Semiconductor device and protection system

Abstract

The purpose of the present invention is to provide a technology capable of suppressing abnormality due to a short-circuit current and surge voltage of a power semiconductor switching element. This semiconductor device comprises: a protective circuit that, on the basis of the voltage of a first terminal of a power semiconductor switching element, decreases the control voltage of the power semiconductor switching element; a voltage-dividing resistor that, on the basis of counter electromotive force generated in an internal inductance, generates divided voltage; and a first semiconductor switching element that, on the basis of the divided voltage, decreases the control voltage of the power semiconductor switching element at a timing earlier than the protective circuit and more sharply than the protective circuit.

Description

[Technical Field]

[0001] The present disclosure relates to semiconductor devices and protection systems. [Background technology]

[0002] In recent years, various technologies have been proposed for semiconductor devices. For example, Patent Documents 1 and 2 propose a technology for suppressing the short-circuit current and surge voltage of a power semiconductor switching element by reducing the gate voltage of the power semiconductor switching element when a short circuit of the power semiconductor switching element is detected. [Prior art documents] [Patent documents]

[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 [Problem to be solved by the invention]

[0004] In the prior art, a circuit for detecting a short circuit is provided with a filter circuit for suppressing false detection of a short circuit, or a circuit for reducing the gate voltage of a power semiconductor switching element is provided with a blanking function. As a result, a relatively long delay occurs between the occurrence of a short circuit and the performance of a protective operation to reduce the gate voltage, which results in a problem that the short circuit current and surge voltage of the power semiconductor switching element cannot be sufficiently suppressed.

[0005] Therefore, the present disclosure has been made in consideration of the above-mentioned problems, and aims to provide a technology capable of suppressing abnormalities caused by short-circuit currents and surge voltages in power semiconductor switching elements. [Means for solving the problem]

[0006] The semiconductor device according to the present disclosure includes a power semiconductor switching element having a control terminal and first and second terminals controlled by a control voltage applied to the control terminal; a 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; an internal inductance connected to the second terminal of the power semiconductor switching element; a voltage dividing resistor that generates a divided voltage based on a back electromotive force generated in the internal inductance; and a first semiconductor switching element that reduces the control voltage of the power semiconductor switching element based on the divided voltage at an earlier timing than the protection circuit and more steeply than the protection circuit. [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 based on the voltage division at an earlier timing and more steeply than the protection circuit. With this configuration, it is possible to suppress abnormalities in the power semiconductor switching element due to short-circuit current and surge voltage.

[0008] The objects, features, aspects and advantages of the present disclosure will become more apparent from the following detailed description and the accompanying drawings. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a circuit diagram showing a configuration of a semiconductor device according to a first embodiment. [Figure 2] 10A and 10B are diagrams for explaining problems with the drive protection IC. [Figure 3] FIG. 2 is a diagram for explaining the operation of the semiconductor device according to the first embodiment. [Figure 4] FIG. 2 is a diagram for explaining the operation of the semiconductor device according to the first embodiment. [Figure 5] FIG. 10 is a circuit diagram showing a configuration of a semiconductor device according to a second embodiment. [Figure 6]FIG. 10 is a circuit diagram showing a configuration of a semiconductor device according to a third embodiment. [Figure 7] FIG. 10 is a circuit diagram showing a configuration of a semiconductor device according to a fourth embodiment. [Figure 8] FIG. 10 is a circuit diagram showing a configuration of a semiconductor device according to a fifth embodiment. [Figure 9] FIG. 13 is a circuit diagram showing a configuration of a semiconductor device according to a sixth embodiment. [Figure 10] FIG. 13 is a circuit diagram showing a configuration of a semiconductor device according to a seventh embodiment. [Figure 11] FIG. 13 is a circuit diagram showing a configuration of a semiconductor device according to an eighth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments will be described with reference to the accompanying drawings. The features described in each of the following embodiments are merely examples, and not all features are necessarily required. In addition, in the following description, similar components in multiple embodiments are denoted by the same or similar reference numerals, and different components will be mainly described.

[0011] <First Embodiment> 1 is a circuit diagram showing the configuration of a semiconductor device according to the present embodiment 1. The semiconductor device according to the present embodiment 1 includes drive protection integrated circuits (ICs) 1 and 2 which are protection circuits, an RSP (Real Time Synchronous Protection) circuit 3, power elements M1 and M2 which are power semiconductor switching elements, internal inductances L1 and L2, and a power supply V1.

[0012] The power device M1, which is the upper arm, and the power device M2, which is the lower arm, are connected in series between both ends of the power supply V1. The power device M1 is the same as the power device M2, and the internal inductance L1 and drive protection IC1 connected to the power device M1 are the same as the internal inductance L2 and drive protection IC2 connected to the power device M2. Therefore, the following description will mainly focus on the power device M2, the internal inductance L2, and the drive protection IC2.

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

[0014] The material of the power element M2 may be silicon (Si) or a wide bandgap semiconductor such as silicon carbide (SiC), gallium nitride (GaN), diamond, etc. When the material of the power element M2 is a wide bandgap semiconductor, stable operation under high temperatures and high voltages and high switching speeds are possible.

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

[0016] The drive protection IC2 is connected to the drain terminal of the power device M2 via a high-voltage diode D1 and a CR filter circuit. The CR filter circuit includes a resistor R1 and a capacitor C1 connected in parallel with a resistor R2 connected in series. A current source V2 is connected to the junction of the resistor R2 and the high-voltage diode D1 via a resistor R3.

[0017] The drive protection IC2 is capable of detecting a short circuit (hereinafter also referred to as a short circuit current) of the power element M2 based on the voltage at 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 drive protection IC2 determines that a short circuit (corresponding to the short circuit current I in FIG. 1) has occurred in the power element M2 when a signal corresponding to the voltage at the drain terminal of the power element M2 exceeds a threshold value. This method of detecting a short circuit in the power element M2 is generally called a DESAT detection method.

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

[0019] The drive protection IC2 selects one or a combination of gate resistors R4, R5, and R6 based on whether a short circuit has occurred in the power element M2, and connects the selected gate resistor to the gate terminal of the power element M2. For example, if the drive protection IC2 determines that a short circuit has occurred in the power element M2, it reduces the gate voltage of the power element M2 so that the power element M2 is turned off. From the perspective of suppressing short-circuit current, it is preferable to reduce the gate voltage of the power element M2 as quickly as possible, but doing so would result in an excessive surge voltage in the power element M2 that exceeds its withstand voltage.

[0020] Therefore, when the drive protection IC2 determines that a short circuit has occurred in the power device M2, it connects the gate terminal of the power device M2 through gate resistor R6, which has a higher resistance than the gate resistors R4 and R5 used during normal operation when no short circuit has occurred. This allows the gate voltage of the power device M2 to gradually decrease. The drive protection IC2, which has a soft shutdown mechanism that gradually decreases the gate voltage of the power device M2, can suppress surge voltages in the power device M2 when a short circuit current is interrupted. However, short-circuit protection relying solely on the drive protection IC2 can result in excessive short-circuit current due to a protection delay. In such cases, even if the soft shutdown mechanism is activated, the current that should be interrupted is too large, making it difficult to suppress surge voltages. Furthermore, short-circuit current suppression and surge voltage suppression are mutually exclusive characteristics.

[0021] FIG. 2 illustrates the problems with the drive protection IC2. Specifically, it illustrates the behavior of the drive protection IC2 alone, without the RSP circuit 3 (described later), when a short circuit occurs. FIG. 2 shows the waveforms of the drain voltage (DRAIN), drain current (ID), source voltage (SOURCE), and gate voltage (GATE). The drive protection IC2 includes a CR filter circuit (here, a circuit consisting of resistors R1 and R2 and capacitor C1) as described above to prevent erroneous detection of a short circuit in the power device M2. The drive protection IC2 may also have a blanking function to prevent erroneous detection. However, such a configuration results in a relatively long delay between the occurrence of a short circuit and the start of the drive protection IC2's protective operation. Therefore, protection using the drive protection IC2 alone not only results in excessive short-circuit current (see ID in FIG. 2 ) in the power device M2, but also insufficient suppression of surge voltages (see DRAIN in FIG. 2 ) generated by the excessive short-circuit current. In other words, when a short circuit occurs, a delay in suppressing the gate voltage causes an excessive short-circuit current, and even if the soft shutdown mechanism operates due to the excessive current, the surge voltage cannot be suppressed (see GATE in FIG. 2). Therefore, the semiconductor device according to the first embodiment includes an RSP circuit 3 (circuit within the dashed line in FIG. 1) that operates cooperatively and complementarily with the drive protection IC 2 as a circuit to solve this problem. The RSP circuit 3 will be described below.

[0022] The RSP circuit 3 includes voltage-dividing resistors R7 and R8, a first resistor R9, a second resistor R10, a third resistor R11, and a first semiconductor switching element Q1. In the example of Fig. 1, the first semiconductor switching element Q1 is an NPN bipolar transistor, but as will be described in other embodiments, the present invention is not limited to this.

[0023] The voltage dividing resistors R7 and R8 are connected in parallel to the internal inductance L2 via the wiring W1, W2, and W3 in FIG. 1 and the terminal LE. The resistor R9 is connected in parallel to the internal inductance L2, just like the voltage dividing resistors R7 and R8. The resistor R10 is connected between the voltage dividing resistors R7 and R8 and the base terminal of the first semiconductor switching element Q1. The resistor R11 is connected between the gate terminal of the power element M2 and the collector terminal of the first semiconductor switching element Q1. The emitter terminal of the first semiconductor switching element Q1 is connected to a second end of the internal inductance L2, which is the end opposite to the power element M2, via the terminal LE.

[0024] Here, when 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, the voltage dividing resistors R7 and R8 connected to the internal inductance L2 via the wires W1, W2, and W3 and terminal LE in Figure 1 generate a divided voltage based on the counter electromotive force VL1 generated in the internal inductance L2.

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

[0026] Here, no filter circuit or blanking function is provided between the base terminal of the first semiconductor switching element Q1 and the internal inductance L2. Therefore, the first semiconductor switching element Q1 can lower the gate voltage of the power element M2 at an earlier timing than the drive protection IC2. Furthermore, by adjusting the resistance value of the resistor R11 and the resistance values ​​of the gate resistors R4 to R6, the first semiconductor switching element Q1 can lower the gate voltage of the power element M2 more steeply than the drive protection IC2.

[0027] In the above configuration, when a short-circuit current several times to several dozen times the rated current of the power element M2 flows through the internal inductance L2, a large current change (dI / dt) occurs in the internal inductance L2, generating a large back electromotive force VL1. In this case, the RSP circuit 3 is configured so that the voltage divided by the voltage-dividing resistors R7 and R8 based on the back electromotive force VL1 exceeds the threshold voltage of the first semiconductor switching element Q1. The RSP circuit 3 is configured to distinguish between normal operation, including rated current, and the occurrence of a short circuit based on whether this large back electromotive force VL1 exceeds the threshold. Only when a short circuit occurs, the RSP circuit 3 lowers the gate voltage of the power element M2 earlier and more steeply than the drive protection IC2.

[0028] FIG. 3 is a diagram illustrating the operation of the semiconductor device according to the first embodiment when a short circuit occurs. In addition to the waveforms shown in FIG. 2, FIG. 3 also shows the waveforms of the voltage (LE) at the terminal LE and the on / off (Q1) of the first semiconductor switching element Q1. The RSP circuit 3 reduces the gate voltage of the power element M2 at an earlier timing than the drive protection IC2, thereby suppressing the short-circuit current (see ID in FIG. 3) earlier than in a configuration without the RSP circuit 3. The drive protection IC2 then reduces the gate voltage of the power element M2 more slowly than the RSP circuit 3 by its own soft shutdown mechanism, thereby suppressing the occurrence of a surge voltage (see DRAIN in FIG. 3) in the power element M2. The gate voltage control described above makes it possible to suppress both the short-circuit current and the surge voltage (see GATE in FIG. 3).

[0029] By appropriately setting the resistance values ​​of the voltage-dividing resistors R7, R8 and resistor R10 in accordance with the value of the large counter electromotive force VL1 that occurs during a short circuit, it is possible to prevent the first semiconductor switching element Q1 from turning on and reducing the gate voltage of the power element M2 during normal operation of the power element M2. Fig. 4 shows the operation during normal operation of the semiconductor device according to the first embodiment when the resistance values ​​of the voltage-dividing resistors R7, R8 and resistor R10 are appropriately set.

[0030] <Summary of the First Embodiment> According to the semiconductor device of the first embodiment, the first semiconductor switching element Q1 of the RSP circuit 3 distinguishes between normal operation and the occurrence of a short circuit based on the value of the back electromotive force VL1 generated in the event of a short circuit, based on the voltage division of the voltage dividing resistors R7 and R8. When a short circuit occurs, the first semiconductor switching element Q1 reduces the gate voltage of the power element M2 earlier and more steeply than the drive protection IC2. This effect can be achieved while suppressing the influence on normal operation. This configuration can suppress abnormalities caused by short-circuit current and surge voltage in the power element M2 when a short circuit occurs.

[0031] The RSP circuit 3 has a negative feedback characteristic in which the larger the short-circuit current, the larger the back electromotive force VL1, thereby strengthening the suppression of the short-circuit current. The resistor R9 is connected in parallel with the internal inductance L2, and therefore it is possible to stabilize the negative feedback characteristic of the closed loop that includes a first end that is one end of the internal inductance L2 on the power element M2 side, voltage dividing resistors R7 and R8, the first semiconductor switching element Q1, the terminal LE, and a second end that is one end of the internal inductance L2 opposite the power element M2.

[0032] When the power element M2 is made of a wide-bandgap semiconductor, it is often constructed using a unipolar element such as a MOSFET, which allows for faster switching speeds. However, fast switching speeds reduce switching losses, improving power conversion efficiency but also increasing short-circuit current during short circuits. When the power element M2 is made of a wide-bandgap semiconductor, stable operation is possible under high voltages. However, while the use of high voltages reduces current flow, improving power conversion efficiency, the high voltages also increase short-circuit current during short circuits. Furthermore, when the gate structure of the power element M2 is trench-structured, the on-resistance decreases, improving power conversion efficiency, but the saturation current increases, increasing short-circuit current during short circuits. In response to this, the RSP circuit 3 utilizes a back electromotive force VL1 proportional to the value of the short-circuit current. Therefore, the larger the short-circuit current, the greater the back electromotive force VL1, which deeply biases the first semiconductor switching element Q1 and sharply reduces the gate voltage, thereby suppressing short-circuit current through negative feedback. For this reason, 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] <Modification> In the first embodiment, the RSP circuit 3 is provided in the drive protection IC 2, but this is not limiting. For example, the RSP circuit 3 may be provided in the drive protection IC 1, or may be provided in both the drive protection IC 1 and the drive protection IC 2.

[0034] <Embodiment 2> In the semiconductor device according to the first embodiment, when a short-circuit current occurs, the RSP circuit 3 reduces the gate voltage of the power element M2, thereby suppressing the short-circuit current. However, if the short-circuit current is large and the base current or base voltage of the first semiconductor switching element Q1 is high, the time the first semiconductor switching element Q1 remains on, i.e., the time the RSP circuit 3 continues to operate, may be longer than expected. As a result, if the RSP circuit 3 continues to operate after the drive protection IC2 starts its protection operation to reduce the gate voltage, the drive protection IC2 may not be able to gradually reduce the gate voltage of the power element M2. In this case, an excessive surge voltage may occur. In contrast, the semiconductor device according to the second embodiment can solve this problem, as described below.

[0035] Fig. 5 is a circuit diagram showing the configuration of a semiconductor device according to the second embodiment. The configuration in Fig. 5 is similar to the configuration in Fig. 1, except that the resistors R10 and R11 are deleted and a fourth resistor R16 is added. The resistor R16 is connected between the first semiconductor switching element Q1 and a second end of the internal inductance L2, which is one end opposite to the power element M2.

[0036] In the semiconductor device according to the second embodiment, an emitter-follower circuit including the first semiconductor switching element Q1 is formed. With this configuration, resistor R16, which serves as the emitter-follower's ground resistor, has negative feedback characteristics. This allows the first semiconductor switching element Q1 to be quickly turned off and the RSP circuit 3 to quickly stop operating after the short-circuit current is suppressed. As a result, after the drive protection IC2 starts its protection operation, the RSP circuit 3 quickly stops lowering the gate voltage, enabling the soft shutdown function of the drive protection IC2's gate voltage and suppressing surge voltages. This prevents the RSP circuit 3 from continuing to operate, thereby more reliably suppressing the short-circuit current and surge voltage of the power element M2.

[0037] <Third Embodiment> Fig. 6 is a circuit diagram showing the configuration of a semiconductor device according to the third embodiment. The configuration in Fig. 6 is similar to the configuration in Fig. 5, except that a diode D2 serving as the first diode, the resistor R11 in Fig. 1, and a capacitor C2 serving as the first capacitor are added.

[0038] The diode D2 is connected between the base and collector terminals of the first semiconductor switching element Q1, which is a bipolar transistor. In the example of FIG. 6, the anode of the diode D2 is connected to the base terminal of the first semiconductor switching element Q1, and the cathode of the diode D2 is connected to the collector terminal of the first semiconductor switching element Q1. This configuration forms a negative feedback circuit by branching a portion of the current on the base terminal side of the first semiconductor switching element Q1 to the collector terminal side. This allows the base current of the first semiconductor switching element Q1 to be reduced quickly, preventing the RSP circuit 3 from remaining on for longer than expected. As a result, the RSP circuit 3 is prevented from continuing to operate after the drive protection IC2 begins its protection operation, enabling the soft shutdown function of the gate voltage of the drive protection IC2 and suppressing surge voltages. This ensures that the short-circuit current and surge voltage of the power element M2 are suppressed more reliably than in the second embodiment.

[0039] Similar to the first embodiment, the resistor R11 is connected between the gate terminal of the power element M2 and the collector terminal of the first semiconductor switching element Q1. With this configuration, it is possible to achieve both the amount of gate voltage suppression of the power element M2 by the resistor R11 and the amount of base bias negative feedback by the resistor R16. This makes it possible to control both the on-time of the first semiconductor switching element Q1 and the gate voltage (i.e., the amount of collector current) of the power element M2.

[0040] The capacitor C2, like the resistor R9, is connected in parallel with the internal inductance L2. This configuration reduces the impedance of the RSP circuit 3, and efficiently applies a divided voltage based on the back electromotive force VL1 generated during a short circuit to the base terminal of the first semiconductor switching element Q1. Furthermore, excessive back electromotive force VL1 can be prevented, and the GND potential (reference potential) of the drive protection IC2 can be stabilized, thereby preventing malfunctions in the entire circuit, including the semiconductor device.

[0041] <Fourth Embodiment> In the semiconductor device described above, when the power element M2 turns off the short-circuit current, a voltage VL2 is generated across the internal inductance L2 at that timing, the voltage VL2 being in the opposite direction to when the short-circuit current occurs (i.e., when the current increases). This voltage VL2 is applied in the opposite direction to the base terminal of the first semiconductor switching element Q1, and if it exceeds the base withstand voltage of the first semiconductor switching element Q1, a malfunction may occur in the first semiconductor switching element Q1. Furthermore, a malfunction may occur not only in the first semiconductor switching element Q1 but also in the drive protection IC2. In contrast, the semiconductor device according to the fourth embodiment is able to solve this problem, as will be described below.

[0042] Fig. 7 is a circuit diagram showing the configuration of a semiconductor device according to the present embodiment 4. The configuration of Fig. 7 is similar to the configuration of Fig. 6, except that a diode D3, which is a second diode, is added.

[0043] Like resistor R9, diode D3 is connected in parallel with internal inductance L2. In the example of FIG. 7, the anode of diode D3 is electrically connected to the second end of internal inductance L2, and the cathode of diode D3 is electrically connected to the first end of internal inductance L2. With this configuration, when voltage VL2 is generated, diode D3 turns on, and the voltage applied to the base terminal of first semiconductor switching element Q1 is clipped to the forward voltage. This makes it possible to suppress malfunctions of first semiconductor switching element Q1 and drive protection IC2 caused by voltage VL2.

[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 clipped to the Zener voltage, thereby preventing malfunctions of the first semiconductor switching element Q1 and the drive protection IC2 caused by the back electromotive force VL1.

[0045] <Fifth Embodiment> Fig. 8 is a circuit diagram showing the configuration of a semiconductor device according to the fifth embodiment. The configuration in Fig. 8 is similar to the configuration in Fig. 7, except that a power supply V3 is connected to drive protection IC2, drive protection IC2 can operate on both positive and negative power supplies, and a third diode D4 is added.

[0046] 8, in a configuration in which the drive protection IC2 operates from both a positive power supply and a negative power supply, a through current may flow through the first semiconductor switching element Q1 from the power supply V3 used as the negative power supply. In this case, a current may flow from the base terminal to the collector terminal of the first semiconductor switching element Q1, causing a malfunction in the first semiconductor switching element Q1. In contrast, the semiconductor device according to the fifth embodiment is able to solve this problem, as will be described below.

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

[0048] 8, in a configuration in which the drive protection IC2 operates on both the positive and negative power supplies, a through current may flow from the GND potential (midpoint potential) to the negative power supply side during the off period of the power element M2, creating a load on the negative power supply. In contrast, in the fifth embodiment, the diode D4 is expected to suppress the load on the negative power supply, and the operation of the RSP circuit 3 can be expected to be stabilized.

[0049] <Sixth Embodiment> In the semiconductor device described above, if it takes a long time for the drive protection IC2 to perform protection operation after a short circuit occurs, the time from when the RSP circuit 3 completes peak suppression of the short-circuit current until the drive protection IC2 starts protection operation may become long. As a result, the short-circuit current may increase again during that time, and the short-circuit current and surge voltage of the power element M2 may not be properly suppressed. In contrast, the semiconductor device according to the sixth embodiment can solve this problem, as described below.

[0050] Fig. 9 is a circuit diagram showing the configuration of a semiconductor device according to the sixth embodiment. The configuration in Fig. 9 is similar to the configuration in Fig. 8, except that the diode D2, capacitor C2, and resistor R16 are deleted and a capacitor C3, which is a second capacitor, and a diode D5, which is a fourth diode, are added.

[0051] Capacitor C3 is connected in parallel with voltage-dividing resistors R7 and R8. This configuration charges capacitor C3 with the back electromotive force VL1 generated during a short circuit, allowing the divided voltage across voltage-dividing resistors R7 and R8—that is, the gate voltage of the first semiconductor switching element Q1—to be maintained for a certain period of time. This allows the RSP circuit 3 to suppress the short-circuit current for a certain period of time after the short-circuit current occurs, shortening the time between when the RSP circuit 3 completes peak suppression of the short-circuit current and when the drive protection IC2 begins its protection operation. This enables the soft shutdown function of the gate voltage of the drive protection IC2, thereby suppressing surge voltages. This allows the short-circuit current and surge voltage of the power element M2 to be appropriately suppressed.

[0052] The diode D5 is connected in series with a parallel part including the voltage dividing resistors R7 and R8 and the capacitor C3. With this configuration, when the counter electromotive force VL1 is relatively large, the counter electromotive force VL1 is consumed to charge the capacitor C3 via the diode D5, thereby mitigating the counter electromotive force VL1 and protecting the semiconductor device.

[0053] <Seventh Embodiment> FIG. 10 is a circuit diagram showing the configuration of a semiconductor device according to the seventh embodiment. The configuration shown in FIG. 10 is similar to that shown in FIG. 9, except that the first semiconductor switching element Q1 is replaced by a MOSFET instead of a bipolar transistor. Generally, when adjusting the on-time of a semiconductor switching element, a voltage-driven MOSFET with gate capacitance is preferable to a bipolar transistor. Therefore, the configuration of the seventh embodiment, in which the first semiconductor switching element Q1 is a MOSFET, facilitates coordination between the RSP circuit 3 and the drive protection IC2. Specifically, the RSP circuit 3 suppresses short-circuit current, and when the soft shutdown function of the gate voltage of the drive protection IC2 becomes effective, the RSP circuit 3 quickly stops, thereby simultaneously suppressing surge voltage. This facilitates the configuration that realizes a series of operations. Therefore, the short-circuit current and surge voltage of the power element M2 can be appropriately suppressed.

[0054] <Embodiment 8> Fig. 11 is a circuit diagram showing the configuration of a semiconductor device according to the eighth embodiment. The configuration of Fig. 11 is similar to the configuration of Fig. 9, except that a semiconductor switch unit is added. The semiconductor switch unit includes a Darlington-connected second semiconductor switching element Q2 and a third semiconductor switching element Q3, and resistors R21 and R22.

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

[0056] The collector terminal of the third semiconductor switching element Q3 is connected to the collector terminal of the second semiconductor switching element Q2, and the emitter terminal of the third semiconductor switching element Q3 is connected to the base terminal of the second semiconductor switching element Q2. The base terminal of the third semiconductor switching 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 the resistor R22 is connected to the connection point between the base terminal of the third semiconductor switching element Q3 and the resistor R21, and the other end of the resistor R22 is connected to a resistor R9, a diode D5, etc.

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

[0058] According to the semiconductor device of the eighth embodiment, the semiconductor switch unit can connect the gate terminal of the power device M2 to the first semiconductor switching element Q1 only when a short circuit occurs in the power device M2. Therefore, even if the first semiconductor switching element Q1 is turned on during normal operation of the power device M2, the semiconductor switch unit can prevent the on-state of the first semiconductor switching element Q1 from affecting the normal operation of the power device M2. In other words, the RSP circuit 3 can operate only when a short circuit occurs. Furthermore, because the semiconductor switch unit includes the second semiconductor switching element Q2 and the third semiconductor switching element Q3 connected in a Darlington configuration, it can detect the occurrence of a short circuit and operate even if the DESAT signal, i.e., the voltage at the drain terminal of the power device M2, is small.

[0059] <Modification> The functions of the semiconductor device described above may be realized by a protection system that protects the semiconductor device via communications. For example, the semiconductor device may include a power device M2. The protection system may include a first protection circuit that reduces the gate voltage of the power device M2 based on the voltage at the drain terminal of the power device M2, and a second protection circuit that reduces the gate voltage of the power device M2 earlier and more steeply than the first protection circuit based on the back electromotive force VL1 generated in an internal inductance L2 connected to the source terminal of the power device M2. The first protection circuit corresponds to the drive protection IC2, and the second protection circuit corresponds to the RSP circuit 3.

[0060] It should be noted that the embodiments and modifications may be freely combined, and the embodiments and modifications may be modified or omitted as appropriate.

[0061] The above description is illustrative in all respects and is not restrictive. It is understood that countless variations not illustrated can be envisioned. [Explanation of symbols]

[0062] 2 Drive protection IC, C2, C3 Capacitors, D2, D3, D4, D5 Diodes, L2 Internal inductance, M2 Power element, Q1 First semiconductor switching element, Q2 Second semiconductor switching element, Q3 Third semiconductor switching element, R7, R8 Voltage dividing resistors, R9, R10, R11, R16 Resistors, VL1 Back electromotive force.

Claims

1. a power semiconductor switching element having a control terminal and first and second terminals controlled by a control voltage applied to the control terminal; a protection circuit that reduces the control voltage of the power semiconductor switching element based on a voltage of the first terminal of the power semiconductor switching element; an internal inductance connected to the second terminal of the power semiconductor switching element; a voltage dividing resistor that generates a divided voltage based on a back electromotive force generated in the internal inductance; 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 steeply than the protection circuit, based on the voltage division; A semiconductor device comprising:

2. 2. The semiconductor device according to claim 1, The semiconductor device further comprises a first resistor connected in parallel with the internal inductance.

3. 3. The semiconductor device according to claim 1, a second resistor connected between the voltage dividing resistor and the first semiconductor switching element; a third resistor connected between the control terminal of the power semiconductor switching element and the first semiconductor switching element; The semiconductor device further comprises:

4. 3. The semiconductor device according to claim 1, The semiconductor device further comprises a fourth resistor connected between the first semiconductor switching element and one end of the internal inductance opposite to the power semiconductor switching element.

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

6. 5. The semiconductor device according to claim 4, The semiconductor device further comprises a first capacitor connected in parallel with the internal inductance.

7. 7. The semiconductor device according to claim 6, The semiconductor device further comprises a second diode connected in parallel with the internal inductance.

8. 8. The semiconductor device according to claim 7, The semiconductor device further comprises a third diode connected between the control terminal of the power semiconductor switching element and the first semiconductor switching element.

9. 3. The semiconductor device according to claim 1, a second diode connected in parallel with the internal inductance; a third diode connected between the control terminal of the power semiconductor switching element and the first semiconductor switching element; a second capacitor connected in parallel with the voltage dividing resistor; a fourth diode connected in series with a parallel part including the voltage dividing resistor and the second capacitor; The semiconductor device further comprises:

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

11. 10. The semiconductor device according to claim 9, a semiconductor switch unit including a second semiconductor switching element and a third semiconductor switching element connected in Darlington connection; The semiconductor switch unit connects the control terminal of the power semiconductor switching element and the first semiconductor switching element based on the voltage of the first terminal of the power semiconductor switching element.

12. A protection system for a semiconductor device, comprising: 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 a voltage at the first terminal of the power semiconductor switching element; a second protection circuit that reduces the control voltage of the power semiconductor switching element at an earlier timing and more steeply 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 switching element; A protection system comprising:

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