Semiconductor device and protection system

Abstract

The purpose of the present invention is to provide a technique capable of suppressing an abnormality caused by a short-circuit current and a surge voltage of a power semiconductor switching element. The semiconductor device includes: a protection circuit that reduces a control voltage of the power semiconductor switching element on the basis of a voltage of a first terminal of the power semiconductor switching element; a divider resistor that generates a divided voltage on the basis of the back electromotive force generated by the internal inductor; and a first semiconductor switching element that, on the basis of the divided voltage, reduces the control voltage of the power semiconductor switching element at an earlier timing than the protection circuit and more rapidly than the protection circuit.

Description

Technical Field

[0001] The present disclosure relates to a semiconductor device and a protection system. Background Art

[0002] In recent years, various technologies have been proposed for semiconductor devices. For example, Patent Documents 1 and 2 propose technologies that, when a short circuit is detected in a power semiconductor switching element, reduce the gate voltage of the power semiconductor switching element to suppress the short-circuit current and surge voltage of the power semiconductor switching element. Prior art literature Patent Literature

[0003] Patent Document 1: Japanese Patent Application Laid-Open No. 2007-228769 Patent Document 2: Japanese Patent Application Laid-Open No. 2001-008492 Summary of the Invention Technical problem to be solved by the invention

[0004] Conventional technologies incorporate a filter circuit in the short-circuit detection circuit to prevent false short-circuit detection, or incorporate a blanking function into the circuit that reduces the gate voltage of the power semiconductor switching element. This results in a significant delay between the occurrence of a short circuit and the protective action of reducing the gate voltage, leading to an inability to adequately suppress the short-circuit current and surge voltage of the power semiconductor switching element.

[0005] Therefore, the present disclosure has been made in view of the above-mentioned problems, and an object of the present disclosure is to provide a technology capable of suppressing abnormalities caused by short-circuit current and surge voltage in power semiconductor switching elements. Technical means for solving technical problems

[0006] The semiconductor device involved in the present disclosure includes: a control terminal; a power semiconductor switching element having a first terminal and a second terminal controlled by a control voltage applied to the control terminal; a protection circuit, which reduces the control voltage of the power semiconductor switching element based on the voltage of the first terminal of the power semiconductor switching element; an internal inductor, which is connected to the second terminal of the power semiconductor switching element; a voltage dividing resistor, which generates a divided voltage based on the back electromotive force generated in the internal inductor; and a first semiconductor switching element, which reduces the control voltage of the power semiconductor switching element at an earlier timing and more sharply than the protection circuit based on the divided voltage. Effects of the Invention

[0007] According to the present disclosure, the first semiconductor switching element reduces the control voltage of the power semiconductor switching element earlier and more rapidly than the protection circuit based on voltage division. This configuration can suppress abnormalities caused by short-circuit current and surge voltage in the power semiconductor switching element.

[0008] The objects, features, aspects and advantages of the present disclosure will become more apparent from the following detailed description and accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 This is a circuit diagram showing the structure of the semiconductor device according to the first embodiment. Figure 2 This is a diagram for explaining the problem of driving a protection IC. Figure 3 These are diagrams for explaining the operation of the semiconductor device according to the first embodiment. Figure 4 These are diagrams for explaining the operation of the semiconductor device according to the first embodiment. Figure 5 This is a circuit diagram showing the structure of a semiconductor device according to the second embodiment. Figure 6 This is a circuit diagram showing the structure of a semiconductor device according to a third embodiment. Figure 7 This is a circuit diagram showing the structure of a semiconductor device according to a fourth embodiment. Figure 8 This is a circuit diagram showing the structure of a semiconductor device according to the fifth embodiment. Figure 9 This is a circuit diagram showing the structure of a semiconductor device according to a sixth embodiment. Figure 10 This is a circuit diagram showing the structure of a semiconductor device according to a seventh embodiment. Figure 11 This is a circuit diagram showing the structure of a semiconductor device according to an eighth embodiment. DETAILED DESCRIPTION

[0010] The following describes the embodiments with reference to the accompanying drawings. The features described in the following embodiments are illustrative only, and not all features are required. In addition, in the above description, the same or similar reference numerals are attached to the same structural elements in multiple embodiments, and the description mainly focuses on the different structural elements.

[0011] <Implementation Method 1> Figure 1This is a circuit diagram showing the structure of a semiconductor device according to Embodiment 1. The semiconductor device according to Embodiment 1 includes protection circuits, namely driver protection ICs (Integrated Circuits) 1 and 2, an RSP (Real Time Synchronous Protection) circuit 3, power semiconductor switching elements, namely power elements M1 and M2, internal inductors L1 and L2, and a power supply V1.

[0012] Power element M1 (the upper arm) and power element M2 (the lower arm) are connected in series between the two ends of power supply V1. Power element M1 and power element M2 are identical, and the internal inductor L1 and driver protection IC1 connected to power element M1 are identical to the internal inductor L2 and driver protection IC2 connected to power element M2. Therefore, the following description focuses on power element M2, internal inductor L2, and driver protection IC2.

[0013] The power element M2 has a control terminal and a first terminal and a second terminal controlled by a control voltage applied to the control terminal. Figure 1 In the example, power element M2 is a MOSFET (Metal Oxide Semiconductor Field Effect Transistor), and the control terminal, control voltage, first terminal, and second terminal are the gate terminal, gate voltage, drain terminal, and source terminal, respectively. Power element M2 is not limited to a MOSFET and may also be an IGBT (Insulated Gate Bipolar Transistor) or an RC-IGBT (Reverse Conducting-IGBT). Furthermore, the control terminal, first terminal, and second terminal may be the base terminal, collector terminal, and emitter terminal, respectively.

[0014] The material of power element M2 can be silicon (Si) or a wide-bandgap semiconductor such as silicon carbide (SiC), gallium nitride (GaN), or diamond. Using a wide-bandgap semiconductor allows for stable operation at high temperatures and voltages, as well as faster switching speeds.

[0015] The internal inductor L2 is connected to the source terminal of the power element M2. The internal inductor L2 is, for example, the parasitic inductance of a bus bar of a device package (not shown) that includes the power element M2.

[0016] Driver protection IC2 is connected to the drain terminal of power element M2 via high-voltage diode D1 and a CR filter circuit. The CR filter circuit consists of resistor R1 and capacitor C1 connected in parallel, and resistor R2 connected in series with them. Current source V2 is connected to the junction of resistor R2 and high-voltage diode D1 via resistor R3.

[0017] The driving protection IC2 can detect a short circuit (hereinafter sometimes referred to as a short-circuit current) of the power element M2 based on the voltage of the drain terminal of the power element M2 connected via the high-voltage diode D1 and the CR filter circuit. In the first embodiment, the driving protection IC2 determines that a short circuit (short-circuit current) has occurred in the power element M2 when the signal corresponding to the voltage of the drain terminal of the power element M2 exceeds a threshold value. Figure 1 This method of detecting a short circuit of the power element M2 is generally called a DESAT detection method.

[0018] The method for detecting a short circuit in power element M2 is not limited to DESAT detection. For example, if power element M2 has a sense terminal (not shown), a current sensor method may be used, in which the protection IC2 is driven to detect a short circuit in power element M2 based on the current flowing through the sense terminal. For example, a method may also be used in which the protection IC2 is driven to detect a short circuit in power element M2 based on the voltage across a shunt resistor connected in series with the source terminal of power element M2.

[0019] The driver protection IC2 selects one or a combination of gate resistors R4, R5, and R6 based on whether power element M2 is short-circuited, and connects it to the gate terminal of power element M2 via the selected gate resistor. For example, if the driver protection IC2 determines that power element M2 is short-circuited, it lowers the gate voltage of power element M2, shutting down power element M2. To minimize short-circuit current, it is preferable to reduce the gate voltage of power element M2 as quickly as possible. However, in this case, a surge voltage exceeding the withstand voltage of power element M2 is generated.

[0020] Therefore, when the driver protection IC2 determines that a short circuit has occurred in the power element M2, it is connected to the gate terminal of the power element M2 via a gate resistor R6 having a resistance value larger than the gate resistors R4 and R5, not via the gate resistors R4 and R5 used in normal operation when no short circuit has occurred. As a result, the gate voltage of the power element M2 is slowly reduced. Therefore, according to the driver protection IC2 having a soft cut-off mechanism that slowly reduces the gate voltage of the power element M2, it is possible to suppress the generation of a surge voltage in the power element M2 when the short-circuit current is cut off. However, in the short-circuit protection based only on the driver protection IC2, the short-circuit current may become too large due to the protection delay. In this case, even if the soft cut-off mechanism works, it is difficult to suppress the surge voltage because the current to be cut off is too large. In addition, there is a side of short-circuit current suppression and surge voltage suppression having opposite characteristics.

[0021] Figure 2 This is a diagram for explaining a problem of the driving protection IC 2 , specifically, a diagram for explaining an operation when a short circuit occurs in a single driving protection IC 2 that is not provided with an RSP circuit 3 described later. Figure 2 The waveforms represent the drain voltage (DRAIN), drain current (ID), source voltage (SOURCE), and gate voltage (GATE). In the driver protection IC2, in order to prevent the normal switching action in the power element M2 from being mistakenly detected as a short circuit, a CR filter circuit as described above is provided (here, a circuit of resistors R1, R2, and capacitor C1). In addition, the driver protection IC2 sometimes also has a blanking function for suppressing false detections. However, in such a structure, there will be a relatively large delay from the occurrence of a short circuit to the protection action of the driver protection IC2. Therefore, when only the protection of the driver protection IC2 is performed, not only is there a short-circuit current of the power element M2 (see Figure 2 The ID) is too large, and there is a possibility that the surge voltage generated by the excessive short-circuit current cannot be fully suppressed (refer to Figure 2 That is, due to the delay in suppressing the gate voltage when a short circuit occurs, the short circuit current becomes too large, and there is a possibility that the surge voltage cannot be suppressed even if the soft cutoff mechanism operates due to the excessive current (see Figure 2 Therefore, the semiconductor device according to the first embodiment includes an RSP circuit 3 ( Figure 1 The following describes the RSP circuit 3.

[0022] The RSP circuit 3 includes voltage dividing resistors R7 and R8, a first resistor (ie, a resistor R9), a second resistor (ie, a resistor R10), a third resistor (ie, a resistor R11), and a first semiconductor switch element Q1. Figure 1 In the example shown in FIG. 5 , the first semiconductor switch element Q1 is an NPN bipolar transistor, but as described in other embodiments, the present invention is not limited thereto.

[0023] The voltage dividing resistors R7 and R8 are connected through Figure 1 Wiring lines W1, W2, and W3 and terminal LE are connected in parallel with the internal inductor L2. Resistor R9 is connected in parallel with the internal inductor L2 in the same manner as voltage-dividing resistors R7 and R8. Resistor R10 is connected between voltage-dividing resistors R7 and R8 and the base terminal of the first semiconductor switch element Q1. Resistor R11 is connected between the gate terminal of power element M2 and the collector terminal of the first semiconductor switch element Q1. The emitter terminal of the first semiconductor switch element Q1 is connected to the second end of the internal inductor L2, which is opposite to the power element M2, via terminal LE.

[0024] Here, if a current change (dI / dt) occurs in the internal inductance L2, a counter electromotive force VL1 is generated in the internal inductance L2. When the counter electromotive force VL1 is generated in the internal inductance L2, Figure 1 The voltage-dividing resistors R7 and R8 connected to the wirings W1 , W2 , and W3 and the terminal LE and the internal inductor L2 generate a divided voltage based on the back electromotive force VL1 generated in the internal inductor L2 .

[0025] The first semiconductor switch element Q1 reduces the gate voltage of the power element M2 based on the divided voltage generated by the voltage-dividing resistors R7 and R8. For example, when the divided voltage generated by the voltage-dividing resistors R7 and R8 exceeds the threshold voltage of the first semiconductor switch element Q1, the first semiconductor switch element Q1 turns on, thereby reducing the gate voltage of the power element M2.

[0026] Here, no filtering circuit or blanking function is provided between the base terminal of the first semiconductor switch element Q1 and the internal inductor L2. Therefore, the first semiconductor switch element Q1 can reduce the gate voltage of the power element M2 earlier than the driver protection IC2. Furthermore, by adjusting the resistance values ​​of resistor R11 and gate resistors R4 to R6, the first semiconductor switch element Q1 can reduce the gate voltage of the power element M2 more rapidly than the driver protection IC2.

[0027] In the above configuration, when a short-circuit current, several to dozens of times greater than the rated current of power element M2, flows through internal inductor L2, a significant current change (dI / dt) occurs in internal inductor L2, generating a large back electromotive force VL1. In this case, RSP circuit 3 is configured so that the voltage divided by back electromotive force VL1, generated by voltage-dividing resistors R7 and R8, exceeds the threshold voltage of first semiconductor switch element Q1. RSP circuit 3 is configured to distinguish between normal operation with the rated current and a short-circuit, based on whether this large back electromotive force VL1 exceeds the threshold voltage. Only when a short-circuit occurs does RSP circuit 3 lower the gate voltage of power element M2 at an earlier timing and more abruptly than when driving protection IC2.

[0028] Figure 3 1 is a diagram for explaining the operation of the semiconductor device according to the first embodiment when a short circuit occurs. Figure 3 In addition to Figure 2 In addition, the waveforms of the voltage at the terminal LE (LE) and the on / off state of the first semiconductor switch element Q1 (Q1) are also shown. Since the RSP circuit 3 reduces the gate voltage of the power element M2 at an earlier timing than the driving protection IC2, the short-circuit current can be suppressed earlier than in a configuration without the RSP circuit 3 (see Figure 3 After that, the driving protection IC2 reduces the gate voltage of the power element M2 more slowly than the RSP circuit 3 by its own soft cutoff mechanism, thereby suppressing the surge voltage in the power element M2 (refer to Figure 3 By controlling the gate voltage as described above, both short-circuit current and surge voltage can be suppressed (see Figure 3 GATE).

[0029] By appropriately setting the resistance values ​​of the voltage-dividing resistors R7 , R8 and the resistor R10 according to the value of the large back electromotive force VL1 generated during a short circuit, it is possible to suppress a decrease in the gate voltage of the power element M2 caused by the first semiconductor switch element Q1 being turned on during normal operation of the power element M2 . Figure 4 The operation of the semiconductor device according to the first embodiment during normal operation is shown when the resistance values ​​of the voltage-dividing resistors R7 and R8 and the resistor R10 are appropriately set.

[0030] Summary of Implementation 1 According to the semiconductor device of the first embodiment described above, the first semiconductor switch element Q1 of the RSP circuit 3 distinguishes between normal operation and short circuit occurrence based on the value of the back electromotive force VL1 generated during a short circuit, based on the voltage divided by the voltage-dividing resistors R7 and R8. When a short circuit occurs, the gate voltage of the power element M2 is lowered earlier and more rapidly than when the protection IC2 is driven. This effect is achieved while suppressing the effects of normal operation. This configuration suppresses abnormalities caused by the short-circuit current and surge voltage of the power element M2 during a short circuit.

[0031] RSP circuit 3 exhibits negative feedback characteristics: as the short-circuit current increases, the back electromotive force VL1 increases, enhancing short-circuit current suppression. Resistor R9 is connected in parallel with internal inductor L2, stabilizing the negative feedback characteristics of a closed loop. This closed loop includes a first end (the end of internal inductor L2 facing power element M2), voltage-dividing resistors R7 and R8, first semiconductor switch element Q1, terminal LE, and a second end (the end of internal inductor L2 opposite power element M2).

[0032] When power element M2 is made of a wide-bandgap semiconductor, it is often constructed using a unipolar element such as a MOSFET. Due to its operational characteristics, it can achieve faster switching speeds. However, faster switching speeds increase the short-circuit current generated during a short circuit, contrary to the improved power conversion efficiency due to reduced switching losses. Furthermore, when power element M2 is made of a wide-bandgap semiconductor, stable operation at high voltages is possible. However, as the voltage increases, the short-circuit current generated during a short circuit increases, contrary to the improved power conversion efficiency achieved by reducing the current. Furthermore, when power element M2 has a trench gate structure, on-resistance decreases, improving power conversion efficiency. However, this also increases the saturation current, increasing the short-circuit current generated during a short circuit. In contrast, RSP circuit 3 utilizes a back electromotive force VL1 that is proportional to the short-circuit current. Therefore, as the short-circuit current increases, the back electromotive force VL1 increases, causing the first semiconductor switch element Q1 to be deeply biased, which can rapidly reduce the gate voltage and thus suppress the short-circuit current through negative feedback. Therefore, the semiconductor device according to the first embodiment is particularly effective when the material of the power element M2 is a wide-bandgap semiconductor.

[0033] Modifications In the first embodiment, the RSP circuit 3 is provided in the driving protection IC 2 , but the present invention is not limited thereto. For example, the RSP circuit 3 may be provided in the driving protection IC 1 , or in both the driving protection IC 1 and the driving protection IC 2 .

[0034] <Implementation Method 2> In the semiconductor device according to Embodiment 1, if a short-circuit current occurs, RSP circuit 3 reduces the gate voltage of power element M2, thereby suppressing the short-circuit current. However, when the short-circuit current is large and the base current or base voltage of first semiconductor switch element Q1 is high, the duration of on-state conduction of first semiconductor switch element Q1, i.e., the duration of RSP circuit 3 operation, may be longer than expected. As a result, if RSP circuit 3 continues to operate after the driver protection IC2 begins its protective action to reduce the gate voltage, the driver protection IC2 may not be able to gradually reduce the gate voltage of power element M2. In this case, an excessive surge voltage may be generated. In contrast, the semiconductor device according to Embodiment 2, as described below, can resolve this problem.

[0035] Figure 5 This is a circuit diagram showing the structure of a semiconductor device according to the second embodiment. Figure 5 The structure and Figure 1 The structure is the same as that in which the resistors R10 and R11 are deleted and a fourth resistor, namely, a resistor R16, is added. The resistor R16 is connected between the first semiconductor switch element Q1 and the second end of the internal inductor L2, which is the end opposite to the power element M2.

[0036] In the semiconductor device according to the second embodiment, thus configured, an emitter-follower circuit is formed, including the first semiconductor switch element Q1. This configuration prevents the emitter-follower circuit from operating continuously, as resistor R16, the grounding resistor, from providing negative feedback. Therefore, after suppressing the short-circuit current, the first semiconductor switch element Q1 can be quickly turned off, and the operation of the RSP circuit 3 can be quickly stopped. Consequently, after the protection driver IC2 begins its protection operation, the RSP circuit 3 quickly stops reducing the gate voltage, activating the soft cutoff function of the protection driver IC2's gate voltage and suppressing surge voltage. Consequently, continued operation of the RSP circuit 3 is prevented, enabling more reliable suppression of the short-circuit current and surge voltage in the power element M2.

[0037] <Implementation Method 3> Figure 6 This is a circuit diagram showing the structure of a semiconductor device according to the third embodiment. Figure 6 The structure and Figure 5 The first diode D2 is added to the structure of Figure 1 The resistor R11 and the first capacitor, namely the capacitor C2, have the same structure.

[0038] The diode D2 is connected between the base terminal and the collector terminal of the first semiconductor switch element Q1, which is a bipolar transistor. Figure 6In the example, the anode of diode D2 is connected to the base terminal of the first semiconductor switch element Q1, and the cathode of diode D2 is connected to the collector terminal of the first semiconductor switch element Q1. This structure forms negative feedback that branches a portion of the current on the base terminal side of the first semiconductor switch element Q1 to the collector terminal side. As a result, the base current of the first semiconductor switch element Q1 can be quickly reduced, thereby preventing the RSP circuit 3 from remaining on for longer than expected. As a result, after the driver protection IC2 begins its protection operation, the RSP circuit 3 is prevented from continuing to operate, thereby enabling the soft cutoff function of the gate voltage of the driver protection IC2 to be effective, thereby suppressing surge voltage. Therefore, compared with the second embodiment, the short-circuit current and surge voltage of the power element M2 can be more reliably suppressed.

[0039] Resistor R11 is connected between the gate terminal of power element M2 and the collector terminal of first semiconductor switch element Q1 in the same manner as in Embodiment 1. This configuration allows for both gate voltage suppression of power element M2 by resistor R11 and base bias negative feedback by resistor R16. Consequently, both the on-time of first semiconductor switch element Q1 and the gate voltage (i.e., collector current) of power element M2 can be controlled.

[0040] Capacitor C2 is connected in parallel with internal inductor L2 in the same manner as resistor R9. This configuration reduces the impedance of RSP circuit 3 and efficiently applies the divided voltage based on back electromotive force VL1 generated during a short circuit to the base terminal of first semiconductor switch element Q1. Furthermore, since excessive back electromotive force VL1 can be suppressed, the GND potential (reference potential) of driver protection IC2 can be stabilized, thereby preventing malfunction of the entire circuit, including the semiconductor device.

[0041] <Implementation Method 4> In the semiconductor device described above, when power element M2 blocks the short-circuit current, a voltage VL2 is generated across internal inductor L2 at this time, in the opposite direction to that generated when the short-circuit current is generated (i.e., when the current is increasing). Because this voltage VL2 is applied in the opposite direction to the base terminal of first semiconductor switch element Q1, if it exceeds the base withstand voltage of first semiconductor switch element Q1, failure may occur in first semiconductor switch element Q1. Furthermore, failure may occur not only in first semiconductor switch element Q1 but also in driver protection IC2. In contrast, the semiconductor device according to this fourth embodiment, as described below, can resolve this problem.

[0042] Figure 7 This is a circuit diagram showing the structure of a semiconductor device according to the fourth embodiment. Figure 7 The structure and Figure 6 The structure is the same as that of the embodiment except that a second diode, namely diode D3, is added to the structure.

[0043] Diode D3 is connected in parallel with the internal inductor L2 in the same manner as resistor R9. Figure 7 In the example shown, the anode of diode D3 is electrically connected to the second end of internal inductor L2, and the cathode of diode D3 is electrically connected to the first end of internal inductor L2. With this configuration, diode D3 conducts when voltage VL2 is generated, clamping the voltage applied to the base terminal of first semiconductor switch element Q1 to a forward voltage. Consequently, malfunctions of first semiconductor switch element Q1 and driver protection IC2 caused by voltage VL2 can be suppressed.

[0044] The diode D3 may be a Zener diode. In this case, when the back electromotive force VL1 is generated, the voltage applied to the voltage-dividing resistors R7 and R8 is clamped to the Zener voltage, thereby suppressing malfunction of the first semiconductor switch element Q1 and the driver protection IC2 caused by the back electromotive force VL1.

[0045] <Implementation Method 5> Figure 8 This is a circuit diagram showing the structure of a semiconductor device according to the fifth embodiment. Figure 8 The structure and Figure 7 In the structure of , the driving protection IC2 is connected to the power supply V3, the driving protection IC2 can operate under both the positive power supply and the negative power supply, and the structure is the same as that of the diode D4.

[0046] like Figure 8 As shown in FIG. 1 , in a configuration where the driver protection IC2 operates from both the positive and negative power supplies, a through-current may flow from the power supply V3, which serves as the negative power supply, to the first semiconductor switch element Q1. In this case, current flows from the base terminal to the collector terminal of the first semiconductor switch element Q1, potentially causing a malfunction in the first semiconductor switch element Q1. In contrast, the semiconductor device according to Embodiment 5, as described below, can resolve this problem.

[0047] The diode D4 is connected between the gate terminal of the power element M2 and the first semiconductor switch element Q1. Figure 8 In the example shown, the anode of diode D4 is connected to the gate terminal of power element M2, and the cathode of diode D4 is connected to the collector terminal of first semiconductor switch element Q1 via resistor R11. With this configuration, diode D4 prevents current from flowing from the base terminal to the collector terminal of first semiconductor switch element Q1, thereby preventing malfunction of first semiconductor switch element Q1.

[0048] In addition, if Figure 8 As shown, in a configuration where the driver protection IC2 operates from both the positive and negative power supplies, during the off period of the power element M2, a through current flows from the GND potential (midpoint potential) to the negative power supply side, potentially placing a load on the negative power supply. In contrast, in the fifth embodiment, the load on the negative power supply can be reduced by diode D4, thereby stabilizing the operation of the RSP circuit 3.

[0049] <Implementation Method 6> In the semiconductor device described above, if the time from short circuit occurrence to protection IC2 being driven and taking protective action is long, the time from when RSP circuit 3 completes peak short-circuit current suppression to when protection IC2 starts its protection action may also be extended. As a result, the short-circuit current increases again during this time, potentially preventing the short-circuit current and surge voltage of power element M2 from being properly suppressed. In contrast, the semiconductor device according to Embodiment 6, as described below, resolves this issue.

[0050] Figure 9 This is a circuit diagram showing the structure of a semiconductor device according to the sixth embodiment. Figure 9 The structure and Figure 8 The structure is the same as that in which the diode D2, capacitor C2 and resistor R16 are deleted and the second capacitor, namely capacitor C3, and the fourth diode, namely diode D5, are added.

[0051] Capacitor C3 is connected in parallel with voltage-dividing resistors R7 and R8. This configuration allows capacitor C3 to be charged by the back electromotive force VL1 generated during a short circuit, thus maintaining the divided voltage of resistors R7 and R8, i.e., the gate voltage of the first semiconductor switch element Q1, for a certain period of time. Consequently, RSP circuit 3 can suppress the short-circuit current for a certain period of time after the short-circuit current has occurred. This shortens the time from when the RSP circuit 3 completes peak short-circuit current suppression to when the driver protection IC2 initiates protection operation. As a result, the soft cutoff function of the gate voltage of the driver protection IC2 is activated, suppressing surge voltage. Consequently, the short-circuit current and surge voltage of power element M2 can be appropriately suppressed.

[0052] Diode D5 is connected in series with the parallel portion including voltage-dividing resistors R7 and R8 and capacitor C3. With this configuration, when back electromotive force VL1 is relatively large, it is consumed by diode D5 while charging capacitor C3, thereby alleviating back electromotive force VL1 and protecting the semiconductor device.

[0053] <Implementation Method 7> Figure 10 This is a circuit diagram showing the structure of a semiconductor device according to the seventh embodiment. Figure 10 The structure and Figure 9 The structure is similar to that in which the first semiconductor switch element Q1 is changed from a bipolar transistor to a MOSFET. Generally speaking, when adjusting the on-time of a semiconductor switch element, a voltage-driven MOSFET having gate capacitance is preferred over a bipolar transistor. Therefore, according to the structure of this embodiment 7 in which the first semiconductor switch element Q1 is a MOSFET, coordination between the RSP circuit 3 and the driver protection IC2 can be easily achieved. That is, the RSP circuit 3 suppresses short-circuit current, and when the soft cutoff function of the gate voltage of the driver protection IC2 is effective, the RSP circuit 3 quickly stops, thereby simplifying the structure of a series of actions that simultaneously suppress surge voltage. Therefore, the short-circuit current and surge voltage of the power element M2 can be appropriately suppressed.

[0054] <Implementation Method 8> Figure 11 This is a circuit diagram showing the structure of a semiconductor device according to the eighth embodiment. Figure 11 The structure and Figure 9 The semiconductor switch section includes a second semiconductor switch element Q2 and a third semiconductor switch element Q3 connected in a Darlington manner, and resistors R21 and R22.

[0055] The collector terminal of the second semiconductor switch element Q2 is connected to the gate terminal of the power element M2 via the resistor R11 and the diode D4 , and the emitter terminal of the second semiconductor switch element Q2 is connected to the collector terminal of the first semiconductor switch element Q1 .

[0056] The collector terminal of the third semiconductor switch element Q3 is connected to the collector terminal of the second semiconductor switch element Q2, and the emitter terminal of the third semiconductor switch element Q3 is connected to the base terminal of the second semiconductor switch element Q2. The base terminal of the third semiconductor switch element Q3 is connected to the drain terminal of the power element M2 via a resistor R21 and a high-voltage diode D1. One end of a resistor R22 is connected to the connection point between the base terminal of the third semiconductor switch element Q3 and the resistor R21, and the other end of the resistor R22 is connected to a resistor R9, a diode D5, and the like.

[0057] The semiconductor switch unit configured as described above connects the gate terminal of power element M2 and the first semiconductor switch element Q1 based on the voltage at the drain terminal of power element M2. For example, when power element M2 is conducting during normal operation, the second semiconductor switch element Q2 of the semiconductor switch unit remains off, disconnecting the gate terminal of power element M2 from the first semiconductor switch element Q1. On the other hand, when power element M2 is off during normal operation or when a short circuit occurs, the second semiconductor switch element Q2 of the semiconductor switch unit turns on, connecting the gate terminal of power element M2 to the first semiconductor switch element Q1. To enable this operation of the semiconductor switch unit, the resistance values ​​of resistors R21 and R22 are appropriately set. During normal operation, when power element M2 is off, even if the second semiconductor switch element Q2 of the semiconductor switch unit turns on, the first semiconductor switch element Q1 does not turn on unless a short circuit occurs, and therefore, the RSP circuit 3 does not operate.

[0058] In the semiconductor device according to the eighth embodiment, the semiconductor switch unit connects the gate terminal of power element M2 and first semiconductor switch element Q1 only when a short circuit occurs in power element M2. Therefore, even if first semiconductor switch element Q1 is turned on during normal operation of power element M2, the semiconductor switch unit can suppress the effect of the conduction of first semiconductor switch element Q1 on the normal operation of power element M2. In other words, RSP circuit 3 can be activated only when a short circuit occurs. Furthermore, because the semiconductor switch unit includes second semiconductor switch element Q2 and third semiconductor switch element Q3 connected in a Darlington configuration, it is possible to detect the occurrence of a short circuit and perform an action even when the DESAT signal, i.e., the voltage at the drain terminal of power element M2, is low.

[0059] Modifications The functions of the semiconductor device described above can also be implemented by a protection system that protects the semiconductor device via communication. For example, the semiconductor device may also include a power element M2. Furthermore, the protection system may also include: a first protection circuit that reduces the gate voltage of power element M2 based on the voltage at the drain terminal of power element M2; and a second protection circuit that reduces the gate voltage of power element M2 at an earlier timing and more rapidly than the first protection circuit based on the back electromotive force VL1 generated in internal inductance L2 connected to the source terminal of power element M2. The first protection circuit corresponds to the driver protection IC2, and the second protection circuit corresponds to the RSP circuit 3.

[0060] Furthermore, the embodiments and modifications can be freely combined, and the embodiments and modifications can be appropriately modified or omitted.

[0061] The above description is intended in all respects to be illustrative rather than restrictive, and it will be understood that numerous variations not shown are conceivable. Label Description

[0062] 2 driver protection IC, C2, C3 capacitors, D2, D3, D4, D5 diodes, L2 internal inductor, M2 power element, Q1 first semiconductor switch element, Q2 second semiconductor switch element, Q3 third semiconductor switch element, R7, R8 voltage divider resistors, R9, R10, R11, R16 resistors, VL1 back electromotive force.

Claims

1. A semiconductor device, characterized in that: include: a power semiconductor switching element having a control terminal and a first terminal and a second terminal controlled by a control voltage applied to the control terminal; a protection circuit that reduces the control voltage of the power semiconductor switch element based on the voltage of the first terminal of the power semiconductor switch element; an internal inductor connected to the second terminal of the power semiconductor switch element; a voltage-dividing resistor that generates a divided voltage based on a back electromotive force generated in the internal inductor; as well as A first semiconductor switching element that reduces the control voltage of the power semiconductor switching element at an earlier timing than the protection circuit and more rapidly than the protection circuit based on the divided voltage.

2. The semiconductor device according to claim 1, wherein Also included is a first resistor connected in parallel with the internal inductor.

3. The semiconductor device according to claim 1 or 2, wherein: Also includes: a second resistor connected between the voltage dividing resistor and the first semiconductor switch element; as well as A third resistor is connected between the control terminal of the power semiconductor switch element and the first semiconductor switch element.

4. The semiconductor device according to claim 1 or 2, wherein: The device further includes a fourth resistor connected between the first semiconductor switch element and one end of the internal inductor on the opposite side to the power semiconductor switch element.

5. The semiconductor device according to claim 4, wherein: The first semiconductor switch element is a bipolar transistor, The semiconductor device further includes a first diode connected between a base terminal and a collector terminal of the bipolar transistor.

6. The semiconductor device according to claim 4 or 5, characterized in that Also included is a first capacitor connected in parallel with the internal inductor.

7. The semiconductor device according to claim 6, wherein: Also included is a second diode connected in parallel with the internal inductor.

8. The semiconductor device according to claim 7, wherein: A third diode connected between the control terminal of the power semiconductor switching element and the first semiconductor switching element is also included.

9. The semiconductor device according to claim 1 or 2, wherein: Also includes: a second diode connected in parallel with the internal inductor; a third diode connected between the control terminal of the power semiconductor switch element and the first semiconductor switch element; a second capacitor connected in parallel with the voltage dividing resistor; as well as A fourth diode is connected in series with a parallel portion including the voltage dividing resistor and the second capacitor.

10. The semiconductor device according to claim 9, wherein: The first semiconductor switch element is a MOSFET.

11. The semiconductor device according to claim 9, wherein The semiconductor switch section further includes a second semiconductor switch element and a third semiconductor switch element connected in a Darlington manner. The semiconductor switch unit connects the control terminal of the power semiconductor switch element and the first semiconductor switch element based on the voltage at the first terminal of the power semiconductor switch element.

12. A semiconductor device protection system, characterized in that: The semiconductor device includes a power semiconductor switching element having a control terminal and a first terminal and a second terminal controlled by a control voltage applied to the control terminal. The protection system comprises: a first protection circuit that reduces the control voltage of the power semiconductor switching element based on the voltage of the first terminal of the power semiconductor switching element; and A second protection circuit that reduces the control voltage of the power semiconductor switch element at an earlier timing and more sharply than the first protection circuit based on a back electromotive force generated in an internal inductance connected to the second terminal of the power semiconductor switch element.

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