Circuit for switchgear, switching system, and processing method for switchgear

Abstract

The present invention suppresses power loss of a switching device. This switching device circuit (20) is used in a switching device (10). The switching device (10) comprises a first path (11) and a second path (12). The first path (11) includes a first field effect transistor (Q1) and a first inductor (L1). The second path (12) includes a second field effect transistor (Q2) and a second inductor (L2). The first path (11) and the second path (12) are connected in parallel with respect to a power supply (Vdc). A first maximum current, which is the maximum current when the first field effect transistor (Q1) is conductive, is smaller than a second maximum current, which is the maximum current when the second field effect transistor (Q2) is conductive. The switching device circuit (20) is provided with a processing unit (26). The processing unit (26) executes a specific operation according to the voltage difference between a voltage (VL1) between two ends of the first inductor (L1) and the voltage between two ends of the second inductor (VL2).

Description

[Technical field]

[0001] The present disclosure relates to a circuit for a switchgear, a switching system, and a processing method for the switchgear, and more particularly to a circuit for a switchgear used in a switchgear including a field effect transistor, a switching system including the circuit for the switchgear, and a processing method used in the switchgear. [Background technology]

[0002] Patent Document 1 discloses a power semiconductor device that can prevent an erroneous determination that an overcurrent is flowing even when the main current is within a normal current value range.

[0003] The power semiconductor device disclosed in Patent Document 1 includes a gate resistor, a gate voltage determination unit, a sense current determination unit, and an overcurrent determination unit. The sense current determination unit has a sense resistor with one terminal connected to a sense terminal of a power device and the other terminal grounded. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2006-32393 A Summary of the Invention

[0005] In the power semiconductor device disclosed in Patent Document 1, power loss occurs in the sense resistor when the power device is in an on-state (conducting).

[0006] 2. Description of the Related Art In a switchgear circuit used for detecting an overcurrent in a switchgear, it is sometimes desirable to perform processing while suppressing power loss in the switchgear.

[0007] An object of the present disclosure is to provide a circuit for a switchgear, a switching system, and a processing method for a switchgear that are capable of suppressing power loss in the switchgear.

[0008] A switching device circuit according to an embodiment of the present disclosure is used in a switching device. The switching device includes a first path and a second path. The first path includes a first field effect transistor and a first inductor. The first field effect transistor has a gate and a source. The first inductor is connected to the source of the first field effect transistor. The second path includes a second field effect transistor and a second inductor. The second field effect transistor has a gate and a source. The second inductor is connected to the source of the second field effect transistor. The first path and the second path are connected in parallel to a power source. A first maximum current, which is a maximum current when the first field effect transistor is conductive, is smaller than a second maximum current, which is a maximum current when the second field effect transistor is conductive. The switching device circuit includes a processing unit that executes a specific operation according to a voltage difference between a voltage across the first inductor and a voltage across the second inductor.

[0009] A switching system according to another aspect of the present disclosure includes the above-described switching device circuit and a switching device.

[0010] A processing method according to another aspect of the present disclosure is used in a switching device. The switching device includes a first path and a second path. The first path includes a first field effect transistor and a first inductor. The first field effect transistor has a gate and a source. The first inductor is connected to the source of the first field effect transistor. The second path includes a second field effect transistor and a second inductor. The second field effect transistor has a gate and a source. The second inductor is connected to the source of the second field effect transistor. The first path and the second path are connected in parallel to a power source. A first maximum current, which is a maximum current when the first field effect transistor is conductive, is smaller than a second maximum current, which is a maximum current when the second field effect transistor is conductive. The processing method performs a specific operation according to a voltage difference between a voltage across the first inductor and a voltage across the second inductor.

[0011] The switchgear circuit, the switchgear system, and the switchgear processing method disclosed herein make it possible to suppress power loss in the switchgear. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a circuit diagram of a switching system including a switching device circuit according to a first embodiment. [Diagram 2] FIG. 2 is an explanatory diagram of the operation of a switchgear to which the above-mentioned switchgear circuit is applied. [Figure 3A] FIG. 3A is a diagram illustrating the normal operation of the switching system including the switching device circuit. [Figure 3B] FIG. 3B is an explanatory diagram of an operation at the time of starting up the switching system including the switching device circuit of the above embodiment. [Figure 4] FIG. 4 is a circuit diagram showing an example of a determination circuit in the switching device circuit of the above embodiment. [Diagram 5] FIG. 5 is a circuit diagram showing another example of the determination circuit in the switching device circuit of the above embodiment. [Figure 6] FIG. 6 is an explanatory diagram of the operation of a switching system including a switching device circuit according to a modified example of the first embodiment. [Figure 7] FIG. 7 is an explanatory diagram of the operation of a switching system including a switching device circuit according to a modified example of the first embodiment. [Figure 8] FIG. 8 is a circuit diagram of a switching system including a switching device circuit according to the second embodiment. [Figure 9] FIG. 9 is an explanatory diagram of the operation of the switching system including the switching device circuit of the above embodiment. [Figure 10] FIG. 10 is a circuit diagram of a switching system including a switching device circuit according to the third embodiment. [Figure 11] FIG. 11 is a circuit diagram of a switching system including a switching device circuit according to the fourth embodiment. [Figure 12] FIG. 12 is a gate voltage-gate current characteristic diagram of a JFET and a MOSFET. [Figure 13]FIG. 13 is a circuit diagram of a switching system including a switching device circuit according to the fifth embodiment. [Figure 14] FIG. 14 is a circuit diagram of a switching system including a switching device circuit according to the sixth embodiment. [Figure 15] FIG. 15 is a circuit diagram of a switching system including a switching device circuit according to the seventh embodiment. [Figure 16] FIG. 16 is an explanatory diagram of the operation of the switching system including the switching device circuit of the above embodiment. [Figure 17] FIG. 17 is a circuit diagram of a switching system including a switching device circuit according to the eighth embodiment. [Figure 18] FIG. 18 is a circuit diagram of a switching system including a switching device circuit according to the ninth embodiment. [Figure 19] FIG. 19 is an explanatory diagram of the operation of the switching system including the switching device circuit. [Figure 20] FIG. 20 is a circuit diagram of a main part of a switching system including a switching device circuit according to the tenth embodiment. [Figure 21] FIG. 21 is a circuit diagram of a switching system including a switching device circuit according to a modification of the tenth embodiment. [Figure 22] FIG. 22 is a circuit diagram of a switching system including a switching device circuit according to the eleventh embodiment. [Figure 23] FIG. 23 is a circuit diagram of a switching system including a switching device circuit according to the twelfth embodiment. [Figure 24] FIG. 24 is a circuit diagram of a switching system including a switching device circuit according to the thirteenth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] (Embodiment 1) Hereinafter, a switching device circuit 20 according to a first embodiment and a switching system 30 including the same will be described with reference to Figs. 1 to 5.

[0014] (1) Overview FIG. 1 shows a circuit diagram of a switching system 30 including a switchinggear circuit 20 according to the first embodiment of the present disclosure. The switchinggear circuit 20 is used in a switchinggear 10. In the switching system 30, for example, a power supply Vdc is connected to the switchinggear 10. The power supply Vdc is a DC power supply. For example, a load Loa is connected between the power supply Vdc and the switchinggear 10. In this case, a load circuit including a series circuit of the load Loa and the power supply Vdc is connected to the switchinggear 10. Note that the load Loa may be an element such as a resistor element or a light emitting diode (LED), a circuit such as a matching circuit, or a device such as a calculator or a display. In the switchinggear 10, a first path 11 including a first field effect transistor (first FET, FET: Field Effect Transistor) Q1 and a second path 12 including a second field effect transistor (second FET) Q2 are connected in parallel. The first path 11 further includes a first inductor L1 connected in series with the first field effect transistor Q1, and the second path 12 further includes a second inductor L2 connected in series with the second field effect transistor Q2.

[0015] The switchgear circuit 20 performs a specific operation when an overcurrent flows through the switchgear 10 due to, for example, an abnormality such as a short circuit in a load circuit connected to the switchgear 10. The specific operation includes, for example, an operation of detecting an overcurrent. The operation of detecting an overcurrent includes, for example, determining whether or not an overcurrent is flowing through the switchgear 10. An overcurrent is a current whose magnitude exceeds the rated current of the main current flowing through the switchgear 10, such as a short-circuit current. The specific operation may include an operation of controlling the switchgear 10.

[0016] (2) Components of the opening and closing system (2.1) Switchgear The switching device 10 includes a first path 11 and a second path 12. The first path 11 includes a first field effect transistor Q1 and a first inductor L1. The first field effect transistor Q1 has a gate 1G and a source 1S. The first field effect transistor Q1 also has a drain 1D. The first inductor L1 is connected to the source 1S of the first field effect transistor Q1. The second path 12 includes a second field effect transistor Q2 and a second inductor L2. The second field effect transistor Q2 has a gate 2G and a source 2S. The second field effect transistor Q2 also has a drain 2D. The second inductor L2 is connected to the source 2S of the second field effect transistor Q2. The first path 11 and the second path 12 are connected in parallel to a power supply Vdc. In the switching device 10, the drain 1D of the first field effect transistor Q1 and the drain 2D of the second field effect transistor Q2 are connected. In the switching device 10, a first inductor L1 is connected to a source 1S of the first field effect transistor Q1, and a second inductor L2 is connected to a source 2S of the second field effect transistor Q2.

[0017] The operation of the switching device 10 to which the switching device circuit 20 is applied will be described with reference to Fig. 2. Fig. 2 is an explanatory diagram of the operation of the switching device 10 to which the switching device circuit 20 is applied.

[0018] The first maximum current ImQ1 (see the voltage-current characteristic in FIG. 2), which is the maximum current when the first field effect transistor Q1 is conductive, is smaller than the second maximum current ImQ2 (see the voltage-current characteristic in FIG. 2), which is the maximum current when the second field effect transistor Q2 is conductive. The voltage-current characteristic in FIG. 2 is the drain voltage-drain current characteristic of the first field effect transistor Q1 and the second field effect transistor Q2. FIG. 2 is a schematic voltage-current characteristic diagram in the case where the on-resistance of the first field effect transistor Q1 and the on-resistance of the second field effect transistor Q2 are the same value, and the inductance of the first inductor L1 and the inductance of the second inductor L2 are the same value. In FIG. 2, I0 indicates the magnitude of the current flowing through the first field effect transistor Q1 and the second field effect transistor Q2 in normal operation. In the example shown in FIG. 2, the gate voltage Vgon1 when the first field effect transistor Q1 is conductive is smaller than the gate voltage Vgon2 when the second field effect transistor Q2 is conductive. Vp1 in FIG. 2 is the pinch-off voltage of the first field effect transistor Q1. Vp2 in FIG. 2 is the pinch-off voltage of the second field effect transistor Q2. The first maximum current ImQ1 is the saturation current of the first field effect transistor Q1 in a state where a gate voltage Vgon1 larger than the threshold voltage is applied as the first gate voltage VgQ1 to the gate 1G of the first field effect transistor Q1. The gate voltage Vgon1 is the gate voltage when the first field effect transistor Q1 is conductive. The second maximum current ImQ2 is the saturation current of the second field effect transistor Q2 in a state where a gate voltage Vgon2 larger than the threshold voltage is applied as the second gate voltage VgQ2 to the gate 2G of the second field effect transistor Q2. The gate voltage Vgon2 is the gate voltage when the second field effect transistor Q2 is conductive. The first maximum current ImQ1 is larger than the rated current of the main current (drain current) of the first field effect transistor Q1. The second maximum current ImQ2 is greater than the rated current of the main current (drain current) of the second field effect transistor Q2. In the example of FIG. 2, I0 is 10 A, the first maximum current ImQ1 is 20 A, and the second maximum current ImQ2 is 80 A, but are not limited to these values.

[0019] If the voltage between the drain 1D and source 1S of the first field effect transistor Q1 is Vds1, the voltage across the first inductor L1 is VL1, the voltage between the drain 2D and source 2S of the second field effect transistor Q2 is Vds2, and the voltage across the second inductor L2 is VL2, then Vds1+VL1=Vds2+VL2. Furthermore, when Vds1≦Vp1, VL1=VL2, and so Vds1=Vds2.

[0020] Each of the first field effect transistor Q1 and the second field effect transistor Q2 is, for example, a junction field effect transistor (JFET). The JFET includes at least a JFET chip, but may further include a package that houses the JFET chip. The JFET constituting each of the first field effect transistor Q1 and the second field effect transistor Q2 is, for example, a GaN-based GIT (Gate Injection Transistor). Each of the first field effect transistor Q1 and the second field effect transistor Q2 is not limited to a JFET, but may be, for example, a MOSFET (Metal-Oxide-Semiconductor Field Effect Transistor). The MOSFET includes at least a MOSFET chip, but may further include a package that houses the MOSFET chip. In the switching device 10, the first field effect transistor Q1 and the second field effect transistor Q2 may be included in a single semiconductor chip.

[0021] The JFET chip includes, for example, a substrate, a buffer layer, a first nitride semiconductor layer, a second nitride semiconductor layer, a source electrode, a gate electrode, a drain electrode, and a p-type layer. The buffer layer is formed on the substrate. The first nitride semiconductor layer is formed on the buffer layer. The second nitride semiconductor layer is formed on the first nitride semiconductor layer. The source electrode, the gate electrode, and the drain electrode are formed on the second nitride semiconductor layer. The p-type layer is interposed between the gate electrode and the second nitride semiconductor layer. In the JFET, the second nitride semiconductor layer and the p-type layer form a diode. The gate in the JFET includes a gate electrode and a p-type layer. The source in the JFET includes a source electrode. The drain in the JFET includes a drain electrode. The substrate is, for example, a silicon substrate. The buffer layer is, for example, an undoped GaN layer. The first nitride semiconductor layer is, for example, an undoped GaN layer. The second nitride semiconductor layer is, for example, an undoped AlGaN layer. The p-type layer is, for example, a p-type AlGaN layer. The buffer layer, the first nitride semiconductor layer, and the second nitride semiconductor layer may each contain impurities such as Mg, H, Si, C, and O that are inevitably mixed in during growth by MOVPE (Metal Organic Vapor Phase Epitaxy) or the like.

[0022] (2.2) Switchgear circuit The switching device circuit 20 includes a processing unit 26. The processing unit 26 executes a specific operation in response to a voltage difference ΔV (=VL2-VL1) between a voltage VL1 across the first inductor L1 and a voltage VL2 across the second inductor L2. The switching device circuit 20 further includes a first drive circuit 21 that drives the first field effect transistor Q1 and a second drive circuit 22 that drives the second field effect transistor Q2.

[0023] The processing unit 26 is activated when the first current I1 flowing through the first path 11 and the second current I2 flowing through the second path 12 change from a current value less than the first maximum current (ImQ1) to the first maximum current (ImQ1) or more. The specific operation includes an operation of determining that an overcurrent is flowing in the switching device 10 when a predetermined change occurs in the voltage difference ΔV.

[0024] The operation of the switching system 30 including the switching gear circuit 20 will be described with reference to Fig. 3A and Fig. 3B. That is, Fig. 3A and Fig. 3B are diagrams for explaining the operation of the switching system 30 including the switching gear circuit 20. The graph shown in Fig. 3A is a graph showing the magnitudes of the first current I1, the second current I2, and the voltage difference ΔV during operation of the switching system 30 before and after the occurrence of an abnormality. Also, the graph shown in Fig. 3B is a graph showing the magnitudes of the first current I1, the second current I2, and the voltage difference ΔV during start-up in the switching system 30.

[0025] In the switching system 30, the magnitudes of the first current I1 and the second current I2 are both I0 during normal operation, as shown in FIG. 3A and FIG. 3B. Note that "normal operation" refers to the time up to time t1 during operation in FIG. 3, and the time after time t12 during startup. Assume that an abnormality such as a short circuit fault occurs in the switching system 30 at a certain time t1 during operation. At that time, the first current I1 and the second current I2 start to increase from I0. In the switching system 30, the first current I1 reaches the first maximum current ImQ1 at time t2 after time t1. Thereafter, the first current I1 is saturated at the first maximum current ImQ1. On the other hand, the second current I2 increases at a current change rate (di / dt) greater after time t2 than between time t1 and t2. The voltage VL1 across the first inductor L1 is generated in response to the change in the first current I1. Furthermore, a voltage VL2 across the second inductor L2 is generated in response to a change in the second current I2. Therefore, the voltage difference ΔV (=VL2-VL1) changes at time t2. When the voltage VL1 is generated, the potential VsQ1 of the source 1S of the first field effect transistor Q1 changes. When the voltage VL2 is generated, the potential VsQ2 of the source 2S of the second field effect transistor Q2 changes.

[0026] At the start of the switching system 30, the switching system 30 starts at time t11, and the first current I1 and the second current I2 become I0 at time t12. At that time, the first current I1 and the second current I2 change from 0 A at time t11 to I0 at time t12, as shown by the solid line in FIG. 3B. At this time, a voltage VL1 is generated across the first inductor L1, and a voltage VL2 is generated across the second inductor L2. However, the voltages VL1 and VL2 are the same value, and the voltage difference ΔV does not change, as shown by the solid line. In the switching system 30, when the switching device 10 is turned on, the voltage difference ΔV does not change, as in the case of start-up.

[0027] The processing unit 26 further includes, for example, a determination circuit 261 and a control circuit 262. FIG. 4 is a circuit diagram showing an example of the determination circuit 261 in the switching device circuit 20. The determination circuit 261 includes, for example, a comparator CP0 as shown in FIG. 4. The comparator CP0 compares the potential VsQ1 (voltage VL1 across the first inductor L1) of the source 1S of the first field effect transistor Q1 with the potential VsQ2 (voltage VL2 across the second inductor L2) of the source 2S of the second field effect transistor Q2. When the voltage VL2 changes from the same value as the voltage VL1 to a value larger than the voltage VL1, the output signal of the comparator CP0 changes from the first voltage level (low level) to the second voltage level (high level). Therefore, the determination circuit 261 can detect the occurrence of an overcurrent and can suppress erroneous detection.

[0028] The control circuit 262 controls the first field effect transistor Q1 and the second field effect transistor Q2, for example, based on the determination result of the determination circuit 261. Here, the control circuit 262 controls the first field effect transistor Q1 by controlling the first drive circuit 21. For example, the control circuit 262 sets the first gate voltage VgQ1 applied to the first field effect transistor Q1 from the first gate power supply 211 of the first drive circuit 21 to 0V. In addition, the control circuit 262 controls the second field effect transistor Q2 by controlling the second drive circuit 22. For example, the control circuit 262 sets the second gate voltage VgQ2 applied to the second field effect transistor Q2 from the second gate power supply 221 of the second drive circuit 22 to 0V.

[0029] The first driving circuit 21 includes a first gate power supply 211 connected to the gate 1G of the first field effect transistor Q1, and drives the first field effect transistor Q1. The first gate power supply 211 includes a first DC power supply and a first driver IC (Integrated Circuit). The first driver IC is, for example, a CMOS (Complementary Metal-Oxide Semiconductor) inverter, and includes an anti-series circuit of a p-channel MOSFET and an n-channel MOSFET. This anti-series circuit is connected between the high-potential output terminal and the low-potential output terminal of the first DC power supply. In this anti-series circuit, the drains of the p-channel MOSFET and the n-channel MOSFET are connected to each other. In addition, the source of the p-channel MOSFET is connected to the high-potential output terminal of the first DC power supply. Furthermore, the source of the n-channel MOSFET is connected to the low-potential output terminal of the first DC power supply.

[0030] The second drive circuit 22 includes a second gate power supply 221 connected to the gate 2G of the second field effect transistor Q2, and drives the second field effect transistor Q2. The second gate power supply 221 includes, for example, a second DC power supply and a second driver IC. The second driver IC is, for example, a CMOS inverter, and includes an anti-series circuit of a p-channel MOSFET and an n-channel MOSFET. This anti-series circuit is connected between the high-potential output terminal and the low-potential output terminal of the second DC power supply. In this anti-series circuit, the drains of the p-channel MOSFET and the n-channel MOSFET are connected to each other. In addition, the source of the p-channel MOSFET is connected to the high-potential output terminal of the second DC power supply. Furthermore, the source of the n-channel MOSFET is connected to the low-potential output terminal of the second DC power supply.

[0031] In the switching gear circuit 20, the negative electrode of the first gate power supply 211 is connected to the source 1S of the first field effect transistor Q1. Here, in the switching gear circuit 20 according to the first embodiment, the negative electrode of the first gate power supply 211 is connected to the source 1S of the first field effect transistor Q1 via the first inductor L1. Also, in the switching gear circuit 20, the negative electrode of the second gate power supply 221 is connected to the source 2S of the second field effect transistor Q2. Here, in the switching gear circuit 20 according to the first embodiment, the negative electrode of the second gate power supply 221 is connected to the source 2S of the second field effect transistor Q2 via the second inductor L2.

[0032] The judgment circuit 261 is not limited to the example shown in FIG. 4, and may include a first comparator CP1 and a second comparator CP2, as in another example shown in FIG. 5. That is, FIG. 5 is a circuit diagram showing another example of the judgment circuit 261 in the switchgear circuit 20. In this case, in the judgment circuit 261, the first comparator CP1 compares the voltage VL1 between both ends of the first inductor L1 (potential VsQ1 of the source 1S of the first field effect transistor Q1) with the reference voltage of the reference voltage source Vref. In the first comparator CP1, when the voltage VL1 becomes larger than the reference voltage from a value smaller than the reference voltage, the output signal changes from the first voltage level (low level) to the second voltage level (high level). Also, in the judgment circuit 261, the second comparator CP2 compares the voltage VL2 between both ends of the second inductor L2 (potential VsQ2 of the source 2S of the second field effect transistor Q2) with the reference voltage of the reference voltage source Vref. In the second comparator CP2, when the voltage VL2 changes from a value less than the reference voltage to a value greater than the reference voltage, the output signal changes from the first voltage level (low level) to the second voltage level (high level). Therefore, in the determination circuit 261, by appropriately setting the reference voltage, it is possible to make the output signal of the first comparator CP1 become low level and the output signal of the second comparator CP2 become high level only when an overcurrent occurs in the switching device 10.

[0033] The control circuit 262 controls the first driving circuit 21 and the second driving circuit 22 based on the determination result of the determination circuit 261. The executing entity of the control circuit 262 (control unit) includes a computer system. The computer system has one or more computers. The computer system is mainly composed of a processor and a memory as hardware. The processor executes a program recorded in the memory of the computer system, thereby realizing the function of the executing entity of the control circuit 262 (control unit) in the present disclosure. The program may be pre-recorded in the memory of the computer system, or may be provided through an electric communication line, or may be recorded and provided in a non-transitory recording medium such as a memory card, an optical disk, or a hard disk drive (magnetic disk) that can be read by the computer system. The processor of the computer system is composed of one or more electronic circuits including a semiconductor integrated circuit (IC) or a large scale integrated circuit (LSI). The multiple electronic circuits may be integrated in one chip, or may be distributed among multiple chips. The multiple chips may be integrated in one device, or may be distributed among multiple devices.

[0034] (3) Advantages In the switchinggear circuit 20 according to the first embodiment, the processing unit 26 executes a specific operation in response to the voltage difference ΔV between the voltage VL1 across the first inductor L1 and the voltage VL2 across the second inductor L2, so that it is possible to suppress power loss in the switchinggear 10. Here, in the switchinggear circuit 20 according to the first embodiment, for example, when the specific operation is overcurrent detection, it is possible to suppress erroneous detection. In the switchinggear 10, it is possible to detect an overcurrent without connecting a shunt resistor for overcurrent detection to the source 1S of the first field effect transistor Q1 and without connecting a shunt resistor for overcurrent detection to the source 2S of the second field effect transistor Q2, and thus it is possible to suppress power loss.

[0035] Moreover, since the switching system 30 according to the first embodiment includes the switching device circuit 20 and the switching device 10, it is possible to suppress power loss in the switching device 10.

[0036] (4)Other In the first embodiment, the following processing method is disclosed.

[0037] The processing method is used in a switching device 10. The switching device 10 includes a first path 11 and a second path 12. The first path 11 includes a first field effect transistor Q1 and a first inductor L1. The first field effect transistor Q1 has a gate 1G and a source 1S. The first inductor L1 is connected to the source 1S of the first field effect transistor Q1. The second path 12 includes a second field effect transistor Q2 and a second inductor L2. The second field effect transistor Q2 has a gate 2G and a source 2S. The second inductor L2 is connected to the source 2S of the second field effect transistor Q2. The first path 11 and the second path 12 are connected in parallel to a power supply Vdc. A first maximum current ImQ1 of the first field effect transistor Q1 is smaller than a second maximum current ImQ2 of the second field effect transistor Q2. The processing method executes a specific operation in response to a voltage difference ΔV between a voltage VL1 across the first inductor L1 and a voltage VL2 across the second inductor L2. According to this processing method, it is possible to suppress power loss in the switchgear 10.

[0038] (5) Variations The operation of the switching system 30 including the switching device circuit 20 according to the modified example of the first embodiment will be described with reference to Figs.

[0039] The circuit configurations of the switching device circuit 20 and the switching system 30 according to the modified example are similar to those of the switching device circuit 20 and the switching system 30 according to the first embodiment, and therefore illustration and description thereof will be omitted.

[0040] The opening and closing system 30 of the modified example differs from the opening and closing system 30 of embodiment 1 in that the inductance value of the first inductor L1 connected to the first field effect transistor Q1 is smaller than the inductance value of the second inductor L2 connected to the second field effect transistor Q2.

[0041] FIG. 6 is a diagram for explaining the operation of the switching system 30 including the switching device circuit 20 according to this modification. In the switching system 30 according to the modification, as shown in FIG. 6, it is assumed that an abnormality occurs at a certain time t1 during normal operation. At that time, the drain 1D-source 1S voltage Vds1 of the first field effect transistor Q1 increases, and the drain 2D-source 2S voltage Vds2 of the second field effect transistor Q2 increases. In addition, the first current I1 and the second current I2 each change so as to increase from the normal current I0. Note that "normal" refers to the time up to time t1 in FIG. 6. At this time, in the switching system 30 according to the modification, the current change rate of the first current I1 and the current change rate of the second current I2 are different from each other. More specifically, the current change rate of the current I1 flowing through the first inductor having a relatively smaller inductance value out of the first inductor L1 and the second inductor L2 becomes larger than the current change rate of the current I2 flowing through the second inductor L2. Therefore, the current I1 flowing through the first field effect transistor Q1 reaches the first maximum current ImQ1 of the first field effect transistor Q1 before the current I2 flowing through the second field effect transistor Q2. In the opening and closing system 30 according to the modified example, the current change rate of the first current I1 from time t1 to time t2 is larger than the current change rate of the second current I2, and ΔV is a negative value during the period from time t1 to time t2.

[0042] FIG. 7 is a diagram for explaining the operation of the switching system 30 including the switching device circuit 20 according to this modification at the time of startup. In the switching system 30 according to the modification, at the time of startup, the first current I1 changes as shown by the dashed line in FIG. 7, while the second current I2 changes as shown by the broken line in FIG. 7. At the time of startup, the current change rate of the first current I1 from time t11 to time t12 is larger than the current change rate of the second current I2, and ΔV becomes a negative value during the period from time t11 to time t12. In addition, during the period from time t11 to time t12, the first current I1 may temporarily become larger than the current I0 under normal conditions (stable state). Therefore, ΔV may become a positive value during the period from time t12 to time t13 when the first current I1 and the second current I2 become the same value. Therefore, the processing unit 26 of the switching device circuit 20 according to the modified example may be configured to determine that an overcurrent has occurred when ΔV exceeds the threshold voltage Vr for a period of time equal to or longer than a predetermined fixed time. In this case, for example, the processing unit 26 may include a comparator that compares ΔV with the threshold voltage Vr, and a circuit that determines that an overcurrent has occurred when the voltage level of the output voltage of the comparator continues for a period of time equal to or longer than the fixed time. Here, the fixed time is predetermined to be longer than the period from time t12 to time t13.

[0043] (Embodiment 2) Hereinafter, the switchinggear circuit 20 according to the second embodiment and the switching system 30 including the same will be described with reference to Figs. 8 and 9. Fig. 8 is a circuit diagram of the switching system 30 including the switchinggear circuit 20 according to the second embodiment. Fig. 9 is a diagram for explaining the operation of the switching system 30 including the switchinggear circuit 20 according to the second embodiment. The circuit configurations of the switchinggear circuit 20 and the switching system 30 according to the second embodiment are similar to those of the switchinggear circuit 20 and the switching system 30 according to the first embodiment, and therefore will not be described. Note that Fig. 8 illustrates the parasitic inductance L100 of the load circuit connected between both ends of the switchinggear 10.

[0044] In the opening / closing device 10 to which the circuit 20 for an opening / closing device according to Embodiment 2 is applied, the on-resistance of the first field-effect transistor Q1 and the on-resistance of the second field-effect transistor Q2 are different from each other.

[0045] In the opening / closing device 10, the on-resistance of the first field-effect transistor Q1 and the on-resistance of the second field-effect transistor Q2 are made different from each other by making the size of the first field-effect transistor Q1 and the size of the second field-effect transistor Q2 different from each other. In the opening / closing system 30, for example, the first gate voltage VgQ1 and the second gate voltage VgQ2 have the same value, and the on-resistance of the first field-effect transistor Q1 is twice the value of the on-resistance of the second field-effect transistor Q2.

[0046] In the opening / closing system 30 according to Embodiment 2, as shown in FIG. 9, in the normal state before an abnormality occurs at time t1, each of the first current I1 and the second current I2 is substantially constant, but the first current I1 is smaller than the second current I2. After time t1, assuming that the first current I1 reaches the first maximum current ImQ1 at time t2, a ΔV occurs also during the period from time t1 to time t2, and a ΔV occurs also after time t2. Here, the ΔV that occurs during the period from time t1 to time t2 is, for convenience of explanation, referred to as ΔV1 (see FIG. 9). Assuming that the inductance of the first inductor L1 is L1 and the inductance of the second inductor L2 is L2, ΔV1 = L2·dI2 / dt - L1·dI1 / dt. Also, after time t2, for convenience of explanation, assuming that ΔV is ΔV2 (see FIG. 9), ΔV2 = L2·dI2 / dt. Also, the ΔV that occurs at the time of turn-on is a value determined by the same formula as ΔV1.

[0047] Therefore, for overcurrent detection, when a comparator that compares ΔV with a threshold value Vt (see FIG. 9) is employed in the determination circuit 261 of the processing unit 26, the threshold value Vt may be determined in advance so as to satisfy the condition of ΔV1 < Vt < ΔV2.

[0048] The switchinggear circuit 20 according to the second embodiment can suppress power loss, similarly to the switchinggear circuit 20 according to the first embodiment. The switchinggear 10 according to the second embodiment has the advantage that the on-resistance of the first field effect transistor Q1 and the on-resistance of the second field effect transistor Q2 may be made different from each other. The switching system 30 according to the second embodiment can make the first maximum current ImQ1 of the first field effect transistor Q1 and the second maximum current ImQ2 of the second field effect transistor Q2 different from each other, without making the first gate voltage VgQ1 and the second gate voltage VgQ2 different from each other.

[0049] (Embodiment 3) Hereinafter, a switching gear circuit 20 according to embodiment 3 and a switching system 30 including the same will be described with reference to Fig. 10. Fig. 10 is a circuit diagram of the switching system 30 including the switching gear circuit 20 according to embodiment 3. Regarding the switching gear circuit 20 and the switching system 30 according to embodiment 3, components similar to those of the switching gear circuit 20 and the switching system 30 according to embodiment 1 are given the same reference numerals and descriptions thereof will be omitted as appropriate.

[0050] 1, the switching device circuit 20 according to the first embodiment has a negative electrode of the first gate power supply 211 of the first drive circuit 21 and a negative electrode of the second gate power supply 221 of the second drive circuit 22 connected to each other. In contrast, the switching device circuit 20 according to the third embodiment differs from the switching device circuit 20 according to the first embodiment in that the first drive circuit 21 and the second drive circuit 22 are independent of each other.

[0051] In the switchgear circuit 20 according to the third embodiment, the negative electrode of the first gate power supply 211 is connected to the source 1S of the first field effect transistor Q1 without the first inductor L1, and the negative electrode of the second gate power supply 221 is connected to the source 2S of the second field effect transistor Q2 without the second inductor L2. As a result, in the switchgear circuit 20 according to the third embodiment, the first gate voltage VgQ1 of the first field effect transistor Q1 is given with the potential VsQ1 of the source 1S as a reference, and the second gate voltage VgQ2 of the second field effect transistor Q2 is given with the potential VsQ2 of the source 2S as a reference. As a result, in the switchgear circuit 20, the first gate voltage VgQ1 is less susceptible to the voltage VL1 of the first inductor L1, and the second gate voltage VgQ2 is less susceptible to the voltage VL2 of the second inductor L2. Therefore, the switchgear system 30 including the switchgear circuit 20 can be expected to operate more stably than the switchgear system 30 according to the first embodiment.

[0052] (Embodiment 4) Hereinafter, the switching gear circuit 20 according to the fourth embodiment and the switching system 30 including the same will be described with reference to Fig. 11 and Fig. 12. Fig. 11 is a circuit diagram of the switching system 30 including the switching gear circuit 20 according to the fourth embodiment. Fig. 12 is a gate voltage-gate current characteristic diagram of a JFET and a MOSFET. Regarding the switching gear circuit 20 and the switching system 30 according to the fourth embodiment, the same components as those of the switching gear circuit 20 and the switching system 30 according to the first embodiment are designated by the same reference numerals, and the description thereof will be omitted as appropriate.

[0053] In a switching system 30 including a switching device circuit 20 according to the fourth embodiment, each of the first field effect transistor Q1 and the second field effect transistor Q2 in the switching device 10 is a JFET (for example, the GaN-based GIT described in the first embodiment). Here, the JFET is, for example, the GaN-based GIT described in the first embodiment, and has a gate voltage Vg-gate current Ig characteristic as shown by the dashed line in Fig. 12. For comparison, the gate voltage Vg-gate current Ig characteristic of a MOSFET is shown by a dashed line in Fig. 12.

[0054] The switching device circuit 20 according to the fourth embodiment further includes a gate power supply 25, a first gate resistor RgQ1, and a second gate resistor RgQ2. The first gate resistor RgQ1 is connected between the gate power supply 25 and the gate 1G of the first field effect transistor Q1. The second gate resistor RgQ2 is connected between the gate power supply 25 and the gate 2G of the second field effect transistor Q2. In the switching device circuit 20, the resistance value of the first gate resistor RgQ1 is greater than the resistance value of the second gate resistor RgQ2. As a result, in the switching device circuit 20, the first gate current flowing through the gate 1G of the first field effect transistor Q1 is smaller than the second gate current flowing through the gate 2G of the second field effect transistor Q2. Therefore, in the switching device circuit 20, the first gate voltage VgQ1 when the first field effect transistor Q1 is on is smaller than the second gate voltage VgQ2 when the second field effect transistor Q2 is on.

[0055] The switching device circuit 20 according to the fourth embodiment can reduce costs compared to the switching device circuit 20 according to the first embodiment, which includes the first gate power supply 211 and the second gate power supply 221.

[0056] (Embodiment 5) Hereinafter, the switchinggear circuit 20 according to the fifth embodiment and the switching system 30 including the same will be described with reference to Fig. 13. Fig. 13 is a circuit diagram of the switching system 30 including the switchinggear circuit 20 according to the fifth embodiment. Regarding the switchinggear circuit 20 and the switching system 30 according to the fifth embodiment, the same components as those of the switchinggear circuit 20 and the switching system 30 according to the first embodiment are given the same reference numerals and the description thereof will be omitted as appropriate.

[0057] In the switching device circuit 20 according to the fifth embodiment, the reference potential of the first drive circuit 21 and the reference potential of the second drive circuit 22 are set to a common potential with the potential VsQ1 of the source 1S of the first field effect transistor Q1. More specifically, in the switching device circuit 20, the negative electrode of the first gate power supply 211 in the first drive circuit 21 and the negative electrode of the second gate power supply 221 in the second drive circuit 22 are connected to the source 1S of the first field effect transistor Q1 without passing through either the first inductor L1 or the second inductor L2. The maximum current ImQ1 of the first field effect transistor Q1 is smaller than the maximum current ImQ2 of the second field effect transistor Q2.

[0058] In the switching device circuit 20 according to the fifth embodiment, the first gate voltage VgQ1 of the first field effect transistor Q1 is smaller than the second gate voltage VgQ2 of the second field effect transistor Q2.

[0059] In the switching device circuit 20, when the current change rate dI1 / dt of the first current I1 becomes smaller than the current change rate dI2 / dt of the second current I2, the difference between the potential VsQ1 of the source 1S of the first field effect transistor Q1 and the potential VsQ2 of the source 2S of the second field effect transistor Q2 becomes larger (potential VsQ1 of the source 1S<potential VsQ2 of the source 2S). As a result, the voltage between the gate 2G and the source 2S of the second field effect transistor Q2 becomes smaller, the second gate voltage VgQ2 applied to the second field effect transistor Q2 becomes smaller, and the second current I2 flowing through the second field effect transistor Q2 becomes smaller, so that the overcurrent can be suppressed.

[0060] In the switching device circuit 20 according to the fifth embodiment, the negative electrode of the first gate power supply 211 in the first drive circuit 21 and the negative electrode of the second gate power supply 221 in the second drive circuit 22 are connected to the source 1S of the first field effect transistor Q1 without passing through either the first inductor L1 or the second inductor L2. The processing unit 26 has a determination circuit 261 that determines an electromotive voltage generated in the inductor and a control circuit 262 that controls the first field effect transistor Q1 and the second field effect transistor Q2. As a result, in the switching device circuit 20 according to the fifth embodiment, it is possible to suppress an overcurrent from flowing through the second field effect transistor Q2.

[0061] (Embodiment 6) Hereinafter, a switchinggear circuit 20 according to embodiment 6 and a switching system 30 including the same will be described with reference to Fig. 14. Fig. 14 is a circuit diagram of the switching system 30 including the switchinggear circuit 20 according to embodiment 6. Regarding the switchinggear circuit 20 and the switching system 30 according to embodiment 6, components similar to those of the switchinggear circuit 20 and the switching system 30 according to embodiment 4 described with reference to Fig. 11 are given the same reference numerals and descriptions thereof will be omitted as appropriate.

[0062] In the switching device circuit 20 according to the sixth embodiment, the reference potential of the gate power supply 25 is set to a common potential with the potential VsQ1 of the source 1S of the first field effect transistor Q1. More specifically, in the switching device circuit 20, the negative electrode of the gate power supply 25 is connected to the source 1S of the first field effect transistor Q1 without passing through either the first inductor L1 or the second inductor L2. The maximum current ImQ1 of the first field effect transistor Q1 is smaller than the maximum current ImQ2 of the second field effect transistor Q2.

[0063] In the switching device circuit 20 according to the sixth embodiment, the first gate voltage VgQ1 of the first field effect transistor Q1 is smaller than the second gate voltage VgQ2 of the second field effect transistor Q2.

[0064] In the switching device circuit 20, when the current change rate dI1 / dt of the first current I1 becomes smaller than the current change rate dI2 / dt of the second current I2, the difference between the potential VsQ1 of the source 1S of the first field effect transistor Q1 and the potential VsQ2 of the source 2S of the second field effect transistor Q2 becomes larger (potential VsQ1 of the source 1S<potential VsQ2 of the source 2S). As a result, the voltage between the gate 2G and the source 2S of the second field effect transistor Q2 becomes smaller, the second gate voltage VgQ2 applied to the second field effect transistor Q2 becomes smaller, and the second current I2 flowing through the second field effect transistor Q2 becomes smaller, so that the overcurrent can be suppressed.

[0065] In the switching device circuit 20 according to the sixth embodiment, the negative electrode of the gate power supply 25 is connected to the source 1S of the first field effect transistor Q1 without passing through either the first inductor L1 or the second inductor L2. The processing unit 26 has a determination circuit 261 that determines the electromotive voltage generated in the inductor and a control circuit 262 that controls the first field effect transistor Q1 and the second field effect transistor Q2. As a result, in the switching device circuit 20 according to the sixth embodiment, it is possible to suppress an overcurrent from flowing through the second field effect transistor Q2.

[0066] (Embodiment 7) Hereinafter, a switching system 30 including the switchinggear circuit 20 according to the seventh embodiment will be described with reference to Fig. 15 and Fig. 16. Fig. 15 is a circuit diagram of the switching system 30 including the switchinggear circuit 20 according to the seventh embodiment. Fig. 16 is a diagram for explaining the operation of the switching system 30 including the switchinggear circuit 20 according to the seventh embodiment.

[0067] In the switchgear circuit 20 and the switching system 30 according to the seventh embodiment, the same components as those in the switchgear circuit 20 and the switching system 30 according to the first embodiment are given the same reference numerals and the description thereof will be omitted as appropriate.

[0068] The switchinggear circuit 20 according to the seventh embodiment differs from the switchinggear circuit 20 according to the first embodiment in that a switchinggear 10 to which the switchinggear circuit 20 is applied further includes a third path 13 and a fourth path 14 in addition to the first path 11 and the second path 12. The third path 13 and the fourth path 14 are connected in parallel to the first path 11 and the second path 12.

[0069] The third path 13 includes a third field effect transistor Q3 and a third inductor L3 connected in series to the third field effect transistor Q3. The third field effect transistor Q3 has a gate 3G, a source 3S, and a drain 3D. The source 3S of the third field effect transistor Q3 is connected to the third inductor L3. A third gate voltage VgQ3 is applied to the gate 3G of the third field effect transistor Q3 from, for example, a third drive circuit (not shown). The drain 3D of the third field effect transistor Q3 is connected to the drain 1D of the first field effect transistor Q1 and the drain 2D of the second field effect transistor Q2.

[0070] The fourth path 14 includes a fourth field effect transistor Q4 and a fourth inductor L4 connected in series to the fourth field effect transistor Q4. The fourth field effect transistor Q4 has a gate 4G, a source 4S, and a drain 4D. The source 4S of the fourth field effect transistor Q4 is connected to the fourth inductor L4. A fourth gate voltage VgQ4 is applied to the gate 4G of the fourth field effect transistor Q4, for example, from a fourth drive circuit (not shown). The drain 4D of the fourth field effect transistor Q4 is connected to the drain 1D of the first field effect transistor Q1, the drain 2D of the second field effect transistor Q2, and the drain 3D of the third field effect transistor Q3.

[0071] In addition, the circuit 20 for an opening / closing device according to Embodiment 7 further includes a common inductor L10. The common inductor L10 has the first inductor L1 and the second inductor L2 commonly connected thereto. Here, in addition to the first inductor L1 and the second inductor L2, a third inductor L3 and a fourth inductor L4 are also commonly connected to the common inductor L10. In short, three or more inductors (here, the first inductor L1 to the fourth inductor L4) are commonly connected to the common inductor L10.

[0072] A specific operation of the processing unit 26 is an operation of performing overcurrent detection by comparing a voltage difference ΔV between the voltage VL10 across the common inductor L10 and the voltage VL1 across the first inductor L1 with a threshold value Vt. Hereinafter, the current flowing through the common inductor L10 will be described as a total current I10.

[0073] In the opening / closing system 30 according to Embodiment 7, as shown in FIG. 16, in a normal state before an abnormality occurs at time t1, each of the first current I1 and the total current I10 is substantially constant, but the first current I1 is smaller than the total current I10. After time t1, assuming that the first current I1 reaches the first maximum current ImQ1 at time t2, ΔV also occurs during the period from time t1 to time t2, and ΔV also occurs after time t2. Here, the ΔV that occurs during the period from time t1 to time t2 is referred to as ΔV1 (see FIG. 16) for convenience of explanation. Assuming that the inductance of the first inductor L1 is L1 and the inductance of the common inductor L10 is L10, ΔV1 = L10·dI10 / dt - L1·dI1 / dt. Further, after time t2, for convenience of explanation, if ΔV is referred to as ΔV2 (see FIG. 16), then ΔV2 = L10·dI10 / dt. Also, the ΔV that occurs at the time of turn-on is a value determined by the same formula as ΔV1.

[0074] Therefore, for overcurrent detection, when a comparator that compares ΔV with a threshold value Vt (see FIG. 16) is adopted in the determination circuit 261 of the processing unit 26, the threshold value Vt may be determined in advance so as to satisfy the condition of ΔV1 < Vt < ΔV2.

[0075] In the switchgear circuit 20 according to the seventh embodiment, like the switchgear circuit 20 according to the first embodiment, it is possible to suppress power loss.

[0076] In the switchgear circuit 20 according to the seventh embodiment, the specific operation of the processing unit 26 is an operation of detecting an overcurrent by comparing the voltage difference between the voltage VL10 across the common inductor L0 and the voltage VL1 across the first inductor L1 with the threshold value Vt. This makes it possible for the switchgear circuit 20 to suppress erroneous detection of an overcurrent, since the absolute value of the voltage VL10 across the common inductor L10 is greater than the absolute value of the voltage VL2 across the second inductor L2.

[0077] (Embodiment 8) Hereinafter, a switching system 30 including the switching device circuit 20 according to the eighth embodiment will be described with reference to Fig. 17. Fig. 17 is a circuit diagram of the switching system 30 including the switching device circuit 20 according to the eighth embodiment.

[0078] In the switchgear circuit 20 and the switching system 30 according to the eighth embodiment, the same components as those in the switchgear circuit 20 and the switching system 30 according to the first embodiment are given the same reference numerals and the description thereof will be omitted as appropriate.

[0079] The first path 11 further includes a third field effect transistor Q3 and a third inductor L3. The third field effect transistor Q3 has a gate 3G and a source 3S, and is connected in anti-series to the first field effect transistor Q1. The third field effect transistor Q3 also has a drain 3D. The third inductor L3 is connected to the source 3S of the third field effect transistor Q3.

[0080] The second path 12 further includes a fourth field effect transistor Q4 and a fourth inductor L4. The fourth field effect transistor Q4 has a gate 4G and a source 4S, and is connected in anti-series to the second field effect transistor Q2. The fourth field effect transistor Q4 has a drain 4D. The fourth inductor L4 is connected to the source 4S of the fourth field effect transistor Q4.

[0081] The switching device circuit 20 further includes a gate power supply 251, a first gate resistor RgQ1, and a second gate resistor RgQ2. The first gate resistor RgQ1 is connected between the gate power supply 251 and the gate 1G of the first field effect transistor Q1. The second gate resistor RgQ2 is connected between the gate power supply 251 and the gate 2G of the second field effect transistor Q2. The resistance value of the first gate resistor RgQ1 is greater than the resistance value of the second gate resistor RgQ2. In the switching device circuit 20, the negative electrode of the gate power supply 251 is connected to the source 1S of the first field effect transistor Q1. The first gate voltage VgQ1 of the first field effect transistor Q1 is smaller than the second gate voltage VgQ2 of the second field effect transistor Q2.

[0082] The switching device circuit 20 further includes a gate power supply 252, a third gate resistor RgQ3, and a fourth gate resistor RgQ4. The third gate resistor RgQ3 is connected between the gate power supply 252 and the gate 3G of the third field effect transistor Q3. The fourth gate resistor RgQ4 is connected between the gate power supply 252 and the gate 4G of the fourth field effect transistor Q4. The resistance value of the third gate resistor RgQ3 is greater than the resistance value of the fourth gate resistor RgQ4. In the switching device circuit 20, the negative electrode of the gate power supply 252 is connected to the source 3S of the third field effect transistor Q3. The third gate voltage VgQ3 of the third field effect transistor Q3 is smaller than the fourth gate voltage VgQ4 of the fourth field effect transistor Q4.

[0083] The switching device 10 in the switching system 30 according to the eighth embodiment configures a first bidirectional switch with a first field effect transistor Q1 and a third field effect transistor Q3. Also, the switching device 10 configures a second bidirectional switch with a second field effect transistor Q2 and a fourth field effect transistor Q4.

[0084] In the switching system 30 according to the eighth embodiment, the power source Vac connected to the switching device 10 is an AC power source.

[0085] For ease of explanation, in the following description of the first bidirectional switch, a state in which a voltage equal to or greater than the first threshold voltage is not applied between the gate 1G and source 1S of the first field effect transistor Q1 is also referred to as the gate 1G being in an off state, and a state in which a voltage equal to or greater than the first threshold voltage is applied between the gate 1G and source 1S with the gate 1G serving as the high potential side is also referred to as the gate 1G being in an on state.

[0086] A state in which a voltage equal to or greater than the second threshold voltage is not applied between the gate 2G and source 2S of the second field effect transistor Q2 is also referred to as the gate 2G being in an off state. A state in which a voltage equal to or greater than the second threshold voltage is applied between the gate 2G and source 2S, with the gate 2G serving as the high potential side, is also referred to as the gate 2G being in an on state.

[0087] A state in which a voltage equal to or greater than the third threshold voltage is not applied between the gate 3G and source 3S of the third field effect transistor Q3 is also referred to as the gate 3G being in an off state. A state in which a voltage equal to or greater than the third threshold voltage is applied between the gate 3G and source 3S, with the gate 3G serving as the high potential side, is also referred to as the gate 3G being in an on state.

[0088] A state in which a voltage equal to or greater than the fourth threshold voltage is not applied between the gate 4G and source 4S of the fourth field effect transistor Q4 is also referred to as the gate 4G being in an off state. A state in which a voltage equal to or greater than the fourth threshold voltage is applied between the gate 4G and source 4S, with the gate 4G serving as the high potential side, is also referred to as the gate 4G being in an on state.

[0089] The first bidirectional switch can switch among a bidirectional on state, a bidirectional off state, a first diode state, and a second diode state according to a combination of a first gate voltage VgQ1 and a third gate voltage VgQ3 applied to the gate 1G and the gate 3G, respectively. The bidirectional on state is a state in which a current passes in both directions (a first direction and a second direction opposite to the first direction). The bidirectional off state is a state in which a current passes in both directions. The first diode state is a state in which a current passes in the first direction. The second diode state is a state in which a current passes in the second direction.

[0090] The first bidirectional switch is in a bidirectional on state when gate 1G is in the on state and gate 3G is in the on state. The first bidirectional switch is in a bidirectional off state when gate 1G is in the off state and gate 3G is in the off state. The first bidirectional switch is in a first diode state when gate 1G is in the off state and gate 3G is in the on state. The first bidirectional switch is in a second diode state when gate 1G is in the on state and gate 3G is in the off state.

[0091] The second bidirectional switch can switch among a bidirectional on state, a bidirectional off state, a first diode state, and a second diode state according to a combination of a second gate voltage VgQ2 and a fourth gate voltage VgQ4 applied to the gate 2G and the gate 4G, respectively. The bidirectional on state is a state in which a bidirectional current (a first direction and a second direction opposite to the first direction) passes. The bidirectional off state is a state in which a bidirectional current is blocked. The first diode state is a state in which a current in the first direction passes. The second diode state is a state in which a current in the second direction passes.

[0092] The second bidirectional switch is in a bidirectional on state when gate 2G is in the on state and gate 4G is in the on state. The second bidirectional switch is in a bidirectional off state when gate 2G is in the off state and gate 4G is in the off state. The second bidirectional switch is in a first diode state when gate 2G is in the off state and gate 4G is in the on state. The second bidirectional switch is in a second diode state when gate 2G is in the on state and gate 4G is in the off state.

[0093] The processing unit 26 executes a first specific operation and a second specific operation. The first specific operation is an operation performed in response to a voltage difference ΔV between the voltage VL1 across the first inductor L1 and the voltage VL2 across the second inductor L2, similar to the specific operation described in the first embodiment. The second specific operation is an operation performed in response to a voltage difference between the voltage VL3 across the third inductor L3 and the voltage VL4 across the fourth inductor L4, and is similar to the first specific operation.

[0094] The processing unit 26 has a first judgment circuit 2611, a second judgment circuit 2612, a third judgment circuit 2613, and a control circuit 262.

[0095] The first determination circuit 2611 includes, for example, a comparator that compares a voltage difference ΔV (=VL2-VL1) between the voltage VL1 across the first inductor L1 and the voltage VL2 across the second inductor L2 with a threshold value, and when the voltage difference ΔV becomes larger than the threshold value, the output signal of the comparator changes from a first voltage level (low level) to a second voltage level (high level). The first voltage level of the output signal is taken as a logical value 0, and the second voltage level is taken as a logical value 1.

[0096] The second determination circuit 2612 includes, for example, a comparator that compares a voltage difference ΔV (=VL4-VL3) between the voltage VL3 across the third inductor L3 and the voltage VL4 across the fourth inductor L4 with a threshold value, and when the voltage difference ΔV becomes larger than the threshold value, the output signal of the comparator changes from a first voltage level (low level) to a second voltage level (high level). The first voltage level of the output signal is taken as a logical value 0, and the second voltage level is taken as a logical value 1.

[0097] The third judgment circuit 2613 judges the direction of the overcurrent based on the judgment results of the first judgment circuit 2611 and the second judgment circuit 2612 as shown in Table 1 below. In Table 1 below, S1 is the source 4S of the fourth field effect transistor Q4, and S2 is the source 2S of the second field effect transistor Q2. In addition, Vs2Q1 in Fig. 17 is the potential of the source 1S of the first field effect transistor Q1, Vs2Q2 is the potential of the source 2S of the second field effect transistor Q2, Vs1Q3 is the potential of the source 3S of the third field effect transistor Q3, and Vs1Q4 is the potential of the source 4S of the fourth field effect transistor Q4.

[0098] [Table 1]

[0099] In the third judgment circuit 2613, as shown in Table 1, if the logical value of the judgment result of the first judgment circuit 2611 and the logical value of the judgment result of the second judgment circuit 2612 are the same, it judges that there is no abnormality, and if the logical value of the judgment result of the first judgment circuit 2611 and the logical value of the judgment result of the second judgment circuit 2612 are different from each other, it judges whether the overcurrent is flowing from S1 to S2 (S1 → S2) or from S2 to S1 (S2 → S1) depending on the combination.

[0100] The control circuit 262 controls the second field effect transistor Q2 and the fourth field effect transistor Q4 based on the determination result of the third determination circuit 2613.

[0101] When the control circuit 262 determines that the direction of the overcurrent is S1→S2, it turns off the gate 2G of the second field effect transistor Q2 and the gate 1G of the first field effect transistor Q1, and then turns off the gate 4G of the fourth field effect transistor Q4 and the gate 3G of the third field effect transistor Q3. This enables the opening and closing device circuit 20 to suppress heat generation from the second field effect transistor Q2 and the fourth field effect transistor Q4.

[0102] When the control circuit 262 determines that the direction of the overcurrent is from S2 to S1, it turns off the gate 4G of the fourth field effect transistor Q4 and the gate 3G of the third field effect transistor Q3, and then turns off the gate 2G of the second field effect transistor Q2 and the gate 1G of the first field effect transistor Q1. This allows the opening and closing device circuit 20 to suppress heat generation from the second field effect transistor Q2 and the fourth field effect transistor Q4.

[0103] (Embodiment 9) Hereinafter, a switching system 30 including the switchinggear circuit 20 according to the ninth embodiment will be described with reference to Fig. 18 and Fig. 19. Fig. 18 is a circuit diagram of the switching system 30 including the switchinggear circuit 20 according to the ninth embodiment. Fig. 19 is a diagram for explaining the operation of the switching system 30 including the switchinggear circuit 20 according to the ninth embodiment.

[0104] In the switchgear circuit 20 and the switching system 30 according to the ninth embodiment, the same components as those in the switchgear circuit 20 and the switching system 30 according to the first embodiment are given the same reference numerals and the description thereof will be omitted as appropriate.

[0105] The switchgear circuit 20 according to the ninth embodiment differs from the switchgear circuit 20 according to the first embodiment in that the switchgear circuit 20 according to the ninth embodiment further includes a first clamp circuit CC1 and a second clamp circuit CC2.

[0106] The first clamp circuit CC1 is connected in parallel to the first inductor L1 and clamps the voltage VL1 across the first inductor L1. The first clamp circuit CC1 is configured with a diode D1, but is not limited to this and may be configured with, for example, a Zener diode.

[0107] The second clamp circuit CC2 is connected in parallel to the second inductor L2 and clamps the voltage VL2 across the second inductor L2. The second clamp circuit CC2 is configured with a diode D2, but is not limited to this and may be configured with, for example, a Zener diode.

[0108] In the switching device circuit 20 according to the ninth embodiment, when an abnormality occurs, as shown in FIG. 19, the voltage difference ΔV (=VsQ2-VsQ1) can be clamped to the voltage indicated by the dashed line, which is lower in voltage level than the voltage indicated by the solid line.

[0109] The switching device circuit 20 according to the ninth embodiment makes it possible to suppress variations in the voltage VL1 due to variations in the inductance of the first inductor L1 and the like before the source current (first current I1) of the first field effect transistor Q1 is saturated.

[0110] Moreover, in the switching device circuit 20 according to the ninth embodiment, by providing the first clamp circuit CC1 and the second clamp circuit CC2, it is possible to prevent the input of the comparator from becoming too large when, for example, a comparator is used in the determination circuit 261. Moreover, in the switching device circuit 20 according to the ninth embodiment, it is possible to prevent the second field effect transistor Q2 from being turned off.

[0111] (Embodiment 10) Hereinafter, a switching system 30 including the switching device circuit 20 according to the tenth embodiment will be described with reference to Fig. 20. Fig. 20 is a main circuit diagram of the switching system 30 including the switching device circuit 20 according to the tenth embodiment.

[0112] The basic configurations of the switchgear circuit 20 and the switching system 30 according to the tenth embodiment are similar to those of the switchgear circuit 20 and the switching system 30 according to the first embodiment, respectively, and therefore some of the circuit diagrams are omitted. Note that the same components as those of the switchgear circuit 20 and the switching system 30 according to the first embodiment are given the same reference numerals and descriptions thereof are omitted as appropriate.

[0113] The switchgear circuit 20 according to the tenth embodiment differs from the switchgear circuit 20 according to the first embodiment in that it further includes a clamp circuit CC3.

[0114] The clamp circuit CC3 clamps the voltage difference between the voltage VL1 across the first inductor L1 and the voltage VL2 across the second inductor L2. Here, the clamp circuit CC3 includes a series circuit of an inductor L21 and a diode D21 connected between the source 2S of the second field effect transistor Q2 and the source 1S of the first field effect transistor Q1. The anode of the diode D21 is connected to the connection point between the source 2S of the second field effect transistor Q2 and the second inductor L2 via the inductor L21. The cathode of the diode D21 is connected to the connection point between the source 1S of the first field effect transistor Q1 and the first inductor L1. When the forward voltage of the diode D21 is Vf, the clamp circuit CC3 can set the potential of the anode of the diode D21 to VsQ1+Vf. The switchgear circuit 20 according to the tenth embodiment performs a predetermined operation based on the potential difference between VsQ1+Vf and a reference potential.

[0115] In the switching device circuit 20 according to the tenth embodiment, by providing the clamp circuit CC3, it becomes possible to prevent the input of the comparator from becoming too large when the comparator is used in the determination circuit 261, for example.

[0116] (Modification of the 10th embodiment) Hereinafter, a switching system 30 including a switching device circuit 20 according to a modification of the tenth embodiment will be described with reference to Fig. 21. Fig. 21 is a circuit diagram of a switching system 30 including a switching device circuit 20 according to a modification of the tenth embodiment.

[0117] In the switching device circuit 20 and the switching system 30 according to the modified example of the tenth embodiment, the same components as those in the switching device circuit 20 and the switching system 30 according to the tenth embodiment are given the same reference numerals and the description thereof will be omitted as appropriate.

[0118] A switching device 10 to which a switching device circuit 20 according to a modification of the tenth embodiment is applied is different from the switching device circuit 20 according to the tenth embodiment in that the switching device 10 further includes a third path 13 and a fourth path 14 in addition to the first path 11 and the second path 12. The third path 13 and the fourth path 14 are connected in parallel to the first path 11 and the second path 12.

[0119] The third path 13 includes a third field effect transistor Q3 and a third inductor L3 connected in series to the third field effect transistor Q3. The third field effect transistor Q3 has a gate 3G, a source 3S, and a drain 3D. The source 3S of the third field effect transistor Q3 is connected to the third inductor L3. A third gate voltage VgQ3 is applied to the gate 3G of the third field effect transistor Q3 from, for example, a third drive circuit (not shown).

[0120] The fourth path 14 includes a fourth field effect transistor Q4 and a fourth inductor L4 connected in series to the fourth field effect transistor Q4. The fourth field effect transistor Q4 has a gate 4G, a source 4S, and a drain 4D. The source 4S of the fourth field effect transistor Q4 is connected to the fourth inductor L4. A fourth gate voltage VgQ4 is applied to the gate 4G of the fourth field effect transistor Q4 from, for example, a fourth drive circuit (not shown).

[0121] In addition, in the switching device circuit 20 according to the modification of the tenth embodiment, the connection point between the source 3S of the third field effect transistor Q3 and the third inductor L3 is connected to the anode of the diode D21 via the inductor L31. In addition, the connection point between the source 4S of the fourth field effect transistor Q4 and the fourth inductor L4 is connected to the anode of the diode D21 via the inductor L41. The switching device circuit 20 according to the modification of the tenth embodiment can suppress the variation in the current flowing through each of the first inductor L1 to the fourth inductor L4, and is expected to stabilize the operation.

[0122] (Embodiment 11) Hereinafter, a switching system 30 including the switching device circuit 20 according to the eleventh embodiment will be described with reference to Fig. 22. Fig. 22 is a circuit diagram of the switching system 30 including the switching device circuit 20 according to the eleventh embodiment.

[0123] In the switching device circuit 20 and the switching system 30 according to the eleventh embodiment, the same components as those in the switching device circuit 20 and the switching system 30 according to the sixth embodiment (see FIG. 14) are given the same reference numerals and the description thereof will be omitted as appropriate.

[0124] The switching device circuit 20 according to the eleventh embodiment further includes a gate power supply 25, a first resistive voltage divider circuit RV1, and a second resistive voltage divider circuit RV2. The first resistive voltage divider circuit RV1 is connected between the positive electrode of the gate power supply 25 and the source 1S of the first field effect transistor Q1. The first resistive voltage divider circuit RV1 includes a series circuit of resistors Rg1Q1 and Rg2Q1. The second resistive voltage divider circuit RV2 is connected between the positive electrode of the gate power supply 25 and the source 2S of the second field effect transistor Q2. The output terminal (the connection point between the resistors Rg1Q1 and Rg2Q1) of the first resistive voltage divider circuit RV1 is connected to the gate 1G of the first field effect transistor Q1. The second resistive voltage divider circuit RV2 includes a series circuit of resistors Rg1Q2 and Rg2Q2. The output terminal of the second resistive voltage divider circuit RV2 (the connection point between the resistor Rg1Q2 and the resistor Rg2Q2) is connected to the gate 2G of the second field effect transistor Q2.

[0125] The switching device circuit 20 according to the eleventh embodiment can make the first gate voltage VgQ1 of the first field effect transistor Q1 and the second gate voltage VgQ2 of the second field effect transistor Q2 different from each other.

[0126] (Embodiment 12) Hereinafter, a switching system 30 including the switching device circuit 20 according to the twelfth embodiment will be described with reference to Fig. 23. Fig. 23 is a circuit diagram of the switching system 30 including the switching device circuit 20 according to the twelfth embodiment.

[0127] In the switching device circuit 20 and the switching system 30 according to the twelfth embodiment, the same components as those in the switching device circuit 20 and the switching system 30 according to the sixth embodiment (see FIG. 14) are given the same reference numerals and the description thereof will be omitted as appropriate.

[0128] The first field effect transistor Q1 and the second field effect transistor Q2 are MOSFETs or normally-on type JFETs. The switching device circuit 20 further includes a gate power supply 25, a first capacitance CQ1, and a second capacitance CQ2. The first capacitance CQ1 is connected between the positive electrode of the gate power supply 25 and the gate 1G of the first field effect transistor Q1. The second capacitance CQ2 is connected between the positive electrode of the gate power supply 25 and the gate 2G of the second field effect transistor Q2.

[0129] The switching device circuit 20 according to the twelfth embodiment can make the first gate voltage VgQ1 of the first field effect transistor Q1 and the second gate voltage VgQ2 of the second field effect transistor Q2 different from each other.

[0130] (Embodiment 13) Hereinafter, a switching system 30 including the switching device circuit 20 according to the thirteenth embodiment will be described with reference to Fig. 24. Fig. 24 is a circuit diagram of the switching system 30 including the switching device circuit 20 according to the thirteenth embodiment.

[0131] In the switching device circuit 20 and the switching system 30 according to the thirteenth embodiment, the same components as those in the switching device circuit 20 and the switching system 30 according to the fourth embodiment described based on FIG. 11 are given the same reference numerals, and the description thereof will be omitted as appropriate.

[0132] The switchgear circuit 20 according to the thirteenth embodiment differs from the switchgear circuit 20 according to the fourth embodiment in that the switchgear 10 to which the switchgear circuit 20 is applied further includes a third path 13 and a fourth path 14 in addition to the first path 11 and the second path 12. The third path 13 and the fourth path 14 are connected in parallel to the first path 11 and the second path 12.

[0133] Moreover, the switching device circuit 20 according to the thirteenth embodiment differs from the switching device circuit 20 according to the first embodiment in that it further includes a first gate resistor RgQ1, a second gate resistor RgQ2, a third gate resistor RgQ3, and a fourth gate resistor RgQ4.

[0134] A first gate voltage VgQ1 is applied to the gate 1G of the first field effect transistor Q1 from a gate power supply 25 via a first gate resistor RgQ1.

[0135] A second gate voltage VgQ2 is applied to the gate 2G of the second field effect transistor Q2 from a gate power supply 25 via a second gate resistor RgQ2.

[0136] The third path 13 includes a third field effect transistor Q3 and a third inductor L3 connected in series to the third field effect transistor Q3. The third field effect transistor Q3 has a gate 3G, a source 3S, and a drain 3D. The source 3S of the third field effect transistor Q3 is connected to the third inductor L3. For example, a third gate voltage VgQ3 is applied to the gate 3G of the third field effect transistor Q3 from a gate power supply 25 via a third gate resistor RgQ3.

[0137] The fourth path 14 includes a fourth field effect transistor Q4 and a fourth inductor L4 connected in series to the fourth field effect transistor Q4. The fourth field effect transistor Q4 has a gate 4G, a source 4S, and a drain 4D. The source 4S of the fourth field effect transistor Q4 is connected to the fourth inductor L4. For example, a fourth gate voltage VgQ4 is applied to the gate 4G of the fourth field effect transistor Q4 from the gate power supply 25 via a fourth gate resistor RgQ4.

[0138] In the switching system 30 including the switchinggear circuit 20 according to the thirteenth embodiment, it is possible to suppress power loss, similarly to the switchinggear circuit 20 according to the fourth embodiment.

[0139] (Modification) The above-mentioned embodiments 1 to 13 are merely one of various embodiments of the present disclosure. The above-mentioned embodiments 1 to 13 can be modified in various ways depending on the design and the like as long as the object of the present disclosure can be achieved.

[0140] For example, the trigger for performing a predetermined operation is not limited to a change determined by comparing the voltage difference ΔV with a threshold value, and may include a change determined by the amount of change in the voltage difference ΔV.

[0141] Furthermore, the determination that an overcurrent is flowing in the determination circuit includes a case where the output of the determination circuit differs between when an overcurrent is flowing and when it is not flowing.

[0142] In addition, the p-type layer in the GaN-based GIT is not limited to a p-type AlGaN layer, and may be, for example, a p-type GaN layer or a p-type metal oxide semiconductor layer. The p-type metal oxide semiconductor layer is, for example, a NiO layer. The NiO layer may contain, as an impurity, at least one alkali metal selected from the group consisting of lithium, sodium, potassium, rubidium, and cesium. The NiO layer may also contain, for example, a transition metal such as silver or copper that becomes monovalent when added as an impurity.

[0143] The GaN-based GIT may include one or more nitride semiconductor layers between the buffer layer and the first nitride semiconductor layer. The buffer layer is not limited to a single-layer structure, and may have, for example, a superlattice structure.

[0144] Furthermore, the substrate in the GaN-based GIT is not limited to a silicon substrate, but may be, for example, a GaN substrate, a SiC substrate, a sapphire substrate, or the like.

[0145] The switchgear 10 can be applied to, for example, a circuit breaker.

[0146] (Aspect) From the above-described embodiments, the present specification discloses the following aspects.

[0147] A switching device circuit (20) according to a first embodiment is used in a switching device (10). The switching device (10) includes a first path (11) and a second path (12). The first path (11) includes a first field effect transistor (Q1) and a first inductor (L1). The first field effect transistor (Q1) has a gate (1G) and a source (1S). The first inductor (L1) is connected to the source (1S) of the first field effect transistor (Q1). The second path (12) includes a second field effect transistor (Q2) and a second inductor (L2). The second field effect transistor (Q2) has a gate (2G) and a source (2S). The second inductor (L2) is connected to the source (2S) of the second field effect transistor (Q2). The first path (11) and the second path (12) are connected in parallel to a power supply (Vdc). A first maximum current (ImQ1), which is a maximum current when the first field effect transistor (Q1) is conductive, is smaller than a second maximum current (ImQ2), which is a maximum current when the second field effect transistor (Q2) is conductive. The switchgear circuit (20) includes a processing unit (26). The processing unit (26) executes a specific operation in response to a voltage difference (ΔV) between a voltage (VL1) across the first inductor (L1) and a voltage (VL2) across the second inductor (VL2).

[0148] The switchgear circuit (20) according to the first aspect can reduce power loss.

[0149] In the first aspect of the switching device circuit (20) according to the second aspect, the processing unit (26) is triggered to operate when the first current (I1) flowing in the first path (11) and the second current (I2) flowing in the second path (12) change from a current value less than the first maximum current (ImQ1) to the first maximum current (ImQ1) or more.

[0150] In the switchgear circuit (20) according to the second aspect, it is possible to suppress the occurrence of malfunction.

[0151] In the switching device circuit (20) according to the third aspect, in the first or second aspect, the specific operation includes an operation of determining that an overcurrent is flowing in the switching device (10) when a predetermined change occurs in the voltage difference (ΔV).

[0152] In the switchgear circuit (20) according to the third aspect, it is possible to detect the flow of an overcurrent in the switchgear (10).

[0153] In the switching device circuit (20) according to the fourth aspect, in any one of the first to third aspects, the gate voltage (Vgon1) of the first field effect transistor (Q1) when conductive is lower than the gate voltage (Vgon2) of the second field effect transistor (Q2) when conductive.

[0154] In the switchgear circuit (20) according to the fourth aspect, the first maximum current (ImQ1) of the first field effect transistor (Q1) can be made smaller than the second maximum current (ImQ2).

[0155] In the switchgear circuit (20) according to the fifth aspect, in any one of the first to fourth aspects, the inductance of the first inductor (L1) is smaller than the inductance of the second inductor (L2).

[0156] In the switchgear circuit (20) of the fifth aspect, the current change rate (dI1 / dt) of the first current (I1) when an overcurrent flows through the switchgear (10) can be made larger than the current change rate (dI2 / dt) of the second current (I2).

[0157] In the switching device circuit (20) according to the sixth aspect, in any one of the first to fifth aspects, the on-resistance of the first field effect transistor (Q1) and the on-resistance of the second field effect transistor (Q2) are different from each other.

[0158] In the opening and closing device circuit (20) according to the sixth aspect, the on-resistance of the first field effect transistor (Q1) and the on-resistance of the second field effect transistor (Q2) can be made different from each other, so that the first maximum current (ImQ1) of the first field effect transistor (Q1) and the second maximum current (ImQ2) of the second field effect transistor (Q2) can be made different from each other.

[0159] The switching device circuit (20) according to the seventh aspect is any one of the first to sixth aspects, and further includes a first drive circuit (21) and a second drive circuit (22). The first drive circuit (21) includes a first gate power supply (211) connected to the gate (1G) of the first field effect transistor (Q1) and drives the first field effect transistor (Q1). The second drive circuit (22) includes a second gate power supply (221) connected to the gate (2G) of the second field effect transistor (Q2) and drives the second field effect transistor (Q2). The negative electrode of the first gate power supply (211) is connected to the source (1S) of the first field effect transistor (Q1). The negative electrode of the second gate power supply (221) is connected to the source (2S) of the second field effect transistor (Q2).

[0160] In the switchgear circuit (20) according to the seventh aspect, the first gate voltage (VgQ1) is less susceptible to the voltage (VL1) of the first inductor (L1), and the second gate voltage (VgQ2) is less susceptible to the voltage (VL2) of the second inductor (L2).

[0161] In a switching device circuit (20) according to an eighth aspect, in any one of the first to sixth aspects, each of the first field effect transistor (Q1) and the second field effect transistor (Q2) is a junction field effect transistor. The switching device circuit (20) further includes a gate power supply (25), a first gate resistor (RgQ1), and a second gate resistor (RgQ2). The first gate resistor (RgQ1) is connected between the gate power supply (25) and the gate (1G) of the first field effect transistor (Q1). The second gate resistor (RgQ2) is connected between the gate power supply (25) and the gate (2G) of the second field effect transistor (Q2). The resistance value of the first gate resistor (RgQ1) is greater than the resistance value of the second gate resistor (RgQ2).

[0162] In the switchgear circuit (20) according to the eighth aspect, the first gate current flowing through the gate (1G) of the first field effect transistor (Q1) is smaller than the second gate current flowing through the gate (2G) of the second field effect transistor (Q2). Therefore, in the switchgear circuit (20) according to the eighth aspect, the first gate voltage (VgQ1) when the first field effect transistor (Q1) is on is smaller than the second gate voltage (VgQ2) when the second field effect transistor (Q2) is on.

[0163] In the switching device circuit (20) according to the ninth aspect, in the first to sixth aspects, the specific operation includes an operation of limiting a current flowing through the second field effect transistor (Q2).

[0164] In the switching device circuit (20) according to the ninth aspect, it is possible to suppress an overcurrent in the second field effect transistor (Q2).

[0165] The switching device circuit (20) according to the tenth aspect is the same as that of the ninth aspect, and further includes a first drive circuit (21) and a second drive circuit (22). The first drive circuit (21) includes a first gate power supply (211) connected to the gate (1G) of the first field effect transistor Q1, and drives the first field effect transistor (Q1). The second drive circuit (22) includes a second gate power supply (221) connected to the gate (2G) of the second field effect transistor (Q2), and drives the second field effect transistor (Q2). The negative electrode of the first gate power supply (211) and the negative electrode of the second gate power supply (221) are connected to the source (1S) of the first field effect transistor (Q1).

[0166] The switching device circuit (20) according to the tenth aspect can suppress an overcurrent in the second field effect transistor (Q2).

[0167] In the switchgear circuit (20) according to an eleventh aspect, in the ninth aspect, each of the first field effect transistor (Q1) and the second field effect transistor (Q2) is a junction field effect transistor. The switchgear circuit (20) further includes a gate power supply (25), a first gate resistor (RgQ1), and a second gate resistor (RgQ2). The first gate resistor (RgQ1) is connected between the gate power supply (25) and the gate (1G) of the first field effect transistor (Q1). The second gate resistor (RgQ2) is connected between the gate power supply (25) and the gate (2G) of the second field effect transistor (Q2). The resistance value of the first gate resistor (RgQ1) is greater than the resistance value of the second gate resistor (RgQ2). The negative electrode of the gate power supply (25) is connected to the source (1S) of the first field effect transistor (Q1).

[0168] In the switchgear circuit (20) according to the eleventh aspect, it is possible to suppress an overcurrent in the second field effect transistor (Q2).

[0169] The switching device circuit (20) according to the twelfth aspect is the first aspect, and further includes a common inductor (L0). The common inductor (L0) is a common connection between the first inductor (L1) and the second inductor (L2). The specific operation is an operation of detecting an overcurrent by comparing a voltage difference between the voltage (VL10) across the common inductor (L10) and the voltage (VL1) across the first inductor (L1) with a threshold value.

[0170] The switchgear circuit (20) according to the twelfth aspect makes it possible to suppress erroneous detection of an overcurrent.

[0171] In the switching device circuit (20) according to a thirteenth aspect, in any one of the first to eleventh aspects, the first path (11) further includes a third field effect transistor (Q3) and a third inductor (L3). The third field effect transistor (Q3) has a gate (3G) and a source (3S), and is connected in anti-series to the first field effect transistor (Q1). The third inductor (L3) is connected to the source (3S) of the third field effect transistor (Q3). The second path (12) further includes a fourth field effect transistor (Q4) and a fourth inductor (L4). The fourth field effect transistor (Q4) has a gate (4G) and a source (4S), and is connected in anti-series to the second field effect transistor (Q2). The fourth inductor (L4) is connected to the source (4S) of the fourth field effect transistor (Q4). The processing unit (26) includes a first determination circuit (2611) and a second determination circuit (2612). The first determination circuit (2611) determines whether or not an overcurrent occurs in the switching device (10) based on a voltage difference between the voltage (VL2) across the second inductor (L2) and the voltage (VL1) across the first inductor (L1). The second determination circuit (2612) determines whether or not an overcurrent occurs in the switching device (10) based on a voltage difference between the voltage (VL3) across the third inductor (L3) and the voltage (VL4) across the fourth inductor (L4).

[0172] In the switching device circuit (20) according to the fourteenth aspect, in the thirteenth aspect, the switching device circuit (20) further includes a third determination circuit (2613) and a control circuit (262). The third determination circuit (2613) determines the direction in which the overcurrent flows based on the determination result of the first determination circuit (2611) and the determination result of the second determination circuit (2612). The control circuit (262) controls the first field effect transistor (Q1) and the second field effect transistor (Q2) based on the determination result of the third determination circuit (2613).

[0173] The switching device circuit (20) according to the fourteenth aspect is capable of controlling the first field effect transistor Q1 and the second field effect transistor Q2 based on the direction of the overcurrent.

[0174] A switchgear circuit (20) according to a fifteenth aspect is any one of the first to fourteenth aspects, further including a first clamp circuit (CC1) and a second clamp circuit (CC2). The first clamp circuit (CC1) is connected in parallel to the first inductor (L1) and clamps a voltage (VL1) between both ends of the first inductor (L1). The second clamp circuit (CC2) is connected in parallel to the second inductor (L2) and clamps a voltage (VL2) between both ends of the second inductor (L2).

[0175] The switching device circuit (20) according to the fifteenth aspect makes it possible to suppress variations in voltage (VL1) due to variations in inductance of the first inductor (L1) and the like before the source current of the first field effect transistor (Q1) is saturated.

[0176] The switchgear circuit (20) according to a sixteenth aspect is any one of the first to fourteenth aspects, further including a clamp circuit (CC3). The clamp circuit (CC3) clamps a voltage difference between a voltage (VL1) across the first inductor (L1) and a voltage (VL2) across the second inductor (L2).

[0177] The switching device circuit (20) according to the sixteenth aspect makes it possible to prevent the voltage difference between the voltage (VL1) across the first inductor (L1) and the voltage (VL2) across the second inductor (L2) from becoming too large.

[0178] A switching device circuit (20) according to a seventeenth aspect is any one of the first to sixth aspects, further comprising a gate power supply (25), a first resistive voltage divider circuit (RV1), and a second resistive voltage divider circuit (RV2). The first resistive voltage divider circuit (VR1) is connected between a positive electrode of the gate power supply (25) and a source (1S) of the first field effect transistor (Q1). The second resistive voltage divider circuit (RV2) is connected between a positive electrode of the gate power supply (25) and a source (2S) of the second field effect transistor (Q2). An output terminal of the first resistive voltage divider circuit (RV1) is connected to a gate (1G) of the first field effect transistor (Q1). An output terminal of the second resistive voltage divider circuit (RV2) is connected to a gate (2G) of the second field effect transistor (Q2).

[0179] The switching device circuit (20) according to the seventeenth aspect can make the first gate voltage (VgQ1) of the first field effect transistor (Q1) and the second gate voltage (VgQ2) of the second field effect transistor (Q2) different from each other.

[0180] A switching device circuit (20) according to an eighteenth aspect is any one of the first to sixth aspects, in which the first field effect transistor (Q1) and the second field effect transistor (Q2) are MOSFETs or normally-on type JFETs. The switching device circuit (20) further includes a gate power supply (25), a first capacitance (CQ1), and a second capacitance (CQ2). The first capacitance (CQ1) is connected between the positive electrode of the gate power supply (25) and the gate (1G) of the first field effect transistor (Q1). The second capacitance (CQ2) is connected between the positive electrode of the gate power supply (25) and the gate (2G) of the second field effect transistor (Q2).

[0181] The switching device circuit (20) according to the eighteenth aspect can make the first gate voltage (VgQ1) of the first field effect transistor (Q1) and the second gate voltage (VgQ2) of the second field effect transistor (Q2) different from each other.

[0182] A switching system (30) according to a nineteenth aspect includes the switching device circuit (20) according to any one of the first to eighteenth aspects, and a switching device (10).

[0183] The opening and closing system (30) according to the nineteenth aspect can reduce power loss.

[0184] A processing method according to a twentieth aspect is used in a switchgear (10). The switchgear (10) includes a first path (11) and a second path (12). The first path (11) includes a first field effect transistor (Q1) and a first inductor (L1). The first field effect transistor (Q1) has a gate (1G) and a source (1S). The first inductor (L1) is connected to the source (1S) of the first field effect transistor (Q1). The second path (12) includes a second field effect transistor (Q2) and a second inductor (L2). The second field effect transistor (Q2) has a gate (2G) and a source (2S). The second inductor (L2) is connected to the source (2S) of the second field effect transistor (Q2). The first path (11) and the second path (12) are connected in parallel to a power supply (Vdc). A first maximum current (ImQ1), which is a maximum current when the first field effect transistor (Q1) is conductive, is smaller than a second maximum current (ImQ2), which is a maximum current when the second field effect transistor (Q2) is conductive. The processing method performs a specific operation according to a voltage difference (ΔV) between a voltage (VL1) across the first inductor (L1) and a voltage (VL2) across the second inductor (L2).

[0185] The processing method according to the twentieth aspect makes it possible to suppress power loss. [Industrial Applicability]

[0186] The switchgear circuit, the switching system, and the processing method for the switchgear of the present disclosure can suppress the power loss of the switchgear. Therefore, the switchgear circuit, the switching system, and the processing method for the switchgear of the present disclosure can realize a switchgear with lower power consumption, and can reduce the power consumption of equipment using the switchgear. In this way, the switchgear circuit, the switching system, and the processing method for the switchgear of the present disclosure are industrially useful. [Explanation of symbols]

[0187] 10 Switchgear 20 Switchgear circuits 21 First drive circuit 211 Power supply for 1st gate 22 Second drive circuit 221 Power supply for 2nd gate 25, 251, 252 Gate power supply 26 Processing section 261 Judgment circuit 2611 1st judgment circuit 2612 Second judgment circuit 2613 Third judgment circuit 262 Control Circuit 30 Opening and Closing System CC1 First clamp circuit CC2 Second clamp circuit CC3 clamp circuit CQ1 1st capacity CQ2 2nd capacity I0, I1, I2 current Loa load L1 First inductor L2 Second inductor L0, L10 Common inductor Q1 First field effect transistor Q2 Second field effect transistor Q3 Third field effect transistor Q4 Fourth field effect transistor 1D, 2D, 3D, 4D Drain 1G, 2G, 3G, 4G Gates 1S, 2S, 3S, 4S Source Ig Gate current RgQ1 First gate resistor RgQ2 Second gate resistor RV1 First resistor divider circuit RV2 Second resistor divider circuit Vdc, Vac power supply VL1, VL2, VL3, VL4, VL10 Voltage Vg, Vgon1, Vgon2 gate voltages VgQ1 First gate voltage VgQ2 Second gate voltage VgQ3 3rd gate voltage VgQ4 4th gate voltage VsQ1, VsQ2 potential

Claims

1. a first path including a first field effect transistor having a gate and a source and a first inductor connected to the source of the first field effect transistor; a second path including a second field effect transistor having a gate and a source, and a second inductor connected to the source of the second field effect transistor, the first path and the second path are connected in parallel to a power source; a first maximum current, which is a maximum current when the first field effect transistor is conductive, is smaller than a second maximum current, which is a maximum current when the second field effect transistor is conductive; a processing unit that executes a specific operation in response to a voltage difference between a voltage across the first inductor and a voltage across the second inductor. Switchgear circuit.

2. The processing unit is activated in response to a trigger that a first current flowing through the first path and a second current flowing through the second path change from a current value less than the first maximum current to a current value equal to or greater than the first maximum current. A circuit for a switchgear device according to claim 1.

3. The specific operation includes an operation of determining that an overcurrent is flowing in the switching device when a predetermined change occurs in the voltage difference. A circuit for a switching device according to claim 1 or 2.

4. a gate voltage of the first field effect transistor when the first field effect transistor is conductive is smaller than a gate voltage of the second field effect transistor when the second field effect transistor is conductive; A circuit for a switchgear device according to any one of claims 1 to 3.

5. The inductance of the first inductor is smaller than the inductance of the second inductor. A circuit for a switching device according to any one of claims 1 to 4.

6. an on-resistance of the first field effect transistor is different from an on-resistance of the second field effect transistor; A circuit for a switching device according to any one of claims 1 to 5.

7. a first drive circuit including a first gate power supply connected to the gate of the first field effect transistor and driving the first field effect transistor; a second drive circuit including a second gate power supply connected to the gate of the second field effect transistor and driving the second field effect transistor; a negative electrode of the first gate power supply is connected to the source of the first field effect transistor; a negative electrode of the second gate power supply is connected to the source of the second field effect transistor; A circuit for a switchgear device according to any one of claims 1 to 6.

8. each of the first field effect transistor and the second field effect transistor is a junction field effect transistor; A gate power supply; a first gate resistor connected between the gate power supply and the gate of the first field effect transistor; a second gate resistor connected between the gate power supply and the gate of the second field effect transistor, a resistance value of the first gate resistor is greater than a resistance value of the second gate resistor; A circuit for a switchgear device according to any one of claims 1 to 6.

9. the specific operation includes an operation of limiting a current flowing through the second field effect transistor. A circuit for a switchgear device according to any one of claims 1 to 6.

10. a first drive circuit including a first gate power supply connected to the gate of the first field effect transistor and driving the first field effect transistor; a second drive circuit including a second gate power supply connected to the gate of the second field effect transistor and driving the second field effect transistor; a negative electrode of the first gate power supply and a negative electrode of the second gate power supply are connected to the source of the first field effect transistor; A circuit for a switchgear device according to claim 9.

11. each of the first field effect transistor and the second field effect transistor is a junction field effect transistor; A gate power supply; a first gate resistor connected between the gate power supply and the gate of the first field effect transistor; a second gate resistor connected between the gate power supply and the gate of the second field effect transistor, a resistance value of the first gate resistor is greater than a resistance value of the second gate resistor, The negative electrode of the gate power supply is connected to the source of the first field effect transistor. A circuit for a switchgear device according to claim 9.

12. a common inductor in which the first inductor and the second inductor are commonly connected; the specific operation is an operation of detecting an overcurrent by comparing a voltage difference between both ends of the common inductor and the voltage between both ends of the first inductor with a threshold value; A circuit for a switchgear device according to claim 1.

13. the first path further includes a third field effect transistor having a gate and a source, connected in anti-series to the first field effect transistor, and a third inductor connected to the source of the third field effect transistor; the second path further includes a fourth field effect transistor having a gate and a source, the fourth field effect transistor being connected in anti-series with the second field effect transistor, and a fourth inductor connected to the source of the fourth field effect transistor; The processing unit includes: a first determination circuit that determines whether or not an overcurrent occurs in the switching device 10 according to a voltage difference between a voltage across the first inductor and a voltage across the second inductor; a second determination circuit that determines whether or not an overcurrent occurs in the switching device based on a voltage difference between the voltage across the third inductor and the voltage across the fourth inductor. A circuit for a switching device according to any one of claims 1 to 11.

14. The processing unit includes: a third determination circuit that determines a direction in which an overcurrent is flowing based on a determination result of the first determination circuit and a determination result of the second determination circuit; a control circuit that controls the first field effect transistor and the second field effect transistor based on a determination result of the third determination circuit. A circuit for a switchgear device according to claim 13.

15. a first clamp circuit connected in parallel with the first inductor to clamp the voltage across the first inductor; a second clamp circuit connected in parallel to the second inductor and clamping the voltage across the second inductor. A circuit for a switching device according to any one of claims 1 to 14.

16. The switchgear circuit according to any one of claims 1 to 14, further comprising a clamp circuit that clamps a voltage difference between the voltage across the first inductor and the voltage across the second inductor.

17. A gate power supply; a first resistor voltage divider circuit connected between the positive electrode of the gate power supply and the source of the first field effect transistor; a second resistive voltage divider circuit connected between the positive electrode of the gate power supply and the source of the second field effect transistor, an output terminal of the first resistor voltage divider circuit is connected to the gate of the first field effect transistor; an output terminal of the second resistive voltage divider circuit is connected to the gate of the second field effect transistor; A circuit for a switchgear device according to any one of claims 1 to 6.

18. the first field effect transistor and the second field effect transistor are MOSFETs or normally-on JFETs, A gate power supply; a first capacitance connected between the positive electrode of the gate power supply and the gate of the first field effect transistor; a second capacitance connected between the positive electrode of the gate power supply and the gate of the second field effect transistor, A circuit for a switchgear device according to any one of claims 1 to 6.

19. A circuit for a switching device according to any one of claims 1 to 18; The opening and closing device, Opening and closing system.

20. a first path including a first field effect transistor having a gate and a source and a first inductor connected to the source of the first field effect transistor; a second path including a second field effect transistor having a gate and a source, and a second inductor connected to the source of the second field effect transistor, the first path and the second path are connected in parallel to a power source; a first maximum current, which is a maximum current when the first field effect transistor is conductive, is smaller than a second maximum current, which is a maximum current when the second field effect transistor is conductive; performing a particular action in response to a voltage difference between a voltage across the first inductor and a voltage across the second inductor; Processing methods.

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