Short circuit determination device, switch device and short circuit determination method

Abstract

A short circuit determination device is provided, the short circuit determination device comprising: a sensor for detecting a change over time of a main current flowing between a first main terminal and a second main terminal in a switching element having a control terminal, a first main terminal and a second main terminal; and a short circuit determination unit for determining that a short circuit has occurred in the switching element when the change over time of the main current becomes above a first threshold value after a first moment after a control signal for driving the control terminal becomes an on signal.

Description

Technical Field

[0001] The present invention relates to a short circuit determination device, a switch device and a short circuit determination method. Background Art

[0002] Conventionally, there is known a power conversion device that uses a Rogowski coil to detect a short circuit of a switching element (for example, refer to Patent Document 1).

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2001-169533 Summary of the invention

[0006] Technical issues

[0007] In the power converter of Patent Document 1, the voltage between the terminals of the Rogowski coil is integrated, and when the value of the integrated output is detected to be equal to or higher than a certain level, it is determined that the switching element is short-circuited. However, it is desirable to determine that the switching element is short-circuited as early as possible.

[0008] Technical Solution

[0009] In order to solve the above-mentioned problem, in a first embodiment of the present invention, a short circuit determination device is provided. The short circuit determination device may include a sensor that detects the change over time of a main current flowing between the first main terminal and the second main terminal in a switch element having a control terminal, a first main terminal and a second main terminal. The short circuit determination device may include a short circuit determination unit that determines that a short circuit has occurred in the switch element when the change over time of the main current becomes above a first threshold value after a first moment after a control signal for driving the control terminal becomes a conduction signal.

[0010] The short circuit determination unit may include: a timing detection unit that detects a first timing; and a first determination unit that starts determining whether a temporal change in the main current is equal to or greater than a first threshold value when the timing detection unit detects the first timing.

[0011] The timing detection unit may detect, as the first timing, a timing at which the temporal change in the main current becomes equal to or smaller than a second threshold value.

[0012] The timing detection unit may detect, as the first timing, a timing when a predetermined period of time has elapsed since the control signal changed to the on signal.

[0013] The short-circuit determination unit may further include a timing change unit configured to change the length of a preset period based on at least one of the magnitude of the main current, the temperature of the switching element, and the characteristics of the switching element.

[0014] The short-circuit determination unit may further include: an integrator that integrates the change in the main current over time; and a second determination unit that determines whether the switching element is short-circuited based on an output of the integrator.

[0015] The short-circuit determination device may further include a short-circuit current cutoff unit that cuts off the short-circuit current when it is determined that the switching element is short-circuited.

[0016] The sensor may be a Rogowski coil.

[0017] The switching element may be a wide bandgap semiconductor element.

[0018] The wide bandgap semiconductor element may include at least any one of silicon carbide, gallium nitride, gallium oxide, and diamond.

[0019] In a second aspect of the present invention, a switch device is provided. The switch device may include a short-circuit determination device. The switch device may include a switch element.

[0020] In a third aspect of the present invention, a short circuit determination method is provided. The short circuit determination method can determine a short circuit of a switching element having a control terminal, a first main terminal, and a second main terminal. The short circuit determination method can include a step of detecting a change over time of a main current flowing between the first main terminal and the second main terminal. The short circuit determination method can include a step of determining that a short circuit has occurred in the switching element when the change over time of the main current becomes above a first threshold value after a first moment after a control signal for driving the control terminal becomes a conduction signal.

[0021] It should be noted that the above invention summary does not list all the essential features of the present invention. In addition, sub-combinations of these feature groups can also constitute inventions. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 An example of a block diagram of a switch device 10 including the short-circuit determination device 100 according to the present embodiment is shown.

[0023] Figure 2 An example of various signal waveforms when a short circuit occurs during conduction is shown.

[0024] Figure 3 An example of various signal waveforms when a short circuit occurs during steady-state operation is shown.

[0025] Figure 4An example of a block diagram of a switch device 10 including a short-circuit determination device 100 according to a modification of the present embodiment is shown.

[0026] Explanation of symbols

[0027] 10: Switching device

[0028] 20: Switching element

[0029] 22: Control terminal

[0030] 24: First main terminal

[0031] 26: Second main terminal

[0032] 30: Control terminal drive unit

[0033] 100: Short circuit determination device

[0034] 110: Sensor

[0035] 120: Short circuit determination unit

[0036] 130: Short circuit determination unit during steady-state operation

[0037] 132: Time detection unit

[0038] 134: First Judgment Unit

[0039] 140: Short circuit determination unit during conduction

[0040] 142: Integrator

[0041] 144: Second Judgment Unit

[0042] 150: Short circuit signal output

[0043] 160: Short-circuit current cutoff unit

[0044] 410: Time Change Department DETAILED DESCRIPTION

[0045] Hereinafter, the present invention will be described by way of the embodiments of the invention, but the following embodiments do not limit the invention according to the claims. In addition, all combinations of features described in the embodiments are not necessarily essential to the solution of the invention.

[0046] Here, in this specification, expressions such as "disposed between ... and ..." do not limit physical configurations, but also mean "electrically connected to ... and ...". In addition, in this specification, expressions such as "connected" are not limited to direct connection without passing through other elements, but also include indirect connection through other elements.

[0047] Figure 1An example of a block diagram of a switch device 10 having a short circuit determination device 100 according to the present embodiment is shown. In this figure, each module represents a functionally separated functional module, which may not necessarily be consistent with the actual configuration. That is, although it is shown as one module in this figure, it may not necessarily be composed of one circuit or device. In addition, although it is shown as different modules in this figure, these modules may not necessarily be composed of different circuits or devices.

[0048] The switch device 10 includes a switching element 20 , a control terminal driving unit 30 , and a short-circuit determination device 100 .

[0049] As an example, the switch element 20 may be a wide bandgap semiconductor element, which may include at least one of silicon carbide, gallium nitride, gallium oxide, and diamond as a main material. Such a device with a fast switching speed generally tends to have a low short-circuit tolerance. Therefore, by setting such a high-speed device as the object of short-circuit determination, the short-circuit determination device 100 can further improve the effect of this embodiment.

[0050] The switch element 20 has a control terminal 22, a first main terminal 24, and a second main terminal 26, and electrically connects (conducts) or electrically disconnects (shuts off) the first main terminal 24 and the second main terminal 26 according to a voltage or current input to the control terminal 22. As an example, in the present embodiment, the switch element 20 is an nMOS transistor having a gate as the control terminal 22, a drain as the first main terminal 24, and a source as the second main terminal 26, and is turned off when the voltage of the control terminal 22 (also referred to as "bias voltage") based on the second main terminal 26, that is, when the gate-source voltage Vgs is below the gate threshold voltage, for example, and is turned on when the gate-source voltage Vgs exceeds the gate threshold voltage.

[0051] In the following, the case where the switching element 20 is an nMOS transistor is used as an example for explanation, but each embodiment can be applied to various types of switching elements 20, such as a MOS transistor in which the control terminal is called a gate and the two main terminals are called a drain and a source, an IGBT (insulated gate bipolar transistor) in which the control terminal is called a gate and the two main terminals are called a collector and an emitter, and a bipolar transistor in which the control terminal is called a base and the two main terminals are called a collector and an emitter.

[0052] The control terminal driving unit 30 is connected to the control terminal 22, for example, the gate, of the switching element 20. The control terminal driving unit 30 receives power supply from a power supply (not shown) and drives the control terminal 22 of the switching element 20 according to a control signal input from the outside. Thus, the control terminal driving unit 30 switches the conduction / disconnection between the first main terminal 24 and the second main terminal 26 of the switching element 20, for example, between the drain and the source.

[0053] The short-circuit determination device 100 detects the change over time of the main current of the switching element 20, and based on the detected result, determines whether the switching element 20 is short-circuited. At this time, the short-circuit determination device 100 of the present embodiment determines that the switching element 20 is short-circuited when the change over time of the main current becomes greater than a preset threshold value after the first moment after the control signal becomes the on signal.

[0054] The short circuit determination device 100 includes a sensor 110, a short circuit determination unit 120, and a short circuit current cutoff unit 160. Here, the short circuit determination device 100 may be implemented by one or more integrated circuits, or may be implemented by a combination of a plurality of discrete components.

[0055] The sensor 110 detects the time-dependent change of the main current flowing between the first main terminal 24 and the second main terminal 26 in the switching element 20. As an example, the sensor 110 may be a Rogowski coil. Generally, the Rogowski coil is formed by setting an air-core coil around the primary conductor, thereby inducing a voltage corresponding to the primary current flowing in the primary conductor at both ends of the coil. At this time, the induced voltage becomes the time-dependent change of the primary current, that is, the differential waveform (di / dt). Since such a Rogowski coil has no magnetic core and no heat, saturation, and hysteresis caused by magnetic loss, it is preferred. In the present embodiment, as an example, the sensor 110 may be a Rogowski coil provided around a conductor connected to the second main terminal 26, such as the source, in the switching element 20. Moreover, the sensor 110 outputs, for example, the voltage induced at both ends of the Rogowski coil, that is, the time-dependent change of the main current flowing between the first main terminal 24 and the second main terminal 26 in the switching element 20, to the short-circuit determination unit 120.

[0056] The short circuit determination unit 120 determines whether the switching element 20 is short-circuited based on the output of the sensor 110. The short circuit determination unit 120 includes a short circuit determination unit 130 during steady-state operation, a short circuit determination unit 140 during conduction operation, and a short circuit signal output unit 150.

[0057] The short-circuit determination unit 130 in steady-state operation is a module for determining a short circuit of the switching element 20 that occurs in steady-state operation. The short-circuit determination unit 130 in steady-state operation determines that a short circuit has occurred in the switching element 20 when the change in the main current over time becomes greater than or equal to the first threshold value Th1 after the first moment after the control signal for driving the control terminal 22 becomes the on signal. More specifically, the short-circuit determination unit 130 in steady-state operation includes a moment detection unit 132 and a first determination unit 134.

[0058] The moment detection unit 132 detects the first moment. In the present embodiment, the moment detection unit 132 can detect the moment when the change of the main current over time becomes less than the second threshold value Th2 as the first moment. As an example, the moment detection unit 132 can be a comparator, etc., and the output of the sensor 110 can be connected to one input terminal. In addition, the moment detection unit 132 can compare the output of the sensor 110 input to one input terminal, that is, the change of the main current over time, with the second threshold value Th2 input to another input terminal, and when the change of the main current over time becomes less than the second threshold value Th2, the first moment is detected and a detection signal is output to the first determination unit 134.

[0059] When the time detection unit 132 detects the first time, the first determination unit 134 starts to determine whether the change of the main current over time is greater than the first threshold value Th1. As an example, when the first determination unit 134 receives the detection signal from the time detection unit 132, it latches the edge of the detection signal and starts to determine whether the output of the sensor 110, that is, the change of the main current over time is greater than the first threshold value Th1. Then, when it is determined that the change of the main current over time is greater than the first threshold value Th1, the first determination unit 134 determines that a short circuit has occurred in the switching element 20, and outputs a first short circuit detection signal to the short circuit signal output unit 150.

[0060] Thus, the first determination unit 134 starts short-circuit determination with the detection signal supplied from the timing detection unit 132 as a trigger. In other words, the first determination unit 134 does not perform short-circuit determination before the detection signal is supplied from the timing detection unit 132. Therefore, even if, for example, the switching element 20 is short-circuited when it is turned on, and the output of the sensor 110, that is, the change in the main current over time becomes greater than the first threshold value Th1, the first determination unit 134 does not output the first short-circuit detection signal. This will be described later using waveforms.

[0061] The conduction operation short circuit determination unit 140 is a module for determining a short circuit of the switch element 20 that occurs during the conduction operation. When the main current becomes greater than or equal to the third threshold value Th3, the conduction operation short circuit determination unit 140 determines that a short circuit has occurred in the switch element 20. More specifically, the conduction operation short circuit determination unit 140 includes an integrator 142 and a second determination unit 144.

[0062] The integrator 142 is provided between the sensor 110 and the second determination unit 144, and integrates the output of the sensor 110. That is, the integrator 142 integrates the change over time (di / dt) of the main current. Then, the integrator 142 outputs the value of the main current, which is the result of integrating the change over time of the main current, to the second determination unit 144.

[0063] The second determination unit 144 determines whether the switching element 20 is short-circuited based on the output of the integrator 142. As an example, the second determination unit 144 determines whether the value of the main current, which is the output of the integrator 142, is greater than or equal to the third threshold value Th3. Then, when it is determined that the output of the integrator 142 is greater than or equal to the third threshold value Th3, the second determination unit 144 determines that the switching element 20 is short-circuited, and outputs a second short-circuit detection signal to the short-circuit signal output unit 150.

[0064] Here, as described above, the first determination unit 134 starts short-circuit determination by being triggered by the detection signal supplied from the timing detection unit 132. In contrast, the second determination unit 144 is not provided with such a trigger and always performs short-circuit determination. Therefore, when the short circuit of the switching element 20 occurs when the second determination unit 144 is turned on, and the output of the integrator 142 becomes greater than the third threshold value Th3, it is determined that the switching element 20 is short-circuited, and the second short-circuit detection signal is output. This will also be described later using waveforms.

[0065] The short-circuit signal output unit 150 is connected to the first determination unit 134 and the second determination unit 144, and receives the first short-circuit detection signal and the second short-circuit detection signal. The short-circuit signal output unit 150 can be, for example, a logic OR circuit. Moreover, when at least one of the first short-circuit detection signal and the second short-circuit detection signal is input, the short-circuit signal output unit 150 determines that the switching element 20 is short-circuited, and outputs a short-circuit signal to the short-circuit current cutoff unit 160.

[0066] As an example, the short-circuit current cutoff unit 160 is connected to the short-circuit signal output unit 150 and the control terminal 22 of the switch element 20. Furthermore, when a short-circuit signal is supplied from the short-circuit signal output unit 150, that is, when it is determined that the switch element 20 is short-circuited in at least any one of the cases when it is turned on or in a steady-state operation, the short-circuit current cutoff unit 160 cuts off the short-circuit current while suppressing the surge voltage. As an example, the short-circuit current cutoff unit 160 may include a transistor, the control terminal of which is connected to the short-circuit signal output unit 150, one of the main terminals is connected to the control terminal 22 of the switch element 20, and the other main terminal is connected to the second main terminal 26 of the switch element 20. Furthermore, when a short-circuit signal is supplied from the short-circuit signal output unit 150, the short-circuit current cutoff unit 160 may turn on the transistor to reduce the control terminal voltage of the switch element 20, such as the gate-source voltage Vgs, and cut off the short-circuit current. At this time, the short-circuit current cutoff unit 160 can reduce the surge voltage applied to the switching element 20 when the short-circuit current is cut off by gradually reducing the control terminal voltage of the switching element 20, thereby preventing damage to the switching element 20. It should be noted that in this figure, the short-circuit current cutoff unit 160 is shown as a module different from the control terminal drive unit 30, but the short-circuit current cutoff unit 160 can also be configured as a part of the control terminal drive unit 30.

[0067] Figure 2 An example of various signal waveforms in the case of a short circuit during conduction is shown. At time t21, if the control signal becomes an on signal, the control terminal driving unit 30 drives the control terminal 22 of the switching element 20. In response, the control terminal voltage of the switching element 20, such as the gate-source voltage Vgs, starts to rise.

[0068] At time t22, if the control terminal voltage exceeds the gate threshold voltage, the switch element 20 is turned on. Accordingly, the main current of the switch element 20 begins to increase. Therefore, the output of the sensor 110 that detects the change of the main current over time rises at time t22. This figure shows an example of various signal waveforms when the switch element 20 is short-circuited for some reason while the switch element 20 is turned on.

[0069] It should be noted that at time t22, when the switch element 20 is turned on, the output of the sensor 110 becomes equal to or higher than the first threshold Th1. However, at this time point, since the timing detection unit 132 has not yet output a detection signal, the first determination unit 134 does not output a first short-circuit detection signal.

[0070] Here, when the switching element 20 is not short-circuited, that is, in a normal conduction operation, the current flowing through the switching element 20 decreases due to the reverse recovery operation of the freewheeling diode (FWD) of the opposing arm element (not shown), so the output of the sensor 110 takes a negative value. However, when the switching element 20 is short-circuited for some reason, the output of the sensor 110 remains in the state after rising, and the main current continues to increase.

[0071] At time t23, when the value of the main current, which is the output of the integrator 142 that integrates the output of the sensor 110, becomes equal to or greater than the third threshold value Th3, the second determination unit 144 outputs a second short-circuit detection signal to the short-circuit signal output unit 150 as a short-circuit occurs when the switch element 20 is turned on. In response, the short-circuit signal output unit 150 outputs a short-circuit signal to the short-circuit current cutoff unit 160.

[0072] At time t24, after a delay from the short-circuit signal output unit 150 outputting the short-circuit signal to the transition to the cut-off operation, the short-circuit current cut-off unit 160 starts to cut off the short-circuit current. At this time, the short-circuit current cut-off unit 160 reduces the control terminal voltage of the switching element 20. Accordingly, the main current starts to decrease. It should be noted that at this time, the output of the sensor 110 becomes less than the second threshold value Th2, so the timing detection unit 132 outputs a detection signal to the first determination unit 134.

[0073] At time t25, when the control terminal voltage becomes equal to or lower than the gate threshold voltage, the switching element 20 is turned off. Accordingly, the main current of the switching element 20 becomes 0. Therefore, the output of the sensor 110 that detects the temporal change of the main current also becomes 0 at this time.

[0074] As described above, when a short circuit occurs in the switching element 20 while the switching element 20 is turned on, the short-circuit determination device 100 of the present embodiment detects the short circuit of the switching element 20 and cuts off the short-circuit current.

[0075] Figure 3 An example of various signal waveforms when a short circuit occurs during steady-state operation is shown. At time t31, similarly to time t21, if the control signal becomes an on signal, the control terminal driving unit 30 drives the control terminal 22 of the switching element 20. Accordingly, the control terminal voltage of the switching element 20, such as the gate-source voltage Vgs, begins to rise.

[0076] At time t32, similarly to time t22, when the control terminal voltage exceeds the gate threshold voltage, the switch element 20 turns on. Accordingly, the main current of the switch element 20 begins to increase. Therefore, the output of the sensor 110 that detects the temporal change of the main current rises at time t32. Figure 2In FIG. 1 , a case where the switching element 20 is short-circuited while being turned on is described, but in this figure, it is assumed that the switching element 20 is not short-circuited but is normally turned on.

[0077] It should be noted that at time t32, when the switch element 20 is turned on, the output of the sensor 110 becomes equal to or higher than the first threshold Th1. However, at this time point, since the timing detection unit 132 has not yet output a detection signal, the first determination unit 134 does not output a first short-circuit detection signal.

[0078] At time t33, the current flowing through the switch element 20 decreases due to the reverse recovery action of the freewheeling diode (FWD) of the opposing arm element (not shown), so the output of the sensor 110 takes a negative value. Correspondingly, the output of the sensor 110 becomes less than the second threshold value Th2, so the timing detection unit 132 outputs a detection signal to the first determination unit 134. That is, the timing detection unit 132 detects the time t33 as the first time. Thus, the first determination unit 134 starts the short-circuit determination. It should be noted that in this way, when the switch element 20 is not short-circuited and is normally turned on, during the period until time t33, the output of the integrator 142 that integrates the output of the sensor 110, that is, the value of the main current, will not become more than the third threshold value Th3.

[0079] At time t34, the switching element 20 passes through a transition period accompanied by conduction, and starts a steady-state operation.

[0080] Assume that at time t35, for some reason, the switching element 20 is short-circuited. In this way, the main current increases sharply. In response, the output of the sensor 110 that detects the change in the main current over time increases. In addition, when the change in the main current over time becomes greater than the first threshold value Th1, the first determination unit 134 outputs a first short-circuit detection signal to the short-circuit signal output unit 150 as a judgment that the switching element 20 is short-circuited during steady-state operation. In response, the short-circuit signal output unit 150 outputs a short-circuit signal to the short-circuit current cutoff unit 160.

[0081] At time t36, after a delay from the short-circuit signal output unit 150 outputting the short-circuit signal to the transition to the cut-off operation, the short-circuit current cut-off unit 160 starts to cut off the short-circuit current. At this time, the short-circuit current cut-off unit 160 reduces the control terminal voltage of the switching element 20. In response, the main current starts to decrease.

[0082] At time t37, when the control terminal voltage becomes equal to or lower than the on-voltage, the switching element 20 is turned off. Accordingly, the main current of the switching element 20 becomes 0. Therefore, the output of the sensor 110 that detects the temporal change of the main current also becomes 0 at this time.

[0083] In this way, the short-circuit determination device 100 of the present embodiment detects the short-circuit of the switching element 20 and cuts off the short-circuit current when the switching element 20 is short-circuited during steady-state operation. At this time, the short-circuit determination device 100 of the present embodiment determines that the switching element 20 is short-circuited when the change of the main current over time becomes greater than the first threshold value Th1. Therefore, according to the short-circuit determination device 100 of the present embodiment, it is possible to determine at a relatively early stage that the switching element 20 is short-circuited during steady-state operation. That is, assuming that the short-circuit determination unit 140 also performs short-circuit determination during steady-state operation when the conduction operation is desired, at the time t35' when the value obtained by integrating the output of the sensor 110, that is, the main current becomes greater than the third threshold value Th3, it is determined that the switching element 20 is short-circuited. In contrast, according to the short-circuit determination device 100 of the present embodiment, it is possible to determine that the switching element 20 is short-circuited at the time t35 earlier than the time t35'. In addition, the first determination unit 134 of the short-circuit determination device 100 of the present embodiment does not perform short-circuit determination before the first moment, and performs short-circuit determination after the first moment. Therefore, according to the short-circuit determination device of the present embodiment, it is possible to prevent the first determination unit 134 from erroneously determining that the switch element 20 is short-circuited even when the switch element 20 is normally turned on. Figure 2 and Figure 3 As described in , a short circuit occurring during conduction and a short circuit occurring during steady-state operation are determined by different determination units. Therefore, according to the short circuit determination device 100 of this embodiment, a short circuit occurring in either case can be detected at a relatively early time.

[0084] Figure 4 An example of a block diagram of a switch device 10 including a short-circuit determination device 100 according to a modified example of the present embodiment is shown. Figure 4 In the Figure 1 Components with the same functions and configurations are denoted by the same reference numerals, and descriptions thereof will be omitted below except for differences. In the above description, the case where the time detection unit 132 detects the first time based on the temporal change of the main current, which is the output of the sensor 110, is described as an example. However, the present invention is not limited to this.

[0085] In this modification, the timing detection unit 132 detects the first moment without using the output of the sensor 110. As an example, the timing detection unit 132 can obtain the control signal input to the control terminal driving unit 30. Then, the timing detection unit 132 detects the moment when the control signal becomes the on signal and reaches the preset period as the first moment. In more detail, the timing detection unit 132 can be, for example, a timer, and the timer can be started when the control signal becomes the on signal, and the moment when the preset period is reached can be detected as the first moment.

[0086] Here, the preset period may be, for example, the period from when the control signal becomes the on signal to when the reverse recovery of the freewheeling diode is completed when the switching element 20 is normally turned on without short circuit. Such a period may be, for example, a period preset based on experiments and / or simulations.

[0087] Furthermore, in this modification, the short-circuit determination unit 130 in the steady-state operation may further include a timing change unit 410 .

[0088] The time change unit 410 can be connected to the time detection unit 132. As an example, the time change unit 410 can change the length of the pre-set period based on at least any one of the magnitude of the main current, the temperature of the switching element 20, and the characteristics of the switching element 20. Moreover, the time change unit 410 can notify the time detection unit 132 of information related to the length of the changed period. Thus, the time detection unit 132 can detect the first moment based on the changed period. Usually, the period from the control signal becoming the conduction signal to the completion of the recovery of the freewheeling diode depends on the use environment and / or characteristics of the switching element 20. Therefore, by optimizing the period based on at least any one of the magnitude of the main current, the temperature of the switching element 20, and the characteristics of the switching element 20 by the time change unit 410, the short-circuit determination device 100 of this modified example can optimize the moment when the first determination unit 134 starts the short-circuit determination in accordance with the use environment and / or characteristics of the switching element 20.

[0089] It should be noted that the detection signal needs to reset the output to the first determination unit 134 in preparation for the next conduction when the switch element 20 is normally turned off. The detection signal can automatically reset the output when it is output for a certain period of time, or it can be reset when the output of the sensor 110 becomes negative due to the turning off of the switch element. Figure 4 In the embodiment, the output of the detection signal to the first determination unit 134 may be reset using the control signal input to the control terminal driving unit 30 .

[0090] The present invention has been described above using the embodiments, but the technical scope of the present invention is not limited to the scope described in the above embodiments. It is obvious to those skilled in the art that various changes or improvements can be made to the above embodiments. According to the description of the claims, the method of making such changes or improvements can also be included in the technical scope of the present invention.

[0091] It should be noted that the execution order of each process such as actions, sequences, steps and stages in the apparatus, system, program and method shown in the claims, specifications and drawings can be implemented in any order unless it is specifically stated "before...", "in advance", etc., and the result of the previous process is not used in the subsequent process. Even if the action flow in the claims, specifications and drawings is described using "first", "next", etc. for convenience, it does not mean that it must be implemented in this order.

Claims

1. A short circuit determination device, It is characterized in that have: a sensor for detecting a change over time in a main current flowing between a first main terminal and a second main terminal in a switching element having a control terminal, a first main terminal, and a second main terminal; as well as a short-circuit determination unit having a first determination unit configured to determine that the switching element is short-circuited only when the change in the main current over time becomes equal to or greater than a first threshold value after a first time after a control signal for driving the control terminal becomes an on signal, The short-circuit determination unit includes a timing detection unit that compares the temporal change of the main current with a second threshold value and detects the first timing when the temporal change of the main current becomes equal to or less than the second threshold value.

2. The short circuit determination device according to claim 1, It is characterized in that The first determination unit starts determining whether the temporal change of the main current is equal to or greater than the first threshold value when the timing detection unit detects the first timing.

3. The short circuit determination device according to claim 1 or 2, It is characterized in that The short circuit determination unit further comprises: an integrator that integrates the change of the main current over time; and A second determination unit determines whether the switching element is short-circuited based on the output of the integrator.

4. The short-circuit determination device according to any one of claims 1 to 3, It is characterized in that The short-circuit determination device further includes a short-circuit current cutoff unit configured to cut off a short-circuit current when it is determined that a short circuit has occurred in the switching element.

5. The short-circuit determination device according to any one of claims 1 to 4, It is characterized in that The sensor is a Rogowski coil.

6. The short-circuit determination device according to any one of claims 1 to 5, It is characterized in that The switch element is a wide bandgap semiconductor element.

7. The short circuit determination device according to claim 6, It is characterized in that The wide bandgap semiconductor element includes at least any one of silicon carbide, gallium nitride, gallium oxide and diamond.

8. A switch device, It is characterized in that have: The short-circuit determination device according to any one of claims 1 to 7; and The switching element.

9. A short circuit determination method, It is characterized in that determining whether a switching element having a control terminal, a first main terminal, and a second main terminal is short-circuited; The short circuit determination method comprises: detecting a change over time of a main current flowing between the first main terminal and the second main terminal; comparing the temporal change of the main current with a second threshold value, and detecting a first time when the temporal change of the main current becomes less than or equal to the second threshold value; and Only when the change in the main current over time becomes equal to or greater than a first threshold after the first time point after the control signal for driving the control terminal becomes an on signal, it is determined that the switching element is short-circuited.

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