Semiconductor switching element drive circuit

Abstract

This invention provides a semiconductor switching element drive circuit that can more accurately detect failures in the current injection circuit. [Solution] A drive circuit for a semiconductor switching element is provided, comprising: a drive unit that switches the on state and off state of a semiconductor switching element based on a control signal; a voltage detection circuit that detects the voltage between a pair of main terminals of the semiconductor switching element; a current injection circuit that performs a current injection operation to inject current into the control terminal of the semiconductor switching element according to the magnitude of the voltage detected by the voltage detection circuit; a voltage application circuit that can perform a voltage application operation to the current injection circuit that is equal to or greater than a threshold voltage at which the current injection circuit performs a current injection operation; and an abnormality detection circuit that detects an abnormality in the current injection circuit when the voltage application circuit performs a voltage application operation but the current injection circuit does not perform a current injection operation.

Description

Technical Field

[0001] Embodiments of the present invention relate to a drive circuit for a semiconductor switching element.

Background Art

[0002] There is a drive circuit for driving a semiconductor switching element. The semiconductor switching element has a pair of main terminals and a control terminal, and has an on-state in which current flows between the pair of main terminals and an off-state in which the flow of current between the pair of main terminals is interrupted. The drive circuit is connected to the control terminal of the semiconductor switching element and switches between the on-state and the off-state by the voltage applied to the control terminal. The drive circuit sets the switching element to the on-state by applying a first voltage to the control terminal, and sets the switching element to the off-state by applying a second voltage different from the first voltage to the control terminal.

[0003] In such a drive circuit, in order to suppress the generation of an excessive surge voltage equal to or higher than the breakdown voltage of the semiconductor switching element between a pair of main terminals when switching the semiconductor switching element from the on-state to the off-state, it has been proposed to provide a current injection circuit. The current injection circuit injects current into the control terminal according to the voltage between a pair of main terminals when switching the semiconductor switching element from the on-state to the off-state, and suppresses the generation of an excessive surge voltage equal to or higher than the breakdown voltage between a pair of main terminals by slowing down the switching speed.

[0004] The current injection circuit operates only when an excessive surge voltage equal to or higher than the breakdown voltage occurs between a pair of main terminals, and does not operate during normal operation. Also, during the operation of the semiconductor switching element and the drive circuit to which a voltage is applied between a pair of main terminals, it is difficult for an operator or the like to inspect the current injection circuit, and the inspection of the current injection circuit is limited to when the semiconductor switching element and the drive circuit are stopped. Therefore, when the current injection circuit fails during the operation of the semiconductor switching element and the drive circuit, and an excessive surge voltage actually equal to or higher than the breakdown voltage occurs between a pair of main terminals, there is a possibility that the generated surge voltage cannot be appropriately suppressed.

[0005] Therefore, it is desirable to enable more appropriate detection of failures in the current injection circuit in the drive circuit of semiconductor switching elements. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Patent No. 4342251 [Overview of the project] [Problems that the invention aims to solve]

[0007] Embodiments of the present invention provide a drive circuit for a semiconductor switching element that can more appropriately detect failures in a current injection circuit. [Means for solving the problem]

[0008] According to an embodiment of the present invention, a semiconductor switching element drive circuit for switching between an ON state and an OFF state of a semiconductor switching element having a pair of main terminals and a control terminal, and having an ON state in which current flows between the pair of main terminals and an OFF state in which the flow of current between the pair of main terminals, comprises: a drive unit that receives an input of a control signal having a first state for setting the semiconductor switching element to the ON state and a second state for setting the semiconductor switching element to the OFF state, is connected to the control terminal of the semiconductor switching element, and switches the ON state and the OFF state of the semiconductor switching element based on the control signal; a voltage detection circuit for detecting the voltage between the pair of main terminals of the semiconductor switching element; and a semiconductor switching unit connected to the voltage detection circuit. A drive circuit for a semiconductor switching element is provided, comprising: a current injection circuit connected to the control terminal of the switching element, which, when the semiconductor switching element switches from the ON state to the OFF state, performs a current injection operation in which current is injected into the control terminal according to the magnitude of the voltage between the pair of main terminals detected by the voltage detection circuit, thereby slowing down the rate of change of the semiconductor switching element from the ON state to the OFF state and suppressing a rise in the voltage between the pair of main terminals above a set voltage; a voltage application circuit capable of performing a voltage application operation in which a voltage above a threshold voltage for the current injection circuit to perform the current injection operation is applied to the current injection circuit; and an abnormality detection circuit that detects an abnormality in the current injection circuit when the voltage application circuit performs the voltage application operation but the current injection circuit does not perform the current injection operation. [Effects of the Invention]

[0009] A semiconductor switching element drive circuit is provided that can more accurately detect failures in the current injection circuit. [Brief explanation of the drawing]

[0010] [Figure 1] This is a block diagram schematically representing the drive circuit according to the embodiment. [Figure 2]This is a schematic block diagram showing a modified example of the drive circuit according to the embodiment. [Figure 3] This is a schematic block diagram showing a modified example of the drive circuit according to the embodiment. [Figure 4] This is a schematic block diagram showing a modified example of the drive circuit according to the embodiment. [Figure 5] This is a block diagram schematically representing an example of a drive unit. [Modes for carrying out the invention]

[0011] Each embodiment will be described below with reference to the drawings. In this specification and in each figure, elements similar to those described above are denoted by the same reference numerals, and detailed explanations are omitted as appropriate.

[0012] Figure 1 is a schematic block diagram showing the drive circuit according to the embodiment. As shown in Figure 1, the drive circuit 10 is a drive circuit for the semiconductor switching element 2, which is used in connection with the semiconductor switching element 2. The semiconductor switching element 2 and the drive circuit 10 are used, for example, in a power conversion device that converts power by switching multiple semiconductor switching elements 2. When the semiconductor switching element 2 and the drive circuit 10 are applied to a power conversion device, for example, a rectifier element 4 is connected in antiparallel to the semiconductor switching element 2. The rectifier element 4 is, for example, a freewheeling diode. However, the semiconductor switching element 2 and the drive circuit 10 are not limited to power conversion devices, but can be applied to any device that requires a semiconductor switching element 2.

[0013] The semiconductor switching element 2 has a pair of main terminals 2a and 2b and a control terminal 2c, and has an ON state in which current flows between the pair of main terminals 2a and 2b, and an OFF state in which the flow of current between the pair of main terminals 2a and 2b is interrupted. The OFF state is not limited to a state in which no current flows between the pair of main terminals 2a and 2b, but may also be a state in which a weak current flows between the pair of main terminals 2a and 2b, within a range that does not affect the operation of the semiconductor switching element 2 and the device to which the semiconductor switching element 2 is applied (for example, a power converter).

[0014] The drive circuit 10 is connected to the control terminal 2c of the semiconductor switching element 2, and switches the semiconductor switching element 2 between an on state and an off state by applying a voltage to the control terminal 2c. The drive circuit 10 sets the semiconductor switching element 2 to an on state by applying a first voltage to the control terminal 2c, and sets the semiconductor switching element 2 to an off state by applying a second voltage different from the first voltage to the control terminal 2c.

[0015] The second voltage is, for example, lower than the first voltage. The semiconductor switching element 2 turns on when, for example, the potential of the control terminal 2c relative to the potential of the main terminal 2b on the low-potential side becomes higher than the threshold voltage between the main terminal 2b and the control terminal 2c of the semiconductor switching element 2, and turns off when it becomes lower than the threshold voltage. The first voltage is, for example, a positive bias voltage where the potential of the control terminal 2c is higher than the potential of the main terminal 2b on the low-potential side. The second voltage is, for example, a negative bias voltage where the potential of the control terminal 2c is lower than the potential of the main terminal 2b on the low-potential side.

[0016] The semiconductor switching element 2 is, for example, a self-excited semiconductor switching element such as a MOSFET, IGBT, or IEGT. More specifically, the semiconductor switching element 2 is an insulated gate type semiconductor switching element. However, the semiconductor switching element 2 is not limited to the above and may be any semiconductor switching element that can be switched between an on state and an off state by the drive circuit 10.

[0017] The drive circuit 10 includes a drive unit 12, a voltage detection circuit 14, and a current injection circuit 16. The drive unit 12 is connected to the control terminal 2c of the semiconductor switching element 2. Also, the drive unit 12 receives an input of a control signal. The drive unit 12 receives an input of a control signal from, for example, a higher-level controller or the like. The drive unit 12 switches the on-state and off-state of the semiconductor switching element 2 based on the input control signal.

[0018] The control signal has a first state for setting the semiconductor switching element 2 to the on-state and a second state for setting the semiconductor switching element 2 to the off-state. The drive unit 12 switches the semiconductor switching element 2 from the off-state to the on-state in response to the transition of the control signal from the second state to the first state, and switches the semiconductor switching element 2 from the on-state to the off-state in response to the transition of the control signal from the first state to the second state.

[0019] The control signal is, for example, a pulse signal (PWM signal). The first state is, for example, the high state of the pulse signal, and the second state is, for example, the low state of the pulse signal. However, the control signal is not limited to the above, and may be any signal that can appropriately switch the on-state and off-state of the semiconductor switching element 2 in the drive unit 12.

[0020] The voltage detection circuit 14 is connected to the pair of main terminals 2a, 2b of the semiconductor switching element 2. The drive circuit 10 is connected to the control terminal 2c of the semiconductor switching element 2 and is also connected to the pair of main terminals 2a, 2b of the semiconductor switching element 2. The voltage detection circuit 14 detects the voltage between the pair of main terminals 2a, 2b of the semiconductor switching element 2.

[0021] The current injection circuit 16 is connected to the voltage detection circuit 14 and is also connected to the control terminal 2c of the semiconductor switching element 2. The voltage detection circuit 14 inputs a voltage having a magnitude corresponding to the magnitude of the voltage between the pair of main terminals 2a, 2b of the semiconductor switching element 2 to the current injection circuit 16 as a detection result. For example, the voltage detection circuit 14 inputs a voltage having a magnitude proportional to the magnitude of the voltage between the pair of main terminals 2a, 2b and smaller than the voltage between the pair of main terminals 2a, 2b to the current injection circuit 16 as a detection result.

[0022] The current injection circuit 16 performs a current injection operation of injecting a current into the control terminal 2c of the semiconductor switching element 2 according to the magnitude of the voltage between the pair of main terminals 2a, 2b of the semiconductor switching element 2 detected by the voltage detection circuit 14. In other words, the current injection circuit 16 performs a current injection operation according to the magnitude of the voltage input from the voltage detection circuit 14.

[0023] For example, when the voltage between the pair of main terminals 2a, 2b becomes equal to or higher than a predetermined set voltage, the current injection circuit 16 injects a current into the control terminal 2c so that the magnitude of the current injected into the control terminal 2c increases as the voltage between the pair of main terminals 2a, 2b becomes larger than the set voltage. In other words, when the magnitude of the voltage input from the voltage detection circuit 14 becomes equal to or higher than a threshold voltage corresponding to the set voltage, the current injection circuit 16 injects a current into the control terminal 2c so that the magnitude of the current injected into the control terminal 2c increases as the magnitude of the voltage input from the voltage detection circuit 14 becomes larger than the threshold voltage.

[0024] The current injection circuit 16 performs a current injection operation when the semiconductor switching element 2 switches from the ON state to the OFF state, injecting current into the control terminal 2c according to the magnitude of the voltage between the pair of main terminals 2a and 2b detected by the voltage detection circuit 14. When current is injected into the control terminal 2c from the current injection circuit 16, the drop in voltage at the control terminal 2c is suppressed. As a result, the switching speed of the semiconductor switching element 2 slows down, and the slope of the decrease in current flowing between the pair of main terminals 2a and 2b becomes smaller. Consequently, the rise in voltage between the pair of main terminals 2a and 2b is suppressed. In other words, the surge voltage is prevented from exceeding the breakdown voltage of the semiconductor switching element 2.

[0025] In this way, when the semiconductor switching element 2 switches from the ON state to the OFF state, the current injection circuit 16 performs a current injection operation in which it injects current into the control terminal 2c according to the magnitude of the voltage between the pair of main terminals 2a and 2b detected by the voltage detection circuit 14. This slows down the rate of change of the semiconductor switching element 2 from the ON state to the OFF state (reduces the slope of the decrease in the current flowing between the pair of main terminals 2a and 2b), thereby suppressing a rise in the voltage between the pair of main terminals 2a and 2b above a set voltage. In other words, when the semiconductor switching element 2 switches from the ON state to the OFF state, the current injection circuit 16 suppresses the generation of a surge voltage between the pair of main terminals 2a and 2b that exceeds the breakdown voltage of the semiconductor switching element 2. The set voltage is set lower than the breakdown voltage of the semiconductor switching element 2. The current injection circuit 16 is sometimes called, for example, an active gate circuit.

[0026] The drive circuit 10 further comprises a voltage application circuit 18, an OR circuit 19, a current detection circuit 20, and an abnormality detection circuit 22. The voltage detection circuit 14 also has a determination circuit 14a.

[0027] The determination circuit 14a determines whether the magnitude of the voltage between the pair of main terminals 2a and 2b of the semiconductor switching element 2 is equal to or greater than the set voltage at which the current injection circuit 16 performs current injection operation. The determination circuit 14a is connected to the OR circuit 19. The determination circuit 14a inputs the determination result to the OR circuit 19. For example, the determination circuit 14a inputs a determination signal to the OR circuit 19 as the determination result, which becomes low (low voltage state) when it determines that the magnitude of the voltage between the pair of main terminals 2a and 2b is less than the set voltage, and high (high voltage state) when it determines that it is equal to or greater than the set voltage.

[0028] The voltage application circuit 18 is connected to the current injection circuit 16. More specifically, the voltage application circuit 18 is connected between the voltage detection circuit 14 and the current injection circuit 16. In other words, the voltage application circuit 18 is connected to the input terminal of the current injection circuit 16, to which the voltage detected by the voltage detection circuit 14 is input.

[0029] The voltage application circuit 18 is configured to perform a voltage application operation in which it applies a voltage to the input terminal of the current injection circuit 16 that is equal to or greater than the threshold voltage at which the current injection circuit 16 performs a current injection operation in which it injects current into the control terminal 2c of the semiconductor switching element 2. By enabling the voltage application circuit 18 to apply a voltage equal to or greater than the threshold voltage to the input terminal of the current injection circuit 16 at any timing, the voltage application circuit 18 enables the current injection circuit 16 to perform a current injection operation at any timing.

[0030] The magnitude of the voltage applied by the voltage application circuit 18 to the current injection circuit 16 is set to a voltage equivalent to the output voltage of the voltage detection circuit 14. More specifically, the magnitude of the voltage applied by the voltage application circuit 18 to the current injection circuit 16 is set to the magnitude of the output voltage of the voltage detection circuit 14 when the voltage between the pair of main terminals 2a and 2b of the semiconductor switching element 2 is greater than or equal to a set voltage and less than or equal to the withstand voltage of the semiconductor switching element 2.

[0031] Furthermore, the voltage application circuit 18 is connected to the current injection circuit 16 and also to the OR circuit 19. The voltage application circuit 18 inputs an operation signal to the OR circuit 19 that indicates whether or not it is performing a voltage application operation. For example, the operation signal is low (low voltage) when the voltage application operation is not being performed and high (high voltage) when the voltage application operation is being performed. However, the operation signal is not limited to the above and may be any signal that can appropriately indicate whether or not the voltage application circuit 18 is performing a voltage application operation.

[0032] The OR circuit 19 has a pair of input terminals and an output terminal. One input terminal of the OR circuit 19 is connected to the determination circuit 14a of the voltage detection circuit 14 and receives a determination signal input from the determination circuit 14a. The other input terminal of the OR circuit 19 is connected to the voltage application circuit 18 and receives an operation signal input from the voltage application circuit 18.

[0033] The output terminal of the OR circuit 19 is connected to the anomaly detection circuit 22. The OR circuit 19 calculates the logical OR of the judgment signal and the operation signal, and inputs an output signal corresponding to the calculation result to the anomaly detection circuit 22.

[0034] The output signal of the OR circuit 19 is low when both the judgment signal and the operation signal are low, and high when at least one of the judgment signal and the operation signal is high. That is, the output signal of the OR circuit 19 is low when, for example, the judgment circuit 14a determines that the magnitude of the voltage between the pair of main terminals 2a and 2b is less than the set voltage and the voltage application circuit 18 is not performing a voltage application operation, and high when the judgment circuit 14a determines that the magnitude of the voltage between the pair of main terminals 2a and 2b is equal to or greater than the set voltage, or when the voltage application circuit 18 is performing a voltage application operation.

[0035] The current detection circuit 20 detects the magnitude of the current injected from the current injection circuit 16 to the control terminal 2c of the semiconductor switching element 2. In other words, the current detection circuit 20 detects whether or not the current injection circuit 16 is performing a current injection operation.

[0036] The current detection circuit 20 is connected to the abnormality detection circuit 22. The current detection circuit 20 inputs a current detection signal to the abnormality detection circuit 22, which represents the result of detecting the magnitude of the current injected from the current injection circuit 16 to the control terminal 2c of the semiconductor switching element 2.

[0037] The current detection circuit 20 sets the current detection signal to low when the magnitude of the current injected from the current injection circuit 16 to the control terminal 2c of the semiconductor switching element 2 is less than a predetermined value, and sets the current detection signal to high when the magnitude of the current injected from the current injection circuit 16 to the control terminal 2c of the semiconductor switching element 2 is equal to or greater than the predetermined value. This makes it possible for the abnormality detection circuit 22 to recognize whether or not the current injection circuit 16 is performing a current injection operation based on the state of the current detection signal. However, the current detection signal is not limited to the above, and may be any signal that allows the abnormality detection circuit 22 to recognize whether or not the current injection circuit 16 is performing a current injection operation.

[0038] The abnormality detection circuit 22 detects abnormalities in the current injection circuit 16. The abnormality detection circuit 22 detects an abnormality in the current injection circuit 16 when the voltage application circuit 18 performs a voltage application operation and the current injection circuit 16 does not perform a current injection operation.

[0039] The anomaly detection circuit 22 detects an anomaly in the current injection circuit 16 based on, for example, the output signal input from the OR circuit 19 and the current detection signal input from the current detection circuit 20. The anomaly detection circuit 22 includes, for example, an exclusive OR circuit 24 and a latch circuit 26. The exclusive OR circuit 24 has a pair of input terminals and an output terminal. The anomaly detection circuit 22 inputs the input output signal and the current detection signal to the pair of input terminals of the exclusive OR circuit 24.

[0040] The exclusive OR circuit 24 outputs a low signal from its output terminal when the high and low signals of the pair of input terminals are the same, and outputs a high signal from its output terminal when the high and low signals of the pair of input terminals are different. As described above, the output signal of the OR circuit 19 is low when both the decision signal and the operation signal are low, and high when at least one of the decision signal and the operation signal is high. The current detection signal is low when the magnitude of the current injected into the control terminal 2c detected by the current detection circuit 20 is less than a predetermined value, and high when the magnitude of the current is greater than or equal to the predetermined value. In other words, the current detection signal is low when the current injection circuit 16 is not performing a current injection operation, and high when it is performing a current injection operation.

[0041] In this case, if the determination circuit 14a determines that the voltage is less than the set voltage, and the voltage application circuit 18 is not performing a voltage application operation, then both input terminals of the exclusive OR circuit 24 become low, and the output of the exclusive OR circuit 24 also becomes low.

[0042] Furthermore, when the determination circuit 14a determines that the voltage is below the set voltage, the voltage application circuit 18 performs a voltage application operation, the current injection circuit 16 performs a normal current injection operation, and the current detection circuit 20 detects current, both input terminals of the exclusive OR circuit 24 become high, and the output of the exclusive OR circuit 24 becomes low.

[0043] On the other hand, if the voltage application circuit 18 performs a voltage application operation but no current is injected from the current injection circuit 16 to the control terminal 2c, the operation signal becomes high, the current detection signal becomes low, and the output of the exclusive OR circuit 24 becomes high. Similarly, if the determination circuit 14a determines that the voltage is above the set voltage but no current is injected from the current injection circuit 16 to the control terminal 2c, the determination signal becomes high, the current detection signal becomes low, and the output of the exclusive OR circuit 24 becomes high. This makes it possible to detect an abnormality in the current injection circuit 16.

[0044] Thus, the abnormality detection circuit 22 detects an abnormality in the current injection circuit 16 if, for example, the operation signal indicates that the voltage application operation of the voltage application circuit 18 is being performed, but the current detection signal does not indicate that current has been detected, and if the determination signal indicates that the voltage is above the set voltage (the input voltage of the current injection circuit 16 has reached the operating level), but the current detection signal does not indicate that current has been detected.

[0045] Furthermore, when the voltage application circuit 18 is not performing a voltage application operation, the determination circuit 14a determines that the voltage is above the set voltage, the current injection circuit 16 performs a normal current injection operation, and the current detection circuit 20 detects current, both input terminals of the exclusive OR circuit 24 become high, and the output of the exclusive OR circuit 24 becomes low. In other words, when the voltage input from the voltage detection circuit 14 to the current injection circuit 16 becomes above the threshold voltage, the current injection circuit 16 performs a normal current injection operation, and the current detection circuit 20 detects current, the output of the exclusive OR circuit 24 becomes low.

[0046] In this way, the abnormality detection circuit 22 detects the current injection circuit 16 as normal when the voltage input from the voltage detection circuit 14 to the current injection circuit 16 is equal to or greater than the threshold voltage and the current injection circuit 16 performs a current injection operation. This prevents the abnormality detection circuit 22 from mistakenly detecting an abnormality in the current injection circuit 16 at the actual timing of the operation of the voltage detection circuit 14 and the current injection circuit 16, even if, for example, a voltage application circuit 18 is provided to allow the current injection circuit 16 to perform a current injection operation at any desired timing.

[0047] Furthermore, if the determination circuit 14a determines that the voltage is below the set voltage, and the voltage application circuit 18 is not performing a voltage application operation, but the current detection signal input from the current detection circuit 20 to the abnormality detection circuit 22 becomes high, the current detection signal becomes high, the output signal of the OR circuit 19 becomes low, and the output of the exclusive OR circuit 24 becomes high. This makes it possible to detect abnormal operation of the current injection circuit 16, such as when some abnormality occurs in a component within the current injection circuit 16, causing it to constantly inject current, or when it performs current injection operation at a voltage lower than the set voltage.

[0048] The anomaly detection circuit 22 determines, for example, whether the voltage input from the voltage detection circuit 14 to the current injection circuit 16 is above a threshold voltage, based on the determination result of the judgment circuit 14a. In this example, the anomaly detection circuit 22 determines whether the voltage input from the voltage detection circuit 14 to the current injection circuit 16 is above a threshold voltage, based on the output signal of the OR circuit 19. However, the configuration in which the anomaly detection circuit 22 determines whether the voltage input from the voltage detection circuit 14 to the current injection circuit 16 is above a threshold voltage, based on the determination result of the judgment circuit 14a, is not limited to this example. Any configuration that can appropriately determine whether the voltage input from the voltage detection circuit 14 to the current injection circuit 16 is above a threshold voltage, based on the determination result of the judgment circuit 14a, is acceptable.

[0049] In this example, the abnormality detection circuit 22 determines whether the current injection circuit 16 has performed a current injection operation based on the current detection signal from the current detection circuit 20. The method for determining whether the current injection circuit 16 has performed a current injection operation is not limited to the above; for example, it may be determined by receiving a signal from the current injection circuit 16 indicating whether or not a current injection operation is being performed. In this case, the current detection circuit 20 can be omitted. The method for determining whether the current injection circuit 16 has performed a current injection operation may be any method that allows the abnormality detection circuit 22 to appropriately determine whether or not a current injection operation has been performed. On the other hand, in the method in which the current injected from the current injection circuit 16 to the control terminal 2c is detected by the current detection circuit 20, for example, by directly detecting the current output from the current injection circuit 16, the presence or absence of a current injection operation can be detected more reliably.

[0050] The latch circuit 26 is connected to the output terminal of the exclusive OR circuit 24. The latch circuit 26 switches its output from low to high when the output of the exclusive OR circuit 24 switches from low to high. After the output of the exclusive OR circuit 24 switches from low to high, the latch circuit 26 maintains the output in a high state until a predetermined reset operation is performed, even when the output of the exclusive OR circuit 24 switches from high to low. For example, when the output of the exclusive OR circuit 24 indicates that an abnormality has been detected in the current injection circuit 16, the latch circuit 26 maintains the detected abnormality state of the current injection circuit 16 even after the voltage application circuit 18 has finished its voltage application operation, until a predetermined reset operation is performed.

[0051] The anomaly detection circuit 22 outputs an anomaly detection signal when it detects an anomaly in the current injection circuit 16. The anomaly detection circuit 22 outputs, for example, the output of the latch circuit 26 as the anomaly detection signal. The anomaly detection signal is, for example, low when no anomaly has been detected in the current injection circuit 16, and high when an anomaly has been detected in the current injection circuit 16. However, the anomaly detection signal is not limited to the above and may be any signal that can recognize whether or not an anomaly has been detected in the current injection circuit 16.

[0052] The abnormality detection circuit 22 outputs an abnormality detection signal to external devices, such as a higher-level controller or a terminal of the administrator of the semiconductor switching element 2 (power converter). The abnormality detection circuit 22 may, for example, output an abnormality detection signal to the notification unit, causing the notification unit to perform notification regarding the detection of an abnormality. The notification unit may be, for example, a display device that provides notification by displaying characters or patterns, a speaker that provides notification by outputting sound, or an indicator light that provides notification by emitting light. However, the configuration of the notification unit is not limited to the above, and may be any configuration that can appropriately provide notification of abnormality detection in the current injection circuit 16.

[0053] In this way, by outputting an abnormality detection signal to external devices and notification units, it is possible to notify higher-level controllers and managers of semiconductor switching elements 2 of the occurrence of an abnormality in the current injection circuit 16.

[0054] The drive unit 12 has an interlock circuit 28. The interlock circuit 28 performs an interlock process that sets the semiconductor switching element 2 to the off state regardless of the state of the input control signal when the drive unit 12 (drive circuit 10) is started. This prevents, for example, the semiconductor switching element 2 from being unintentionally switched to the on state when the drive unit 12 is started. The drive circuit 10 starts up each part, such as the drive unit 12, voltage detection circuit 14, current injection circuit 16, voltage application circuit 18, OR circuit 19, current detection circuit 20, and abnormality detection circuit 22, by receiving power from, for example, a power supply circuit provided in a power converter.

[0055] The voltage application circuit 18 performs a voltage application operation, for example, when the interlock circuit 28 is performing an interlock process that sets the semiconductor switching element 2 to the off state. In other words, the voltage application circuit 18 detects abnormalities in the current injection circuit 16, for example, during the interlock process of the interlock circuit 28 when the drive unit 12 is started up. The voltage application circuit 18 may determine whether or not the interlock circuit 28 is performing an interlock process by receiving a signal from the drive unit 12 (interlock circuit 28) indicating whether or not an interlock process is being performed, or it may be determined based on the elapsed time since the voltage application circuit 18 was started up.

[0056] In this case, the abnormality detection circuit 22 outputs an abnormality detection signal to an external device or notification unit, for example, and also outputs an abnormality detection signal to the interlock circuit 28.

[0057] If no abnormality in the current injection circuit 16 is detected during the interlock process, the interlock circuit 28 releases the interlock process in accordance with the completion of the drive unit 12's startup (stopping the interlock process and enabling the semiconductor switching element 2 to switch between on and off states according to the control signal).

[0058] On the other hand, if an abnormality in the current injection circuit 16 is detected during the interlock process, the interlock circuit 28 continues the interlock process even after the drive unit 12 has finished starting up. This prevents the semiconductor switching element 2 from being driven while there is an abnormality in the current injection circuit 16.

[0059] However, the timing at which the voltage application circuit 18 performs the voltage application operation is not limited to the above; it may be any timing that does not affect the operation of the semiconductor switching element 2, even when the voltage application operation causes the current injection circuit 16 to perform the current injection operation.

[0060] For example, when the semiconductor switching element 2 and the drive circuit 10 are used in a power converter, the initial charging of the charge storage element of the power converter may occur after the drive circuit 10 (drive unit 12) is started and the interlock processing of the interlock circuit 28 is released. The voltage application circuit 18 may, for example, perform a voltage application operation at the timing when the initial charging of the power converter is being performed, and detect an abnormality in the current injection circuit 16.

[0061] As described above, the drive circuit 10 for the semiconductor switching element 2 according to this embodiment includes a voltage application circuit 18 capable of performing a voltage application operation that applies a voltage to the input terminal of the current injection circuit 16 that is equal to or greater than the threshold voltage at which the current injection circuit 16 performs a current injection operation in which it injects current into the control terminal 2c of the semiconductor switching element 2, and an abnormality detection circuit 22 that detects an abnormality in the current injection circuit 16 when the voltage application circuit 18 performs a voltage application operation and the current injection circuit 16 does not perform a current injection operation.

[0062] As a result, the drive circuit 10 of the semiconductor switching element 2 according to this embodiment can detect abnormalities in the current injection circuit 16 at any timing, for example, during the interlock process of the interlock circuit 28 when the drive unit 12 is started up. Therefore, the drive circuit 10 of the semiconductor switching element 2 according to this embodiment can more appropriately detect failures in the current injection circuit 16. When the current injection circuit 16 fails during the operation of the semiconductor switching element 2 and the drive circuit 10, and an excessive surge voltage exceeding the withstand voltage is actually generated between the pair of main terminals 2a and 2b, it is possible to prevent the surge voltage from being properly suppressed. In the drive circuit 10 according to this embodiment, when an excessive surge voltage exceeding the withstand voltage is generated between the pair of main terminals 2a and 2b, the surge voltage suppression operation can be executed more reliably. In addition, for example, it is not necessary for workers to inspect the current injection circuit 16 one by one while the drive circuit 10 is stopped, and abnormalities in the current injection circuit 16 can be easily detected.

[0063] Figure 2 is a block diagram schematically showing a modified example of the drive circuit according to the embodiment. As shown in Figure 2, the drive circuit 10a omits the determination circuit 14a and the OR circuit 19. On the other hand, the drive circuit 10a further includes a comparison circuit 23 in their place. Components that are substantially the same in function and configuration as those in the above embodiment are denoted by the same reference numerals, and detailed explanations are omitted.

[0064] The comparison circuit 23 compares whether the voltage input to the current injection circuit 16 is equal to or greater than the threshold voltage. The comparison circuit 23 has a pair of input terminals and an output terminal. One input terminal of the comparison circuit 23 is connected to the input terminal of the current injection circuit 16. As a result, the voltage input to the current injection circuit 16 is input to one input terminal of the comparison circuit 23. The other input terminal of the comparison circuit 23 is set to the threshold voltage. As a result, the comparison circuit 23 compares whether the voltage input to the current injection circuit 16 is equal to or greater than the threshold voltage.

[0065] The output terminal of the comparison circuit 23 is connected to the anomaly detection circuit 22. The comparison circuit 23 inputs a comparison signal to the anomaly detection circuit 22 that represents the comparison result of whether the voltage input to the current injection circuit 16 is equal to or greater than the threshold voltage. The comparison signal is, for example, low when the voltage input to the current injection circuit 16 is less than the threshold voltage, and high when the voltage input to the current injection circuit 16 is equal to or greater than the threshold voltage.

[0066] In the drive circuit 10a, the abnormality detection circuit 22 inputs the input comparison signal and the current detection signal to the pair of input terminals of the exclusive OR circuit 24. In this case, when the comparison circuit 23 compares the value to less than the threshold voltage, both input terminals of the pair of input terminals of the exclusive OR circuit 24 become low, and the output of the exclusive OR circuit 24 also becomes low.

[0067] On the other hand, if the comparison circuit 23 compares the voltage to be above the threshold voltage, but no current is injected from the current injection circuit 16 to the control terminal 2c, the comparison signal becomes high, the current detection signal becomes low, and the output of the exclusive OR circuit 24 becomes high. As a result, the drive circuit 10a can also detect an abnormality in the current injection circuit 16, similar to the embodiment described above.

[0068] Furthermore, when the comparison circuit 23 compares the voltage to be above the threshold voltage, the current injection circuit 16 performs its current injection operation normally, and the current detection circuit 20 detects current, both input terminals of the exclusive OR circuit 24 become high, and the output of the exclusive OR circuit 24 becomes low. In other words, when the voltage input from the voltage detection circuit 14 to the current injection circuit 16 is above the threshold voltage, the current injection circuit 16 performs its current injection operation normally, and the current detection circuit 20 detects current, the output of the exclusive OR circuit 24 becomes low.

[0069] As a result, even if the drive circuit 10a is also provided with a voltage application circuit 18, similar to the embodiment described above, and the current injection circuit 16 is made to perform a current injection operation at any desired timing, it is possible to suppress the abnormality detection circuit 22 from mistakenly detecting an abnormality in the current injection circuit 16 at the timing of the actual operation of the voltage detection circuit 14 and the current injection circuit 16.

[0070] Furthermore, if the comparison circuit 23 compares the voltage to be less than the threshold voltage, and the voltage application circuit 18 does not perform a voltage application operation, but the current detection signal input from the current detection circuit 20 to the abnormality detection circuit 22 becomes high, the current detection signal becomes high, the comparison signal of the comparison circuit 23 becomes low, and the output of the exclusive OR circuit 24 becomes high. In this way, the drive circuit 10a can also detect abnormal operation of the current injection circuit 16, similar to the embodiment described above, for example, if some abnormality occurs in a component within the current injection circuit 16, causing it to constantly inject current, or if it performs current injection operation at a voltage lower than the set voltage.

[0071] Thus, in the drive circuit 10a as well, the abnormality detection circuit 22 detects the current injection circuit 16 as normal when the voltage input from the voltage detection circuit 14 to the current injection circuit 16 is equal to or greater than the threshold voltage, and the current injection circuit 16 performs a current injection operation.

[0072] In the drive circuit 10a, the abnormality detection circuit 22 determines whether the voltage input from the voltage detection circuit 14 to the current injection circuit 16 is equal to or greater than the threshold voltage, based on the comparison result of the comparison circuit 23. Thus, the abnormality detection circuit 22 may determine whether the voltage input from the voltage detection circuit 14 to the current injection circuit 16 is equal to or greater than the threshold voltage, based on the comparison result of the comparison circuit 23, rather than being limited to the determination result of the judgment circuit 14a.

[0073] In this example, the comparison signal from the comparison circuit 23 is input to the anomaly detection circuit 22 as the comparison result. The configuration in which the anomaly detection circuit 22 determines whether the voltage input from the voltage detection circuit 14 to the current injection circuit 16 is above the threshold voltage, based on the comparison result from the comparison circuit 23, is not limited to this configuration. Any configuration that can appropriately determine whether the voltage input from the voltage detection circuit 14 to the current injection circuit 16 is above the threshold voltage, based on the comparison result from the comparison circuit 23, is acceptable.

[0074] Figure 3 is a schematic block diagram showing a modified example of the drive circuit according to the embodiment. As shown in Figure 3, the drive circuit 10b further includes an abnormality detection circuit 22 and a current value comparison circuit 30. Components that are substantially the same in function and configuration as those in the above embodiment are denoted by the same reference numerals, and detailed explanations are omitted.

[0075] In the drive circuit 10b, the current detection circuit 20 detects the magnitude of the current injected from the current injection circuit 16 to the control terminal 2c of the semiconductor switching element 2, and inputs the detection result representing the magnitude of the detected current to the current value comparison circuit 30 of the abnormality detection circuit 22.

[0076] The current value comparison circuit 30 receives the detection result from the current detection circuit 20, as well as a reference value representing the magnitude of the current to be injected from the current injection circuit 16 to the control terminal 2c of the semiconductor switching element 2 when the voltage application circuit 18 performs a voltage application operation.

[0077] The current value comparison circuit 30 calculates the difference between the detection result of the input current detection circuit 20 and the reference value. In other words, when the voltage application circuit 18 performs a voltage application operation, the current value comparison circuit 30 calculates the difference between the magnitude of the current actually detected by the current detection circuit 20 and the reference value. The current value comparison circuit 30 inputs a difference signal representing the calculation result of the difference between the detection result of the current detection circuit 20 and the reference value to the current injection circuit 16.

[0078] Furthermore, the current value comparison circuit 30 generates a current detection signal that indicates whether the magnitude of the current injected from the current injection circuit 16 to the control terminal 2c of the semiconductor switching element 2 is greater than or equal to a predetermined value, similar to the current detection circuit 20 in the above embodiment, and inputs the generated current detection signal to one input terminal of the exclusive OR circuit 24. The current value comparison circuit 30 sets the current detection signal to low when the magnitude of the current injected from the current injection circuit 16 to the control terminal 2c of the semiconductor switching element 2 is less than a predetermined value, and sets the current detection signal to high when the magnitude of the current injected from the current injection circuit 16 to the control terminal 2c of the semiconductor switching element 2 is greater than or equal to a predetermined value, similar to the above embodiment. As a result, similar to the above embodiment, an abnormality in the current injection circuit 16 can be detected based on the output signal input from the OR circuit 19 and the current detection signal generated by the current value comparison circuit 30. Note that the configuration for detecting an abnormality in the current injection circuit 16 is not limited to the configuration using the OR circuit 19, but may be any configuration described in the above embodiment.

[0079] In the drive circuit 10b, the current injection circuit 16 has an operating point adjustment circuit 32. The operating point adjustment circuit 32 adjusts the operating point of the current injection operation by the current injection circuit 16 based on the difference signal input from the current value comparison circuit 30. More specifically, the operating point adjustment circuit 32 adjusts the threshold voltage set for the voltage input from the voltage detection circuit 14 to the current injection circuit 16 based on the difference signal input from the current value comparison circuit 30. In other words, the operating point adjustment circuit 32 adjusts the set voltage set for the magnitude of the voltage between the pair of main terminals 2a and 2b of the semiconductor switching element 2 detected by the voltage detection circuit 14, based on the difference signal.

[0080] The operating point adjustment circuit 32 adjusts the threshold voltage (operating point) based on the difference signal so that, during current injection, a current of a magnitude corresponding to a reference value is injected into the control terminal 2c of the semiconductor switching element 2.

[0081] The operating point adjustment circuit 32 adjusts the threshold voltage so that, for example, if the magnitude of the current injected from the current injection circuit 16 to the control terminal 2c of the semiconductor switching element 2 during current injection operation is lower than a reference value, the threshold voltage is lowered according to the difference from the reference value. As a result, the current injection operation starts from a state where the voltage between the pair of main terminals 2a and 2b is lower, and the magnitude of the current injected to the control terminal 2c can be increased relative to a predetermined voltage between the pair of main terminals 2a and 2b.

[0082] Furthermore, the operating point adjustment circuit 32 adjusts the threshold voltage so that, for example, if the magnitude of the current injected from the current injection circuit 16 to the control terminal 2c of the semiconductor switching element 2 during current injection operation is higher than a reference value, the threshold voltage is increased according to the difference from the reference value. As a result, the current injection operation starts when the voltage between the pair of main terminals 2a and 2b is higher, and the magnitude of the current injected to the control terminal 2c can be reduced relative to a predetermined voltage between the pair of main terminals 2a and 2b.

[0083] Thus, in the drive circuit 10b, the abnormality detection circuit 22 has a current value comparison circuit 30 which calculates the difference between the detection result of the current detection circuit 20 and a reference value, and the current injection circuit 16 has an operating point adjustment circuit 32 which adjusts the operating point of the current injection operation by the current injection circuit 16 based on the calculated difference.

[0084] As a result, the drive circuit 10b can detect an abnormality in the current injection circuit 16 if it does not perform a current injection operation when the voltage application circuit 18 performs a voltage application operation. Furthermore, when the voltage application circuit 18 performs a voltage application operation and the current injection circuit 16 performs a current injection operation, the drive circuit 10b can adjust the operating point of the current injection operation by the current injection circuit 16 according to the magnitude of the current injected from the current injection circuit 16 to the control terminal 2c of the semiconductor switching element 2. This allows the drive circuit 10b to automatically adjust for variations in current injection operation due to variations in circuit components, for example, and also to adjust for changes in operating characteristics due to aging after operation. For example, it eliminates the need for workers to inspect the drive circuit 10b and manually adjust the operating point of the current injection operation of the current injection circuit 16 in response to changes in operating characteristics, making adjustment of the operating point easy.

[0085] Figure 4 is a schematic block diagram showing a modified example of the drive circuit according to the embodiment. As shown in Figure 4, the drive circuit 10c further includes a timing adjustment circuit 34. The timing adjustment circuit 34, like the drive unit 12, receives control signals from a higher-level controller or the like. The timing adjustment circuit 34 performs a process to delay the timing of the switch from the first state to the second state of the control signal, and the timing of the switch from the second state to the first state of the control signal, by a predetermined time. In other words, the timing adjustment circuit 34 is a delay circuit. The timing adjustment circuit 34 inputs the processed control signals to the drive unit 12.

[0086] The timing adjustment circuit 34 generates a second control signal, which delays the timing of the first control signal input from a higher-level controller, etc., from the first state to the second state by a predetermined time, and a third control signal, which delays the timing of the first control signal switching from the second state to the first state by a predetermined time, and inputs the generated second control signal and third control signal to the drive unit 12.

[0087] In this example, the drive unit 12 switches the semiconductor switching element 2 from the ON state to the OFF state by applying a second voltage to the control terminal 2c in response to the switching of the control signal from the first state to the second state, and then applies the second voltage to the control terminal 2c in a state of lower resistance. Furthermore, the drive unit 12 switches the semiconductor switching element 2 from the OFF state to the ON state by applying a first voltage to the control terminal 2c in response to the switching of the control signal from the second state to the first state, and then applies the first voltage to the control terminal 2c in a state of lower resistance. In this way, the drive unit 12 switches the ON state and the OFF state of the semiconductor switching element 2 using a two-stage drive method.

[0088] The predetermined time for which the timing adjustment circuit 34 delays the timing of the control signal switching is set to a time longer than the time required for the semiconductor switching element 2 to switch when the drive unit 12 applies the first or second voltage to the control terminal 2c of the semiconductor switching element 2 while the drive unit 12 is in a high resistance state (first stage of the two-stage drive method). If the drive unit 12 applies the first or second voltage to the control terminal 2c of the semiconductor switching element 2 while the semiconductor switching element 2 is switching while the resistance is low (second stage of the two-stage drive method), the voltage at the control terminal 2c may drop or rise sharply, potentially causing the switching speed of the semiconductor switching element 2 to increase more than necessary. This can cause the slope of the current flowing through the semiconductor switching element 2 to become steep, potentially generating excessive surge voltages and putting significant stress on the semiconductor switching element 2. In the worst case, this could lead to damage to the semiconductor switching element 2. As described above, by setting a predetermined time longer than the time required for switching of the semiconductor switching element 2 when the drive unit 12 applies the first or second voltage to the control terminal 2c of the semiconductor switching element 2 while the resistance value is high, it is possible to switch the semiconductor switching element 2 at an appropriate speed while suppressing unnecessary stress on the semiconductor switching element 2, even when performing a two-stage drive method.

[0089] The drive unit 12 switches to a low-resistance state based on the processed control signal input from the timing adjustment circuit 34. For example, in response to the switching of the first control signal from the first state to the second state, the drive unit 12 applies a second voltage to the control terminal 2c, thereby switching the semiconductor switching element 2 from the on state to the off state. Then, in response to the switching of the second control signal from the first state to the second state, it applies a second voltage to the control terminal 2c in a lower-resistance state. Then, for example, in response to the switching of the first control signal from the second state to the first state, the drive unit 12 applies a first voltage to the control terminal 2c, thereby switching the semiconductor switching element 2 from the off state to the on state. Then, in response to the switching of the third control signal from the second state to the first state, it applies a first voltage to the control terminal 2c in a lower-resistance state.

[0090] Figure 5 is a block diagram schematically representing an example of a drive unit. As shown in Figure 5, the drive unit 12 includes, for example, switching elements 41-44 and a resistive element 45. The drive unit 12 receives a positive control power supply P (first control power supply) for applying a first voltage to the control terminal 2c of the semiconductor switching element 2 and a negative control power supply N (second control power supply) for applying a second voltage to the control terminal 2c of the semiconductor switching element 2 from a power supply circuit (not shown). The drive unit 12 has a first input terminal 12p for receiving the positive control power supply P and a second input terminal 12n for receiving the negative control power supply N.

[0091] Switching elements 41 and 42 are connected in series between the first input terminal 12p and the second input terminal 12n (between the positive control power supply P and the negative control power supply N). The connection point of switching elements 41 and 42 is connected to one end of a resistive element 45. The other end of the resistive element 45 is connected to the control terminal 2c of the semiconductor switching element 2. Switching elements 41 and 42 are connected to the control terminal 2c of the semiconductor switching element 2 via the resistive element 45. The resistive element 45 is, for example, a gate resistor.

[0092] Switching elements 43 and 44 are connected in parallel with switching elements 41 and 42, and in series between the first input terminal 12p and the second input terminal 12n. The connection point of switching elements 43 and 44 is connected between the other end of the resistor 45 and the control terminal 2c of the semiconductor switching element 2. Therefore, switching elements 43 and 44 are connected to the control terminal 2c of the semiconductor switching element 2 without going through the resistor 45.

[0093] The control terminals of switching elements 41 and 42 receive a first control signal input from a higher-level controller. Meanwhile, the control terminals of switching elements 43 and 44 are connected to the timing adjustment circuit 34. The control terminal of switching element 43 receives a third control signal generated by the timing adjustment circuit 34. The control terminal of switching element 44 receives a second control signal generated by the timing adjustment circuit 34.

[0094] Switching elements 41 and 43 are, for example, NPN type transistors. Switching elements 42 and 44 are, for example, PNP type transistors. Switching elements 41 and 43 are turned on when the potential of their control terminals is higher than the potential of their main terminals on the low-potential side, and are turned off when the potential of their control terminals is lower than or equal to the potential of their main terminals on the low-potential side. Switching elements 42 and 44 are turned on when the potential of their control terminals is lower than or equal to the potential of their main terminals on the low-potential side, and are turned off when the potential of their control terminals is higher than the potential of their main terminals on the low-potential side.

[0095] In the drive unit 12, by turning on the switching element 41 and turning off the switching elements 42 to 44, the control terminal 2c of the semiconductor switching element 2 is connected to the first input terminal 12p (positive control power supply P) via the switching element 41 and the resistor element 45, and the first applied state is achieved by applying the first voltage to the control terminal 2c via the resistor element 45.

[0096] In the drive unit 12, by turning on the switching element 43 and turning off the switching elements 42 and 44, the control terminal 2c of the semiconductor switching element 2 is connected to the first input terminal 12p (positive control power supply P) via the switching element 43 without going through the resistor element 45. This results in a second applied state in which the first voltage is applied to the control terminal 2c with a lower resistance between the first input terminal 12p and the control terminal 2c than in the first applied state.

[0097] In the drive unit 12, by turning on the switching element 42 and turning off the switching elements 41, 43, and 44, the control terminal 2c of the semiconductor switching element 2 is connected to the second input terminal 12n (negative control power supply N) via the switching element 42 and the resistor element 45, resulting in a third applied state where a second voltage is applied to the control terminal 2c via the resistor element 45.

[0098] Then, in the drive unit 12, by turning on the switching element 44 and turning off the switching elements 41 and 43, the control terminal 2c of the semiconductor switching element 2 is connected to the second input terminal 12n (negative control power supply N) via the switching element 44 without going through the resistor element 45, resulting in a fourth applied state in which the second voltage is applied to the control terminal 2c with a resistance lower than that of the third applied state between the second input terminal 12n and the control terminal 2c.

[0099] Thus, the drive unit 12 can switch between a first application state in which a first voltage is applied to the control terminal 2c, a second application state in which the first voltage is applied to the control terminal 2c with a lower resistance between the first input terminal 12p and the control terminal 2c than in the first application state, a third application state in which a second voltage is applied to the control terminal 2c, and a fourth application state in which the second voltage is applied to the control terminal 2c with a lower resistance between the second input terminal 12n and the control terminal 2c than in the third application state. However, the configuration of the drive unit 12 is not limited to the above, and may be any configuration that can appropriately switch between the above four states.

[0100] In the drive circuit 10c, the voltage application circuit 18 performs a voltage application operation when the drive unit 12 is in a low-resistance state and a second voltage is applied to the control terminal 2c. In other words, the voltage application circuit 18 performs a voltage application operation when the drive unit 12 is in the fourth application state and detects an abnormality in the current injection circuit 16.

[0101] When the drive unit 12 is in the fourth applied state, the current injected from the current injection circuit 16 to the control terminal 2c of the semiconductor switching element 2 flows to the second input terminal 12n (negative control power supply N), thereby suppressing changes in the control terminal 2c. Therefore, in the drive circuit 10c, even if the voltage application circuit 18 is made to perform a voltage application operation and the current injection circuit 16 is made to perform a current injection operation when the drive unit 12 is in the fourth applied state, it is possible to suppress any impact on the operation of the semiconductor switching element 2.

[0102] In the drive circuit 10c, when the drive unit 12 is in the fourth applied state, the voltage application circuit 18 is made to perform a voltage application operation. This allows for the detection of abnormalities in the current injection circuit 16 while suppressing any impact on the operation of the semiconductor switching element 2, even during the operation of the semiconductor switching element 2 and the drive circuit 10c. Therefore, the drive circuit 10c can more appropriately detect failures in the current injection circuit 16.

[0103] This embodiment includes the following aspects. (Note 1) A semiconductor switching element drive circuit that switches between the ON state and the OFF state of a semiconductor switching element having a pair of main terminals and a control terminal, and having an ON state in which current flows between the pair of main terminals and an OFF state in which the flow of current between the pair of main terminals, A drive unit receives a control signal having a first state that sets the semiconductor switching element to the ON state and a second state that sets the semiconductor switching element to the OFF state, is connected to the control terminal of the semiconductor switching element, and switches the ON state and the OFF state of the semiconductor switching element based on the control signal. A voltage detection circuit for detecting the voltage between the pair of main terminals of the semiconductor switching element, A current injection circuit is connected to the voltage detection circuit and to the control terminal of the semiconductor switching element, and when the semiconductor switching element switches from the ON state to the OFF state, it performs a current injection operation to inject current into the control terminal according to the magnitude of the voltage between the pair of main terminals detected by the voltage detection circuit, thereby slowing down the rate of change of the semiconductor switching element from the ON state to the OFF state and suppressing the voltage between the pair of main terminals to rise above a set voltage, A voltage application circuit capable of performing a voltage application operation, which applies a voltage to the current injection circuit that is equal to or greater than the threshold voltage at which the current injection circuit performs the current injection operation, An abnormality detection circuit detects an abnormality in the current injection circuit when the voltage application circuit performs the voltage application operation and the current injection circuit does not perform the current injection operation, A drive circuit for a semiconductor switching element equipped with [a specific feature / feature].

[0104] (Note 2) The abnormality detection circuit is a drive circuit for a semiconductor switching element as described in Appendix 1, which detects the current injection circuit as normal when the voltage input from the voltage detection circuit to the current injection circuit is equal to or greater than the threshold voltage and the current injection circuit performs the current injection operation.

[0105] (Note 3) The voltage detection circuit includes a determination circuit that determines whether the magnitude of the voltage between the pair of main terminals of the semiconductor switching element has become equal to or greater than the set voltage at which the current injection circuit performs the current injection operation. The abnormality detection circuit is a drive circuit for a semiconductor switching element as described in Appendix 2, which determines whether the voltage input from the voltage detection circuit to the current injection circuit is equal to or greater than the threshold voltage, based on the determination result of the determination circuit.

[0106] (Note 4) The current injection circuit is further provided with a comparison circuit that compares whether the voltage input to the current injection circuit is equal to or greater than the threshold voltage. The abnormality detection circuit is a drive circuit for a semiconductor switching element as described in Appendix 2, which determines whether the voltage input from the voltage detection circuit to the current injection circuit is equal to or greater than the threshold voltage, based on the comparison result of the comparison circuit.

[0107] (Note 5) The system further includes a current detection circuit that detects the magnitude of the current injected from the current injection circuit to the control terminal of the semiconductor switching element, The current detection circuit is connected to the abnormality detection circuit and inputs a current detection signal to the abnormality detection circuit that represents the detection result of the magnitude of the current injected from the current injection circuit to the control terminal of the semiconductor switching element. The abnormality detection circuit is a drive circuit for a semiconductor switching element as described in any one of Appendix 1 to 4, which determines whether the current injection circuit has performed the current injection operation when the voltage application circuit has performed the voltage application operation, based on the current detection signal of the current detection circuit.

[0108] (Note 6) The abnormality detection circuit includes a current value comparison circuit that, when the voltage application circuit performs the voltage application operation, calculates the difference between the magnitude of the current detected by the current detection circuit and a reference value representing the magnitude of the current to be injected from the current injection circuit to the control terminal of the semiconductor switching element when the voltage application circuit performs the voltage application operation, and inputs a difference signal representing the calculation result of the difference to the current injection circuit. The current injection circuit is a drive circuit for a semiconductor switching element as described in Appendix 5, which has an operating point adjustment circuit that adjusts the threshold voltage based on the difference signal so that a current of a magnitude corresponding to the reference value is injected into the control terminal of the semiconductor switching element during the current injection operation.

[0109] (Note 7) The drive unit has an interlock circuit that performs an interlock process to set the semiconductor switching element to the off state, regardless of the state of the input control signal, when the drive unit is started. The voltage application circuit is a drive circuit for a semiconductor switching element described in any one of the appendices 1 to 6, which performs the voltage application operation when the interlock circuit is performing the interlock process.

[0110] (Note 8) The system further includes a timing adjustment circuit that receives the aforementioned control signal, performs a process to delay the timing of the switching of the control signal from the first state to the second state and the timing of the switching of the control signal from the second state to the first state by a predetermined time, and inputs the processed control signal to the drive unit. The aforementioned drive unit is It has a first input terminal for receiving a first control power supply for applying a first voltage to the control terminal, and a second input terminal for receiving a second control power supply for applying a second voltage different from the first voltage to the control terminal, wherein the semiconductor switching element is set to the ON state by applying the first voltage to the control terminal, and the semiconductor switching element is set to the OFF state by applying the second voltage to the control terminal, The following states are switchable: a first application state in which the first voltage is applied to the control terminal; a second application state in which the first voltage is applied to the control terminal with a lower resistance between the first input terminal and the control terminal than in the first application state; a third application state in which the second voltage is applied to the control terminal; and a fourth application state in which the second voltage is applied to the control terminal with a lower resistance between the second input terminal and the control terminal than in the third application state. In response to the switching of the control signal from the first state to the second state, the semiconductor switching element is switched from the on state to the off state by applying the third application state, and then, in response to the switching of the control signal after processing of the timing adjustment circuit from the first state to the second state, the circuit is switched from the third application state to the fourth application state. In response to the switching of the control signal from the second state to the first state, the semiconductor switching element is switched from the off state to the on state by setting it to the first applied state. Then, in response to the switching of the control signal after processing of the timing adjustment circuit from the second state to the first state, the circuit is switched from the first applied state to the second applied state. The voltage application circuit is a drive circuit for a semiconductor switching element described in any one of the appendices 1 to 6 that performs the voltage application operation when the drive unit is in the fourth application state.

[0111] While several embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These novel embodiments can be carried out in a variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents. [Explanation of Symbols]

[0112] 2…Semiconductor switching element, 4…Rectifier element, 10, 10a~10c…Drive circuit, 12…Drive unit, 14…Voltage detection circuit, 14a…Decision circuit, 16…Current injection circuit, 18…Voltage application circuit, 19…OR circuit, 20…Current detection circuit, 22…Anomaly detection circuit, 23…Comparison circuit, 24…Exclusive OR circuit, 26…Latch circuit, 28…Interlock circuit, 30…Current value comparison circuit, 32…Operating point adjustment circuit, 34…Timing adjustment circuit, 41~44…Switching element, 45…Resistor element

Claims

1. A semiconductor switching element drive circuit that switches between the ON state and the OFF state of a semiconductor switching element having a pair of main terminals and a control terminal, and having an ON state in which current flows between the pair of main terminals and an OFF state in which the flow of current between the pair of main terminals, A drive unit receives a control signal having a first state that sets the semiconductor switching element to the ON state and a second state that sets the semiconductor switching element to the OFF state, is connected to the control terminal of the semiconductor switching element, and switches the ON state and the OFF state of the semiconductor switching element based on the control signal. A voltage detection circuit for detecting the voltage between the pair of main terminals of the semiconductor switching element, A current injection circuit is connected to the voltage detection circuit and to the control terminal of the semiconductor switching element, and when the semiconductor switching element switches from the ON state to the OFF state, it performs a current injection operation to inject current into the control terminal according to the magnitude of the voltage between the pair of main terminals detected by the voltage detection circuit, thereby slowing down the rate of change of the semiconductor switching element from the ON state to the OFF state and suppressing the voltage between the pair of main terminals to rise above a set voltage, A voltage application circuit capable of performing a voltage application operation, which applies a voltage to the current injection circuit that is equal to or greater than the threshold voltage at which the current injection circuit performs the current injection operation, An abnormality detection circuit detects an abnormality in the current injection circuit when the voltage application circuit performs the voltage application operation and the current injection circuit does not perform the current injection operation, A drive circuit for a semiconductor switching element equipped with [a specific feature / feature].

2. The semiconductor switching element drive circuit according to claim 1, wherein the abnormality detection circuit detects the current injection circuit as normal when the voltage input from the voltage detection circuit to the current injection circuit is equal to or greater than the threshold voltage and the current injection circuit performs the current injection operation.

3. The voltage detection circuit includes a determination circuit that determines whether the magnitude of the voltage between the pair of main terminals of the semiconductor switching element has become equal to or greater than the set voltage at which the current injection circuit performs the current injection operation. The abnormality detection circuit determines, based on the determination result of the determination circuit, whether the voltage input from the voltage detection circuit to the current injection circuit is equal to or greater than the threshold voltage, according to the semiconductor switching element drive circuit according to claim 2.

4. The current injection circuit is further provided with a comparison circuit that compares whether the voltage input to the current injection circuit is equal to or greater than the threshold voltage. The abnormality detection circuit determines, based on the comparison result of the comparison circuit, whether the voltage input from the voltage detection circuit to the current injection circuit is equal to or greater than the threshold voltage, according to claim 2, for the driving circuit of a semiconductor switching element.

5. The system further includes a current detection circuit that detects the magnitude of the current injected from the current injection circuit to the control terminal of the semiconductor switching element, The current detection circuit is connected to the abnormality detection circuit and inputs a current detection signal to the abnormality detection circuit that represents the detection result of the magnitude of the current injected from the current injection circuit to the control terminal of the semiconductor switching element. The semiconductor switching element drive circuit according to claim 1, wherein the abnormality detection circuit determines whether the current injection circuit has performed the current injection operation when the voltage application circuit has performed the voltage application operation, based on the current detection signal of the current detection circuit.

6. The abnormality detection circuit includes a current value comparison circuit that, when the voltage application circuit performs the voltage application operation, calculates the difference between the magnitude of the current detected by the current detection circuit and a reference value representing the magnitude of the current to be injected from the current injection circuit to the control terminal of the semiconductor switching element when the voltage application circuit performs the voltage application operation, and inputs a difference signal representing the calculation result of the difference to the current injection circuit. The current injection circuit has an operating point adjustment circuit that adjusts the threshold voltage based on the difference signal so that, during the current injection operation, a current of a magnitude corresponding to the reference value is injected into the control terminal of the semiconductor switching element.

7. The drive unit has an interlock circuit that performs an interlock process to set the semiconductor switching element to the off state, regardless of the state of the input control signal, when the drive unit is started. The voltage application circuit is a drive circuit for a semiconductor switching element according to claim 1, which performs the voltage application operation when the interlock circuit is performing the interlock process.

8. The system further includes a timing adjustment circuit that receives the aforementioned control signal, performs a process to delay the timing of the switching of the control signal from the first state to the second state and the timing of the switching of the control signal from the second state to the first state by a predetermined time, and inputs the processed control signal to the drive unit. The aforementioned drive unit is It has a first input terminal for receiving a first control power supply for applying a first voltage to the control terminal, and a second input terminal for receiving a second control power supply for applying a second voltage different from the first voltage to the control terminal, wherein the semiconductor switching element is set to the ON state by applying the first voltage to the control terminal, and the semiconductor switching element is set to the OFF state by applying the second voltage to the control terminal, The following states are switchable: a first application state in which the first voltage is applied to the control terminal; a second application state in which the first voltage is applied to the control terminal with a lower resistance between the first input terminal and the control terminal than in the first application state; a third application state in which the second voltage is applied to the control terminal; and a fourth application state in which the second voltage is applied to the control terminal with a lower resistance between the second input terminal and the control terminal than in the third application state. In response to the switching of the control signal from the first state to the second state, the semiconductor switching element is switched from the on state to the off state by applying the third application state, and then, in response to the switching of the control signal after processing of the timing adjustment circuit from the first state to the second state, the circuit is switched from the third application state to the fourth application state. In response to the switching of the control signal from the second state to the first state, the semiconductor switching element is switched from the off state to the on state by setting it to the first applied state. Then, in response to the switching of the control signal after the processing of the timing adjustment circuit from the second state to the first state, the circuit is switched from the first applied state to the second applied state. The voltage application circuit is a drive circuit for a semiconductor switching element according to claim 1, which performs the voltage application operation when the drive unit is in the fourth application state.

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