On-state voltage measurement circuit

Abstract

The present invention improves on-voltage measurement accuracy. An on-voltage measurement circuit (1) is provided with a sensing switch element (2), a control unit (3), a resistance element (4), and a voltage sensing unit (5). The control unit (3) has a signal output terminal (31) and a reference potential terminal (32), and controls the sensing switch element (2). The resistance element (4) is connected between a source terminal (2S) of the sensing switch (2) and the reference potential terminal (32). The resistance element (4) has a resistance value greater than an on-resistance of the sensing switch element (2). The control unit (3) turns on the sensing switch element (2) when a semiconductor switch element (9) is turned on. The voltage sensing unit (5) senses an on-voltage of the semiconductor switch element (9), connected between a drain terminal (2D) of the sensing switch (2) and the reference potential terminal (32), from a voltage (V4) across the resistance element (4) when both the semiconductor switch element (9) and the sensing switch element (2) are on.

Description

[Technical Field]

[0001] The present disclosure relates to an on-voltage measurement circuit, and more particularly to an on-voltage measurement circuit that measures the on-voltage of a semiconductor switch element. [Background technology]

[0002] Patent Document 1 discloses a protection circuit that protects a semiconductor switching element (semiconductor switch element) from a short-circuit current. The semiconductor switching element is, for example, an IGBT.

[0003] The protection circuit includes a short circuit detection unit that detects a short circuit based on the voltage between the main electrodes (collector-emitter voltage) of the semiconductor switching element and the control voltage of the semiconductor switching element, and outputs a short circuit detection signal when a short circuit is detected. Here, the protection circuit includes a diode for detecting the voltage between the main electrodes of the semiconductor switching element.

[0004] In the protection circuit disclosed in Patent Document 1, the short-circuit detection unit receives as input a voltage that is the sum of the on-voltage of the semiconductor switching element and the forward voltage of the diode. This means that the short-circuit detection unit needs to know the forward voltage of the diode. If the on-voltage of the object to be measured is small, there is a concern that variations in the forward voltage of the diode may have a significant effect on the measurement accuracy of the on-voltage. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-32984 Summary of the Invention

[0006] An object of the present disclosure is to provide an on-voltage measurement circuit that can improve the measurement accuracy of the on-voltage.

[0010] An on-voltage measurement circuit according to one aspect of the present disclosure measures the on-voltage of a semiconductor switch element having a first control terminal, a first main terminal corresponding to the first control terminal, a second control terminal, and a second main terminal corresponding to the second control terminal. The on-voltage is the voltage between the first main terminal and the second main terminal when the semiconductor switch element is in an on-state. The on-voltage measurement circuit includes a detection switch element, a first control unit, a first resistor element, a first voltage detection unit, a second control unit, a second resistor element, and a second voltage detection unit. The detection switch element has a first gate terminal, a first source terminal corresponding to the first gate terminal, a second gate terminal, and a second source terminal corresponding to the second gate terminal. The first control unit has a first signal output terminal and a first reference potential terminal and controls a first gate voltage of the first gate terminal of the detection switch element. The first resistor element is connected between the first source terminal and the first reference potential terminal. The second control unit has a second signal output terminal and a second reference potential terminal and controls a second gate voltage of the second gate terminal of the detection switch element. The second resistance element is connected between the second source terminal and the second reference potential terminal. The resistance value of the first resistance element is greater than the on-resistance of the detection switch element. The resistance value of the second resistance element is greater than the on-resistance of the detection switch element. The first voltage detection unit detects the on-voltage of the semiconductor switch element connected between the first reference potential terminal and the second reference potential terminal from the voltage across the first resistance element when both the semiconductor switch element and the detection switch element are on. The second voltage detection unit detects the on-voltage of the semiconductor switch element connected between the first reference potential terminal and the second reference potential terminal from the voltage across the second resistance element when both the semiconductor switch element and the detection switch element are on.

[0011] An on-voltage measurement circuit according to one aspect of the present disclosure measures the on-voltage of a semiconductor switch element having a first control terminal, a first main terminal corresponding to the first control terminal, a second control terminal, and a second main terminal corresponding to the second control terminal. The on-voltage is the voltage between the first main terminal and the second main terminal when the semiconductor switch element is in an on-state. The on-voltage measurement circuit includes a first detection switch element, a first control unit, a second detection switch element, a second control unit, a resistive element, and a voltage detection unit. The first detection switch element has a first drain terminal, a first source terminal, and a first gate terminal. The first control unit has a first signal output terminal and a first reference potential terminal and controls the first detection switch element. The second detection switch element has a second drain terminal, a second source terminal, and a second gate terminal. The second control unit has a second signal output terminal and a second reference potential terminal and controls the second detection switch element. The resistive element is connected between the first source terminal of the first detecting switch element and the second source terminal of the second detecting switch element. The first signal output terminal of the first control unit is connected to the first gate terminal of the first detecting switch element. The first reference potential terminal of the first control unit is connected to the second source terminal of the second detecting switch element. The second signal output terminal of the second control unit is connected to the second gate terminal of the second detecting switch element. The second reference potential terminal of the second control unit is connected to the first source terminal of the first detecting switch element. The resistance value of the resistive element is greater than the on-resistance of the first detecting switch element and the on-resistance of the second detecting switch element. The voltage detecting unit detects the on-voltage of the semiconductor switch element connected between the first reference potential terminal and the second reference potential terminal from the voltage across the resistive element when the semiconductor switch element is on.

[0012] An on-voltage measurement circuit according to one aspect of the present disclosure measures the on-voltage of a semiconductor switch element having a first control terminal, a first main terminal corresponding to the first control terminal, a second control terminal, and a second main terminal corresponding to the second control terminal. The on-voltage is the voltage between the first main terminal and the second main terminal when the semiconductor switch element is in an on-state. The on-voltage measurement circuit includes a normally-on first detection switch element, a normally-on second detection switch element, a resistive element, and a voltage detection unit. The first detection switch element has a first drain terminal, a first source terminal, and a first gate terminal. The second detection switch element has a second drain terminal, a second source terminal, and a second gate terminal. The resistive element is connected between the first source terminal of the first detection switch element and the second source terminal of the second detection switch element. In the on-voltage measurement circuit, the first source terminal of the first detection switch element is connected to the second gate terminal of the second detection switch element. The second source terminal of the second detecting switch element is connected to the first gate terminal of the first detecting switch element. The resistance value of the resistive element is greater than the on-resistance of the first detecting switch element and the on-resistance of the second detecting switch element. The voltage detection unit detects the on-voltage of the semiconductor switch element connected between the first source terminal and the second source terminal from the voltage across the resistive element when the semiconductor switch element is on. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a circuit diagram of a switch system including an on-state voltage measurement circuit according to a first embodiment. [Figure 2] FIG. 2 is an operational waveform diagram of the switch system including the on-state voltage measurement circuit. [Figure 3] FIG. 3 is an operational waveform diagram of the switch system including the on-state voltage measurement circuit. [Figure 4] FIG. 4 is a circuit diagram of a modified example of the switch system including the on-state voltage measurement circuit. [Figure 5] FIG. 5 is a circuit diagram of a switch system including an on-state voltage measurement circuit according to the second embodiment. [Figure 6] FIG. 6 is a circuit diagram of a switch system including an on-state voltage measurement circuit according to the third embodiment. [Figure 7] FIG. 7 is a circuit diagram of a switch system including an on-state voltage measurement circuit according to the fourth embodiment. [Figure 8] FIG. 8 is a timing chart for explaining the operation of the switch system including the on-state voltage measurement circuit. [Figure 9] FIG. 9 is an equivalent circuit diagram of a switch system including an on-state voltage measurement circuit according to the first embodiment, illustrating the influence of parasitic inductance in the switch system. [Figure 10] FIG. 10 is an operational waveform diagram of the equivalent circuit diagram of the above. [Figure 11] FIG. 11 is a timing chart for explaining another example of the operation of the switch system including the on-state voltage measurement circuit according to the fourth embodiment. [Figure 12] FIG. 12 is a circuit diagram of a switch system including an on-state voltage measurement circuit according to the fifth embodiment. [Figure 13] FIG. 13 is a timing chart for explaining the operation of the switch system including the on-state voltage measurement circuit. [Figure 14] FIG. 14 is a timing chart for explaining another example of the operation of the switch system including the on-state voltage measurement circuit according to the fifth embodiment. [Figure 15] FIG. 15 is a circuit diagram of a switch system including an on-state voltage measurement circuit according to the sixth embodiment. [Figure 16] FIG. 16 is a circuit diagram of a switch system including an on-state voltage measurement circuit according to the seventh embodiment. [Figure 17] FIG. 17 is a circuit diagram of a switch system including an on-state voltage measurement circuit according to the eighth embodiment. [Figure 18]18A and 18B are explanatory diagrams illustrating the operation of the switch system including the on-state voltage measurement circuit of the same. [Figure 19] 19A and 19B are explanatory diagrams of an example of operation when the on-state voltage measurement circuit does not include a first capacitor and a second capacitor, respectively. [Figure 20] FIG. 20 is a circuit diagram of a switch system including an on-state voltage measurement circuit according to the ninth embodiment. [Figure 21] FIG. 21 is a circuit diagram of a switch system including an on-state voltage measurement circuit according to the tenth embodiment. [Figure 22] FIG. 22 is a circuit diagram of a switch system including an on-state voltage measurement circuit according to the eleventh embodiment. [Figure 23] FIG. 23 is a circuit diagram of a switch system including an on-state voltage measurement circuit according to the twelfth embodiment. [Figure 24] FIG. 24 is a circuit diagram of a switch system including an on-state voltage measurement circuit according to the thirteenth embodiment. [Figure 25] FIG. 25 is a circuit diagram of a switch system including an on-state voltage measurement circuit according to the fourteenth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0014] (Embodiment 1) A switch system 10 including an on-state voltage measurement circuit 1 according to the first embodiment will be described below with reference to FIGS.

[0015] (1) Overview 1, the switch system 10 includes an on-state voltage measurement circuit 1 and a semiconductor switch element 9. The semiconductor switch element 9 has a control terminal 90, a first main terminal 91, and a second main terminal 92. The on-state voltage measurement circuit 1 measures the on-state voltage of the semiconductor switch element 9. The on-state voltage of the semiconductor switch element 9 is the voltage between the first main terminal 91 and the second main terminal 92 when the semiconductor switch element 9 is in the on state.

[0016] The on-state voltage measuring circuit 1 includes a detection switch element 2, a control unit 3, a resistance element 4, and a voltage detection unit 5. The detection switch element 2 has a drain terminal 2D, a source terminal 2S, and a gate terminal 2G.

[0017] The switch system 10 further includes a switch control unit 11 that controls the semiconductor switch element 9. In the switch system 10, for example, a series circuit of a load 15 and a power supply 16 is connected between a first main terminal 91 and a second main terminal 92 of the semiconductor switch element 9. The load 15 and the power supply 16 are not components of the switch system 10.

[0018] (2) Components of the switch system (2.1) Semiconductor Switching Elements The semiconductor switch element 9 is, for example, a normally-off type JFET (Junction Field Effect Transistor). More specifically, the semiconductor switch element 9 is a GaN-based GATE INJECTION TRANSISTOR (GIT). Here, a control terminal 90, a first main terminal 91, and a second main terminal 92 of the semiconductor switch element 9 are a gate terminal, a drain terminal, and a source terminal, respectively.

[0019] The GaN-based GIT includes, for example, a GIT chip and a package accommodating the GIT chip. The GIT 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. The second nitride semiconductor layer and the first nitride semiconductor layer form a heterojunction. In the first nitride semiconductor layer, two-dimensional electron gas is generated near the heterojunction. The region containing the two-dimensional electron gas (hereinafter also referred to as the "two-dimensional electron gas layer") can function as an n-channel layer (electron conduction layer). In the GIT chip, the p-type layer, the second nitride semiconductor layer, and the n-channel layer form a pin diode structure. The second nitride semiconductor layer and the p-type layer form a diode. The gate in the GIT chip includes a gate electrode and a p-type layer. The source in the GIT chip includes a source electrode. The drain in the GIT chip 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. The package has a control terminal 90, a first main terminal 91 and a second main terminal 92 connected to the gate electrode, drain electrode and source electrode, respectively.

[0020] (2.2) Switch control section The switch control unit 11 outputs a control signal S9 (see FIG. 2) that controls the semiconductor switch element 9. The control signal S9 is a voltage signal that is applied between the control terminal 90 and the second main terminal 92 of the semiconductor switch element 9. When turning on the semiconductor switch element 9, the switch control unit 11 outputs, as the control signal S9, a voltage signal (ON signal) whose voltage level is higher than the threshold voltage Vth9 (see FIG. 2) of the semiconductor switch element 9. When turning off the semiconductor switch element 9, the switch control unit 11 outputs, as the control signal S9, a voltage signal (OFF signal) whose voltage level is lower than the threshold voltage Vth9 of the semiconductor switch element 9.

[0021] The switch control section 11 includes, for example, a drive circuit that drives the semiconductor switch element 9 and a control circuit that controls the drive circuit, but is not limited to this and may be, for example, a driver IC (Integrated Circuit).

[0022] (2.3) On-state voltage measurement circuit The on-state voltage measuring circuit 1 includes a detection switch element 2, a control unit 3, a resistance element 4, and a voltage detection unit 5. The detection switch element 2 has a drain terminal 2D, a source terminal 2S, and a gate terminal 2G. The control unit 3 has a signal output terminal 31 and a reference potential terminal 32, and controls the detection switch element 2. The resistance element 4 is connected between the source terminal 2S and the reference potential terminal 32. One end of the resistance element 4 is connected to the source terminal 2S, and the other end of the resistance element 4 is connected to the reference potential terminal 32. The voltage detection unit 5 detects the on-state voltage of the semiconductor switch element 9.

[0023] The detection switch element 2 is a normally-off type switch element. Here, the detection switch element 2 is a normally-off type JFET, similar to the semiconductor switch element 9. More specifically, the detection switch element 2 is a GaN-based GaN transistor.

[0024] The control unit 3 turns off the detection switch element 2 when the semiconductor switch element 9 is turned off, and turns on the detection switch element 2 when the semiconductor switch element 9 is turned on. The voltage detection unit 5 detects the on-voltage of the semiconductor switch element 9 connected between the drain terminal 2D and the reference potential terminal 32 from the voltage V4 across the resistor element 4 when both the semiconductor switch element 9 and the detection switch element 2 are turned on.

[0025] In the control unit 3, the signal output terminal 31 is connected to the gate terminal 2G of the detection switch element 2. In addition, in the control unit 3, the reference potential terminal 32 is connected to the source terminal 2S of the detection switch element 2 via the resistor element 4. When turning on the detection switch element 2, the control unit 3 outputs an ON signal as the control signal S2 (see FIG. 2) to turn on the detection switch element 2. The ON signal that turns on the detection switch element 2 is a voltage signal of a voltage level (e.g., 5 V) such that the gate voltage (voltage between the gate terminal 2G and the source terminal 2S) of the detection switch element 2 is greater than the threshold voltage Vth2 of the detection switch element 2. When turning off the detection switch element 2, the control unit 3 outputs an OFF signal as the control signal S2 to turn off the detection switch element 2. The OFF signal that turns off the detection switch element 2 is a voltage signal of a voltage level (e.g., 0 V) ​​such that the gate voltage (voltage between the gate terminal 2G and the source terminal 2S) of the detection switch element 2 is less than the threshold voltage Vth2 of the detection switch element 2.

[0026] The control unit 3 is also connected to the voltage detection unit 5. The control unit 3 controls the detection switch element 2 based on the on-voltage detected by the voltage detection unit 5. More specifically, the control unit 3 turns off the detection switch element 2 when the on-voltage detected by the voltage detection unit 5 becomes equal to or greater than a threshold Vt (see FIGS. 2 and 3). In the switch system 10 including the on-voltage measurement circuit 1, the switch control unit 11 turns off the semiconductor switch element 9 when the on-voltage detected by the voltage detection unit 5 becomes equal to or greater than the threshold Vt. The threshold Vt is a voltage value set for detecting an abnormality when the semiconductor switch element 9 is in the on state.

[0027] The control unit 3 includes, but is not limited to, a drive circuit that provides a control signal S2 to the detection switch element 2 and a power supply connected to the drive circuit.

[0028] The control unit 3 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. At least a portion of the functions of the control unit 3 in the present disclosure are realized by the processor executing a program recorded in the memory of the computer system. The program may be pre-recorded in the memory of the computer system, provided via a telecommunications line, or recorded and provided on a non-transitory recording medium such as a memory card, optical disk, or hard disk drive (magnetic disk) readable 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 into a single chip or distributed across multiple chips. The multiple chips may be integrated into a single device or distributed across multiple devices.

[0029] The resistance value of the resistive element 4 is greater than the on-resistance Ron2 of the detecting switch element 2. The resistance value of the resistive element 4 is, for example, 10 times the on-resistance Ron2 of the detecting switch element 2.

[0030] The voltage detection unit 5 is connected across the resistance element 4. The voltage detection unit 5 detects the on-voltage of the semiconductor switch element 9 connected between the drain terminal 2D and the reference potential terminal 32 from the voltage V4 across the resistance element 4 when both the semiconductor switch element 9 and the detection switch element 2 are on.

[0031] If the on-voltage of the semiconductor switch element 9 is Von9, the resistance value of the resistor element 4 is R4, and the on-resistance of the detection switch element 2 is Ron2, the voltage output to the voltage detection unit 5 (voltage V4 across the resistor element 4) is V4={R4 / (Ron2+R4)}×Von9 This becomes:

[0032] The on-resistance of the detection switch element 2 is the resistance value between the drain terminal 2D and the source terminal 2S when the detection switch element 2 is in the on-state. The on-resistance of the detection switch element 2 is affected by the temperature and gate voltage of the detection switch element 2. Therefore, if the effect of the on-resistance of the detection switch element 2 on the voltage V4 across the resistor element 4 is to be N (%) or less, the resistance value R4 of the resistor element 4 is R4≧{(100-N) / N}×Ron2 This becomes:

[0033] Therefore, in order to keep N at 10% or less, it is desirable that the resistance value of the resistive element 4 be 9 times or more the on-resistance Ron2 of the detection switch element 2.

[0034] The voltage detection unit 5 also has a function of determining the state of the semiconductor switch element 9 based on the detected on-voltage. For example, the voltage detection unit 5 compares the detected on-voltage with a threshold Vt, and determines that there is no abnormality if the on-voltage is less than the threshold Vt, and determines that there is an abnormality if the on-voltage is equal to or greater than the threshold Vt. "No abnormality" means that no abnormal current is flowing through the semiconductor switch element 9. "Abnormality" means that an abnormal current is flowing through the semiconductor switch element 9, and the voltage V9 is higher than the voltage V9 in the on-state of the semiconductor switch element 9 when no abnormal current is flowing through the semiconductor switch element 9. The voltage detection unit 5 includes, for example, a comparator that compares the on-voltage with the threshold Vt. In this case, the voltage detection unit 5 is configured so that the threshold Vt is input to the inverting terminal of the comparator, and the on-voltage detected by the voltage detection unit 5 (the voltage V4 across the resistor element 4) is input to the non-inverting terminal. In the voltage detection unit 5, when the voltage V4 is equal to or greater than the threshold Vt, the output signal of the comparator becomes H level, and when the voltage V4 is less than the threshold Vt, the output signal of the comparator becomes L level. In the voltage detection unit 5, when the output signal of the comparator is H level, it means that it has determined that an abnormal current is flowing through the semiconductor switch element 9 (there is an abnormality), and when the output signal of the comparator is L level, it means that it has determined that no abnormal current is flowing through the semiconductor switch element 9 (there is no abnormality). In the on-voltage measurement circuit 1, the output terminal of the voltage detection unit 5 is connected to the control unit 3, and the determination result of the voltage detection unit 5 is input to the control unit 3. In the switch system 10, the output terminal of the voltage detection unit 5 is connected to the switch control unit 11, and the determination result of the voltage detection unit 5 is input to the switch control unit 11.

[0035] (3) Switch system operation Fig. 2 is a diagram showing an example of operational waveforms when no abnormality occurs in the semiconductor switch element 9 in the switch system 10. Fig. 3 is a diagram showing an example of operational waveforms when an abnormality occurs in the semiconductor switch element 9 during the operation of the switch system 10.

[0036] In Fig. 2, S9 is a control signal given from the switch control unit 11 to the semiconductor switch element 9. In Fig. 2, S2 is a control signal given from the control unit 3 to the detection switch element 2. In Figs. 1 to 3, V9 is the voltage between the first main terminal (drain terminal) 91 and the second main terminal (source terminal) 92 of the semiconductor switch element 9. Also in Figs. 1 to 3, V2 is the voltage between the drain terminal 2D and the source terminal 2S of the detection switch element 2. Also in Figs. 1 to 3, V4 is the voltage across the resistor element 4.

[0037] (3.1) Example of operation when no abnormality occurs in the semiconductor switch element An example of the operation of the switch system 10 when no abnormality occurs in the semiconductor switch element 9 will be described with reference to FIG.

[0038] In the switch system 10, when an OFF signal is given to the semiconductor switch element 9 and the semiconductor switch element 9 is in an OFF state, the voltage V9 of the semiconductor switch element 9 becomes the voltage across the series circuit of the power supply 16 and the load 15. In addition, in the switch system 10, when the semiconductor switch element 9 is in an OFF state and an OFF signal is given to the detection switch element 2 and the detection switch element 2 is in an OFF state, the voltage V2 of the detection switch element 2 becomes substantially the same voltage value as the voltage V9. In addition, in the switch system 10, when the semiconductor switch element 9 is in an OFF state and the detection switch element 2 is in an OFF state, no current flows through the resistance element 4, and therefore the voltage V4 becomes 0 V.

[0039] In the switch system 10, when an on signal is given to the semiconductor switch element 9 and the semiconductor switch element 9 is in an on state, the voltage V9 of the semiconductor switch element 9 becomes the on voltage Von9 of the semiconductor switch element 9. In addition, in the switch system 10, when the semiconductor switch element 9 is in an off state and an on signal is given to the detection switch element 2 and the detection switch element 2 is in an on state, the voltage V2 of the detection switch element 2 becomes the on voltage Von2 of the detection switch element 2. In addition, in the switch system 10, when the semiconductor switch element 9 is in an on state and the detection switch element 2 is in an on state, a current flows through the resistance element 4, and therefore the voltage V4 becomes a voltage value determined by the resistance value of the resistance element 4 and the current value of the current flowing through the resistance element 4. This voltage value is smaller than the above-mentioned threshold Vt.

[0040] (3.2) Operation when an abnormality occurs in the semiconductor switch element during operation An example of the operation of the switch system 10 when an abnormality occurs in the semiconductor switch element 9 during operation will be described with reference to FIG.

[0041] In switch system 10, when semiconductor switch element 9 is in the on state and detection switch element 2 is in the on state, if an abnormality occurs in semiconductor switch element 9, causing an increase in current flowing through semiconductor switch element 9 and an increase in voltage V9 of semiconductor switch element 9, the current flowing through resistor element 4 also increases and voltage V4 of resistor element 4 also increases. In switch system 10, when the on voltage (voltage V4) detected by voltage detection unit 5 becomes equal to or greater than threshold Vt, switch control unit 11 turns off semiconductor switch element 9 and control unit 3 turns off detection switch element 2. This makes it possible for switch system 10 to cut off the abnormal current flowing through semiconductor switch element 9 when an abnormal current flows through semiconductor switch element 9.

[0042] (4) Advantages The on-state voltage measurement circuit 1 according to the first embodiment includes a series circuit including a detection switch element 2 and a resistance element 4 having a resistance value greater than the on-state resistance of the detection switch element 2, and this series circuit is connected in parallel to a semiconductor switch element 9 whose on-state voltage is to be measured. In the on-state voltage measurement circuit 1 according to the first embodiment, the voltage detection unit 5 detects the on-state voltage of the semiconductor switch element 9 connected between the drain terminal 2D and the reference potential terminal 32 from the voltage V4 across the resistance element 4 when both the semiconductor switch element 9 and the detection switch element 2 are on. In the on-state voltage measurement circuit 1 according to the first embodiment, most of the on-state voltage of the semiconductor switch element 9 is applied to the resistance element 4, which improves the accuracy of measuring the on-state voltage.

[0043] Furthermore, the on-state voltage measuring circuit 1 according to the first embodiment can detect an abnormality in which an abnormal current flows through the semiconductor switch element 9 by comparing the detected on-state voltage with the threshold value Vt in the voltage detection unit 5.

[0044] (Modification of the first embodiment) A switch system 10 according to a modification of the first embodiment will be described below with reference to FIG.

[0045] The circuit configuration of the switch system 10 according to the modified example of the first embodiment is substantially the same as the circuit configuration of the switch system 10 according to the first embodiment shown in Fig. 1. In the switch system 10 according to the modified example, the same components as those in the switch system 10 according to the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted.

[0046] A switch system 10 according to a modification of the first embodiment includes a plurality of semiconductor switch elements 9. The plurality of semiconductor switch elements 9 are connected in parallel. In the on-voltage measurement circuit 1, a series circuit of a detection switch element 2 and a resistance element 4 is connected to a parallel circuit of the plurality of semiconductor switch elements 9. Therefore, the on-voltage measurement circuit 1 measures the on-voltage of the plurality of semiconductor switch elements 9 connected in parallel. This allows the on-voltage measurement circuit 1 to measure on-voltages that have the same voltage value across the plurality of semiconductor switch elements 9 connected in parallel.

[0047] (Embodiment 2) A switch system 10a including an on-state voltage measurement circuit 1a according to the second embodiment will be described below with reference to Fig. 5. Note that, with regard to the on-state voltage measurement circuit 1a and the switch system 10a according to the second embodiment, components similar to those of the on-state voltage measurement circuit 1 and the switch system 10 according to the first embodiment are designated by the same reference numerals, and descriptions thereof will be omitted as appropriate.

[0048] The switch system 10a includes an on-voltage measuring circuit 1a instead of the on-voltage measuring circuit 1 in the switch system 10.

[0049] The on-state voltage measurement circuit 1a according to the second embodiment includes a control unit 3a instead of the control unit 3 of the on-state voltage measurement circuit 1 according to the first embodiment. The control unit 3a, like the control unit 3, has a signal output terminal 31 and a reference potential terminal 32. The control unit 3a not only controls the detection switch element 2 like the on-state voltage measurement circuit 1 according to the first embodiment, but also controls the semiconductor switch element 9. That is, the control unit 3a also functions as the switch control unit 11 in the switch system 10 including the on-state voltage measurement circuit 1 according to the first embodiment. The control unit 3a is connected to both the detection switch element 2 and the semiconductor switch element 9. More specifically, the signal output terminal 31 of the control unit 3a is connected to the gate terminal 2G of the detection switch element 2 and the control terminal (gate terminal) 90 of the semiconductor switch element 9. The reference potential terminal 32 of the control unit 3a is connected to the source terminal 2S of the detection switch element 2 via the resistor 4. The reference potential terminal 32 is also connected to the second main terminal 92 of the semiconductor switch element 9. A switch system 10a including an on-state voltage measurement circuit 1a does not include the switch control unit 11 in the switch system 10 including the on-state voltage measurement circuit 1 according to the first embodiment.

[0050] The on-state voltage measurement circuit 1a according to the second embodiment facilitates control of turning on and off the detection switch element 2 in accordance with the on and off timing of the semiconductor switch element 9. Furthermore, the switch system 10a including the on-state voltage measurement circuit 1a according to the second embodiment can reduce the number of components compared to the switch system 10 including the on-state voltage measurement circuit 1 according to the first embodiment.

[0051] (Embodiment 3) A switch system 10b including an on-state voltage measurement circuit 1b according to the third embodiment will be described below with reference to Fig. 6. Note that, with regard to the on-state voltage measurement circuit 1b and the switch system 10b according to the third embodiment, components similar to those of the on-state voltage measurement circuit 1 and the switch system 10 according to the first embodiment are designated by the same reference numerals, and descriptions thereof will be omitted as appropriate.

[0052] An on-state voltage measurement circuit 1b according to the third embodiment includes a voltage detection unit 5b instead of the voltage detection unit 5 of the on-state voltage measurement circuit 1 according to the first embodiment. A switch system 10b including the on-state voltage measurement circuit 1b according to the third embodiment further includes a temperature detection unit 19. The temperature detection unit 19 detects the temperature of the semiconductor switch element 9. The temperature detection unit 19 is, for example, a thermistor. The temperature detection unit 19 is not limited to a thermistor and may be, for example, a diode.

[0053] The on-resistance of the semiconductor switch element 9 may increase due to a rise in the temperature of the semiconductor switch element 9. In the semiconductor switch element 9, if the on-resistance differs, the current value of the current actually flowing through the semiconductor switch element 9 tends to differ even if the on-voltage is the same. In the semiconductor switch element 9, the larger the on-resistance is, the smaller the current value of the current flowing through the semiconductor switch element 9 tends to be.

[0054] The voltage detection unit 5b corrects the threshold value Vt, which is compared with the detected on-voltage, in accordance with the temperature detected by the temperature detection unit 19. Here, the voltage detection unit 5b corrects the threshold value Vt to a higher voltage value as the detected temperature increases.

[0055] The on-state voltage measuring circuit 1b according to the third embodiment is capable of correcting the detected on-state voltage in the voltage detecting unit 5b in accordance with temperature changes in the semiconductor switch element 9. This makes it possible for the switch system 10b including the on-state voltage measuring circuit 1b to suppress variations in the interruption current value when the semiconductor switch element 9 is interrupted when an abnormal current flows through the semiconductor switch element 9.

[0056] (Embodiment 4) A switch system 10c including an on-state voltage measurement circuit 1c according to the fourth embodiment will be described below with reference to Figures 7 and 8. Note that, with regard to the on-state voltage measurement circuit 1c and the switch system 10c according to the fourth embodiment, components that are the same as those in the on-state voltage measurement circuit 1 and the switch system 10 according to the first embodiment are denoted by the same reference numerals, and descriptions thereof will be omitted as appropriate. Figure 8 is a diagram showing an example of operating waveforms in the switch system 10c when no abnormality occurs in the semiconductor switch element 9, and each waveform can be viewed in the same way as in Figure 2.

[0057] In the on-state voltage measuring circuit 1c, the control unit 3 turns on the detection switch element 2 after the semiconductor switch element 9 is turned on.

[0058] The on-state voltage measuring circuit 1c further includes a gate resistor 121 and a gate capacitor 122. The gate resistor 121 is connected between the signal output terminal 31 of the control unit 3 and the gate terminal 2G of the detection switch element 2. The gate capacitor 122 is connected between the gate terminal 2G and the source terminal 2S of the detection switch element 2. The switch system 10c includes a driver 110 instead of the switch control unit 11, and further includes a resistor 111 and a capacitor 112. In the semiconductor switch element 9, the control terminal 90 is connected to the driver 110 via the resistor 111, and the capacitor 112 is connected between the control terminal 90 and the second main terminal 92. In the on-state voltage measuring circuit 1c, the time constant determined by the gate resistor 121 (its resistance value) and the gate capacitor 122 (its capacitance) is larger than the time constant determined by the resistor 111 (its resistance value) and the capacitor 112 (its capacitance). 8, in the on-state voltage measurement circuit 1c, it is possible to differentiate between a first timing at which the voltage VG9 at the control terminal 90 of the semiconductor switch element 9 reaches the threshold voltage Vth9 and a second timing at which the voltage VG2 at the gate terminal 2G of the detection switch element 2 reaches the threshold voltage Vth2. The second timing is later than the first timing. Note that the on-state voltage measurement circuit 1c may include a control circuit that controls the control unit 3 and the driver 110, or the control unit 3 may be configured to operate based on operation information from the driver 110.

[0059] In the on-state voltage measurement circuit 1 according to the first embodiment (see FIG. 1 ), the voltage V4 across the resistor 4 may be susceptible to the influence of the parasitic inductance of the wiring connected to the second main terminal 92 of the semiconductor switch element 9. More specifically, in the on-state voltage measurement circuit 1 according to the first embodiment, the electromotive force generated due to the parasitic inductance and the rate of change of the current flowing through the semiconductor switch element 9 increases immediately after the semiconductor switch element 9 is turned on, and the voltage V4 tends to increase. FIG. 9 is an equivalent circuit of a switch system 10 including the on-state voltage measurement circuit 1 including a parasitic inductor L1 having a parasitic inductance. FIG. 10 is a waveform diagram illustrating an example of the operation of the switch system 10 in the equivalent circuit of FIG. 9 . FIG. 10 is a diagram illustrating an example of operational waveforms when no abnormality occurs in the semiconductor switch element 9 in the switch system 10, and the interpretation of each waveform is the same as in FIG. 2 . In FIGS. 9 and 10 , VL1 is the electromotive force of the parasitic inductor L1. As can be seen from FIG. 10, immediately after the semiconductor switch element 9 is turned on, V9+VL1 becomes a voltage value greater than the on-voltage Von9, and the voltage V4 across the resistor element 4 may become greater than the threshold value Vt.

[0060] In contrast, in the on-state voltage measurement circuit 1c according to the fourth embodiment, no voltage is applied to the resistance element 4 for the one-point time T1 after the semiconductor switch element 9 is turned on, thereby improving the measurement accuracy of the on-state voltage detected by the voltage detection unit 5. More specifically, in the on-state voltage measurement circuit 1c according to the fourth embodiment, the on-state voltage detected by the voltage detection unit 5 when no abnormal current is flowing through the semiconductor switch element 9 is less susceptible to the influence of the electromotive force of the parasitic inductor L1. As a result, the on-state voltage measurement circuit 1c according to the fourth embodiment can prevent the on-state voltage detected by the voltage detection unit 5 from exceeding the threshold value Vt when no abnormal current is flowing through the semiconductor switch element 9. The one-point time T1 is a time corresponding to the time difference between the first timing and the second timing.

[0061] In the on-state voltage measurement circuit 1c, in order to turn on the detection switch element 2 after the semiconductor switch element 9 is turned on, the time constant determined by the gate resistor 121 and the gate capacitor 122 is set to be larger than the time constant determined by the resistor 111 and the capacitor 112, but this is not limiting. For example, the on-state voltage measurement circuit 1c may be configured to turn on the detection switch element 2 after the semiconductor switch element 9 is turned on by setting the threshold voltage Vth2 of the detection switch element 2 to be larger than the threshold voltage Vth9 of the semiconductor switch element 9.

[0062] In addition, in the on-voltage measuring circuit 1c, the same operation is possible by delaying the control signal S2 (the rising point of the on signal in it) from the control signal S9 (the rising point of the on signal in it) as shown in FIG.

[0063] (Embodiment 5) A switch system 10d including an on-state voltage measurement circuit 1d according to the fifth embodiment will be described below with reference to Figures 12 and 13. Note that, with regard to the on-state voltage measurement circuit 1d and the switch system 10d according to the fifth embodiment, components that are the same as those in the on-state voltage measurement circuit 1 and the switch system 10 according to the first embodiment are designated by the same reference numerals, and descriptions thereof will be omitted as appropriate. Figure 13 is a diagram showing an example of operating waveforms in the switch system 10d when no abnormality occurs in the semiconductor switch element 9, and each waveform can be viewed in the same way as in Figure 2.

[0064] In the on-state voltage measuring circuit 1d, the detection switch element 2 is turned on before the semiconductor switch element 9 is turned on.

[0065] The on-state voltage measuring circuit 1d further includes a gate resistor 121 and a gate capacitor 122. The gate resistor 121 is connected between the signal output terminal 31 and the gate terminal 2G of the detection switch element 2. The gate capacitor 122 is connected between the gate terminal 2G and the source terminal 2S of the detection switch element 2. In the semiconductor switch element 9, the control terminal 90 is connected to the driver 110 via a resistor 111, and the capacitor 112 is connected between the control terminal 90 and the second main terminal 92. In the on-state voltage measuring circuit 1d, the time constant determined by the gate resistor 121 (its resistance value) and the gate capacitor 122 (its capacitance) is smaller than the time constant determined by the resistor 111 (its resistance value) and the capacitor 112 (its capacitance).

[0066] In the on-state voltage measuring circuit 1d, the detection switch element 2 is turned on before the semiconductor switch element 9 is turned on. Therefore, if a current collapse occurs in which the on-state resistance increases when the semiconductor switch element 9 is turned on, it is possible to detect the change over time in the on-state voltage of the semiconductor switch element 9 due to the influence of the current collapse.

[0067] In the on-state voltage measurement circuit 1d, in order to turn on the detection switch element 2 before the semiconductor switch element 9 is turned on, the time constant determined by the gate resistor 121 and the gate capacitor 122 is set to be smaller than the time constant determined by the resistor 111 and the capacitor 112, but this is not limitative. For example, the on-state voltage measurement circuit 1d may be configured to turn on the detection switch element 2 before the semiconductor switch element 9 is turned on by setting the threshold voltage Vth2 of the detection switch element 2 smaller than the threshold voltage Vth9 of the semiconductor switch element 9.

[0068] In addition, in the on-voltage measuring circuit 1d, the same operation is possible by delaying the control signal S9 (the rising point of the on signal in it) from the control signal S2 (the rising point of the on signal in it) as shown in FIG.

[0069] (Embodiment 6) A switch system 10e including an on-state voltage measurement circuit 1e according to the sixth embodiment will be described below with reference to Fig. 15. The on-state voltage measurement circuit 1e according to the sixth embodiment differs from the on-state voltage measurement circuit 1 according to the first embodiment in that the semiconductor switch element 9e to be measured is a bidirectional switch element, and in that the on-state voltage measurement circuit 1e according to the sixth embodiment includes two sets similar to the set of the detection switch element 2, the control unit 3, the resistance element 4, and the voltage detection unit 5.

[0070] The on-voltage measuring circuit 1e measures the on-voltage of a semiconductor switch element 9e having a first control terminal 90A, a first main terminal 91A corresponding to the first control terminal 90A, a second control terminal 90B, and a second main terminal 92B corresponding to the second control terminal 90B. The on-voltage is the voltage between the first main terminal 91A and the second main terminal 92B when the semiconductor switch element 9e is in the on state.

[0071] The semiconductor switch element 9e is a dual-gate GaN-based GIT. The GaN-based GIT includes, for example, a GaN-based GIT chip and a package. The GaN-based GIT chip includes, for example, a substrate, a buffer layer, a first nitride semiconductor layer, a second nitride semiconductor layer, a first source electrode, a first gate electrode, a second gate electrode, a second source electrode, a first p-type layer, and a second p-type layer. The first nitride semiconductor layer is, for example, a GaN layer. The second nitride semiconductor layer is, for example, an AlGaN layer. The first p-type layer is, for example, a p-type AlGaN layer. The second p-type layer is, for example, a p-type AlGaN layer. The first nitride semiconductor layer is formed on the substrate via a buffer layer. The second nitride semiconductor layer is formed on the first nitride semiconductor layer. The band gap of the second nitride semiconductor layer is larger than the band gap of the first nitride semiconductor layer. The first source electrode is formed on the second nitride semiconductor layer. The first gate electrode is formed on the second nitride semiconductor layer and is spaced apart from the first source electrode. The second gate electrode is formed on the second nitride semiconductor layer and is spaced apart from the first gate electrode on the opposite side of the first source electrode as viewed from the first gate electrode. The second source electrode is formed on the second nitride semiconductor layer and is spaced apart from the second gate electrode on the opposite side of the second gate electrode as viewed from the first gate electrode. The first p-type layer is interposed between the first gate electrode and the second nitride semiconductor layer. The second p-type layer is interposed between the second gate electrode and the second nitride semiconductor layer. The first p-type layer and the second p-type layer cover only a portion of the surface of the second nitride semiconductor layer. The first control terminal 90A of the semiconductor switch element 9e is a first gate terminal to which the first gate electrode is connected. The second control terminal 90B is a second gate terminal to which the second gate electrode is connected. The first main terminal 91A is a first source terminal to which the first source electrode is connected. The second main terminal 92B is a second source terminal to which the second source electrode is connected.

[0072] The on-voltage measurement circuit 1e includes a first detection switch element 2A, a first control unit 3A, a first resistor element 4A, a first voltage detection unit 5A, a second detection switch element 2B, a second control unit 3B, a second resistor element 4B, and a second voltage detection unit 5B. The first detection switch element 2A has a first drain terminal 2AD, a first source terminal 2AS, and a first gate terminal 2AG. The first control unit 3A has a first signal output terminal 31A and a first reference potential terminal 32A and controls the first detection switch element 2A. The first resistor element 4A is connected between the first source terminal 2AS and the first reference potential terminal 32A. The second detection switch element 2B has a second drain terminal 2BD, a second source terminal 2BS, and a second gate terminal 2BG. The second control unit 3B has a second signal output terminal 31B and a second reference potential terminal 32B and controls the second detection switch element 2B. The second resistor element 4B is connected between the second source terminal 2BS and the second reference potential terminal 32B. In the on-voltage measuring circuit 1e, the first drain terminal 2AD of the first detecting switch element 2A and the second drain terminal 2BD of the second detecting switch element 2B are connected.

[0073] Each of the first and second detection switch elements 2A and 2B is a normally-off type switch element. Like the detection switch element 2 in the on-state voltage measurement circuit 1 according to embodiment 1, each of the first and second detection switch elements 2A and 2B is a normally-off type JFET. More specifically, each of the first and second detection switch elements 2A and 2B is a GaN-based GaN transistor. In FIG. 15, V2A is the voltage between the first drain terminal 2AD and the first source terminal 2AS of the first detection switch element 2A. Also, in FIG. 15, V2B is the voltage between the second drain terminal 2BD and the second source terminal 2BS of the second detection switch element 2B.

[0074] The first control unit 3A turns off the first detecting switch element 2A when the semiconductor switch element 9e is off, and turns on the first detecting switch element 2A when the semiconductor switch element 9e is on. The first voltage detection unit 5A detects the on-voltage of the semiconductor switch element 9e connected between the first drain terminal 2AD and the first reference potential terminal 32A from the voltage V4A across the first resistor element 4A when both the semiconductor switch element 9e and the first detecting switch element 2A are on. Here, the on-voltage of the semiconductor switch element 9e detected by the first voltage detection unit 5A is half the on-voltage of the semiconductor switch element 9e.

[0075] In the first control unit 3A, the first signal output terminal 31A is connected to the first gate terminal 2AG of the first detection switch element 2A. Furthermore, in the first control unit 3A, the first reference potential terminal 32A is connected to the first source terminal 2AS of the first detection switch element 2A via the first resistor element 4A. When turning on the first detection switch element 2A, the first control unit 3A outputs an ON signal as a control signal to turn on the first detection switch element 2A. The ON signal to turn on the first detection switch element 2A is a voltage signal of a voltage level (e.g., 5 V) such that the gate voltage of the first detection switch element 2A (the voltage between the first gate terminal 2AG and the first source terminal 2AS) is greater than the threshold voltage of the first detection switch element 2A. When turning off the first detection switch element 2A, the first control unit 3A outputs an OFF signal as a control signal to turn off the first detection switch element 2A. The off signal that turns off the first detection switch element 2A is a voltage signal of a voltage level (e.g., 0V) that causes the gate voltage (first gate terminal 2AG and first source terminal 2AS) of the first detection switch element 2A to be less than the threshold voltage of the first detection switch element 2A.

[0076] The first control unit 3A is also connected to the first voltage detection unit 5A. The first control unit 3A controls the first detection switch element 2A based on the on-voltage detected by the first voltage detection unit 5A. More specifically, the first control unit 3A turns off the first detection switch element 2A when the on-voltage detected by the first voltage detection unit 5A exceeds a threshold value. In a switch system 10e including an on-voltage measurement circuit 1e, the first switch control unit 11A turns off the semiconductor switch element 9e when the on-voltage detected by the first voltage detection unit 5A exceeds a threshold value. The threshold value is a voltage value set for detecting an abnormality when the semiconductor switch element 9e is in an on-state.

[0077] The first control unit 3A includes a drive circuit that provides a control signal to the first detecting switch element 2A, but is not limited to this.

[0078] The first control unit 3A 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. At least a portion of the functions of the first control unit 3A in the present disclosure are realized by the processor executing a program recorded in the memory of the computer system. The program may be pre-recorded in the memory of the computer system, provided via a telecommunications line, or recorded and provided on a non-transitory recording medium readable by the computer system, such as a memory card, an optical disk, or a hard disk drive (magnetic disk). 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 into a single chip or distributed across multiple chips. The multiple chips may be integrated into a single device or distributed across multiple devices.

[0079] The resistance value of the first resistor element 4A is greater than the on-resistance of the first detecting switch element 2A. The resistance value of the first resistor element 4A is, for example, 10 times the on-resistance of the first detecting switch element 2A.

[0080] The first voltage detection unit 5A is connected across the first resistor element 4A. The first voltage detection unit 5A detects the on-voltage of the semiconductor switch element 9e connected between the first drain terminal 2AD and the first reference potential terminal 32A from the voltage V4A across the first resistor element 4A when both the semiconductor switch element 9e and the first detection switch element 2A are on. Here, the on-voltage of the semiconductor switch element 9e detected by the first voltage detection unit 5A is half the on-voltage of the semiconductor switch element 9e.

[0081] The first voltage detection unit 5A also has a function of determining the state of the semiconductor switch element 9e based on the detected on-voltage. For example, the first voltage detection unit 5A compares the detected on-voltage with a threshold value, and determines that there is no abnormality if the on-voltage is less than the threshold value, and determines that there is an abnormality if the on-voltage is equal to or greater than the threshold value. "No abnormality" means that no abnormal current is flowing through the semiconductor switch element 9e. "Abnormality" means that an abnormal current is flowing through the semiconductor switch element 9e, and the voltage V9 is higher than the voltage V9 in the on-state of the semiconductor switch element 9e when no abnormal current is flowing through the semiconductor switch element 9e. The first voltage detection unit 5A includes, for example, a first comparator that compares the on-voltage with the threshold value. In this case, the first voltage detection unit 5A is configured so that the threshold value is input to the inverting terminal of the first comparator, and the on-voltage detected by the first voltage detection unit 5A (the voltage V4A across the first resistor element 4A) is input to the non-inverting terminal. In the first voltage detection unit 5A, when the voltage V4A is equal to or greater than the threshold, the output signal of the first comparator becomes H level, and when the voltage V4A is less than the threshold, the output signal of the first comparator becomes L level. In the first voltage detection unit 5A, when the output signal of the first comparator is H level, it means that it has determined that an abnormal current is flowing through the semiconductor switch element 9e (abnormality exists), and when the output signal of the first comparator is L level, it means that it has determined that no abnormal current is flowing through the semiconductor switch element 9e (no abnormality exists). In the on-voltage measurement circuit 1e, the output terminal of the first voltage detection unit 5A is connected to the first control unit 3A, and the determination result of the first voltage detection unit 5A is input to the first control unit 3A. In the switch system 10e, the output terminal of the first voltage detection unit 5A is connected to the first switch control unit 11A, and the determination result of the first voltage detection unit 5A is input to the first switch control unit 11A.

[0082] The on-state voltage measuring circuit 1e includes a first DC power supply E1 that supplies a power supply voltage to the first control unit 3A and the first voltage detection unit 5A.

[0083] The second control unit 3B turns off the second detection switch element 2B when the semiconductor switch element 9e is off, and turns on the second detection switch element 2B when the semiconductor switch element 9e is on. The second voltage detection unit 5B detects the on-voltage of the semiconductor switch element 9e connected between the second drain terminal 2BD and the second reference potential terminal 32B from the voltage V4B across the second resistor element 4B when both the semiconductor switch element 9e and the second detection switch element 2B are on. Here, the on-voltage of the semiconductor switch element 9e detected by the second voltage detection unit 5B is half the on-voltage of the semiconductor switch element 9e.

[0084] In the second control unit 3B, the second signal output terminal 31B is connected to the second gate terminal 2BG of the second detection switch element 2B. Furthermore, in the second control unit 3B, the second reference potential terminal 32B is connected to the second source terminal 2BS of the second detection switch element 2B via the second resistor element 4B. When turning on the second detection switch element 2B, the second control unit 3B outputs an ON signal as a control signal to turn on the second detection switch element 2B. The ON signal to turn on the second detection switch element 2B is a voltage signal of a voltage level (e.g., 5 V) such that the gate voltage of the second detection switch element 2B (the voltage between the second gate terminal 2BG and the second source terminal 2BS) is greater than the threshold voltage of the second detection switch element 2B. When turning off the second detection switch element 2B, the second control unit 3B outputs an OFF signal as a control signal to turn off the second detection switch element 2B. The off signal that turns off the second detection switch element 2B is a voltage signal of a voltage level (e.g., 0V) that causes the gate voltage (second gate terminal 2BG and second source terminal 2BS) of the second detection switch element 2B to be less than the threshold voltage of the second detection switch element 2B.

[0085] The second control unit 3B is also connected to the second voltage detection unit 5B. The second control unit 3B controls the second detection switch element 2B based on the on-voltage detected by the second voltage detection unit 5B. More specifically, the second control unit 3B turns off the second detection switch element 2B when the on-voltage detected by the second voltage detection unit 5B exceeds a threshold value. In the switch system 10e including the on-voltage measurement circuit 1e, the second switch control unit 11B turns off the semiconductor switch element 9e when the on-voltage detected by the second voltage detection unit 5B exceeds a threshold value. The threshold value is a voltage value set for detecting an abnormality when the semiconductor switch element 9e is in the on state.

[0086] The second control unit 3B includes a second drive circuit that provides a control signal to the second detecting switch element 2B, but is not limited to this.

[0087] The second control unit 3B includes a computer system. The computer system has one or more computers. The computer system is mainly composed of a processor and memory as hardware. At least a portion of the functions of the second control unit 3B in the present disclosure are realized by the processor executing a program recorded in the memory of the computer system. The program may be pre-recorded in the memory of the computer system, provided via a telecommunications line, or recorded and provided on a non-transitory recording medium readable by the computer system, such as a memory card, an optical disk, or a hard disk drive (magnetic disk). 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 into a single chip or distributed across multiple chips. The multiple chips may be integrated into a single device or distributed across multiple devices.

[0088] The resistance value of the second resistor element 4B is larger than the on-resistance of the second detecting switch element 2B. The resistance value of the second resistor element 4B is, for example, 10 times the on-resistance of the second detecting switch element 2B. The resistance value of the second resistor element 4B is the same as the resistance value of the first resistor element 4A. Here, "the same" does not necessarily mean strictly the same; for example, the resistance value of the second resistor element 4B may be within a range of ±5% of the resistance value of the first resistor element 4A.

[0089] The second voltage detection unit 5B is connected across the second resistor element 4B. The second voltage detection unit 5B detects the on-voltage of the semiconductor switch element 9e connected between the second drain terminal 2BD and the second reference potential terminal 32B from the voltage V4B across the second resistor element 4B when both the semiconductor switch element 9e and the second detection switch element 2B are on. Here, the on-voltage of the semiconductor switch element 9e detected by the second voltage detection unit 5B is half the on-voltage of the semiconductor switch element 9e.

[0090] The second voltage detection unit 5B also has a function of determining the state of the semiconductor switch element 9e based on the detected on-voltage. For example, the second voltage detection unit 5B compares the detected on-voltage with a threshold value. If the on-voltage is less than the threshold value, the second voltage detection unit 5B determines that there is no abnormality. If the on-voltage is equal to or greater than the threshold value, the second voltage detection unit 5B determines that there is an abnormality. "No abnormality" means that no abnormal current is flowing through the semiconductor switch element 9e. "Abnormality" means that an abnormal current is flowing through the semiconductor switch element 9e, causing the voltage V9 to be higher than the voltage V9 in the on-state of the semiconductor switch element 9e when no abnormal current is flowing through the semiconductor switch element 9e. The second voltage detection unit 5B includes, for example, a second comparator that compares the on-voltage with the threshold value. In this case, the second voltage detection unit 5B is configured so that the threshold value is input to the inverting terminal of the second comparator, and the on-voltage detected by the second voltage detection unit 5B (the voltage V4B across the second resistor element 4B) is input to the non-inverting terminal. In the second voltage detection unit 5B, when the voltage V4B is equal to or greater than the threshold, the output signal of the second comparator becomes H level, and when the voltage V4B is less than the threshold, the output signal of the second comparator becomes L level. In the second voltage detection unit 5B, when the output signal of the second comparator is H level, it means that it has determined that an abnormal current is flowing through the semiconductor switch element 9e (abnormality exists), and when the output signal of the second comparator is L level, it means that it has determined that no abnormal current is flowing through the semiconductor switch element 9e (no abnormality exists). In the on-voltage measurement circuit 1e, the output terminal of the second voltage detection unit 5B is connected to the second control unit 3B, and the determination result of the second voltage detection unit 5B is input to the second control unit 3B. In the switch system 10e, the output terminal of the second voltage detection unit 5B is connected to the second switch control unit 11B, and the determination result of the second voltage detection unit 5B is input to the second switch control unit 11B.

[0091] The on-state voltage measuring circuit 1e further includes a second DC power supply E2 that supplies a power supply voltage to the second control unit 3B and the second voltage detection unit 5B.

[0092] In a switch system 10e including an on-state voltage measurement circuit 1e, a load circuit including, for example, a series circuit of a load 15 and a power supply 16 is connected between a first main terminal (first source terminal) 91A and a second main terminal (second source terminal) 92B of a semiconductor switch element 9e, which is a bidirectional switch element. The power supply 16 is, for example, an AC power supply.

[0093] In the on-voltage measurement circuit 1e, the first voltage detection unit 5A measures the on-voltage of the semiconductor switch element 9e when a current flows from the second main terminal 92B to the first main terminal 91A of the semiconductor switch element 9e. Here, the first voltage detection unit 5A measures a voltage that is half the on-voltage of the semiconductor switch element 9e. Furthermore, when a current flows from the second main terminal 92B to the first main terminal 91A of the semiconductor switch element 9e, the first voltage detection unit 5A determines whether or not an abnormal current is flowing through the semiconductor switch element 9e.

[0094] In the on-voltage measurement circuit 1e, the second voltage detection unit 5B measures the on-voltage of the semiconductor switch element 9e when a current flows from the first main terminal 91A to the second main terminal 92B of the semiconductor switch element 9e. Here, the second voltage detection unit 5B measures a voltage that is half the on-voltage of the semiconductor switch element 9e. Furthermore, the second voltage detection unit 5B determines whether an abnormal current is flowing through the semiconductor switch element 9e when a current flows from the first main terminal 91A to the second main terminal 92B of the semiconductor switch element 9e.

[0095] The on-state voltage measurement circuit 1e according to the sixth embodiment described above can improve the accuracy of measuring the on-state voltage. Here, the on-state voltage measurement circuit 1e can measure the on-state voltage of the semiconductor switch element 9e regardless of the direction of the current flowing through the semiconductor switch element 9e. Furthermore, the on-state voltage measurement circuit 1e can determine whether an abnormal current is flowing through the semiconductor switch element 9e regardless of the direction of the current flowing through the semiconductor switch element 9e.

[0096] Furthermore, in a dual-gate GaN-based GIT, the H-level side and the L-level side are not specified for the first source electrode and the second source electrode, and the protection circuit using a diode disclosed in Patent Document 1 cannot be applied. In contrast, the on-voltage measurement circuit 1e according to the sixth embodiment is a bidirectional on-voltage detection circuit that can be applied to a dual-gate GaN-based GIT.

[0097] (Embodiment 7) A switch system 10f including an on-state voltage measurement circuit 1f according to the seventh embodiment will be described below with reference to Fig. 16. Regarding the on-state voltage measurement circuit 1f and the switch system 10f according to the seventh embodiment, components similar to those of the on-state voltage measurement circuit 1e and the switch system 10e according to the sixth embodiment will be designated by the same reference numerals, and descriptions thereof will be omitted as appropriate.

[0098] The on-state voltage measurement circuit 1f differs from the on-state voltage measurement circuit 1e in that it further includes a first diode D1 and a second diode D2 in comparison with the circuit configuration of the on-state voltage measurement circuit 1e.

[0099] The first diode D1 is connected in parallel to the first resistor element 4A. The first diode D1 has a first anode and a first cathode, with the first anode connected to the first reference potential terminal 32A and the first cathode connected to the first source terminal 2AS of the first detecting switch element 2A.

[0100] The second diode D2 is connected in parallel to the second resistor element 4B. The second diode D2 has a second anode and a second cathode, with the second anode connected to the second reference potential terminal 32B and the second cathode connected to the second source terminal 2BS of the second detection switch element 2B. The forward voltage of the second diode D2 is the same as the forward voltage of the first diode D1. Here, "the same" does not necessarily mean strictly the same; for example, the forward voltage of the second diode D2 may be within a range of ±10% of the forward voltage of the first diode D1.

[0101] In the on-voltage measurement circuit 1f, the voltage across the first resistor element 4A can be clamped by the first diode D1. If the current flowing through the first detection switch element 2A is I1, the on-resistance of the first detection switch element 2A is Ron2A, and the forward voltage of the first diode D1 is VF1, the on-voltage detected by the first voltage detection unit 5A is I1×Ron2A-VF1 Therefore, if I1×Ron2A is greater than 2×VF1, the on-voltage detected by the first voltage detection unit 5A increases as the current I1 increases.

[0102] In the on-voltage measurement circuit 1f, the voltage across the second resistor element 4B can be clamped by the second diode D2. If the current flowing through the second detection switch element 2B is I2, the on-resistance of the second detection switch element 2B is Ron2B, and the forward voltage of the second diode D2 is VF2, the on-voltage detected by the second voltage detection unit 5B is I2×Ron2B-VF2 Therefore, if I2×Ron2B is greater than 2×VF2, the on-voltage detected by the second voltage detection unit 5B increases as the current I2 increases.

[0103] The on-state voltage measuring circuit 1f according to the seventh embodiment can improve the measurement accuracy of the on-state voltage.

[0104] Furthermore, in the on-state voltage measuring circuit 1f according to the seventh embodiment, the first diode D1 and the second diode D2 each constitute a clamp circuit, so there is no need to actively control the first detection switch element 2A and the second detection switch element 2B, which leads to a reduction in the number of components.

[0105] (Embodiment 8) 17, 18A, and 18B, a switch system 10g including an on-state voltage measurement circuit 1g according to embodiment 8 will be described. In the on-state voltage measurement circuit 1g and switch system 10g according to embodiment 8, components similar to those in the on-state voltage measurement circuit 1e and switch system 10e according to embodiment 6 are designated by the same reference numerals, and descriptions thereof will be omitted where appropriate.

[0106] The on-state voltage measurement circuit 1g differs from the on-state voltage measurement circuit 1e in that it further includes a first capacitor C1 and a second capacitor C2 in comparison with the circuit configuration of the on-state voltage measurement circuit 1e.

[0107] The first capacitor C1 is connected in parallel to the first resistor element 4A. The second capacitor C2 is connected in parallel to the second resistor element 4B. The capacitance of the second capacitor C2 is the same as the capacitance of the first capacitor C1. Here, "same" does not necessarily mean strictly the same; for example, the capacitance of the second capacitor C2 may be within ±10% of the capacitance of the first capacitor C1.

[0108] In the on-voltage measurement circuit 1e (see FIG. 15 ) according to the sixth embodiment, for example, when the first detection switch element 2A is turned on, the gate charge current flowing through the first gate terminal 2AG can take two routes: the route indicated by the dashed arrow in FIG. 19A and the route indicated by the dashed arrow in FIG. 19B. In the on-voltage measurement circuit 1e, in the case of the route indicated by the dashed arrow in FIG. 19A, an inrush current flowing through the first gate terminal 2AG of the first detection switch element 2A may flow through the first resistor element 4A, potentially leading to erroneous detection by the first voltage detection unit 5A. In the on-voltage measurement circuit 1e, in the case of the route indicated by the dashed arrow in FIG. 19B, an inrush current flowing through the second gate terminal 2BG of the second detection switch element 2B may flow through the second resistor element 4B, potentially reducing the measurement accuracy of the first voltage detection unit 5A. Similarly, in the on-voltage measurement circuit 1e, for example, when the second detection switch element 2B is turned on, potentially reducing the measurement accuracy of the second voltage detection unit 5B.

[0109] In contrast, in the on-voltage measurement circuit 1g according to the eighth embodiment, the possible routes for the gate charge current flowing to the first gate terminal 2AG when the first detection switch element 2A is turned on are the route indicated by the dashed arrow in FIG. 18A and the route indicated by the dashed arrow in FIG. 18B. In the on-voltage measurement circuit 1g according to the eighth embodiment, in the route indicated by the dashed arrow in FIG. 18A, the inrush current to the first gate terminal 2AG of the first detection switch element 2A flows to the first capacitor C1, thereby improving the measurement accuracy of the first voltage detection unit 5A. Furthermore, in the on-voltage measurement circuit 1g according to the eighth embodiment, in the route indicated by the dashed arrow in FIG. 18B, the inrush current to the second gate terminal 2BG of the second detection switch element 2B flows to the second capacitor C2, thereby improving the measurement accuracy of the first voltage detection unit 5A. Similarly, in the on-state voltage measuring circuit 1g according to the eighth embodiment, for example, when the second detection switch element 2B is turned on, it is possible to improve the measurement accuracy of the second voltage detection section 5B.

[0110] (Embodiment 9) A switch system 10h including an on-state voltage measurement circuit 1h according to the ninth embodiment will be described below with reference to Fig. 20. Regarding the on-state voltage measurement circuit 1h and the switch system 10h according to the ninth embodiment, components similar to those of the on-state voltage measurement circuit 1e and the switch system 10e according to the sixth embodiment are designated by the same reference numerals, and descriptions thereof will be omitted as appropriate.

[0111] The on-state voltage measuring circuit 1h differs from the on-state voltage measuring circuit 1e in that, compared to the circuit configuration of the on-state voltage measuring circuit 1e, the first control unit 3A is configured by a first constant voltage source EA1 and the second control unit 3B is configured by a second constant voltage source EA2.

[0112] The first signal output terminal 31A of the first control unit 3A is the positive electrode of the first constant voltage source EA1, and the first reference potential terminal 32A is the negative electrode of the first constant voltage source EA1. The first signal output terminal 31A of the first control unit 3A is connected to the first gate terminal 2AG of the first detection switch element 2A. The first reference potential terminal 32A of the first control unit 3A is connected to the first source terminal 2AS of the first detection switch element 2A via the first resistor element 4A.

[0113] The second signal output terminal 31B of the second control unit 3B is the positive electrode of the second constant voltage source EA2, and the second reference potential terminal 32B is the negative electrode of the second constant voltage source EA2. The second signal output terminal 31B of the second control unit 3B is connected to the second gate terminal 2BG of the second detection switch element 2B. The second reference potential terminal 32B of the second control unit 3B is connected to the second source terminal 2BS of the second detection switch element 2B via the second resistor element 4B.

[0114] Like the on-voltage measuring circuit 1e according to the sixth embodiment, the on-voltage measuring circuit 1h according to the ninth embodiment detects the voltage V4A across the first resistor element 4A by the first voltage detection unit 5A and detects the voltage V4B across the second resistor element 4B by the second voltage detection unit 5B, thereby improving the measurement accuracy of the on-voltage of the semiconductor switch element 9e.

[0115] Furthermore, in the on-state voltage measuring circuit 1h according to the ninth embodiment, the first constant voltage source EA1 and the first detection switch element 2A function as a clamp circuit, and the second constant voltage source EA2 and the second detection switch element 2B function as a clamp circuit. This eliminates the need to actively control the first detection switch element 2A and the second detection switch element 2B, leading to a reduction in the number of components.

[0116] (Embodiment 10) A switch system 10i including an on-state voltage measurement circuit 1i according to the tenth embodiment will be described below with reference to Fig. 21. Regarding the on-state voltage measurement circuit 1i and the switch system 10i according to the tenth embodiment, components similar to those of the on-state voltage measurement circuit 1e and the switch system 10e according to the sixth embodiment will be designated by the same reference numerals, and descriptions thereof will be omitted as appropriate.

[0117] The on-state voltage measurement circuit 1i differs from the on-state voltage measurement circuit 1e in that the first detection switch element 2A and the second detection switch element 2B are both normally-on switch elements, and the on-state voltage measurement circuit 1i also differs from the on-state voltage measurement circuit 1e in that the on-state voltage measurement circuit 1i does not include the first control unit 3A and the second control unit 3B of the on-state voltage measurement circuit 1e.

[0118] In the on-voltage measuring circuit 1i, a first gate terminal 2AG of a normally-on first detection switch element 2A is connected to a first source terminal 2AS of the first detection switch element 2A via a first resistor element 4A.

[0119] In the on-voltage measuring circuit 1i, the second gate terminal 2BG of the normally-on second detection switch element 2B is connected to the second source terminal 2BS of the second detection switch element 2B via the second resistor element 4B.

[0120] Like the on-voltage measuring circuit 1e according to the sixth embodiment, the on-voltage measuring circuit 1i according to the tenth embodiment detects the voltage V4A across the first resistor element 4A by the first voltage detection unit 5A and detects the voltage V4B across the second resistor element 4B by the second voltage detection unit 5B, thereby improving the measurement accuracy of the on-voltage of the semiconductor switch element 9e.

[0121] Furthermore, in the on-state voltage measuring circuit 1i according to the tenth embodiment, the first resistance element 4A and the normally-on type first detection switch element 2A function as a clamp circuit, and the second resistance element 4B and the normally-on type second detection switch element 2B function as a clamp circuit. This makes it possible to reduce the number of power supplies compared to the on-state voltage measuring circuit 1h according to the ninth embodiment.

[0122] (Embodiment 11) A switch system 10j including an on-state voltage measurement circuit 1j according to the eleventh embodiment will be described below with reference to Fig. 22. Regarding the on-state voltage measurement circuit 1j and the switch system 10j according to the eleventh embodiment, components similar to those of the on-state voltage measurement circuit 1e and the switch system 10e according to the sixth embodiment will be designated by the same reference numerals, and descriptions thereof will be omitted as appropriate.

[0123] The on-state voltage measuring circuit 1j includes a detection switch element 20, a first control unit 61, a first resistive element 41, a first voltage detecting unit 51, a second control unit 62, a second resistive element 42, and a second voltage detecting unit 52.

[0124] The on-state voltage measurement circuit 1j includes a detection switch element 20 instead of the series circuit of the first detection switch element 2A and the second detection switch element 2B in the on-state voltage measurement circuit 1e. The detection switch element 20 has a first gate terminal 21G, a first source terminal 21S corresponding to the first gate terminal 21G, a second gate terminal 22G, and a second source terminal 22S corresponding to the second gate terminal 22G. The detection switch element 20 is a dual-gate GaN-based GIT, similar to the semiconductor switch element 9e. Therefore, the detection switch element 20 is a bidirectional switch element.

[0125] The first control unit 61 has a first signal output terminal 611 and a first reference potential terminal 612. The first control unit 61 controls the first gate voltage of the first gate terminal 21G of the detection switch element 20.

[0126] The first control unit 61 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. At least a portion of the functions of the first control unit 61 in the present disclosure are realized by the processor executing a program recorded in the memory of the computer system. The program may be pre-recorded in the memory of the computer system, provided via a telecommunications line, or recorded and provided on a non-transitory recording medium readable by the computer system, such as a memory card, an optical disk, or a hard disk drive (magnetic disk). 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 into a single chip or distributed across multiple chips. The multiple chips may be integrated into a single device or distributed across multiple devices.

[0127] The first resistor element 41 is connected between the first source terminal 21S of the detection switch element 20 and the first reference potential terminal 612 of the first control unit 61. The resistance value of the first resistor element 41 is larger than the on-resistance of the detection switch element 20. The resistance value of the first resistor element 41 is preferably, for example, nine times or more the on-resistance of the detection switch element 20. As an example, the resistance value of the first resistor element 41 is ten times the on-resistance of the detection switch element 20.

[0128] The first voltage detection unit 51 detects the on-voltage of the semiconductor switch element 9e connected between the first reference potential terminal 612 and the second reference potential terminal 622 from the voltage V41 across the first resistor element 41 when both the semiconductor switch element 9e and the detection switch element 20 are on. Here, the on-voltage of the semiconductor switch element 9e detected by the first voltage detection unit 51 is half the voltage of the on-voltage of the semiconductor switch element 9e.

[0129] The first voltage detection unit 51 also has a function of determining the state of the semiconductor switch element 9e based on the detected on-voltage. For example, the first voltage detection unit 51 compares the detected on-voltage with a threshold value, and determines that there is no abnormality if the on-voltage is less than the threshold value, and determines that there is an abnormality if the on-voltage is equal to or greater than the threshold value. "No abnormality" means that no abnormal current is flowing through the semiconductor switch element 9e. "Abnormality" means that an abnormal current is flowing through the semiconductor switch element 9e, and the voltage V9 is higher than the voltage V9 in the on-state of the semiconductor switch element 9e when no abnormal current is flowing through the semiconductor switch element 9e. The first voltage detection unit 51 includes, for example, a first comparator that compares the on-voltage with the threshold value. In this case, the first voltage detection unit 51 is configured so that the threshold value is input to the inverting terminal of the first comparator, and the on-voltage detected by the first voltage detection unit 51 (the voltage V41 across the first resistor element 41) is input to the non-inverting terminal. In the first voltage detection unit 51, when the voltage V41 is equal to or greater than the threshold, the output signal of the first comparator becomes H level, and when the voltage V41 is less than the threshold, the output signal of the first comparator becomes L level. In the first voltage detection unit 51, when the output signal of the first comparator is H level, it means that it has determined that an abnormal current is flowing through the semiconductor switch element 9e (abnormality exists), and when the output signal of the first comparator is L level, it means that it has determined that no abnormal current is flowing through the semiconductor switch element 9e (no abnormality exists). In the on-voltage measurement circuit 1j, the output terminal of the first voltage detection unit 51 is connected to the first control unit 61, and the determination result of the first voltage detection unit 51 is input to the first control unit 61. In the switch system 10j, the output terminal of the first voltage detection unit 51 is connected to the first switch control unit 11A, and the determination result of the first voltage detection unit 51 is input to the first switch control unit 11A.

[0130] The second control unit 62 has a second signal output terminal 621 and a second reference potential terminal 622. The second control unit 62 controls the second gate voltage of the second gate terminal 22G of the detection switch element 20. Like the first control unit 61, the second control unit 62 includes a computer system. The computer system has one or more computers. The computer system is mainly composed of a processor and memory as hardware. At least a part of the functions of the second control unit 62 in the present disclosure are realized by the processor executing a program recorded in the memory of the computer system.

[0131] The second resistor element 42 is connected between the second source terminal 22S and the second reference potential terminal 622. The resistance value of the second resistor element 42 is larger than the on-resistance of the detection switch element 20. The resistance value of the second resistor element 42 is preferably, for example, nine times or more the on-resistance of the detection switch element 20. As an example, the resistance value of the second resistor element 42 is ten times the on-resistance of the detection switch element 20. The resistance value of the second resistor element 42 is the same as the resistance value of the first resistor element 41. Here, "the same" is not limited to being strictly the same; for example, the resistance value of the second resistor element 42 may be within a range of ±5% of the resistance value of the first resistor element 41.

[0132] The second voltage detection unit 52 detects the on-voltage of the semiconductor switch element 9e connected between the first reference potential terminal 612 and the second reference potential terminal 622 from the voltage V42 across the second resistor element 42 when both the semiconductor switch element 9e and the detection switch element 20 are on. Here, the on-voltage of the semiconductor switch element 9e detected by the second voltage detection unit 52 is half the on-voltage of the semiconductor switch element 9e.

[0133] The second voltage detection unit 52 also has a function of determining the state of the semiconductor switch element 9e based on the detected on-voltage. For example, the second voltage detection unit 52 compares the detected on-voltage with a threshold value, and determines that there is no abnormality if the on-voltage is less than the threshold value, and determines that there is an abnormality if the on-voltage is equal to or greater than the threshold value. "No abnormality" means that no abnormal current is flowing through the semiconductor switch element 9e. "Abnormality" means that an abnormal current is flowing through the semiconductor switch element 9e, and the voltage V9 is higher than the voltage V9 in the on-state of the semiconductor switch element 9e when no abnormal current is flowing through the semiconductor switch element 9e. The second voltage detection unit 52 includes, for example, a second comparator that compares the on-voltage with the threshold value. In this case, the second voltage detection unit 52 is configured so that the threshold value is input to the inverting terminal of the second comparator, and the on-voltage detected by the second voltage detection unit 52 (the voltage V42 across the second resistor element 42) is input to the non-inverting terminal. In the second voltage detection unit 52, when the voltage V42 is equal to or greater than the threshold, the output signal of the second comparator becomes H level, and when the voltage V42 is less than the threshold, the output signal of the second comparator becomes L level. In the second voltage detection unit 52, when the output signal of the second comparator is H level, it means that it has determined that an abnormal current is flowing through the semiconductor switch element 9e (abnormality exists), and when the output signal of the second comparator is L level, it means that it has determined that no abnormal current is flowing through the semiconductor switch element 9e (no abnormality exists). In the on-voltage measurement circuit 1j, the output terminal of the second voltage detection unit 52 is connected to the second control unit 62, and the determination result of the second voltage detection unit 52 is input to the second control unit 62. In the switch system 10j, the output terminal of the second voltage detection unit 52 is connected to the second switch control unit 11B, and the determination result of the second voltage detection unit 52 is input to the second switch control unit 11B.

[0134] In the on-voltage measuring circuit 1j according to the eleventh embodiment, a series circuit of a first resistor element 41, a detection switch element 20, and a second resistor element 42 is connected in parallel to a semiconductor switch element 9e, and a first voltage detector 51 measures the on-voltage of the semiconductor switch element 9e from a voltage V41 across the first resistor element 41, and a second voltage detector 52 measures the on-voltage of the semiconductor switch element 9e from a voltage V42 across the second resistor element 42. This makes it possible to improve the measurement accuracy of the on-voltage, similar to the on-voltage measuring circuit 1e according to the sixth embodiment.

[0135] (Embodiment 12) A switch system 10k including an on-state voltage measurement circuit 1k according to the twelfth embodiment will be described below with reference to Fig. 23. Regarding the on-state voltage measurement circuit 1k and the switch system 10k according to the twelfth embodiment, components similar to those of the on-state voltage measurement circuit 1e and the switch system 10e according to the sixth embodiment are designated by the same reference numerals, and descriptions thereof will be omitted as appropriate.

[0136] The on-state voltage measuring circuit 1k includes a first detection switch element 2A, a first control unit 3A, a second detection switch element 2B, a second control unit 3B, a resistive element 40, and a voltage detection unit .

[0137] The first detecting switch element 2A has a first drain terminal 2AD, a first source terminal 2AS, and a first gate terminal 2AG.

[0138] The first control unit 3A has a first signal output terminal 31A and a first reference potential terminal 32A, and controls the first detecting switch element 2A.

[0139] The second detecting switch element 2B has a second drain terminal 2BD, a second source terminal 2BS, and a second gate terminal 2BG.

[0140] The second control unit 3B has a second signal output terminal 31B and a second reference potential terminal 32B, and controls the second detecting switch element 2B.

[0141] The resistive element 40 is connected between the first source terminal 2AS of the first detecting switch element 2A and the second source terminal 2BS of the second detecting switch element 2B.

[0142] In the on-voltage measuring circuit 1k, the first signal output terminal 31A of the first control unit 3A is connected to the first gate terminal 2AG of the first detection switch element 2A. The first reference potential terminal 32A of the first control unit 3A is connected to the second source terminal 2BS of the second detection switch element 2B. The second signal output terminal 31B of the second control unit 3B is connected to the second gate terminal 2BG of the second detection switch element 2B. The second reference potential terminal 32B of the second control unit 3B is connected to the first source terminal 2AS of the first detection switch element 2A.

[0143] The resistance value of the resistive element 40 is greater than the on-resistance of the first detecting switch element 2A and the on-resistance of the second detecting switch element 2B. The on-resistance of the second detecting switch element 2B is the same as the on-resistance of the first detecting switch element 2A. Here, "the same" is not limited to being strictly the same; for example, it is sufficient if the on-resistance of the second detecting switch element 2B is within a range of ±5% of the on-resistance of the first detecting switch element 2A.

[0144] The resistance value of the resistive element 40 is preferably, for example, 9 times or more the sum of the on-resistance of the first detecting switch element 2A and the on-resistance of the second detecting switch element 2B. As an example, the resistance value of the resistive element 40 is 10 times the on-resistance of the first detecting switch element 2A and the on-resistance of the second detecting switch element 2B.

[0145] The voltage detection unit 50 detects the on-voltage of the semiconductor switch element 9e connected between the first reference potential terminal 32A and the second reference potential terminal 32B from the voltage across the resistor element 40 when the semiconductor switch element 9e is on. This allows the on-voltage measurement circuit 1k to improve the accuracy of measuring the on-voltage. In a switch system 10k including the on-voltage measurement circuit 1k, the first switch control unit 11A and the second switch control unit 11B are connected to the output terminal of the voltage detection unit 50, and when the on-voltage detected by the voltage detection unit 50 exceeds a threshold value, the voltage detection unit 50 turns off the semiconductor switch element 9e. The threshold value is a voltage value set for detecting an abnormality when the semiconductor switch element 9e is on.

[0146] (Embodiment 13) A switch system 10m including an on-state voltage measurement circuit 1m according to the thirteenth embodiment will be described below with reference to Fig. 24. Constituent elements of the on-state voltage measurement circuit 1m and the switch system 10m according to the thirteenth embodiment that are the same as those of the on-state voltage measurement circuit 1k and the switch system 10k according to the twelfth embodiment will be designated by the same reference numerals, and descriptions thereof will be omitted as appropriate.

[0147] The on-state voltage measuring circuit 1m differs from the on-state voltage measuring circuit 1k in that the first control unit 3A is configured by a first constant voltage source EA1 and the second control unit 3B is configured by a second constant voltage source EA2.

[0148] The first signal output terminal 31A of the first control unit 3A is the positive electrode of the first constant voltage source EA1, and the first reference potential terminal 32A is the negative electrode of the first constant voltage source EA1. The first signal output terminal 31A of the first control unit 3A is connected to the first gate terminal 2AG of the first detection switch element 2A. The first reference potential terminal 32A of the first control unit 3A is connected to the first source terminal 2AS of the first detection switch element 2A via a resistor 40.

[0149] The second signal output terminal 31B of the second control unit 3B is the positive electrode of the second constant voltage source EA2, and the second reference potential terminal 32B is the negative electrode of the second constant voltage source EA2. The second signal output terminal 31B of the second control unit 3B is connected to the second gate terminal 2BG of the second detection switch element 2B. The second reference potential terminal 32B of the second control unit 3B is connected to the second source terminal 2BS of the second detection switch element 2B via the resistor element 40.

[0150] Like the on-voltage measurement circuit 1k according to the 12th embodiment, the on-voltage measurement circuit 1m according to the thirteenth embodiment detects the voltage across the resistive element 40 using the voltage detection unit 50, thereby improving the measurement accuracy of the on-voltage of the semiconductor switch element 9e.

[0151] Furthermore, the on-state voltage measuring circuit 1m according to the thirteenth embodiment functions as a clamp circuit with the first constant voltage source EA1 and the first detection switch element 2A, and also functions as a clamp circuit with the second constant voltage source EA2 and the second detection switch element 2B. This eliminates the need to actively control the first detection switch element 2A and the second detection switch element 2B, which leads to a reduction in the number of components.

[0152] (Embodiment 14) A switch system 10n including an on-state voltage measurement circuit 1n according to the fourteenth embodiment will be described below with reference to Fig. 25. Regarding the on-state voltage measurement circuit 1n and the switch system 10n according to the fourteenth embodiment, components similar to those of the on-state voltage measurement circuit 1k and the switch system 10k according to the twelfth embodiment are designated by the same reference numerals, and descriptions thereof will be omitted as appropriate.

[0153] The on-state voltage measurement circuit 1n differs from the on-state voltage measurement circuit 1k in that the first detection switch element 2A and the second detection switch element 2B are both normally-on switch elements, and the on-state voltage measurement circuit 1n also differs from the on-state voltage measurement circuit 1k in that the on-state voltage measurement circuit 1n does not include the first control unit 3A and the second control unit 3B of the on-state voltage measurement circuit 1k.

[0154] In the on-state voltage measuring circuit In, a first gate terminal 2AG of a normally-on first detection switch element 2A is connected via a resistive element 40 to a first source terminal 2AS of the first detection switch element 2A.

[0155] In the on-state voltage measuring circuit 1n, the second gate terminal 2BG of the normally-on second detection switch element 2B is connected via a resistive element 40 to the second source terminal 2BS of the second detection switch element 2B.

[0156] Like the on-voltage measurement circuit 1k according to the 12th embodiment, the on-voltage measurement circuit 1n according to the 14th embodiment detects the voltage across the resistive element 40 using the voltage detection unit 50, thereby improving the measurement accuracy of the on-voltage of the semiconductor switch element 9e.

[0157] Furthermore, in the on-state voltage measurement circuit 1n according to the fourteenth embodiment, the resistance element 40 and the normally-on type first detection switch element 2A function as a clamp circuit, and the resistance element 40 and the normally-on type second detection switch element 2B function as a clamp circuit. This makes it possible to reduce the number of power supplies compared to the on-state voltage measurement circuit 1m according to the thirteenth embodiment.

[0158] (Variation) The above-described embodiments 1 to 14 are merely examples of various embodiments of the present disclosure. The above-described embodiments 1 to 14 can be modified in various ways depending on the design, etc., as long as the object of the present disclosure can be achieved, and different components of different embodiments can be appropriately combined.

[0159] For example, the semiconductor switch element 9 is not limited to a JFET, but may be a MOSFET (Metal-Oxide-Semiconductor Field Effect Transistor) or an IGBT (Insulated Gate Bipolar Transistor).

[0160] Furthermore, each of the detection switch element 2, the first detection switch element 2A, and the second detection switch element 2B is not limited to a JFET, but may be a MOSFET or an IGBT.

[0161] (Aspect) Based on the above-described embodiments 1 to 14, the present specification discloses the following aspects.

[0162] An on-voltage measurement circuit (1; 1a; 1b; 1c; 1d) according to a first aspect measures an on-voltage of a semiconductor switch element (9) having a control terminal (90), a first main terminal (91), and a second main terminal (92). The on-voltage is a voltage (V9) between the first main terminal (91) and the second main terminal (92) when the semiconductor switch element (9) is in an on-state. The on-voltage measurement circuit (1; 1a; 1b) includes a detection switch element (2), a control unit (3; 3a), a resistance element (4), and a voltage detection unit (5; 5b). The detection switch element (2) has a drain terminal (2D), a source terminal (2S), and a gate terminal (2G). The control unit (3; 3a) has a signal output terminal (31) and a reference potential terminal (32), and controls the detection switch element (2). The resistor element (4) is connected between the source terminal (2S) and the reference potential terminal (32). The resistance value (R4) of the resistor element (4) is greater than the on-resistance (Ron2) of the detection switch element (2). The voltage detector (5; 5b) detects the on-voltage of the semiconductor switch element (9) connected between the drain terminal (2D) and the reference potential terminal (32) from the voltage (V4) across the resistor element (4) when both the semiconductor switch element (9) and the detection switch element (2) are on.

[0163] The on-state voltage measuring circuit (1; 1a; 1b; 1c; 1d) according to the first aspect can improve the measurement accuracy of the on-state voltage.

[0164] In the on-state voltage measuring circuit (1a) according to the second aspect, in the first aspect, the control unit (3a) controls the semiconductor switch element (9).

[0165] In the on-state voltage measuring circuit (1a) according to the second aspect, it becomes easy to control the on / off of the detection switch element (2) in accordance with the on / off timing of the semiconductor switch element (9).

[0166] In the on-voltage measurement circuit (1; 1a; 1b; 1c; 1d) according to the third aspect, in the first or second aspect, the on-voltage measurement circuit (1; 1a; 1b; 1c; 1d) measures the on-voltage of a plurality of semiconductor switch elements (9) connected in parallel.

[0167] In the on-state voltage measuring circuit (1; 1a; 1b; 1c; 1d) according to the third aspect, it is possible to measure the on-state voltage that has the same voltage value across a plurality of semiconductor switch elements (9) connected in parallel.

[0168] In the on-voltage measuring circuit (1b) according to the fourth aspect, in any one of the first to third aspects, the voltage detecting unit (5b) has a function of comparing the detected on-voltage with a threshold value (Vt). The voltage detecting unit (5b) corrects the threshold value (Vt) in accordance with a temperature detected by a temperature detecting unit (19) that detects the temperature of the semiconductor switch element (9).

[0169] In the on-voltage measuring circuit (1b) according to the fourth aspect, the voltage detecting section (5b) has a function of comparing the detected on-voltage with a threshold value (Vt), and it becomes possible to correct the threshold value (Vt) in accordance with a temperature change of the semiconductor switch element (9).

[0170] An on-voltage measuring circuit (1c) according to a fifth aspect is based on any one of the first, third, and fourth aspects. In the on-voltage measuring circuit (1c), after the semiconductor switch element (9) is turned on, an on signal is output from the control unit (3; 3a) to turn on the detection switch element (2).

[0171] In the on-state voltage measuring circuit (1c) according to the fifth aspect, it is possible to improve the measurement accuracy of the on-state voltage detected by the voltage detecting section (5).

[0172] The on-state voltage measuring circuit (1c) according to a sixth aspect is the same as that according to any one of the first to fourth aspects, and further includes a gate resistor (121) and a gate capacitor (122). The gate resistor (121) is connected between the signal output terminal (31) and the gate terminal (2G) of the detection switch element (2). The gate capacitor (122) is connected between the gate terminal (2G) and the source terminal (2S) of the detection switch element (2). In the semiconductor switch element (9), the control terminal (90) is connected to the driver (110) via a resistor (111), and the capacitor (112) is connected between the control terminal (90) and the second main terminal (92). A time constant determined by the gate resistor (121) and the gate capacitor (122) is larger than a time constant determined by the resistor (111) and the capacitor (112).

[0173] In the on-state voltage measuring circuit (1c) according to the sixth aspect, it is possible to improve the measurement accuracy of the on-state voltage detected by the voltage detecting section (5).

[0174] In the on-state voltage measuring circuit (1c) according to the seventh aspect, in any one of the first to fourth aspects, the threshold voltage (Vth2) of the detection switch element (2) is greater than the threshold voltage (Vth9) of the semiconductor switch element (9).

[0175] The on-state voltage measuring circuit (1c) according to the seventh aspect has a simpler configuration than the sixth aspect, and can turn on the detection switch element (2) after the semiconductor switch element (9) is turned on.

[0176] An on-state voltage measurement circuit (1d) according to an eighth aspect is based on any one of the first, third, and fourth aspects. In the on-state voltage measurement circuit (1d), before the semiconductor switch element (9) is turned on, an on signal is output from the control unit (3; 3a) to turn on the detection switch element (2).

[0177] In the on-state voltage measuring circuit (1d) according to the eighth aspect, when a current collapse occurs in which the on-state resistance increases when the semiconductor switch element (9) is turned on, it is possible to detect the change in the on-state voltage over time due to the influence of the current collapse.

[0178] The on-state voltage measuring circuit (1d) according to a ninth aspect is the same as any one of the first to fourth aspects, and further includes a gate resistor (121) and a gate capacitor (122). The gate resistor (121) is connected between the signal output terminal (31) and the gate terminal (2G) of the detection switch element (2). The gate capacitor (122) is connected between the gate terminal (2G) and the source terminal (2S) of the detection switch element (2). In the semiconductor switch element (9), the control terminal (90) is connected to the driver (110) via a resistor (111), and the capacitor (112) is connected between the control terminal (90) and the second main terminal (92). A time constant determined by the gate resistor (121) and the gate capacitor (122) is smaller than a time constant determined by the resistor (111) and the capacitor (112).

[0179] In the on-state voltage measuring circuit (1d) according to the ninth aspect, it is possible to improve the measurement accuracy of the on-state voltage of the semiconductor switch element (9).

[0180] In the on-state voltage measuring circuit (1d) according to the tenth aspect, in any one of the first to fourth aspects, the threshold voltage (Vth2) of the detection switch element (2) is lower than the threshold voltage (Vth9) of the semiconductor switch element (9).

[0181] The on-state voltage measuring circuit (1d) according to the tenth aspect has a simpler configuration than the ninth aspect, and is capable of turning on the detection switch element (2) before the semiconductor switch element (9) is turned on.

[0182] An on-voltage measurement circuit (1e; 1f; 1g; 1h) according to an eleventh aspect measures the on-voltage of a semiconductor switch element (9e) having a first control terminal (90A), a first main terminal (91A) corresponding to the first control terminal (90A), a second control terminal (90B), and a second main terminal (92B) corresponding to the second control terminal (90B). The on-voltage is the voltage between the first main terminal (91A) and the second main terminal (92B) when the semiconductor switch element (9e) is in the on state. The on-voltage measurement circuit (1e; 1f; 1g; 1h) includes a first detection switch element (2A), a first control unit (3A), a first resistor element (4A), a first voltage detection unit (5A), a second detection switch element (2B), a second control unit (3B), a second resistor element (4B), and a second voltage detection unit (5B). The first detection switch element (2A) has a first drain terminal (2AD), a first source terminal (2AS), and a first gate terminal (2AG). The first control unit (3A) has a first signal output terminal (31A) and a first reference potential terminal (32A), and controls the first detection switch element (2A). The first resistor element (4A) is connected between the first source terminal (2AS) and the first reference potential terminal (32A). The second detection switch element (2B) has a second drain terminal (2BD), a second source terminal (2BS), and a second gate terminal (2BG). The second control unit (3B) has a second signal output terminal (31B) and a second reference potential terminal (32B), and controls the second detection switch element (2B). The second resistor element (4B) is connected between the second source terminal (2BS) and the second reference potential terminal (32B). In the on-voltage measuring circuit (1e; 1f; 1g; 1h), the first drain terminal (2AD) of the first detection switch element (2A) is connected to the second drain terminal (2BD) of the second detection switch element (2B). The resistance value of the first resistor element (4A) is greater than the on-resistance of the first detection switch element (2A). The resistance value of the second resistor element (4B) is greater than the on-resistance of the second detection switch element (2B).The first voltage detection unit (5A) detects the on-voltage of the semiconductor switch element (9e) connected between the first reference potential terminal (32A) and the second reference potential terminal (32B) from the voltage (V4A) across the first resistor element (4A) when both the semiconductor switch element (9e) and the first detection switch element (2A) are on. The second voltage detection unit (5B) detects the on-voltage of the semiconductor switch element (9e) connected between the first reference potential terminal (32A) and the second reference potential terminal (32B) from the voltage (V4B) across the second resistor element (4B) when both the semiconductor switch element (9e) and the second detection switch element (2B) are on.

[0183] The on-state voltage measuring circuit (1e; 1f; 1g; 1h) according to the eleventh aspect can improve the measurement accuracy of the on-state voltage.

[0184] The on-state voltage measurement circuit (1f) according to a twelfth aspect is the same as that of the eleventh aspect, but further includes a first diode (D1) and a second diode (D2). The first diode (D1) is connected in parallel to the first resistor element (4A). The second diode (D2) is connected in parallel to the second resistor element (4B). The first diode (D1) has a first anode and a first cathode, with the first anode connected to the first reference potential terminal (32A) and the first cathode connected to the first source terminal (2AS) of the first detection switch element (2A). The second diode (D2) has a second anode and a second cathode, with the second anode connected to the second reference potential terminal (32B) and the second cathode connected to the second source terminal (2BS) of the second detection switch element (2B).

[0185] In the on-state voltage measurement circuit (1f) according to the twelfth aspect, the first diode (D1) and the second diode (D2) each constitute a clamp circuit, and therefore it is possible to improve the measurement accuracy of the on-state voltage compared to a case where the first diode (D1) and the second diode (D2) are not provided.

[0186] The on-state voltage measurement circuit (1g) according to a thirteenth aspect is the same as that of the eleventh aspect, and further includes a first capacitor (C1) and a second capacitor (C2). The first capacitor (C1) is connected in parallel to the first resistor element (4A). The second capacitor (C2) is connected in parallel to the second resistor element (4B).

[0187] The on-state voltage measuring circuit (1g) according to the thirteenth aspect can improve the measurement accuracy of the on-state voltage.

[0188] In an on-state voltage measurement circuit (1h) according to a fourteenth aspect, in the eleventh aspect, the first control section (3A) is a first constant voltage source (EA1), and the second control section (3B) is a second constant voltage source (EA2).

[0189] The on-state voltage measurement circuit (1h) according to the fourteenth aspect makes it possible to reduce the number of components.

[0190] An on-voltage measurement circuit (1i) according to a fifteenth aspect measures the on-voltage of a semiconductor switch element (9e) having a first control terminal (90A), a first main terminal (91A) corresponding to the first control terminal (90A), a second control terminal (90B), and a second main terminal (92B) corresponding to the second control terminal (90B). The on-voltage is a voltage between the first main terminal (91A) and the second main terminal (92B) when the semiconductor switch element (9e) is in an on state. The on-voltage measurement circuit (1i) includes a normally-on first detection switch element (2A), a first resistor element (4A), a first voltage detector (5A), a normally-on second detection switch element (2B), a second resistor element (4B), and a second voltage detector (5B). The first detection switch element (2A) has a first drain terminal (2AD), a first source terminal (2AS), and a first gate terminal (2AG). The first resistor element (4A) is connected between the first source terminal (2AS) and the first gate terminal (2AG). The second detection switch element (2B) has a second drain terminal (2BD), a second source terminal (2BS), and a second gate terminal (2BG). The second resistor element (4B) is connected between the second source terminal (2BS) and the second gate terminal (2BG). In the on-voltage measurement circuit (1i), the first drain terminal (2AD) of the first detection switch element (2A) and the second drain terminal (2BD) of the second detection switch element (2B) are connected. The resistance value of the first resistor element (4A) is greater than the on-resistance of the first detection switch element (2A). The resistance value of the second resistor element (4B) is greater than the on-resistance of the second detection switch element (2B). The first voltage detection unit (5A) detects the on-voltage of the semiconductor switch element (9e) connected between the first gate terminal (2AG) and the second gate terminal (2BG) from the voltage (V4A) across the first resistor element (4A) when both the semiconductor switch element (9e) and the first detection switch element (2A) are on. The second voltage detection unit (5B) detects the on-voltage of the semiconductor switch element (9e) connected between the first gate terminal (2AG) and the second gate terminal (2BG) from the voltage (V4B) across the second resistor element (4B) when both the semiconductor switch element (9e) and the second detection switch element (2B) are on.

[0191] The on-state voltage measurement circuit (1i) according to the fifteenth aspect can improve the measurement accuracy of the on-state voltage. Moreover, the on-state voltage measurement circuit (1i) according to the fifteenth aspect can reduce the number of components compared to the on-state voltage measurement circuits (1e; 1f; 1g; 1h) according to the eleventh aspect.

[0192] An on-voltage measurement circuit (1j) according to a sixteenth aspect measures the on-voltage of a semiconductor switch element (9e) having a first control terminal (90A), a first main terminal (91A) corresponding to the first control terminal (90A), a second control terminal (90B), and a second main terminal (92B) corresponding to the second control terminal (90B). The on-voltage is a voltage between the first main terminal (91A) and the second main terminal (92B) when the semiconductor switch element (9e) is in an on state. The on-voltage measurement circuit (1j) includes a detection switch element (20), a first control unit (61), a first resistor element (41), a first voltage detection unit (51), a second control unit (62), a second resistor element (42), and a second voltage detection unit (52). The detection switch element (20) has a first gate terminal (21G), a first source terminal (21S) corresponding to the first gate terminal (21G), a second gate terminal (22G), and a second source terminal (22S) corresponding to the second gate terminal (22G). The first control unit (61) has a first signal output terminal (611) and a first reference potential terminal (612) and controls a first gate voltage of the first gate terminal (21G) of the detection switch element (20). The first resistor element (41) is connected between the first source terminal (21S) and the first reference potential terminal (612). The second control unit (62) has a second signal output terminal (621) and a second reference potential terminal (622) and controls a second gate voltage of the second gate terminal (22G) of the detection switch element (20). The second resistor element (42) is connected between the second source terminal (22S) and the second reference potential terminal (622). The resistance value of the first resistor element (41) is greater than the on-resistance of the detection switch element (20). The resistance value of the second resistor element (42) is greater than the on-resistance of the detection switch element (20). The first voltage detector (51) detects the on-voltage of the semiconductor switch element (9e) connected between the first reference potential terminal (612) and the second reference potential terminal (622) from the voltage (V41) across the first resistor element (41) when both the semiconductor switch element (9e) and the detection switch element (20) are on.The second voltage detection unit (52) detects the on-voltage of the semiconductor switch element (9e) connected between the first reference potential terminal (612) and the second reference potential terminal (622) from the voltage (V42) across the second resistor element (42) when both the semiconductor switch element (9e) and the detection switch element (20) are on.

[0193] The on-state voltage measurement circuit (1j) according to the sixteenth aspect can improve the measurement accuracy of the on-state voltage. Moreover, the on-state voltage measurement circuit (1j) according to the sixteenth aspect can reduce the number of components compared to the on-state voltage measurement circuits (1e; 1f; 1g; 1h) according to the eleventh aspect.

[0194] An on-voltage measurement circuit (1k) according to a seventeenth aspect measures the on-voltage of a semiconductor switch element (9e) having a first control terminal (90A), a first main terminal (91A) corresponding to the first control terminal (90A), a second control terminal (90B), and a second main terminal (92B) corresponding to the second control terminal (90B). The on-voltage is a voltage between the first main terminal (91A) and the second main terminal (92B) when the semiconductor switch element (9e) is in an on-state. The on-voltage measurement circuit (1k) includes a first detection switch element (2A), a first control unit (3A), a second detection switch element (2B), the second control unit (3B), a resistor element (40), and a voltage detection unit (50). The first detection switch element (2A) has a first drain terminal (2AD), a first source terminal (2AS), and a first gate terminal (2AG). The first control unit (3A) has a first signal output terminal (31A) and a first reference potential terminal (32A) and controls the first detection switch element (2A). The second detection switch element (2B) has a second drain terminal (2BD), a second source terminal (2BS), and a second gate terminal (2BG). The second control unit (3B) has a second signal output terminal (31B) and a second reference potential terminal (32B) and controls the second detection switch element (2B). The resistive element (40) is connected between the first source terminal (2AS) of the first detection switch element (2A) and the second source terminal (2BS) of the second detection switch element (2B). The first signal output terminal (31A) of the first control unit (3A) is connected to the first gate terminal (2AG) of the first detection switch element (2A). The first reference potential terminal (32A) of the first control unit (3A) is connected to the second source terminal (2BS) of the second detection switch element (2B). The second signal output terminal (31B) of the second control unit (3B) is connected to the second gate terminal (2BG) of the second detection switch element (2B). The second reference potential terminal (32B) of the second control unit (3B) is connected to the first source terminal (2AS) of the first detection switch element (2A). The resistance value of the resistive element (40) is greater than the on-resistance of the first detection switch element (2A) and the on-resistance of the second detection switch element (2B).The voltage detection unit (50) detects the on-voltage of the semiconductor switch element (9e) connected between the first reference potential terminal (32A) and the second reference potential terminal (32B) from the voltage across the resistor element (40) when the semiconductor switch element (9e) is turned on.

[0195] The on-state voltage measuring circuit (1k) according to the seventeenth aspect can improve the measurement accuracy of the on-state voltage.

[0196] In an on-state voltage measurement circuit (1m) according to an eighteenth aspect, in the seventeenth aspect, the first control unit (3A) is a first constant voltage source (EA1), and the second control unit (3B) is a second constant voltage source (EA2).

[0197] The on-state voltage measurement circuit (1m) according to the eighteenth aspect makes it possible to reduce the number of components.

[0198] An on-voltage measurement circuit (1n) according to a nineteenth aspect measures the on-voltage of a semiconductor switch element (9e) having a first control terminal (90A), a first main terminal (91A) corresponding to the first control terminal (90A), a second control terminal (90B), and a second main terminal (92B) corresponding to the second control terminal (90B). The on-voltage is the voltage between the first main terminal (91A) and the second main terminal (92B) when the semiconductor switch element (9e) is in the on state. The on-voltage measurement circuit (1n) includes a normally-on first detection switch element (2A), a normally-on second detection switch element (2B), a resistor element 40, and a voltage detection unit (50). The first detection switch element (2A) has a first drain terminal (2AD), a first source terminal (2AS), and a first gate terminal (2AG). The second detection switch element (2B) has a second drain terminal (2BD), a second source terminal (2BS), and a second gate terminal (2BG). The resistive element (40) is connected between the first source terminal (2AS) of the first detection switch element (2A) and the second source terminal (2BS) of the second detection switch element (2B). In the on-voltage measuring circuit (1n), the first source terminal (2AS) of the first detection switch element (2A) is connected to the second gate terminal (2BG) of the second detection switch element (2B). The second source terminal (2BS) of the second detection switch element (2B) is connected to the first gate terminal (2AG) of the first detection switch element (2A). The resistance value of the resistive element (40) is greater than the on-resistance of the first detection switch element (2A) and the on-resistance of the second detection switch element (2B). The voltage detection unit (50) detects the on-voltage of the semiconductor switch element (9e) connected between the first source terminal (2AS) and the second source terminal (2BS) from the voltage across the resistor element (40) when the semiconductor switch element (9e) is turned on.

[0199] The on-state voltage measurement circuit (1n) according to the nineteenth aspect can improve the measurement accuracy of the on-state voltage. Moreover, the on-state voltage measurement circuit (1n) according to the nineteenth aspect can reduce the number of components compared to the on-state voltage measurement circuit (1k) according to the seventeenth aspect. [Explanation of symbols]

[0200] 1, 1a, 1b, 1c, 1d, 1e, 1f, 1g, 1h, 1i, 1j, 1k, 1m, 1n On-state voltage measurement circuit 2. Detection switch element 2D drain terminal 2G Gate Terminal 2S Source Terminal 2A First detection switch element 2AD 1st drain terminal 2AG First gate terminal 2AS 1st source terminal 2B Second detection switch element 2BD Second drain terminal 2BG Second gate terminal 2BS Second source terminal 20 Detection switch element 21G First gate terminal 21S First source terminal 22G Second gate terminal 22S Second source terminal 3, 3a Control section 31 Signal output terminal 32 Reference potential terminal 3A First control section 31A 1st signal output terminal 32A 1st reference potential terminal 3B 2nd control section 31B 2nd signal output terminal 32B 2nd reference potential terminal 4 Resistive elements 4A First Resistor 4B Second resistor element 40 Resistive element 41 first resistor element 42 second resistor element 5 Voltage detection section 5A 1st voltage detection unit 5B Second voltage detection unit 50 Voltage detection unit 51 First voltage detection unit 52 Second voltage detection unit 61 First Control Section 611 First signal output terminal 612 First reference potential terminal 62 Second Control Section 621 Second signal output terminal 622 Second reference potential terminal 9, 9e Semiconductor switching element 90 Control terminal 91 1st main terminal 92 2nd main terminal 90A 1st control terminal 91A 1st main terminal 90B Second control terminal 92B 2nd main terminal 10, 10a, 10b, 10c, 10d, 10e, 10f, 10g, 10h, 10i, 10j, 10k, 10m, 10n switch system 11 Switch control section 11A First switch control section 11B Second switch control section 15 Load 16 Power supply 19 Temperature detection unit V2 voltage V4 voltage V4A voltage V4B voltage Vt threshold Vth2 threshold voltage Vth9 threshold voltage

Claims

1. An on-voltage measurement circuit for measuring an on-voltage, which is a voltage between a first control terminal, a first main terminal corresponding to the first control terminal, a second control terminal, and a second main terminal corresponding to the second control terminal, in an on-state of a semiconductor switch element, a detecting switch element having a first gate terminal, a first source terminal corresponding to the first gate terminal, a second gate terminal, and a second source terminal corresponding to the second gate terminal; a first control unit having a first signal output terminal and a first reference potential terminal, and controlling a first gate voltage of the first gate terminal of the detection switch element; a first resistor element connected between the first source terminal and the first reference potential terminal; a first voltage detection unit; a second control unit having a second signal output terminal and a second reference potential terminal, and controlling a second gate voltage of the second gate terminal of the detection switch element; a second resistor element connected between the second source terminal and the second reference potential terminal; a second voltage detection unit, a resistance value of the first resistor element is greater than an on-resistance of the detection switch element, the resistance value of the second resistor element is greater than the on-resistance of the detection switch element, the first voltage detection unit detects an on-voltage of the semiconductor switch element connected between the first reference potential terminal and the second reference potential terminal from a voltage across the first resistor element when both the semiconductor switch element and the detection switch element are on; the second voltage detection unit detects an on-voltage of the semiconductor switch element connected between the first reference potential terminal and the second reference potential terminal from a voltage across the second resistance element when both the semiconductor switch element and the detection switch element are on. On-state voltage measurement circuit.

2. An on-voltage measurement circuit for measuring an on-voltage, which is a voltage between a first control terminal, a first main terminal corresponding to the first control terminal, a second control terminal, and a second main terminal corresponding to the second control terminal, in an on-state of a semiconductor switch element, a first sensing switch element having a first drain terminal, a first source terminal, and a first gate terminal; a first control unit having a first signal output terminal and a first reference potential terminal, and controlling the first detection switch element; a second sensing switch element having a second drain terminal, a second source terminal, and a second gate terminal; a second control unit having a second signal output terminal and a second reference potential terminal, and controlling the second detection switch element; a resistor element connected between the first source terminal of the first detection switch element and the second source terminal of the second detection switch element; a voltage detection unit, the first signal output terminal of the first control unit is connected to the first gate terminal of the first detection switch element, the first reference potential terminal of the first control unit is connected to the second source terminal of the second detection switch element, the second signal output terminal of the second control unit is connected to the second gate terminal of the second detection switch element, the second reference potential terminal of the second control unit is connected to the first source terminal of the first detection switch element, a resistance value of the resistive element is greater than the on-resistance of the first detecting switch element and the on-resistance of the second detecting switch element; the voltage detection unit detects an on-voltage of the semiconductor switch element connected between the first reference potential terminal and the second reference potential terminal from a voltage across the resistor element when the semiconductor switch element is turned on. On-state voltage measurement circuit.

3. The first control unit is a first constant voltage source, The second control unit is a second constant voltage source.

3. The on-state voltage measurement circuit according to claim 2.

4. An on-voltage measurement circuit for measuring an on-voltage, which is a voltage between a first control terminal, a first main terminal corresponding to the first control terminal, a second control terminal, and a second main terminal corresponding to the second control terminal, in an on-state of a semiconductor switch element, a normally-on first detection switch element having a first drain terminal, a first source terminal, and a first gate terminal; a normally-on second detection switch element having a second drain terminal, a second source terminal, and a second gate terminal; a resistor element connected between the first source terminal of the first detection switch element and the second source terminal of the second detection switch element; a voltage detection unit, the first source terminal of the first detecting switch element is connected to the second gate terminal of the second detecting switch element, the second source terminal of the second detecting switch element is connected to the first gate terminal of the first detecting switch element, a resistance value of the resistive element is greater than the on-resistance of the first detecting switch element and the on-resistance of the second detecting switch element; the voltage detection unit detects an on-voltage of the semiconductor switch element connected between the first source terminal and the second source terminal from a voltage across the resistor element when the semiconductor switch element is turned on. On-state voltage measurement circuit.

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