the semiconductor switch 2 to the on or off state by outputting a control signal D1a to the semiconductor switch drive unit 6a that instructs the semiconductor switch 2 to be turned on or off. When the semiconductor switch drive unit 6a receives a control signal D1a that instructs the semiconductor switch 2 to be turned on, it generates a positive voltage using the voltage VDD to sufficiently turn on the semiconductor switch 2 and applies the generated positive voltage to the gate 2c of the semiconductor switch 2. As a result, the semiconductor switch 2 becomes ON. When the semiconductor switch drive unit 6a receives a control signal D1a that instructs the semiconductor switch 2 to be turned off, it generates a negative voltage using the voltage VDD to sufficiently turn off the semiconductor switch 2 and applies the generated negative voltage to the gate 2c of the semiconductor switch 2. As a result, the semiconductor switch 2 becomes OFF.
[0030] The control device 7 controls the switching of the semiconductor switch 3 on or off by outputting a control signal D1b to the semiconductor switch drive unit 6b that instructs the semiconductor switch 3 to be turned on or off. The operation of the semiconductor switch drive unit 6b upon receiving the control signal D1b is the same as the operation of the semiconductor switch drive unit 6a upon receiving the control signal D1a, so a detailed explanation is omitted.
[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 (first capacitor), a capacitor 12a (second capacitor), a capacitor 16a (third capacitor), a diode 21a, a diode 10a, a diode 14a, a diode 15a, and a resistive element 34a.
[0033] Capacitor 11a is connected between the drive power supply 5 and the connection switching unit 13a. Capacitor 11a is a positive power supply capacitor that generates a positive voltage. The positive terminal 111a (one end) of capacitor 11a is connected to the positive terminal 5a of the drive power supply 5 and the connection switching unit 13a. More specifically, the positive terminal 111a of capacitor 11a is connected to the positive terminal 5a of the drive power supply 5 via connection point P2a, wiring L2a and diode 21a. The positive terminal 111a of capacitor 11a is connected to the gate 2c of semiconductor switch 2 via connection point P2a, wiring L2a and wiring L3a and the connection switching unit 13a. The negative terminal 211a (the other end) of capacitor 11a is connected to the source 2b of semiconductor switch 2 via wiring L4a.
[0034] Capacitor 12a is a negative power buffer capacitor that temporarily charges power to generate a negative voltage. 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 end of capacitor 12a, positive electrode 112a, is connected to the positive electrode 5a of the drive power supply 5. More specifically, one end of capacitor 12a, positive electrode 112a, is connected to the positive electrode 5a of the drive power supply 5 via connection point P3a, wiring L6a, resistor 34a, wiring L2a, and diode 21a. One end of capacitor 12a, positive electrode 112a, is connected to the drain 2a of the semiconductor switch 2. More specifically, one end of capacitor 12a, positive electrode 112a, is connected to the drain 2a of the semiconductor switch 2 via connection point P3a, wiring L6a, and diode 10a. The negative terminal 212a (other end) of capacitor 12a is connected to the source 2b of semiconductor switch 2 via wiring L4a. More specifically, the negative terminal 212a (other end) of capacitor 12a is connected to the source 2b of semiconductor switch 2 via diode 15a, switch element 81a, connection point P7a, and wiring L4a. Furthermore, the negative terminal 212a (other end) of capacitor 12a is connected to the source 2b of semiconductor switch 2 via diode 14a, capacitor 16a, connection point P4a, and wiring L4a. In other words, the negative terminal 212a (other end) of capacitor 12a is connected to the source 2b of semiconductor switch 2 via a parallel circuit.
[0035] Capacitor 16a is a negative power supply capacitor that receives power from the charged capacitor 12a and generates 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 the negative terminal 212a of capacitor 12a via wiring L7a, connection point P5a, diode 14a, and 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 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 a reverse current prevention diode. Diode 21a is connected in wiring L2a with the direction from the drive power supply 5 to the 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. A current limiting resistor connected in series with diode 21a may also be added.
[0037] Diode 10a is connected in series between connection point P3a and drain 2a of semiconductor switch 2. Diode 10a is a reverse current prevention diode. Diode 10a is connected in the wiring L6a between connection point P3a and drain 2a of semiconductor switch 2 with the direction from connection point P3a to drain 2a being the forward direction. 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. The cathode of diode 10a is connected to the positive terminal 116a of capacitor 16a via semiconductor switch 2. A current limiting resistor connected in series with diode 10a may also be added.
[0038] Diode 14a is connected in series between connection point P5a and connection point P6a. Diode 14a is 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.
[0039] Diode 15a is positioned between connection point P6a and connection point P7a. More specifically, diode 15a is connected to connection point P7a via a switch element 81a. Diode 15a is connected with forward direction from connection point P6a to connection point P7a. Diode 15a is a diode for preventing reverse current flow to capacitor 16a. Capacitor 16a prevents current flow from connection point P7a to connection point P6a included in wiring L4a when in second operating mode S2.
[0040] One end of the resistor 34a is connected to the cathode of the reverse current blocking diode 21a, and the other end is connected to the anode of the reverse current blocking diode 10a.
[0041] The connection switching unit 13a includes transistors 131a and 132a connected in series with each other. For example, transistor 131a is an NPN bipolar transistor, and transistor 132a is a PNP bipolar transistor. Transistors 131a and 132a constitute a so-called push-pull circuit. The collector terminal of transistor 131a is connected to the positive terminal 111a of capacitor 11a. The emitter terminal of transistor 131a is connected to the emitter terminal of transistor 132a. The connection point between the emitter terminals of transistor 131a and transistor 132a is connected to the gate 2c of semiconductor switch 2. The collector terminal of transistor 132a is connected to the negative terminal 216a of capacitor 16a. The base terminals of transistor 131a and transistor 132a are connected to the control device 7 and receive a control signal D1a from the control device 7.
[0042] The connection switching unit 13a is connected between the drive power supply 5 and the semiconductor switch 2. When the connection switching unit 13a receives a control signal D1a that instructs the semiconductor switch 2 to turn on, it is controlled to a first connection state in which transistor 131a is turned on while transistor 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 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 4, which will be described later).
[0043] The positive voltage application closed circuit C14 is a closed circuit that passes through the path W14 in Figure 4. The positive voltage application closed circuit C14 is formed when the positive electrode 111a of the capacitor 11a is connected to the gate 2c of the semiconductor switch 2 via a transistor 131a that is in the ON state. The positive voltage application closed circuit C14 consists of a capacitor 11a, a transistor 131a, and a semiconductor switch 2. In the positive voltage application closed circuit C14, the charge stored in the capacitor 11a is supplied to the semiconductor switch 2 via the transistor 131a. As a result, the input capacitance of the semiconductor switch 2 begins to charge with the charge discharged from the capacitor 11a. Subsequently, when a certain amount of charge is stored in the input capacitance of the semiconductor switch 2, the semiconductor switch 2 turns ON.
[0044] The negative voltage charging closed circuit C15 is a closed circuit that passes through the path W15 in Figure 4. The negative voltage charging closed circuit C15 is formed when the positive electrode 112a of capacitor 12a is connected to the positive electrode 116a of capacitor 16a via a semiconductor switch 2 that is in the ON state. The negative voltage charging closed circuit C15 is composed of capacitor 12a, diode 10a, semiconductor switch 2, capacitor 16a, and diode 14a. In the negative voltage charging closed circuit C15, the charge stored in capacitor 12a is supplied to capacitor 16a via diode 10a and semiconductor switch 2. Capacitor 16a is charged by this charge from capacitor 12a. At this time, a positive charge is stored in the positive electrode 116a of capacitor 16a, and a negative charge is stored in the negative electrode 216a of capacitor 16a. As a result, a negative voltage is generated in capacitor 16a.
[0045] When the connection switching unit 13a receives a control signal instructing the turn-off of the semiconductor switch 2, the transistor 131a is turned off, while being controlled to a second connection state in which the transistor 132a is turned on. In the second connection state, a negative voltage application closed circuit C13 for applying the negative voltage of the capacitor 16a to the gate 2c of the semiconductor switch 2, a positive voltage charging closed circuit C11 for charging the positive voltage in the capacitor 11a, and a charging closed circuit C12 for temporarily charging the power for negative voltage generation in the capacitor 12a are formed (see FIG. 2 described later).
[0046] The negative voltage application closed circuit C13 is a closed circuit passing through the path W13 in FIG. 2. The negative voltage application closed circuit C13 is formed by connecting the negative electrode 216a of the capacitor 16a to the gate 2c of the semiconductor switch 2 via the turned-on transistor 132a. The negative voltage application closed circuit C13 is configured to include the capacitor 16a, the transistor 132a, and the semiconductor switch 2. In the negative voltage application closed circuit C13, the charge charged in the capacitor 16a is supplied to the semiconductor switch 2 via the transistor 132a. By supplying the negative charge charged in the capacitor 16a to the gate 2c of the semiconductor switch 2, a negative voltage is applied to the gate 2c of the semiconductor switch 2. As a result, the semiconductor switch 2 is turned off.
[0047] The positive voltage charging closed circuit C11 is a closed circuit passing through the path W11 in FIG. 2. The positive voltage charging closed circuit C11 is formed by connecting the negative electrode 211a of the capacitor 11a to the negative electrode 5b of the drive power source 5 via the turned-on semiconductor switch 3. The positive voltage charging closed circuit C11 is configured to include the drive power source 5, the diode 21a, the capacitor 11a, and the semiconductor switch 3. In the positive voltage charging closed circuit C11, the capacitor 11a is charged by the voltage VDD from the drive power source 5.
[0048] The charging closed circuit C12 is a closed circuit passing through the path W12 in FIG. 2. The charging closed circuit C12 is formed by connecting the negative electrode 212a of the capacitor 12a to the negative electrode 5b of the drive power source 5 through the semiconductor switch 3 in an on state. The charging closed circuit C12 is configured to include the drive power source 5, the capacitor 12a, and the semiconductor switch 3. In the charging closed circuit C12, the capacitor 12a is charged by the voltage VDD from the drive power source 5.
[0049] As described above, according to the control signal D1a, the connection switching unit 13a alternately switches between a first connection state in which the positive voltage application closed circuit C14 and the negative voltage charging closed circuit C15 are formed, and a second connection state in which the negative voltage application closed circuit C13, the positive voltage charging closed circuit C11, and the charging closed circuit C12 are formed. In the first connection state, a positive voltage for turning on the semiconductor switch 2 is applied to the gate 2c of the semiconductor switch 2 by the positive voltage application closed circuit C14. In the second connection state, a negative voltage for turning off the semiconductor switch 2 is applied to the gate 2c of the semiconductor switch 2 by the negative voltage application closed circuit C13. Therefore, by alternately switching the connection switching unit 13a between the first connection state and the second connection state, the on or off of the semiconductor switch 2 can be alternately switched.
[0050] [Semiconductor switch driving unit 6b] The semiconductor switch driving unit 6b has the same configuration as the semiconductor switch driving unit 6a. When the part excluding the trailing letter b of the reference numeral attached to the configuration of the semiconductor switch driving unit 6b is the same as the part excluding the trailing letter a of the reference numeral attached to the configuration of the semiconductor switch driving unit 6a, it indicates that the configurations indicated by those reference numerals are the same as each other. Therefore, detailed descriptions of each configuration of the semiconductor switch driving unit 6b are omitted because they overlap with the descriptions of each configuration of the semiconductor switch driving unit 6a.
[0051] 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 the voltage balance, so it is possible to omit the diode 21b, which is a circuit element corresponding to diode 21a. Normally, the voltage VDD (e.g., 15V) of the drive power supply 5 for driving the 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.
[0052] 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 the power supply 4 via semiconductor switch 2, so 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 the drive power supply 5, so 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, so it is necessary to provide diode 21a to prevent such reverse flow.
[0053] 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 input voltage Vin of power supply 4 is not applied to capacitor 11a, etc. Furthermore, the negative electrode 5b of drive power supply 5 is always supplied with GND potential. In this case, in the lower arm, there is no situation in which current flows back from power supply 4 to drive power supply 5 due to the voltage difference between the input voltage Vin and the voltage VDD, so there is no need to provide diode 21b, which is a circuit element corresponding to diode 21a. However, the semiconductor switch drive unit 6b of the lower arm may also be equipped with diode 21b, which is a circuit element corresponding to diode 21a, similar to the semiconductor switch drive unit 6a of the upper arm. In this case, these circuit elements can function as a backup 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 diode 21a.
[0054] [Switch Circuit Section] The switch circuit section 8a is located on the wiring L8a that connects the diode 15a and the wiring L4a. Therefore, the switch circuit section 8a has the function of connecting the diode 15a to the wiring L4a and the function of disconnecting the diode 15a from the wiring L4a. This wiring L4a constitutes part of the closed circuit that charges the capacitor 12a, which will be described later. In other words, the switch circuit section 8a has the function of closing (connecting) the closed circuit that charges the capacitor 12a and the function of opening (disconnecting) the closed circuit that charges the capacitor 12a.
[0055] The switch circuit section 8a is composed of a switch element 81a. The drain 81a1 of the switch element 81a is connected to the diode 15a. The source 81a2 of the switch element 81a is connected to connection point P7a of the wiring L4a. The gate 81a3 of the switch element 81a is connected to the comparator 91a of the switch control circuit section 9a.
[0056] [Switch Control Circuit Section] The switch control circuit section 9a is located between the wirings L2a and L4a. The switch control circuit section 9a has the function of providing a control signal D2a to the switch circuit section 8a. The switch control circuit section 9a generates a control signal D2a to be provided to the switch circuit section 8a according to the voltage output by the capacitor 16a. This paragraph will describe the specific circuit configuration of the switch control circuit section 9a, and the specific operation of the switch control circuit section 9a will be described later.
[0057] The switch control circuit section 9a includes a comparator 91a, a resistor 92a, a resistor 93a, a Zener diode 94a, a resistor 95a, and a Zener diode 96a. In Figure 1, the Zener diode 94a is not within the area enclosed by the dashed line representing the switch control circuit section 9a, but it will be explained as a component of the switch control circuit section 9a.
[0058] The inverting input 91a1 of comparator 91a receives a constant value of the reference voltage. The non-inverting input 91a2 of comparator 91a receives a negative voltage-linked voltage, which changes in response to the negative voltage. The output 91a3 of comparator 91a is connected to the gate 81a3 of switch element 81a. In the HI side circuit, the connection point P7a becomes the reference voltage. Therefore, the reference voltage input 91a4 of comparator 91a is connected to wiring L4a.
[0059] Resistor elements 92a and 93a constitute a so-called resistive voltage divider circuit. Resistor element 92a is connected to wiring L2a. Resistor element 92a is connected to the non-inverting input 91a2 via connection point P8a. Resistor element 93a is connected to the cathode of Zener diode 94a via wiring L9a. Resistor element 93a is connected to the non-inverting input 91a2 via connection point P8a. This circuit element consisting of resistor elements 92a, 93a and Zener diode 94a takes the negative voltage generated at connection point P5a as input and outputs a negative voltage fluctuation voltage to the non-inverting input 91a2 in response to the fluctuation of the negative voltage.
[0060] The resistor 95a is connected to the wiring L2a. The resistor 95a is connected to the inverting input 91a1 via connection point P9a. The anode of the Zener diode 96a is connected to the wiring L4a. The cathode of the Zener diode 96a is connected to the inverting input 91a1 via connection point P9a and wiring L4a. This circuit element consisting of the resistor 95a and the Zener diode 96a takes the drive voltage generated by the drive power supply 5 as input and outputs a judgment reference voltage generated at the inverting input 91a1.
[0061] [Operation of the semiconductor switch driving circuit] Next, the operation of the semiconductor switch driving circuit 6 will be explained with reference to the circuit diagrams shown in Figures 2 to 6.
[0062] In this embodiment, the semiconductor switch drive circuit 6 switches between a first operating mode S1 and a second operating mode S2. First operating mode S1: The connection switching unit 13a of the semiconductor switch drive unit 6a is set to the second connection state, and the connection switching unit 13b of the semiconductor switch drive unit 6b is set to the first connection state. Second operating mode S2: The connection switching unit 13a of the semiconductor switch drive unit 6a is set to the first connection state, and the connection switching unit 13b of the semiconductor switch drive unit 6b is set to the second connection 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 S1 and the second operating mode S2 according to control signals D1a and D1b from the control device 7.
[0063] <First operating mode of semiconductor switch drive unit 6a> Figure 2 shows several closed circuits formed when the first operating mode S1 is in operation. In Figure 2, several closed circuits are shown by thick solid lines.
[0064] In the first operating mode, the connection switching unit 13a enters the second connection state, so that a negative voltage application closed circuit C13 is formed as shown in Figure 2. In the negative voltage application closed circuit C13, the charge stored in the negative voltage generating capacitor 16a passes through a path W13 that includes the semiconductor switch 2, transistor 132a, and capacitor 16a. The negative voltage from capacitor 16a is supplied to the semiconductor switch 2, causing the semiconductor switch 2 to turn off.
[0065] In the first operating mode S1, a positive voltage charging closed circuit C11 is formed by connecting the positive voltage generating capacitor 11a to the drive power supply 5. In the positive voltage charging closed circuit C11, the current from the drive power supply 5 flows through a path W11 that returns to the drive power supply 5 via the positive voltage generating capacitor 11a and the semiconductor switch 3. This current charges the positive voltage generating capacitor 11a. Furthermore, in the first operating mode S1, a charging closed circuit C12 is formed by connecting the negative voltage buffer capacitor 12a to the drive power supply 5. In the charging closed circuit C12, the current from the drive power supply 5 flows through a path W12 that returns to the drive power supply 5 via the negative voltage buffer capacitor 12a and the semiconductor switch 3. This current charges the negative voltage buffer capacitor 12a.
[0066] Here, in the first operating mode S11 (charging enabled state) shown in Figure 2, the path W12 is a closed circuit, which will be described as the charging closed circuit C121. The charging closed circuit C121 is formed when the negative voltage is higher than the threshold voltage. For example, this can be illustrated by the case where the negative voltage supplied to the semiconductor switch 2 by the negative voltage generating capacitor 16a is -4.9V, which is higher than the gate voltage of -5V required to turn off the semiconductor switch 2. From another perspective, the case where the negative voltage is lower than the threshold voltage is a state in which there is little charge stored in the negative voltage generating capacitor 16a. According to the circuit elements of resistors 92a and 93a and Zener diode 94a, for example, when the negative voltage generated at connection point P5a is -4.9V, the negative voltage linked voltage that is linked to the negative voltage generated at the non-inverting input 91a2 of the comparator 91a is +5.1V. Then, when comparing the constant judgment reference voltage (+5V) generated at the inverting input 91a1 of the comparator 91a with the negative voltage linked voltage (+5.1V), the result is positive, so the comparator 91a outputs HI (charge permission signal) as the control signal D2a.
[0067] The operation of the switch control circuit section 9a and the switch circuit section 8a essentially brings the negative voltage output by the negative voltage generating capacitor 16a closer to the gate voltage that should be applied to the semiconductor switch 2. Therefore, the threshold voltage can be treated as the gate voltage. In the specific circuit operation to realize this operation, the comparison performed by the comparator 91a does not need to be a comparison between the value of the negative voltage itself and the value of the gate voltage itself. The comparator 91a only needs to compare a certain reference voltage (judgment reference voltage) with a negative voltage-linked voltage that is linked to the negative voltage. Therefore, the value of the certain reference voltage (judgment reference voltage) may be the value of the gate voltage itself, but it does not necessarily have to be a value directly derived from the gate voltage.
[0068] In contrast, when the negative voltage is lower than the threshold voltage, the first operating mode S12 (charging disabled state) shown in Figure 3 is configured. In the first operating mode S12 shown in Figure 3, this is described as the charging open circuit C122. An example of when the negative voltage is lower than the threshold voltage is when the negative voltage supplied to the semiconductor switch 2 by the negative voltage generating capacitor 16a is -5.1V, which is lower than the gate voltage of -5V required to turn off the semiconductor switch 2. From another perspective, when the negative voltage is lower than the threshold voltage, it means that there is too much charge stored in the negative voltage generating capacitor 16a. Therefore, in order to reduce the amount of charge stored in the negative voltage buffer capacitor 12a, the switch circuit section 8a that constitutes the path W12 is turned OFF. For example, when the negative voltage generated at connection point P5a is -5.1V, the negative voltage linked voltage that is linked to the negative voltage generated at the non-inverting input 91a2 of the comparator 91a is +4.9V. Then, when comparing the constant judgment reference voltage (+5V) generated at the inverting input 91a1 of the comparator 91a with the negative voltage linked voltage (+4.9V), the result is negative, so the comparator 91a outputs LO (charge prohibition signal) as the control signal D2a.
[0069] <Second operating mode S2 of semiconductor switch drive unit 6a> In the second operating mode S2, the connection switching unit 13a enters the first connection state, and as shown in Figure 4, a positive voltage application closed circuit C14 is formed by the connection between the positive voltage generating capacitor 11a and the semiconductor switch 2. In the positive voltage application closed circuit C14, the charge that was stored in the positive voltage generating capacitor 11a passes through a path W14 that returns to the positive voltage generating capacitor 11a via the transistor 131a and the semiconductor switch 2. As the positive charge from the positive voltage generating capacitor 11a is supplied to the semiconductor switch 2, the semiconductor switch 2 transitions from the off state to the on state.
[0070] In the second operating mode S2, a negative voltage charging closed circuit C15 is formed by connecting the capacitor 12a for the negative voltage buffer and the capacitor 16a for generating the negative voltage. In the negative voltage charging closed circuit C15, the charge stored in the capacitor 12a for the negative voltage buffer flows through a path W15 that returns to the capacitor 12a for the negative voltage buffer via the semiconductor switch 2 and the capacitor 16a for generating the negative voltage. As a result, the capacitor 16a for generating the negative voltage is charged.
[0071] <First operating mode of semiconductor switch drive unit 6b> 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 5, 6, and 7.
[0072] As shown in Figure 5, in the first operating mode S1, a positive voltage application closed circuit C24 is formed. In the positive voltage application closed circuit C24, the charge stored in the positive voltage generating capacitor 11b passes through a path W24 that returns to the positive voltage generating capacitor 11b via the transistor 131b and the semiconductor switch 3. Furthermore, in the first operating mode S1, a first connection state is established (transistor 131b: ON state, transistor 132b: OFF state). As a result, the charge stored in the positive voltage generating capacitor 11b is supplied to the semiconductor switch 3 via the transistor 131b. Consequently, the semiconductor switch 3 is turned ON.
[0073] In the first operating mode S1, a negative voltage charging closed circuit C25 is formed. The negative voltage charging closed circuit C25 is composed of a path W25 that passes through a capacitor 12b for negative voltage buffering, a semiconductor switch 3, and a capacitor 16b for negative voltage generation. In the negative voltage charging closed circuit C25, the charge stored in the capacitor 12b for negative voltage buffering is supplied to the capacitor 16b for negative voltage generation via the semiconductor switch 3. As a result, the capacitor 16b for negative voltage generation is charged.
[0074] When in the first operating mode S1, the capacitor 11b for generating positive voltage in the semiconductor switch drive unit 6b is always connected to the drive power supply 5. The path W26 passing through the capacitor 11b for generating positive voltage and the drive power supply 5 constitutes a closed circuit C26.
[0075] In contrast, when in the first operating mode S1, the capacitor 12b for generating negative voltage in the semiconductor switch drive unit 6b can either form a closed circuit or not form a closed circuit depending on the negative voltage generated at the connection point P5b.
[0076] Figure 5 is a circuit diagram for the first operating mode S1, in which a closed circuit is formed (S11). In response to the negative voltage generated at connection point P5b, the comparator 91b provides a control signal D2b [HI] to the switch element 81b, which turns on the switch element 81b. As a result, a closed circuit C271 is formed. The closed circuit C271 is composed of a path W27 that passes through the drive power supply 5, the resistor 34b, the negative voltage buffer capacitor 12b, the diode 15b, and the switch element 81b. As a result, the negative voltage buffer capacitor 12b is charged.
[0077] Figure 6 is a circuit diagram for the first operating mode S1, where an open circuit C272 is configured (S12). In response to the negative voltage generated at connection point P5b, the comparator 91b provides a control signal D2b [LO] to the switch element 81b, which turns off the switch element 81b. As a result, the closed circuit C27 is interrupted at the switch element 81b. Consequently, the capacitor 12b for the negative voltage buffer is not charged.
[0078] <Second operating mode of semiconductor switch drive unit 6b> As shown in Figure 7, in the second operating mode S2, the connection switching unit 13b of the semiconductor switch drive unit 6b enters a second connection state (transistor 131b: off state, transistor 132b: on state). As a result, as shown in Figure 7, a negative voltage application closed circuit C23 is formed. The negative voltage application closed circuit C23 is composed of a capacitor 16b for generating negative voltage and a path W23 that passes through the semiconductor switch 3. With the negative voltage application closed circuit C23, the negative charge of the capacitor 16b for generating negative voltage is supplied to the semiconductor switch 3, thereby maintaining the state in which the semiconductor switch 3 is off.
[0079] Furthermore, in the second operating mode S2, a closed circuit C26 is formed for the capacitor 11b for generating a positive voltage. For the capacitor 12b for generating a negative voltage, a closed circuit C27 may be formed depending on the negative voltage generated at the connection point P5b, or a closed circuit C27 may not be formed.
[0080] [Operation Examples] Several sequence diagrams shown in Figure 8 illustrate the operation of the semiconductor switch drive circuit 6. Figure 8(a) shows the history of the negative voltage supplied to the semiconductor switch 2 by the negative voltage generating capacitor 16a. The dashed line extending horizontally across the page in Figure 8(a) represents the threshold voltage (-5V). Figure 8(b) shows the history of the load. Here, the load refers to transistors 131a and 132a. Figure 8(c) shows the history of the control signal D2a output by the comparator 91a. Figure 8(d) shows the history of the state of the switch element 81a.
[0081] For example, between time t0 and time t1, the negative voltage (see Figure 8(a)) is lower than the threshold voltage (-5V). In other words, it is too low a voltage to be applied to the semiconductor switch 2. To put it another way, there is an excess of charge stored in the capacitor 16a for generating the negative voltage. Therefore, between time t0 and time t1, the comparator 91a (see Figure 8(c)) outputs LO as the control signal D2a. The switch element 81a, upon receiving the control signal D2a (LO), turns OFF. In other words, the capacitor 12a for the negative voltage buffer is not charged.
[0082] For example, between time t1 and time t2, the negative voltage (see Figure 8(a)) is higher than the threshold voltage (-5V). In other words, it is too high a voltage to be applied to the semiconductor switch 2. To put it another way, there is insufficient charge stored in the capacitor 16a for generating the negative voltage. Therefore, between time t1 and time t2, the comparator 91a (see Figure 8(c)) outputs HI as the control signal D2a. The switch element 81a, upon receiving the control signal D2a (HI), turns ON. In other words, power is charged into the capacitor 12a for the negative voltage buffer.
[0083] Similar to the period from time t0 to time t1, during the time t2 to time t3 and from time t4 to time t5, when the negative voltage is lower than the threshold voltage (-5V), the comparator 91a (see Figure 8(c)) outputs LO as the control signal D2a. The switch element 81a is in the OFF state.
[0084] Similar to the period from time t1 to time t2, during the period from time t3 to time t4, when the negative voltage is higher than the threshold voltage (-5V), the comparator 91a (see Figure 8(c)) outputs HI as the control signal D2a. The switch element 81a is in the ON state.
[0085] <Effects> The power conversion device 1 comprises semiconductor switches 2 and 3 electrically connected between the power supply 4 and the load device M, and a semiconductor switch drive circuit 6 electrically connected to the semiconductor switches 2 and 3 and driving the semiconductor switches 2 and 3.
[0086] The semiconductor switch drive circuit 6 comprises a drive power supply 5, and semiconductor switch drive units 6a and 6b that are electrically connected to the drive power supply 5 and drive the semiconductor switches 2 and 3 using power from the drive power supply 5. The semiconductor switch drive units 6a and 6b include connection switching units 13a and 13b that are electrically connected between the drive power supply 5 and the semiconductor switches 2 and 3 and switch the state of the semiconductor switches 2 and 3, capacitors 11a and 11b that are electrically connected between the drive power supply 5 and the connection switching units 13a and 13b and generate a positive voltage to turn on the semiconductor switches 2 and 3 by charging power from the drive power supply 5, capacitors 12a and 12b that are electrically connected in parallel with the capacitors 11a and 11b to the drive power supply 5 and charge power from the drive power supply 5, and capacitors 12a and 12b and the connection switching units 13a and 13b The system includes capacitors 16a and 16b that are electrically connected between the two capacitors and generate a negative voltage to turn off the semiconductor switches 2 and 3 by charging the power discharged from the charged capacitors 12a and 12b; switch circuit sections 8a and 8b that allow or prohibit the charging of power from the drive power supply 5 to the capacitors 12a and 12b; and switch control circuit sections 9a and 9b that mutually switch the switch circuit sections 8a and 8b between a charge-allowed state that allows the charging of power from the drive power supply 5 to the capacitors 12a and 12b and a charge-prohibited state that prohibits the charging of power from the drive power supply 5 to the capacitors 12a and 12b.
[0087] The semiconductor switch drive circuit 6 includes switch circuit sections 8a and 8b and switch control circuit sections 9a and 9b for switching between the switch circuit sections 8a and 8b. The switch circuit sections 8a and 8b have the function of allowing or prohibiting the charging of power from the drive power supply 5 to the capacitors 12a and 12b. This makes it possible to connect or disconnect the drive power supply 5 to the capacitors 12a and 12b, which temporarily store the charge that will be accumulated in the capacitors 16a and 16b for generating a negative voltage. Therefore, it becomes possible to increase or decrease the amount of charge stored in the capacitors 12a and 12b according to the control signals D2a and D2b of the switch control circuit sections 9a and 9b. As a result, even if there are variations or changes in the electrical characteristics (e.g., capacitance of the capacitors, output voltage of the drive power supply) of the components constituting the semiconductor switch drive circuit 6, it becomes possible to apply the gate voltage necessary to switch the semiconductor switches 2 and 3 to the desired operation by increasing or decreasing the amount of charge stored in the capacitors 12a and 12b.
[0088] In other words, the semiconductor switch drive circuit 6 uses a negative voltage-based feedback circuit to suppress fluctuations in the negative voltage caused by component variations and fluctuations in the load of the gate drive circuit. In stabilizing this negative voltage, the semiconductor switch drive circuit 6 can tolerate variations in component characteristics. This means that when manufacturing the semiconductor switch drive circuit 6, it is not necessary to select components with uniform characteristics. As a result, manufacturing costs can be reduced, and the effort required for component management can be minimized.
[0089] One possible method for stabilizing negative voltages is to employ stabilization circuits using Zener diodes or series regulators. However, stabilization circuits using these components generate voltages even lower than the required voltage, which can lead to increased power loss. On the other hand, the semiconductor switch drive circuit 6 does not employ such methods and generates negative voltages using the power of the drive power supply 5 that it already has. Therefore, it can suppress an increase in power loss.
[0090] The switch control circuits 9a and 9b utilize the negative voltage generated by capacitors 16a and 16b to switch between a charging-enabled state and a charging-disabled state. With this configuration, the charging-enabled state and the charging-disabled state can be switched between each other in response to changes in the negative voltage generated by capacitors 16a and 16b.
[0091] The switch control circuits 9a and 9b output a charge permission signal to the switch circuits 8a and 8b to allow power charging from the drive power supply 5 to the capacitors 12a and 12b when the negative voltage is higher than the threshold voltage, and output a charge prohibition signal to the switch circuits 8a and 8b to prohibit power charging from the drive power supply 5 to the capacitors 12a and 12b when the negative voltage is lower than the threshold voltage. With this configuration, when the negative voltage is higher than the threshold voltage, it becomes possible to bring the negative voltage closer to the desired value. Furthermore, even when the negative voltage is lower than the threshold voltage, it becomes possible to bring the negative voltage closer to the desired value.
[0092] The switch control circuits 9a and 9b may generate a threshold voltage based on the voltage output by the drive power supply 5. With this configuration, a threshold voltage can be obtained with a simple configuration.
[0093] The switch control circuits 9a and 9b have comparators 91a and 91b. The comparators 91a and 91b accept a negative voltage and a threshold voltage, compare the negative voltage and the threshold voltage, and based on the result of the comparison, provide either a charge-allow signal or a charge-prohibition signal to the switch circuits 8a and 8b. This configuration makes it possible to select a charge-allow signal or a charge-prohibition signal based on the negative voltage and the threshold voltage.
[0094] The switch control circuits 9a and 9b include a resistive voltage divider circuit that generates a threshold voltage based on the voltage output by the drive power supply 5. With this configuration, the desired threshold voltage can be obtained with a simple configuration.
[0095] The switch circuits 8a and 8b are provided on a closed circuit where the drive power supply 5 is connected to the capacitors 12a and 12b and charges them. With this configuration, the switch circuits 8a and 8b in the off state can prevent the drive power supply 5 from charging the capacitors 12a and 12b. The switch circuits 8a and 8b in the on state can allow the drive power supply 5 to charge the capacitors 12a and 12b.
[0096] The switch circuits 8a and 8b are provided between the capacitors 12a and 12b and the reference potential. With this configuration, the switch circuits 8a and 8b in the off state can prevent charging of the capacitors 12a and 12b from the drive power supply 5. The switch circuits 8a and 8b in the on state can allow charging of the capacitors 12a and 12b from the drive power supply 5.
[0097] <Modifications> The present disclosure is not limited to the embodiments described above, and various modifications are possible without departing from the spirit of the claims.
[0098] In the embodiment, the switch circuit section 8a was arranged on the path W12 between the diode 15a and the wiring L4a. As shown in Figure 9, the semiconductor switch drive circuit 6S provided in the modified power converter 1A has semiconductor switch drive sections 6aa and 6bb. For example, the switch circuit section 8a of the semiconductor switch drive section 6aa may be arranged between the connection point P3a and the capacitor 12a. Similarly, the switch circuit section 8bb of the semiconductor switch drive section 6bb may be arranged between the connection point P3b and the capacitor 12b. Even with such modified semiconductor switch drive circuits 6S, the same effects as the semiconductor switch drive circuit 6 of the embodiment can be obtained.
[0099] <Note> This disclosure includes the following components.
[0100] This disclosure includes: [1] a drive power supply; a semiconductor switch drive unit electrically connected to the drive power supply and driving a semiconductor switch using power from the drive power supply, wherein the semiconductor switch drive unit comprises: a connection switching unit electrically connected between the drive power supply and the semiconductor switch and switching the 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 the power from the drive power supply; a second capacitor electrically connected in parallel with the first capacitor to the drive power supply and charging the power from the drive power supply; 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 the power discharged from the second capacitor in a charged state; and a switch element that permits or prohibits charging of power from the drive power supply to the second capacitor. The semiconductor switch drive circuit includes a switch control unit that switches the switch element between a charge-enabled state, which allows charging of power from the drive power supply to the second capacitor, and a charge-disabled state, which prohibits charging of power from the drive power supply to the second capacitor.
[0101] This disclosure includes [2] "the semiconductor switch driving circuit described in [1] above, wherein the switch control unit uses the negative voltage generated by the third capacitor to switch between the charging enabled state and the charging disabled state."
[0102] This disclosure includes [3] "the semiconductor switch drive circuit according to [1] or [2] above, wherein the switch control unit outputs a charge permission signal to allow the switch element to charge the second capacitor from the drive power supply when the negative voltage is higher than a threshold voltage, and outputs a charge prohibition signal to prohibit the switch element from charging the second capacitor from the drive power supply when the negative voltage is lower than a threshold voltage."
[0103] This disclosure includes [4] "the semiconductor switch drive circuit described in [3] above, wherein the switch control unit generates the threshold voltage based on the voltage output by the drive power supply."
[0104] The present disclosure is [5] "The semiconductor switch driving circuit according to [3] or [4] above, wherein the switch control unit has a comparator, the comparator accepts a voltage based on the negative voltage and a voltage based on the threshold voltage, compares the voltage based on the negative voltage and the voltage based on the threshold voltage, and provides either the charge permit signal or the charge prohibit signal to the switch element based on the result of the comparison."
[0105] This disclosure is [6] "The semiconductor switch driving circuit according to any one of [1] to [5] above, wherein the switch control unit includes a resistive voltage divider circuit that generates the threshold voltage based on the voltage output by the drive power supply."
[0106] This disclosure is [7] "a semiconductor switch drive circuit according to any one of [1] to [6] above, wherein the switch element is provided on a closed circuit in which the drive power supply is connected to the second capacitor and charges the second capacitor."
[0107] This disclosure is [8] "The switching element is provided between the second capacitor and a reference potential in the semiconductor switch driving circuit according to any one of [1] to [7] above."
[0108] This disclosure is [9] "The switch element is provided between the drive power supply and the second capacitor in the semiconductor switch drive circuit described in any one of [1] to [7] above."
[0109] This disclosure relates to
[10] a power conversion device that converts a power source to a power source required by a load device, comprising: a semiconductor switch electrically connected between the power source and the load device; and a semiconductor switch drive circuit electrically connected to the semiconductor switch and driving the semiconductor switch, wherein the switch drive circuit comprises: a drive power source; and a semiconductor switch drive unit electrically connected to the drive power source and driving the semiconductor switch using power from the drive power source, wherein the semiconductor switch drive unit comprises: a connection switching unit electrically connected between the drive power source and the semiconductor switch and switching the state of the semiconductor switch; a first capacitor electrically connected between the drive power source and the connection switching unit and generating a positive voltage to turn on the semiconductor switch by charging the power from the drive power source; a second capacitor electrically connected in parallel with the first capacitor to the drive power source and charging the power from the drive power source; 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 the power discharged from the second capacitor in a charged state. A power conversion device comprising: a switch element that permits or prohibits charging of power from the drive power supply to the second capacitor; and a switch control unit that switches the switch element between a charge-permitted state that permits charging of power from the drive power supply to the second capacitor and a charge-prohibited state that prohibits charging of power from the drive power supply to the second capacitor.
[0110] 1 Power converter 2,3 Semiconductor switch 4 Power supply 5 Drive power supply 6,6S Semiconductor switch drive circuit 6a,6b Semiconductor switch drive unit 7 Control device 8a,8b Switch circuit unit 9a,9b Switch control circuit unit 10a,10b Diode 11a,11b Capacitor (first capacitor) 12a,12b Capacitor (second capacitor) 13a,13b Connection switching unit 14a Diode 15a,15b Diode 16a,16b Capacitor (third capacitor) 21a,21b Diode 81a,81b Switch element 91a,91b Comparator 91a1 Inverting input 91a2 Non-inverting input 92a Resistor element 93a Resistor element 94a,96a Zener diode 95a Resistor element 131a, 131b, 132a, 132b Transistors C11 Positive voltage charging closed circuit C12 Charging closed circuit C13 Negative voltage applied closed circuit C14 Positive voltage applied closed circuit C15 Negative voltage charging closed circuit C23 Negative voltage applied closed circuit C24 Positive voltage applied closed circuit C25 Negative voltage charging closed circuit D1a, D1b, D2a, D2b Control signals M Load device S1 First operating mode S2 Second operating mode
Claims
1. A semiconductor switch drive circuit comprising: a drive power supply; a semiconductor switch drive unit electrically connected to the drive power supply and driving a semiconductor switch using power from the drive power supply, wherein the semiconductor switch drive unit comprises: a connection switching unit electrically connected between the drive power supply and the semiconductor switch and switching the 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 the power from the drive power supply; a second capacitor electrically connected in parallel with the first capacitor to the drive power supply and charging the power from the drive power supply; 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 the power discharged from the charged second capacitor; a switch element that permits or prohibits charging of power from the drive power supply to the second capacitor; and a switch control unit that mutually switches the switch element between a charge-permitted state that permits charging of power from the drive power supply to the second capacitor and a charge-prohibited state that prohibits charging of power from the drive power supply to the second capacitor.
2. The semiconductor switch driving circuit according to claim 1, wherein the switch control unit uses the negative voltage generated by the third capacitor to switch between the charging enabled state and the charging disabled state.
3. The semiconductor switch drive circuit according to claim 2, wherein the switch control unit outputs a charge permission signal to allow the switch element to charge the second capacitor from the drive power supply when the negative voltage is higher than a threshold voltage, and outputs a charge prohibition signal to prohibit the switch element from charging the second capacitor from the drive power supply when the negative voltage is lower than a threshold voltage.
4. The semiconductor switch drive circuit according to claim 3, wherein the switch control unit generates the threshold voltage based on the voltage output by the drive power supply.
5. The semiconductor switch driving circuit according to claim 3, wherein the switch control unit has a comparator, the comparator accepts a voltage based on the negative voltage and a voltage based on the threshold voltage, compares the voltage based on the negative voltage and the voltage based on the threshold voltage, and provides either the charge permit signal or the charge prohibit signal to the switch element based on the result of the comparison.
6. The semiconductor switch drive circuit according to claim 3, wherein the switch control unit includes a resistive voltage divider circuit that generates the threshold voltage based on the voltage output by the drive power supply.
7. The semiconductor switch drive circuit according to claim 1, wherein the switch element is provided on a closed circuit in which the drive power supply is connected to the second capacitor and charges the second capacitor.
8. The semiconductor switch driving circuit according to claim 1, wherein the switching element is provided between the second capacitor and the reference potential.
9. The semiconductor switch drive circuit according to claim 1, wherein the switch element is provided between the drive power supply and the second capacitor.
10. A power conversion device that converts the power provided by a power source to the power required by a load device, comprising: a semiconductor switch electrically connected between the power source and the load device; and a semiconductor switch drive circuit electrically connected to the semiconductor switch and driving the semiconductor switch, wherein the switch drive circuit comprises: a drive power source; and a semiconductor switch drive unit electrically connected to the drive power source and driving the semiconductor switch using power from the drive power source, wherein the semiconductor switch drive unit comprises: a connection switching unit electrically connected between the drive power source and the semiconductor switch and switching the state of the semiconductor switch; a first capacitor electrically connected between the drive power source and the connection switching unit and generating a positive voltage to turn on the semiconductor switch by charging the power from the drive power source; a second capacitor electrically connected in parallel with the first capacitor to the drive power source and charging the power from the drive power source; 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 the power discharged from the second capacitor in a charged state. A power conversion device comprising: a switch element for allowing or prohibiting the charging of power from the drive power supply to the second capacitor; and a switch control unit for switching the switch element between a charge-allowed state, which allows the charging of power from the drive power supply to the second capacitor, and a charge-prohibited state, which prohibits the charging of power from the drive power supply to the second capacitor.