Drive unit and power converter

Abstract

To solve the problem that an arm short circuit occurs due to delay in stopping turn-on when switching is controlled according to an operation waveform of an element to be turned on.SOLUTION: A drive device includes: a detection unit that detects whether a first switching element is in the ON state or the OFF state based on a terminal current flowing through a control terminal of the first switching element; a driving unit that drives a control terminal of a second switching element connected in series with the first switching element according to an input drive signal; and a short circuit prevention unit that maintains the second switching element in the OFF state in response to the first switching element being in the ON state.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a drive device and a power conversion device.

Background Art

[0002] Conventionally, as a technique for preventing an arm short circuit in which both switching elements connected in series are in an on state, a technique has been proposed in which turn-on is aborted in response to the occurrence of a sign of an arm short circuit in the operation waveform of the switching element to be turned on (see, for example, Patent Document 1). Patent Document 1 Japanese Unexamined Patent Application Publication No. 2019-216540

Summary of the Invention

Problems to be Solved by the Invention

[0003] However, when controlling switching according to the operation waveform of the element to be turned on, there is a risk that an arm short circuit may occur because the turn-on cannot be aborted in time.

Means for Solving the Problems

[0004] In order to solve the above problems, in a first aspect of the present invention, a drive device is provided. The drive device may include a detection unit that detects whether the first switching element is in an on state or an off state based on a terminal current flowing through a control terminal of the first switching element. The drive device may include a drive unit that drives a control terminal of a second switching element connected in series with the first switching element in response to an input drive signal. The drive device may include a short-circuit prevention unit that maintains the second switching element in an off state in response to the first switching element being in an on state.

[0005] The detection unit may have a measurement unit that measures a parameter corresponding to the terminal current.

[0006] The measurement unit may have a Rogowski coil provided at a control terminal of the first switching element.

[0007] The detection unit may have a hold unit that holds information indicating that the first switching element is in the ON state when a parameter corresponding to the terminal current falls outside a first reference range, and holds information indicating that the first switching element is in the OFF state when a parameter corresponding to the terminal current falls outside a second reference range.

[0008] The parameter corresponding to the terminal current may be the voltage generated by the terminal current. The first reference range may have an upper limit greater than the peak value of the induced voltage generated by the terminal current when the first switching element is turned off without a short circuit. The second reference range may have a lower limit less than the peak value of the induced voltage generated by the terminal current when the first switching element is turned on without a short circuit.

[0009] The short-circuit prevention unit may supply a drive signal to the drive unit corresponding to the control signal that controls the on / off state of the second switching element when the first switching element is in the off state. The short-circuit prevention unit may supply a drive signal to the drive unit to turn off the second switching element regardless of the control signal when the first switching element is in the on state.

[0010] The short-circuit prevention unit may have a calculation unit that performs a logical AND operation between a control signal indicating that the second switching element is turned off and a signal indicating that the detection unit has detected that the first switching element is in the off state.

[0011] The drive unit may include an output unit that outputs a control signal and a notification signal indicating whether or not the control signal and the drive signal match.

[0012] In a second embodiment of the present invention, a power converter is provided. The power converter may include a first switching element and a second switching element connected in series. The power converter may include a drive device according to the first embodiment.

[0013] The first switching element and the second switching element may be wide-bandgap semiconductor elements.

[0014] It should be noted that the above summary of the invention does not list all the necessary features of the present invention. Furthermore, subcombinations of these features may also constitute an invention. [Brief explanation of the drawing]

[0015] [Figure 1] A power conversion device 1 according to an embodiment is shown. [Figure 2] This shows the operating waveform of power converter 1 under normal conditions. [Figure 3] The operating waveform of the power converter 1 when the first switching element 11 is turned ON due to a malfunction is shown. [Figure 4] This shows the operating waveform of the power converter 1 when the first switching element 11 is turned on due to an incorrect control signal. [Figure 5] This shows the operating waveform of the power converter 1 when the second switching element 12 is turned on due to an incorrect control signal. [Modes for carrying out the invention]

[0016] The present invention will be described below through embodiments of the invention, but these embodiments are not intended to limit the invention as defined in the claims. Furthermore, not all combinations of features described in the embodiments are necessarily essential to the solution of the invention.

[0017] Figure 1 shows a power converter 1 according to this embodiment. In the figure, the white arrow symbols indicate voltage.

[0018] The power converter 1 shows, as an example, one phase of a power converter used for motor drive or power supply. By switching the connection between the positive power line 101 and the negative power line 102 and the power output terminal 105, it outputs a converted voltage from the power output terminal 105.

[0019] Here, a DC voltage Ed of, for example, 600-800V is applied between the positive power line 101 and the negative power line 102.

[0020] The power converter 1 comprises a first switching element 11 and a second switching element 12, a drive unit 2 associated with the first switching element 11, and a drive unit 5 associated with the second switching element 12. Note that the configuration of the drive unit 2 is the same as that of the drive unit 5, so its description is omitted.

[0021] The first switching element 11 and the second switching element 12 are connected sequentially in series between the positive power line 101 and the negative power line 102. A power output terminal 105 may be connected to the midpoint between the first switching element 11 and the second switching element 12.

[0022] The first switching element 11 and the second switching element 12 are switching elements that can be switched on or off by the drive unit 2 and the drive unit 5, respectively. The first switching element 11 and the second switching element 12 may constitute the upper arm and the lower arm of the power converter 1.

[0023] At least one of the first switching element 11 and the second switching element 12 may be a wide-bandgap semiconductor element. A wide-bandgap semiconductor element is a semiconductor element with a larger bandgap than a silicon semiconductor element, and includes, for example, SiC, GaN, diamond, gallium nitride-based materials, gallium oxide-based materials, AlN, AlGaN, or ZnO. Wide-bandgap semiconductor elements can improve the switching speed compared to silicon semiconductor elements.

[0024] In this embodiment, the first switching element 11 and the second switching element 12 are MOSFETs and have parasitic diodes with the positive power supply line 101 side as the cathode. The first switching element 11 and the second switching element 12 can also be replaced with semiconductor elements of other structures, such as IGBTs or bipolar transistors, and diodes, Schottky barrier diodes, etc., can be connected in antiparallel to each semiconductor element as needed.

[0025] The drive unit 5 drives the second switching element 12 based on the input signal. For example, when the drive unit 5 works in cooperation with the drive unit 2 to alternately turn on the first switching element 11 and the second switching element 12, it turns off one element to switch it to the off state, and then turns on the other element. The drive unit 5 includes a drive unit 50, a detection unit 51, a short-circuit prevention unit 52, and an output unit 53. Note that each part of the drive unit 5 may be provided on a gate drive unit (GDU) substrate (not shown).

[0026] The drive unit 50 is connected to the control terminal (also referred to as the gate terminal) of the second switching element 12 and drives the gate terminal of the second switching element 12 according to the input drive signal. This turns the second switching element 12 on or off. The drive signal may be input to the drive unit 50 from the short-circuit prevention unit 52, which will be described later.

[0027] The detection unit 51 detects whether the first switching element 11 is in an ON state or an OFF state based on the terminal current (also called gate current) flowing through the control terminal of the first switching element 11. The first switching element 11 being in an ON state may mean that the first switching element 11 is in an ON state due to normal drive control, or it may mean that the first switching element 11 is mistakenly in an ON state due to a malfunction in the first switching element 11 or the drive device 2, etc. The detection unit 51 may have a measurement unit 510 and a hold unit 511.

[0028] The measurement unit 510 measures a parameter corresponding to the gate current. In this embodiment, as an example, the parameter corresponding to the gate current may be the voltage generated by the gate current. The measurement unit 510 may have a Rogowski coil provided at the gate terminal of the first switching element 11, and may measure the induced voltage generated in the Rogowski coil by the gate current. The measured induced voltage may represent the derivative of the gate current, that is, the rate of change over time. The measurement unit 510 may supply the measurement result to the hold unit 511.

[0029] The hold unit 511 holds information indicating the state of the first switching element 11 based on the measurement results from the measurement unit 510. If the measurement results from the measurement unit 510 indicate that the first switching element 11 is in the ON state, the hold unit 511 may hold information indicating that the first switching element 11 is in the ON state until the measurement results from the measurement unit 510 indicate that the first switching element 11 is in the OFF state. Similarly, if the measurement results from the measurement unit 510 indicate that the first switching element 11 is in the OFF state, the hold unit 511 may hold information indicating that the first switching element 11 is in the OFF state until the measurement results from the measurement unit 510 indicate that the first switching element 11 is in the ON state.

[0030] The hold unit 511 may output a signal corresponding to the information to be held. In this embodiment, as an example, the hold unit 511 may supply a signal (also called a detection signal) to the short-circuit prevention unit 52 indicating whether the first switching element 11 is in an ON state or an OFF state.

[0031] The short-circuit prevention unit 52 prevents a short circuit between the positive power line 101 and the negative power line 102, a so-called arm short circuit. The short-circuit prevention unit 52 may receive an external control signal to control the on / off state of the second switching element 12, and may supply a drive signal to the drive unit 50 to drive the second switching element 12. The short-circuit prevention unit 52 may receive a control signal (not shown) that controls the power converter 1.

[0032] The short-circuit prevention unit 52 may maintain the second switching element 12 in the off state depending on whether the first switching element 11 is in the ON state. When the first switching element 11 is in the ON state, the short-circuit prevention unit 52 may supply a drive signal to the drive unit 50 to turn off the second switching element 12, regardless of the control signal.

[0033] Furthermore, if the first switching element 11 is in the off state, the short-circuit prevention unit 52 may supply a drive signal corresponding to the control signal to the drive unit 50. The drive signal corresponding to the control signal may be a drive signal corresponding to the on / off control content indicated by the control signal. For example, if the control signal is to turn on the second switching element 12, the short-circuit prevention unit 52 may supply a drive signal to the drive unit 50 indicating that the second switching element 12 is in the on state. Similarly, if the control signal is to turn off the second switching element 12, the short-circuit prevention unit 52 may supply a drive signal to the drive unit 50 indicating that the second switching element 12 is in the off state. In this embodiment, as an example, the short-circuit prevention unit 52 may supply a high-level drive signal to the drive unit 50 when the control signal is high level, and a low-level drive signal to the drive unit 50 when the control signal is low level.

[0034] The short-circuit prevention unit 52 may have an arithmetic unit 520 that takes a logical AND of a control signal to turn off the second switching element 12 and a signal indicating that the detection unit 51 has detected that the first switching element 11 is in the off state. For example, the arithmetic unit 520 may be an AND gate.

[0035] In this embodiment, for example, the control signal may indicate ON when it is high and OFF when it is low, and the detection signal of the detection unit 51 may indicate that the first switching element 11 is ON when it is high and indicate that the first switching element 11 is OFF when it is low. In this case, the calculation unit 520 may take the logical AND of the control signal and the inverted signal of the detection signal. The calculation unit 520 may supply a signal indicating the calculation result to the drive unit 50 as a drive signal.

[0036] The output unit 53 outputs a notification signal indicating whether the control signal supplied to the drive device 5 matches the drive signal supplied to the drive unit 50. The output unit 53 may include a calculation unit 530 and a hold unit 531.

[0037] The arithmetic unit 530 may be an XOR gate, and may perform the exclusive OR operation between the control signal and the drive signal. The arithmetic unit 530 may supply a signal indicating the calculation result to the hold unit 531.

[0038] The hold unit 531 retains information indicating that no abnormality has occurred if the signal from the calculation unit 530 indicates that the control signal and the drive signal are not different. Furthermore, the hold unit 531 continues to retain information indicating that an abnormality has occurred if the signal from the calculation unit 530 indicates at least one time point that the control signal and the drive signal are different. The hold unit 531 may supply a signal indicating the information to be retained to the control device (not shown). As a result, if the hold unit 531 retains information indicating an abnormality, a notification signal to that effect is supplied to the control device.

[0039] According to the power conversion device 1 described above, the second switching element 12 connected in series with the first switching element 11 is kept in the off state when the first switching element 11 is in the ON state. Therefore, it is possible to prevent arm short circuits caused by the second switching element 12 being turned on when the first switching element 11 is in the ON state. Furthermore, unlike the conventional method in which the turn-on of the second switching element 12 is stopped in response to signs of arm short-circuit in the operating waveform during the turn-on period of the second switching element 12, this method reliably prevents arm short-circuit regardless of the switching speed. Furthermore, the state of the first switching element 11 is detected based on the gate current of the first switching element 11. Therefore, unlike the case where the state of the first switching element 11 is detected based on the element voltage or gate voltage of the first switching element 11, there is no need to shift the potential of the detection signal by an isolation circuit or the like in accordance with the control potential of the second switching element 12. Therefore, the detection signal can be transmitted quickly without delay caused by shifting the potential of the detection signal, thus preventing arm short circuits more reliably. In addition, the measurement unit 510 can be made smaller compared to the case where the state of the first switching element 11 is detected based on the element current of the first switching element 11, which is a larger current than the gate current, and thus the drive device 5 can be made smaller. Furthermore, the measurement unit 510 can be easily incorporated into the gate drive unit (GDU) board.

[0040] Furthermore, since parameters corresponding to the gate current of the first switching element 11 are measured, it is possible to reliably detect whether the first switching element 11 is in the ON state or the OFF state.

[0041] Furthermore, since the first switching element 11 has a Rogowski coil provided at its gate terminal, parameters corresponding to the gate current are measured while electrically isolated from the gate terminal of the first switching element 11. Therefore, there is no need to shift the potential of the measurement signal by an isolation circuit or the like in accordance with the control potential of the second switching element 12, thus eliminating delays caused by shifting the potential and enabling rapid transmission of the measurement signal. Consequently, it is possible to quickly detect whether the first switching element 11 is in the ON state or the OFF state and use this information for control. Furthermore, since the Rogowski coil does not have a core, the drive unit 5 can be made smaller compared to cases where other current sensors with a core are used. In addition, the measurement unit 510 can be easily incorporated into the gate drive unit (GDU) substrate.

[0042] Furthermore, when the first switching element 11 is in the off state, a drive signal corresponding to the control signal for the second switching element 12 is supplied from the short-circuit prevention unit 52 to the drive unit 50. Therefore, when the first switching element 11 is in the off state, the second switching element 12 is driven as instructed by the control signal. Also, when the first switching element 11 is in the on state, a drive signal to turn off the second switching element 12 is supplied from the short-circuit prevention unit 52 to the drive unit 50, regardless of the control signal. Therefore, when no arm short circuit occurs, the second switching element 12 is driven according to the control signal, and when an arm short circuit occurs, the second switching element 12 can be kept in the off state.

[0043] Furthermore, the short-circuit prevention unit 52 performs a logical AND operation between a control signal to turn off the second switching element 12 and a signal indicating that the detection unit 51 has detected that the first switching element 11 is in the off state. Therefore, based on whether the first switching element 11 is in the on state or the off state, it is possible to reliably switch between driving the second switching element 12 as instructed by the control signal or maintaining the second switching element 12 in the off state regardless of the control signal.

[0044] Furthermore, an alert signal indicating whether the control signal and the drive signal match is output from the output unit 53. Therefore, it is possible to notify the user if an abnormality has occurred in the power converter 1.

[0045] Figure 2 shows the operating waveform of the power converter 1 under normal conditions. In this embodiment, as an example, the control signal and drive signal indicate an ON state when they are high and an OFF state when they are low. The detection signal indicates that the first switching element 11 is ON when it is high and an OFF state when it is low.

[0046] First, at time T1, control signal S1 for the first switching element 11 _11、and in response to the drive signal (not shown) becoming high level, the gate current Ig of the first switching element 11 _11 increases, and the first switching element 11 is turned on. Also, a positive induced voltage Vcoil is generated in the Rogowski coil of the measurement unit 510 by the gate current Ig _11 .

[0047] Next, when the induced voltage Vcoil is outside the first reference range at time point T2, in response to this, the hold unit 511 holds information indicating that the first switching element 11 is in the on state. In the present embodiment, as an example, the first reference range may have an upper limit value V1, and the induced voltage Vcoil may be outside the first reference range by exceeding the upper limit value V1. The upper limit value V1 may be larger than the peak value Vs1 of the induced voltage Vcoil generated by the gate current when the first switching element 11 is turned off without a short circuit occurring. The first reference range may have a lower limit value of 0 or less.

[0048] When the information indicating that the first switching element 11 is in the on state is held in the hold unit 511, the detection signal S2 output from the hold unit 511 _12 becomes high level indicating that the first switching element 11 is in the on state. As a result, the logical product of the inverted signal Inv(S2 _12 ) and the control signal S1 for the second switching element 12 _12 becomes low level regardless of the control signal S1 _12 . As a result, the drive signal S3 output from the short-circuit prevention unit 52 to the second switching element 12 _12 becomes low level regardless of the control signal S1 _12 , and an arm short circuit due to the turn-on of the second switching element 12 is prevented. _12

[0049] Note that at time point T3 within the on period of the first switching element 11, the gate current Ig _11 ​As the voltage begins to decrease, the induced voltage Vcoil reaches a negative peak value Vs2. However, since the peak value Vs2 is within the second reference range described later, the information held in the hold unit 511 remains unchanged.

[0050] Next, at time T5, the control signal S1 for the first switching element 11 _11 Consequently, as the drive signal (not shown) becomes low level, the gate current Ig of the first switching element 11 decreases. _11 The gate current Ig decreases, and the first switching element 11 is turned off. _11 This generates a negative induced voltage Vcoil in the Rogowski coil of the measuring unit 510.

[0051] Next, if the induced voltage Vcoil falls outside the second reference range at time T6, the hold unit 511 accordingly retains information indicating that the first switching element 11 is in the off state. In this embodiment, for example, the second reference range may have a lower limit V2, and the induced voltage Vcoil may fall outside the second reference range if it falls below the lower limit V2. The lower limit V2 may be smaller than the peak value Vs2 of the induced voltage Vcoil generated by the gate current when the first switching element 11 is turned on without a short circuit. The second reference range may have an upper limit of 0 or more.

[0052] When the information that the first switching element 11 is in the off state is held in the hold unit 511, a detection signal S2 is output from the hold unit 511. _12 This becomes a low level, indicating that the first switching element 11 is in the off state. As a result, detection signal S2 _12 The inverted signal Inv(S2 _12 ) and the control signal S1 for the second switching element 12 _12 The logical AND of this is the control signal S1 _12 The signal level will be adjusted accordingly. As a result, the short-circuit prevention unit 52 controls the control signal S1 _12 Drive signal S3 corresponding to the drive signal S3 _12 A low-level signal (in this case, an OFF signal) is output to the second switching element 12.

[0053] Furthermore, at time T7 during the off period of the first switching element 11, the gate current Ig _11 As the voltage begins to increase, the induced voltage Vcoil reaches a positive peak value Vs1. However, since the peak value Vs1 is within the first reference range, the information held in the hold unit 511 remains unchanged.

[0054] Then, at time T8, the control signal S1 for the second switching element 12 _12 When the level becomes high, the short-circuit prevention unit 52 receives a high-level drive signal S3 _12 This is output to the second switching element 12. As a result, the second switching element 12 is turned on.

[0055] According to the above operation, information that the first switching element 11 is in the ON state is retained in the hold unit 511 in response to the induced voltage Vcoil being outside the first reference range, and the gate current Ig _11 When the induced voltage Vcoil generated by this process falls outside the second reference range, information indicating that the first switching element 11 is in the off state is stored in the hold unit 511. Therefore, whether the first switching element 11 is in the on state or the off state can be accurately detected by measuring the induced voltage Vcoil.

[0056] Furthermore, the first reference range has an upper limit V1 that is greater than the peak value Vs1 of the induced voltage Vcoil generated at the gate terminal when the first switching element 11 is turned off without a short circuit occurring. Therefore, unlike the case where the upper limit V1 of the first reference range is less than or equal to the peak value Vs1, it is possible to prevent the first switching element 11 from being mistakenly detected as being in the turned-on state due to the induced voltage Vcoil when the first switching element 11 is turned off. Furthermore, the second reference range has a lower limit V2 that is smaller than the peak value V2 of the induced voltage Vcoil generated at the gate terminal when the first switching element 11 is turned on without a short circuit. Therefore, unlike the case where the lower limit V2 of the second reference range is equal to or greater than the peak value Vs2, it is possible to prevent the first switching element 11 from being mistakenly detected as being in a turned-off state due to the induced voltage Vcoil when the first switching element 11 is turned on.

[0057] Figure 3 shows the operating waveform of the power converter 1 when the first switching element 11 is turned ON due to a failure.

[0058] First, at time T10, during the period when both the first switching element 11 and the second switching element 12 are in the off state (also called the dead time), if a fault such as a gate-source short circuit occurs in the first switching element 11, the gate current Ig of the first switching element 11 will be affected. _11 The current increases and continues to flow, causing the first switching element 11 to turn on.

[0059] Also, the gate current Ig _11 This generates a positive induced voltage Vcoil in the Rogowski coil of the measurement unit 510, and the induced voltage Vcoil exceeds the upper limit V1, falling outside the first reference range. Accordingly, information indicating that the first switching element 11 is in the ON state is held in the hold unit 511, resulting in the output of a detection signal S2 from the hold unit 511. _12 This will be at a high level.

[0060] Next, at time T11, control signal S1 for the first switching element 11 _11 Consequently, the drive signal (not shown) becomes high level. However, in this example of operation, the gate current Ig of the first switching element 11 is already high. _11 As the value increases, the information that the first switching element 11 is in the ON state is held in the hold unit 511, so this control signal S1 _11 Therefore, the control of the second switching element 12 is not affected.

[0061] Furthermore, at time T15, the control signal S1 for the first switching element 11 _11 Consequently, the drive signal (not shown) becomes low level. However, in this example of operation, the gate current Ig is affected by the failure of the first switching element 11. _11 The voltage does not decrease, and the first switching element 11 remains in the ON state.

[0062] Then, at time T18, the control signal S1 for the second switching element 12 _12 The level becomes high. However, in this example of operation, the detection signal S2 output from the hold unit 511 _12 Because the level is high, detection signal S2 _12 The inverted signal Inv(S2 _12 ) and the control signal S1 for the second switching element 12 _12 The logical AND of this results in a low level. As a result, the drive signal S3 is output from the short-circuit prevention unit 52 to the second switching element 12. _12 is the control signal S1 _12 Regardless, the level remains low, preventing arm short-circuiting due to the turn-on of the second switching element 12. Also, notification signal S4 _12 The signal level becomes high, and the control signal S1 _12 and drive signal S3 _12 It is reported that they do not match.

[0063] Figure 4 shows the operating waveform of the power converter 1 when the first switching element 11 is turned on due to an incorrect control signal.

[0064] First, at time T20 within the dead time (in this example, a time after the aforementioned times T1 to T7), a control signal S1 to the first switching element 11 is issued due to a failure of the control device or the like. _11 When it reaches a high level, the gate current Ig of the first switching element 11 _11 The voltage increases, and the first switching element 11 is turned on.

[0065] Also, the gate current Ig _11This generates a positive induced voltage Vcoil in the Rogowski coil of the measurement unit 510, causing the induced voltage Vcoil to fall outside the first reference range. Accordingly, information indicating that the first switching element 11 is in the ON state is retained in the hold unit 511, resulting in the output of a detection signal S2 from the hold unit 511. _12 This will be at a high level.

[0066] Then, at time T28, the control signal S1 for the second switching element 12 _12 The level becomes high. However, in this example of operation, the detection signal S2 output from the hold unit 511 _12 Because the level is high, detection signal S2 _12 The inverted signal Inv(S2 _12 ) and the control signal S1 for the second switching element 12 _12 The logical AND of this results in a low level. As a result, the drive signal S3 is output from the short-circuit prevention unit 52 to the second switching element 12. _12 is the control signal S1 _12 Regardless, the level remains low, preventing arm short-circuiting due to the turn-on of the second switching element 12. Also, notification signal S4 _12 The signal level becomes high, and the control signal S1 _12 and drive signal S3 _12 It is reported that they do not match.

[0067] Figure 5 shows the operating waveform of the power converter 1 when the second switching element 12 is turned on due to an incorrect control signal.

[0068] First, at time T30 (in this example, a time after the aforementioned times T1 to T3) during the period when the first switching element 11 is already in the ON state, a control signal S1 is issued to the second switching element 12 due to a failure of the control device or the like. _12 The signal level becomes high. However, in this example, the first switching element 11 is already in the ON state, and the detection signal S2 output from the hold unit 511 is high. _12 Because the level is high, detection signal S2 _12 The inverted signal Inv(S2 _12) and the control signal S1 for the second switching element 12 _12 The logical AND of this results in a low level. As a result, the drive signal S3 is output from the short-circuit prevention unit 52 to the second switching element 12. _12 is the control signal S1 _12 Regardless, the level remains low, preventing arm short-circuiting due to the turn-on of the second switching element 12. Also, notification signal S4 _12 The signal level becomes high, and the control signal S1 _12 and drive signal S3 _12 It is reported that they do not match.

[0069] Next, at time T31, control signal S1 for the second switching element 12 _12 The signal becomes low. However, in this example of operation, the second switching element 12 is already in the off state, so this control signal S1 _12 Therefore, the control of the second switching element 12 is not affected.

[0070] Next, at time T35, the control signal S1 for the first switching element 11 _11 Consequently, as the drive signal (not shown) becomes low level, the gate current Ig of the first switching element 11 decreases. _11 The gate current Ig decreases, and the first switching element 11 is turned off. _11 This generates a negative induced voltage Vcoil in the Rogowski coil of the measuring unit 510.

[0071] Next, when the induced voltage Vcoil falls outside the second reference range at time T36, the hold unit 511 holds information indicating that the first switching element 11 is in the off state, resulting in the output of a detection signal S2 from the hold unit 511. _12 This results in a low level for the detection signal S2 _12 The inverted signal Inv(S2 _12 ) and the control signal S1 for the second switching element 12 _12 The logical AND of this is the control signal S1 _12 The signal level will be adjusted accordingly.

[0072] Then, at time T38, the control signal S1 for the second switching element 12 _12 When the level becomes high, the short-circuit prevention unit 52 receives a high-level drive signal S3 _12 This is output to the second switching element 12. As a result, the second switching element 12 is turned on.

[0073] In the embodiments described above, the drive unit 5 was described as having an output unit 53, but it does not have to have an output unit 53. Also, in the embodiments described above, the output unit 53 was described as having a hold unit 531, but it does not have to have a hold unit 531.

[0074] Furthermore, although the measurement unit 510 has been described as having a Rogowski coil, it may also have other sensors that measure parameters corresponding to the gate current.

[0075] Although the present invention has been described above using embodiments, the technical scope of the present invention is not limited to the scope described in the above embodiments. It will be apparent to those skilled in the art that various modifications or improvements can be made to the above embodiments. It will be clear from the claims that such modified or improved forms may also be included in the technical scope of the present invention.

[0076] It should be noted that the execution order of operations, procedures, steps, and stages in the apparatus, systems, programs, and methods shown in the claims, specifications, and drawings is not explicitly stated as "before," "prior to," etc., and that these can be implemented in any order unless the output of a previous process is used in a later process. Even if the operation flow in the claims, specifications, and drawings is described using phrases such as "first," "next," etc. for convenience, it does not mean that it is essential to perform the operations in that order. [Explanation of symbols]

[0077] 1. Power converter 2. Drive unit 5. Drive unit 11. First switching elements 12. Related to the second switching 50 Drive unit 51 Detection unit 52 Short-circuit prevention section 53 Output section 101 Positive power line 102 Negative power line 105 Power output terminal 510 Measuring section 511 Holding section 520 Arithmetic unit 530 Arithmetic unit 531 Holding section

Claims

1. A detection unit that detects whether the first switching element is in an on state or an off state based on the terminal current flowing through the control terminal of the first switching element, A drive unit that drives the control terminal of a second switching element connected in series with the first switching element in response to an input drive signal, A short-circuit prevention unit that maintains the second switching element in the off state in accordance with the ON state of the first switching element, Equipped with, The detection unit has a hold unit that holds information indicating that the first switching element is in the ON state when the parameter corresponding to the terminal current falls outside a first reference range, and a hold unit that holds information indicating that the first switching element is in the OFF state when the parameter corresponding to the terminal current falls outside a second reference range. The parameter corresponding to the terminal current is the voltage generated by the terminal current, The first reference range has an upper limit greater than the peak value of the induced voltage generated by the terminal current when the first switching element is turned off without a short circuit occurring. The drive device wherein the second reference range has a lower limit that is smaller than the peak value of the induced voltage generated by the terminal current when the first switching element is turned on without a short circuit occurring.

2. A detection unit that detects whether the first switching element is in an on state or an off state based on the terminal current flowing through the control terminal of the first switching element, A drive unit that drives the control terminal of a second switching element connected in series with the first switching element in response to an input drive signal, A short-circuit prevention unit that receives a control signal to control the on / off state of the second switching element, and, depending on whether the first switching element is in the off state, supplies the drive unit with the drive signal corresponding to the said control signal, and depending on whether the first switching element is in the on state, supplies the drive unit with the drive signal to turn off the second switching element, thereby maintaining the second switching element in the off state. An output unit that outputs a notification signal indicating whether the control signal and the drive signal match, Equipped with, The output unit has a hold unit that holds information indicating that no abnormality has occurred when the control signal and the drive signal match, and holds information indicating that an abnormality has occurred when they do not match at least once.

3. The drive device according to claim 1 or 2, wherein the detection unit has a measurement unit that measures a parameter corresponding to the terminal current.

4. The drive device according to claim 3, wherein the measuring unit has a Rogowski coil provided at the control terminal of the first switching element.

5. The aforementioned short-circuit prevention unit is When the first switching element is in the off state, the drive unit is supplied with the drive signal corresponding to the control signal that controls the on / off state of the second switching element. The drive device according to any one of claims 1 to 4, wherein when the first switching element is in the ON state, the drive unit is supplied with a drive signal indicating that the second switching element will be turned OFF regardless of the control signal.

6. The drive device according to claim 5, wherein the short-circuit prevention unit has a calculation unit that takes the logical AND of the control signal to turn off the second switching element and the signal indicating that the detection unit has detected that the first switching element is in the off state.

7. A first switching element and a second switching element connected in series, A drive device according to any one of claims 1 to 6, A power conversion device equipped with the following features.

8. The power conversion device according to claim 7, wherein the first switching element and the second switching element are wide-bandgap semiconductor elements.

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