Overcurrent protection circuit and switch circuit

Abstract

An overcurrent protection circuit is used to protect overcurrent flowing into a switching element whose opening and closing are controlled based on a driving signal, and comprises: a first transistor, which is an N-channel FET, having a drain connected to the control terminal of the switching element, and a source connected to ground; a second transistor, which is a PNP bipolar transistor, having an emitter connected to the control terminal of the switching element, a collector connected to the gate of the first transistor and grounded via a first capacitor, and a base pulled up to a specified pull-up voltage; and a grounding circuit, which is connected in parallel with the first capacitor.

Description

Technical Field

[0001] The present invention relates to an overcurrent protection circuit and a switch circuit, wherein the switch circuit is a switch circuit such as a boost chopper circuit, a half-bridge inverter circuit, a full-bridge inverter circuit, etc. Background Art

[0002] Semiconductor devices usually have a short-circuit tolerance. If a current exceeding the short-circuit tolerance flows, it may cause damage. By quickly sensing the current flowing through the semiconductor device and stopping the current flowing to the semiconductor device by short circuit, the semiconductor device can be protected from overcurrent.

[0003] For example, patent document 1 provides an overcurrent protection device for an electric power conversion device, which can change the setting level of the sensing voltage for collector short circuit detection at any timing when the DC voltage is high, low, or even certain, thereby reliably protecting the voltage-driven element from overcurrent.

[0004] The overcurrent protection device of patent document 1 comprises: a power conversion device having a voltage-driven power switching element; an overcurrent sensing unit, detecting the voltage of the input-side main terminal of the power switching element and providing a shutdown signal to the power switching element when the voltage exceeds a specified value; and an overcurrent setting unit, which is configured to be connected to the overcurrent sensing unit in parallel at any timing so as to be able to change the specified value.

[0005] GaN devices are semiconductor devices using gallium nitride (GaN). Compared with existing semiconductor devices such as insulated gate bipolar transistors (IGBTs) and SiC devices, they can be driven at high frequencies.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent Application Publication No. 2006-14402 Summary of the invention

[0009] Technical problem to be solved by the invention

[0010] However, GaN devices are less resistant to overcurrent than existing semiconductor devices and may be destroyed by an overcurrent of, for example, 100 nanoseconds. Therefore, existing overcurrent protection technologies such as DESAT, CT detection, or the technology of Patent Document 1 cannot fully protect GaN devices.

[0011] An object of the present invention is to solve the above problems and to provide an overcurrent protection circuit and a switch circuit that can protect a semiconductor switch from overcurrent more quickly than the prior art.

[0012] Technical solutions for solving technical problems

[0013] An overcurrent protection circuit according to one embodiment of the present invention is used to protect an overcurrent flowing to a switch element whose opening and closing is controlled based on a driving signal, and comprises:

[0014] a first transistor, which is an N-channel FET, having a drain connected to the control terminal of the switching element and a source connected to ground;

[0015] a second transistor, which is a PNP bipolar transistor, having an emitter connected to the control terminal of the switch element, a collector connected to the gate of the first transistor and grounded via a first capacitor, and a base pulled up to a prescribed pull-up voltage; and

[0016] A grounding circuit is connected in parallel with the first capacitor.

[0017] Effects of the Invention

[0018] According to the overcurrent protection circuit of the present invention, a semiconductor device can be protected from overcurrent more quickly than in the prior art. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a block diagram showing a configuration example of the step-up chopper circuit 1 according to the first embodiment.

[0020] Figure 2A It is shown Figure 1 A block diagram of a detailed configuration example of a current-driven switching circuit 10.

[0021] Figure 2B This is a block diagram showing a detailed configuration example of a current-driven switching circuit 10 a according to a modification of the first embodiment.

[0022] Figure 3A It is shown Figure 1 A timing diagram of operation waveforms of signals, etc. in the current-driven switching circuit 10.

[0023] Figure 3B yes Figure 1 1 is a timing diagram showing the simulation results of the current driven switching circuit 10, that is, the operating waveforms of the current and the voltage.

[0024] Figure 4 This is a block diagram showing a configuration example of a current-driven switching circuit 10A according to the second embodiment.

[0025] Figure 5 yes Figure 4 1A is a timing diagram showing the simulation results of the current-driven switching circuit 10A, that is, the operating waveforms of the current and voltage.

[0026] Figure 6This is a block diagram showing a configuration example of a current-driven switching circuit 10B according to the third embodiment.

[0027] Figure 7 It is shown Figure 6 10B is a timing diagram of operation waveforms of signals, etc. in the current-driven switching circuit 10B.

[0028] Figure 8 This is a block diagram showing a configuration example of a current-driven switching circuit 10C according to the fourth embodiment.

[0029] Fig. 9 1 is a block diagram showing a configuration example of a half-bridge inverter circuit 1A according to Modification 1.

[0030] Fig.10 1 is a block diagram showing a configuration example of a full-bridge inverter circuit 1B according to a second modification. DETAILED DESCRIPTION

[0031] Hereinafter, embodiments of the present invention will be described based on the accompanying drawings. It should be noted that the embodiments described below are merely illustrative of the present invention in all aspects. Of course, various improvements and modifications may be made without departing from the scope of the present invention. That is, when implementing the present invention, specific structures corresponding to the embodiments may be appropriately adopted.

[0032] (Implementation method 1)

[0033] Figure 1 This is a block diagram showing a configuration example of the step-up chopper circuit 1 according to the first embodiment. Figure 1 In the embodiment of the present invention, the step-up chopper circuit 1 includes a current-driven switching circuit 10 including a semiconductor switch 14 as a switching element, an inductor L1 , a diode D1 , and a capacitor C1 .

[0034] Figure 1 In the embodiment, the input voltage Vi is applied to the connection point of the anode of the diode D1 and the drain of the semiconductor switch 14 via the inductor L1. The source of the semiconductor switch 14 is grounded. The cathode of the diode D1 is connected to one end of the capacitor C1 that outputs the output voltage Vo, and the other end thereof is grounded. A switch drive signal (hereinafter referred to as a drive signal) for step-up chopping is input to the gate of the semiconductor switch 14, and the semiconductor switch 14 is switched to be turned on or off.

[0035] In summary, in the constructed boost chopper circuit 1, the inductor L1 generates an electromotive force in a direction that prevents current changes. Therefore, when the semiconductor switch 14 is switched from on to off, the inductor L1 generates an electromotive force in the same direction as the input voltage Vi to prevent the current from decreasing due to the resistance of the diode D1. As a result, a voltage higher than the input voltage Vi is generated, which is smoothed by the capacitor C1 and converted into the output voltage Vo. Therefore, by periodically and selectively switching the opening and closing of the semiconductor switch 14, the boost chopper circuit 1 converts the input voltage Vi into a DC output voltage Vo higher than the input voltage Vi and outputs it.

[0036] As referenced later Figure 2A and Figure 2B As described in detail, the current-driven switching circuit 10 of the boost chopper circuit 1 is provided with an overcurrent protection circuit 11. The overcurrent protection circuit 11 is characterized in that in order to prevent the drain current Id of an overcurrent exceeding a specified value from flowing between the drain and source of the semiconductor switch 14 and destroying the semiconductor switch 14, the gate of the semiconductor switch 14 is grounded to turn off the semiconductor switch 14, thereby blocking the overcurrent.

[0037] Figure 2A It is shown Figure 1 A block diagram of a detailed configuration example of a current-driven switching circuit 10. Figure 2A In the embodiment, the current driven switch circuit 10 includes an overcurrent protection circuit 11, a control unit 12, a drive unit 13, a semiconductor switch 14, and a resistor R1. The overcurrent protection circuit 11 includes transistors Q1 and Q2, a pull-up resistor R2, a voltage detection circuit 15, a capacitor C11, and a resistor R11. Here, the overcurrent protection circuit 11 prevents the drain current Id of an overcurrent exceeding a predetermined value from flowing between the drain and source of the semiconductor switch 14 and destroying the semiconductor switch 14, thereby shutting off the overcurrent by grounding the gate of the semiconductor switch 14 and turning off the semiconductor switch 14.

[0038] Figure 2A In the embodiment, the control unit 12 controls the driving unit 13 by the driving signal Sdrv which is a pulse signal. In addition, the voltage detection circuit 15 monitors the input detection voltage Vgs1, and when the detection voltage Vgs1 is above a predetermined threshold value, the abnormal detection signal Sa of a high potential is output to the control unit 12. In response to this, the control unit 12 fixes the driving signal Sdrv to a low potential and stops the driving unit 13. It should be noted that the base voltage of the transistor Q2 is set to Vocp.

[0039] The driving unit 13 applies a gate-source voltage Vgs14 to the gate of the semiconductor switch 14 via the resistor R1 based on the driving signal Sdrv from the control unit 12 to control the opening and closing of the semiconductor switch 14. The semiconductor switch 14 is a switching element such as a GaN device, and is controlled by the driving unit 13 to selectively switch whether to conduct the drain current Id.

[0040] In the overcurrent protection circuit 11, the transistor Q1 is, for example, an N-channel FET. The drain of the transistor Q1 is connected to the gate-source voltage Vgs14, the source of the transistor Q1 is grounded, and the gate of the transistor Q1 is connected to the collector of the transistor Q2. In addition, the transistor Q2 is, for example, a PNP-type bipolar transistor, the emitter of the transistor Q2 is connected to the gate-source voltage Vgs14, the collector of the transistor Q2 is grounded via a time constant circuit 19 which is a parallel circuit of a capacitor C11 and a resistor R11, and the base of the transistor Q2 is pulled up to the threshold voltage VTH via a pull-up resistor R2. Here, the time constant circuit 19 is provided in order to discharge the gate-source voltage Vgs of the transistor Q1 through its time constant so as to restore the overcurrent protection circuit 11 from the protection action to the normal action after the drive signal Sdrv stops. It should be pointed out that the threshold voltage VTH is an example of the "pull-up voltage" of the present invention, and the resistor R11 is an example of the "grounding circuit" of the present invention.

[0041] Here, during the normal operation period, both transistors Q1 and Q2 are turned off, and the detection voltage Vgs1 is maintained at a specified voltage. Next, if the gate-source voltage Vgs14 becomes the threshold voltage VTH due to a short circuit, the transistor Q2 is turned on, and if the gate-source voltage Vgs14 exceeds the threshold voltage VTH due to a continuous short circuit, the transistor Q1 is also turned on, and the protection operation starts. Here, the voltage detection circuit 15 detects the detection voltage Vgs1 as the gate-source voltage of the transistor Q1, and outputs a signal indicating the detection voltage Vgs1 to the control unit 12. Next, if the protection operation starts and the detection voltage Vgs is lower than the threshold voltage VTH, the transistor Q2 is turned off.

[0042] Figure 3A It is shown Figure 1 A timing diagram of operation waveforms of signals, etc. in the current-driven switching circuit 10.

[0043] Figure 3AIn the embodiment, the current driven switch circuit 10 starts to operate at time t0, a short circuit occurs in the semiconductor switch 14 at time t1, and the control unit 12 detects the short circuit at time t3. Here, the period from time t0 to t1 is called the normal operation period, the period from time t1 to t2 is called the protection operation period, the period from time t2 to t3 is called the protection holding period, the period from time t3 to t5 is called the Vgs1 off period, and the normal operation period is returned from time t6.

[0044] During the normal operation period, except for the overshoot period of the detection voltage Vgs1 (details will be described later), the current does not flow to the pull-up resistor R2, so the detection voltage Vgs1 is the threshold voltage VTH. The threshold voltage VTH is set higher than the gate-source voltage Vgs14 provided by the driving unit 13 when the drive signal Sdrv is high, so both transistors Q1 and Q2 are always turned off during the normal operation period.

[0045] When an overcurrent generally flows through a semiconductor device, the gate-source voltage of a semiconductor switch included in the semiconductor device overshoots (instantaneously increases). Figure 3A At time t1, the drain current Id flowing to the semiconductor switch 14 also increases excessively, and the gate-source voltage Vgs14 of the semiconductor switch 14 increases sharply to a value higher than the threshold voltage VTH. As a result, the transistor Q2 turns on, and thus the transistor Q1 also turns on.

[0046] Therefore, the gate-source voltage Vgs14 is discharged through the transistor Q1 and becomes 0. As a result, the semiconductor switch 14 is turned off, so that the overcurrent flowing to the semiconductor switch 14 can be stopped, and the overcurrent protection circuit 11 starts the protection action. The time from the occurrence of the short circuit at time t1 to the start of the protection action of the overcurrent protection circuit 11 includes the delay in the switching of the transistors Q1 and Q2, and is shorter, for example, about 20 to 100 nanoseconds.

[0047] In addition, the protection and holding function in the present embodiment is performed by the time constant circuit 19 connected to the gate terminal of the transistor Q1.

[0048] The voltage detection circuit 15 outputs the abnormality detection signal Sa based on the H potential of the detection voltage Vgs1 to the control unit 12. In response to this, the control unit 12 determines that the protection action is performed and stops the output of the drive signal Sdrv (time t3). During the stop period Ph, the drive signal Sdrv is always at a low potential, and the semiconductor switch 14 is always kept off.

[0049] It should be noted that the protection action is maintained until the detection voltage Vgs1 is completely discharged by the time constant circuit 19, so that repeated overcurrent will not be generated.

[0050] If the abnormal state is released during the protection state (time t4), after the drive signal stops, the time constant circuit 19 discharges the gate / source voltage Vgs of the transistor Q1 through its time constant to restore the overcurrent protection circuit 11 from the protection action to the normal action. Therefore, the transistor Q1 is turned off (time t5) and the normal action is restored.

[0051] Figure 3B yes Figure 1 The simulation result of the current-driven switching circuit 10 is a timing diagram showing the operating waveforms of the current and voltage. Figure 3B It is shown that the gate-source voltage Vgs14 can be controlled without a large overshoot.

[0052] In summary, the overcurrent protection circuit 11 in the present embodiment includes a pull-up resistor R2, a transistor Q1 of an N-channel FET, a transistor Q2 of a PNP bipolar transistor, a voltage detection circuit 15, and a time constant circuit 19 composed of a capacitor C11 and a resistor R11. If the gate-source voltage Vgs14 of the semiconductor switch 14 exceeds the threshold voltage VTH, the transistors Q2 and Q1 are turned on in sequence. As a result, the gate-source voltage Vgs14 is instantly reduced to 0V by the transistor Q1, and the protection action of closing the semiconductor switch is started. In addition, the control unit 12 stops the drive unit 13 and closes the semiconductor switch 14 based on the abnormality detection signal Sa from the voltage detection circuit 15. Therefore, according to the present embodiment, compared with the prior art, the overcurrent flowing to the semiconductor switch 14 can be stopped more quickly, thereby protecting the semiconductor switch 14.

[0053] Figure 2B This is a block diagram showing a detailed configuration example of a current-driven switching circuit 10 a according to a modification of the first embodiment. Figure 2B The current driven switching circuit 10a is provided with an overcurrent protection circuit 11a instead of Figure 2A The overcurrent protection circuit 11 of the embodiment 1 is different in that the resistor R2 is provided with a noise elimination diode D2. It should be noted that this modification is also applicable to other embodiments of the embodiment 1.

[0054] (Implementation method 2)

[0055] In the first embodiment, when the gate-source voltage Vgs14 of the semiconductor switch 14 increases, Figure 3B As shown in FIG. 1 , the threshold voltage Vocp temporarily increases. At this time, a delay is generated due to the change of the threshold voltage Vocp, which further causes a delay in the start of the protection action.

[0056] Figure 4 This is a block diagram showing a configuration example of a current-driven switching circuit 10A according to the second embodiment. Figure 4Among them, the current driven switching circuit 10A is different from the current driven switching circuit 10 in the following respects.

[0057] (1) The overcurrent protection circuit 11A further includes a capacitor Ca connected to the base of the transistor Q2 .

[0058] (2) The power supply of the threshold voltage VTH charges the capacitor Ca to the threshold voltage VTH via the pull-up resistor R2.

[0059] In Embodiment 2, a short circuit occurs in the semiconductor switch 14, and the gate-source voltage Vgs14 increases sharply. At this time, the threshold voltage Vocp temporarily increases due to the increase in the gate-source voltage Vgs14, but this change is reduced by the capacitor Ca. Therefore, the delay in the start of the protection action can be suppressed.

[0060] Figure 5 yes Figure 4 The simulation results of the current-driven switching circuit 10A are shown in the timing diagram of the current and voltage operation waveforms. Figure 5 It is shown that the threshold voltage Vocp can be controlled so as not to have a large temporary increase.

[0061] In summary, the overcurrent protection circuit 11A in this embodiment further includes a capacitor Ca in addition to the overcurrent protection circuit 11. Thus, the temporary increase in the threshold voltage Vocp caused by the increase in the gate-source voltage Vgs14 can be reduced to less than Figure 2A The overcurrent protection circuit 11 reduces the delay in the start of the protection action compared to the overcurrent protection circuit 11.

[0062] (Implementation method 3)

[0063] Figure 6 This is a block diagram showing a configuration example of a current-driven switching circuit 10B according to the third embodiment.

[0064] Figure 6 In the embodiment, the current driven switch circuit 10B and Figure 4 Compared with the current-driven switching circuit 10A, it is different in the following aspects.

[0065] (1) The current-driven switching circuit 10B includes a transistor 17 instead of the resistor R11 . The transistor 17 is, for example, an N-channel MOSFET and operates as a grounding circuit.

[0066] Figure 6In the embodiment, the gate of transistor 17 is input with the recovery signal Sm from control unit 12, the drain of transistor 17 is connected to the gate of transistor Q1, and the source of transistor 17 is grounded. After the driving signal stops, control unit 12 outputs recovery signal Sm to the gate of transistor 17 to restore the overcurrent protection circuit 11 from the protection operation to the normal operation. Thus, by turning on transistor 17, gate-source voltage Vgs1 of transistor Q1 is discharged.

[0067] Figure 7 It is shown Figure 6 10B is a timing diagram showing an example of operation waveforms of signals and the like in the current driven switching circuit 10B.

[0068] Figure 7 In the embodiment, the current driven switch circuit 10B and Figure 4 Compared with the operation of the current driven switching circuit 10A, the following contents are different.

[0069] (1) When a short circuit occurs at time t1, the gate voltage of transistor Q1 increases, and the protection operation starts.

[0070] (2) At time t3, after the control unit 12 detects the abnormal state based on the abnormal detection signal Sa from the voltage detection circuit 15, it determines that the abnormal state is resolved when the abnormal detection signal Sa drops to a low potential (time t11), and then outputs the recovery signal Sm to the gate of the transistor 17 after a predetermined period of time (time t4). As a result, the transistor 17 is turned on, and the gate-source voltage Vgs of the transistor Q1 is discharged, whereby the transistor Q1 is turned off, and the semiconductor switch 14 is restored from the protection state to the normal state (time t6).

[0071] As described above, the current driven switch circuit 10B of the third embodiment includes the transistor 17. After the control unit 12 determines that the abnormal state is resolved (time t11) and a predetermined period of time has passed (time t4), it outputs the recovery signal Sm to the gate of the transistor 17. As a result, the transistor 17 is turned on, and the gate-source voltage Vgs of the transistor Q1 is discharged, whereby the transistor Q1 is turned off, and the semiconductor switch 14 is restored from the protection state to the normal state (time t6).

[0072] (Implementation method 4)

[0073] Figure 8 This is a block diagram showing a configuration example of a current-driven switching circuit 10C according to the fourth embodiment. Figure 8 In the current driven switching circuit 10C and Figure 6 Compared with the current-driven switching circuit 10B, the following aspects are different.

[0074] (1) Instead of the transistor 17 which is an N-channel MOSFET, a transistor 17 a which is, for example, an NPN bipolar transistor is provided.

[0075] (2) The transistor driving unit 16 is provided between the control unit 12 and the gate of the transistor 17 a .

[0076] Figure 8 In the embodiment, the control unit 12 controls the base current Itr of the transistor 17a via the transistor driving unit 16 to control the on / off of the transistor 17a. Thus, the same effects as those of the third embodiment are obtained.

[0077] (Variation)

[0078] Above, the embodiments of the present invention are described in detail, but the aforementioned description is only an illustration of the present invention in all aspects. Of course, various improvements and modifications can be made without departing from the scope of the present invention. For example, the following changes can be made. It should be noted that the same symbols will be used for the same components as the above-mentioned embodiments, and the description of the same aspects as the above-mentioned embodiments will be appropriately omitted. The following modifications can be appropriately combined.

[0079] In Embodiments 1 to 4, the step-up chopper circuit 1 is described as a semiconductor device including the current-driven switching circuits 10 and 10A to 10C of the present invention. However, the present invention is not limited thereto, and can also be applied to circuits and devices that control current switching by semiconductor switches.

[0080] For example, Fig. 9 1 is a block diagram showing a configuration example of a half-bridge inverter circuit 1A according to Modification 1. Fig. 9 In FIG. 1 , the half-bridge inverter circuit 1A includes an inductor L2 , two current-driven switching circuits 10 , and a capacitor C2 .

[0081] Fig. 9 In the embodiment, the semiconductor switches 14 of the two current-driven switching circuits 10 are controlled to be opened alternately periodically. Thus, the input voltage Vi is switched, smoothed by the capacitor C2, and converted into an AC output voltage Vo. Thus, the half-bridge inverter circuit 1A switches the DC input voltage Vi, converts it into an AC output voltage Vo, and outputs it. The two current-driven switching circuits 10 can be replaced by any one of the current-driven switching circuits 10A to 10C.

[0082] in addition, Fig.10 1 is a block diagram showing a configuration example of a full-bridge inverter circuit 1B according to a second modification. Fig.10 In FIG. 1 , the full-bridge inverter circuit 1B includes a capacitor C3 , four current-driven switching circuits 10 , and inductors L3 and L4 .

[0083] Fig.10In the four current-driven switching circuits 10, control is performed so that the first and fourth current-driven switching circuits 10 (upper left and lower right in the figure) are turned on, and the second and third current-driven switching circuits 10 (lower left and upper right in the figure) are turned off, and the periods of reversing their opening and closing are periodically alternated. The input voltage Vi is thereby switched, and the switched input voltage Vi is smoothed by the capacitor C3 and the inductors L3 and L4. Thus, the full-bridge inverter circuit 1B switches the DC input voltage Vi, converts it into an AC output voltage Vo, and outputs it. The four current-driven switching circuits 10 can be replaced by any one of the current-driven switching circuits 10A to 10C.

[0084] As such, the current-driven switch circuit and the overcurrent protection circuit of the present invention can be used in circuits and devices that control current switching through semiconductor devices.

[0085] In addition, in Embodiments 1 to 4, a pull-up resistor R2 is used as a device for limiting the current from the power supply of the threshold voltage VTH. However, the present invention is not limited to this, and a diode or the like may be used instead of the pull-up resistor R2. In addition, in Embodiments 1 to 4, current-driven switching circuits 10, 10A to 10C are used as switching circuits. However, the present invention is not limited to this, and a voltage-driven switching circuit may be used instead of a current-driven switching circuit.

[0086] Description of Reference Numerals

[0087] 1 Boost chopper circuit

[0088] 1A Half-bridge Inverter Circuit

[0089] 1B Full-bridge inverter circuit

[0090] 10, 10a, 10A~10C Current driven switching circuit

[0091] 11, 11a, 11A~11C Overcurrent protection circuit

[0092] 12 Control Unit

[0093] 13. Drive unit

[0094] 14 Semiconductor switch

[0095] 15 Voltage detection circuit

[0096] 16 Transistor driver

[0097] 17, 17a transistor

[0098] 18, 19 Time constant circuit

[0099] C1~C11 capacitors

[0100] D1, D2 diodes

[0101] L1, L2 Reactor

[0102] Q1, Q2 transistors

[0103] R1~R11 resistors.

Claims

1. An overcurrent protection circuit for blocking an overcurrent flowing to a switch element whose opening and closing is controlled based on a drive signal, the overcurrent protection circuit comprising: a first transistor, which is an N-channel FET, having a drain connected to the control terminal of the switching element and a source connected to ground; A second transistor is a PNP bipolar transistor having an emitter connected to the control terminal of the switch element, a collector connected to the gate of the first transistor and grounded via a first capacitor, and a base pulled up to a predetermined pull-up voltage; as well as a grounding circuit, including any one of a resistor, a FET, and a bipolar transistor, connected in parallel with the first capacitor, In the case where the grounding circuit is a first resistor, the first capacitor and the first resistor constitute a first time constant circuit, and the first time constant circuit is provided to discharge the gate-source voltage of the first transistor by the time constant of the first time constant circuit so as to restore the overcurrent protection circuit from protection operation to normal operation after the drive signal stops. In the case where the ground circuit is a third transistor of a FET, the third transistor has: a drain and a source connected in parallel with the first capacitor; and a gate to which a recovery signal is applied, wherein the recovery signal is used to restore the protection action of the overcurrent protection circuit to a normal action, In the case where the grounding circuit is a fourth transistor of a bipolar transistor, the fourth transistor has: a collector and an emitter connected in parallel with the first capacitor; and a base, to which a recovery signal is applied, the recovery signal being used to recover from the protection action of the overcurrent protection circuit to the normal action, In the overcurrent protection circuit, a threshold voltage is provided, the threshold voltage being higher than a voltage applied to a control terminal of the switch element when the drive signal is at a high potential, and the predetermined pull-up voltage is the threshold voltage.

2. The overcurrent protection circuit according to claim 1, wherein: In the case where the grounding circuit is the first resistor, The overcurrent protection circuit comprises: a second resistor connected between the base of the second transistor and the pull-up voltage; and a first diode, connected in parallel with the second resistor, An anode of the first diode is connected between the second resistor and the base of the second transistor, and a cathode of the first diode is connected between the pull-up voltage and the second resistor.

3. The overcurrent protection circuit according to claim 1, wherein: In the case where the grounding circuit is the first resistor, The overcurrent protection circuit further comprises: The second capacitor is connected to the base of the second transistor and to ground.

4. The overcurrent protection circuit according to claim 1, wherein: In the case where the grounding circuit is the first resistor, The overcurrent protection circuit further includes a second time constant circuit, and the second time constant circuit includes: a third resistor connected between the base of the second transistor and the pull-up voltage; and A third capacitor is connected between a connection point between the third resistor and the base of the second transistor and ground.

5. The overcurrent protection circuit according to claim 4, wherein: The overcurrent protection circuit further comprises: a third diode, connected in parallel to the third resistor, An anode of the third diode is connected between the third resistor and the base of the second transistor, and a cathode of the third diode is connected between the pull-up voltage and the third resistor.

6. The overcurrent protection circuit according to claim 1, wherein: In the case where the ground circuit is the third transistor, The overcurrent protection circuit further comprises: A control unit, generating the driving signal; as well as The voltage detection circuit generates an abnormality detection signal based on the voltage of the gate of the first transistor and outputs the abnormality detection signal to the control unit, wherein the abnormality detection signal is used to turn off the switch element.

7. The overcurrent protection circuit according to claim 6, wherein: The control unit generates the restoration signal and applies the restoration signal to the gate of the third transistor after a predetermined time has passed since the abnormality detection signal disappears.

8. The overcurrent protection circuit according to claim 1, wherein: In the case where the ground circuit is the fourth transistor, The overcurrent protection circuit further comprises: A control unit, generating the driving signal; as well as The voltage detection circuit generates an abnormality detection signal based on the voltage of the gate of the first transistor and outputs the abnormality detection signal to the control unit, wherein the abnormality detection signal is used to turn off the switch element.

9. The overcurrent protection circuit according to claim 8, wherein: The control unit generates the restoration signal and applies the restoration signal to the base of the fourth transistor after a predetermined time has passed since the abnormality detection signal disappears.

10. A switching circuit comprising: an overcurrent protection circuit and a switching element, The overcurrent protection circuit is an overcurrent protection circuit for blocking an overcurrent flowing to a switch element whose opening and closing are controlled based on a drive signal. The overcurrent protection circuit comprises: a first transistor, which is an N-channel FET, having a drain connected to the control terminal of the switching element and a source connected to ground; A second transistor is a PNP bipolar transistor having an emitter connected to the control terminal of the switch element, a collector connected to the gate of the first transistor and grounded via a first capacitor, and a base pulled up to a predetermined pull-up voltage; as well as a grounding circuit, including any one of a resistor, a FET, and a bipolar transistor, connected in parallel with the first capacitor, In the case where the grounding circuit is a first resistor, the first capacitor and the first resistor constitute a first time constant circuit, and the first time constant circuit is provided to discharge the gate-source voltage of the first transistor by the time constant of the first time constant circuit so as to restore the overcurrent protection circuit from protection operation to normal operation after the drive signal stops. In the case where the ground circuit is a third transistor of a FET, the third transistor has: a drain and a source connected in parallel with the first capacitor; and a gate to which a recovery signal is applied, wherein the recovery signal is used to restore the protection action of the overcurrent protection circuit to a normal action, In the case where the grounding circuit is a fourth transistor of a bipolar transistor, the fourth transistor has: a collector and an emitter connected in parallel with the first capacitor; and a base, to which a recovery signal is applied, the recovery signal being used to recover from the protection action of the overcurrent protection circuit to the normal action, In the overcurrent protection circuit, a threshold voltage is provided, the threshold voltage being higher than a voltage applied to a control terminal of the switch element when the drive signal is at a high potential, and the predetermined pull-up voltage is the threshold voltage.

Images