Gate driver for power semiconductor device and power conversion device

Abstract

To suppress unbalance of a voltage to be applied to an element by aligning switching timing regarding an ON operation and an OFF operation of each power semiconductor element even if there is variations in gate signal transmission time or power semiconductor element characteristics, in a gate drive device for a plurality of power semiconductor elements connected in series and a power conversion device comprising the same.SOLUTION: A gate drive device for a plurality of power semiconductor elements QA and QB connected in series, comprises: gate drive voltage varying units 11-A and 11-B which are provided correspondingly to the power semiconductor elements QA and QB and output variable gate drive voltages; gate lines 12-A and 12-B for supplying the gate drive voltages outputted from the gate drive voltage varying units 11-A and 11-B to gate terminals of the corresponding power semiconductor elements QA and QB; and a magnetic coupling unit 13 for magnetically coupling the gate lines 12-A and 12-B with each other.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a gate drive device for a power semiconductor device and a power conversion device. [Background technology]

[0002] 2. Description of the Related Art Various gate driver devices have been proposed for switching on and off each of a plurality of semiconductor switching elements, which are power semiconductor elements connected in series.

[0003] For example, in a semiconductor switch circuit including a plurality of voltage-driven semiconductor elements connected in series to form an arm, and a gate drive circuit that supplies a gate signal to the gate terminal of each of the plurality of voltage-driven semiconductor elements in each arm, there is known a control device for series-connected voltage-driven semiconductor elements, characterized in that gate lines connecting the gate drive circuit to the gate terminals of each of the voltage-driven semiconductor elements in each arm are magnetically coupled to each other (see, for example, Patent Document 1).

[0004] For example, a gate drive device for voltage-driven semiconductor elements is known that drives on and off a plurality of voltage-driven semiconductor elements connected in series to each arm of a power conversion device, the gate drive device comprising an overvoltage determination circuit that detects the voltage applied to the voltage-driven semiconductor elements and determines whether it is an overvoltage, and an overdrive circuit that turns on the voltage-driven semiconductor elements with a voltage higher than a normal forward bias voltage when the voltage-driven semiconductor elements are turned on, and when an overvoltage is detected by the overvoltage determination circuit, an imbalance occurs in the voltages applied to the voltage-driven semiconductor elements, and the overdrive circuit turns on the voltage-driven semiconductor elements to which an overvoltage has been applied with a voltage higher than a normal forward bias voltage, thereby preventing the application of an overvoltage to the voltage-driven semiconductor elements and the resulting element destruction (see, for example, Patent Document 2). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 4396036 [Patent Document 2] Patent No. 4449190 Summary of the Invention [Problem to be solved by the invention]

[0006] In the invention described in Patent Document 1 (JP Patent No. 4396036), the gate lines of the voltage-driven semiconductor element are magnetically coupled, and if the current values ​​flowing through the gate lines differ when the voltage-driven semiconductor element is turned on or off, the impedance of the gate lines is instantly changed according to the difference, thereby matching the gate currents and suppressing the variation in switching timing. However, the invention described in Patent Document 1 (JP Patent No. 4396036) has the effect of correcting the time difference in gate voltage due to the delay of the gate voltage signal and matching the switching timing of the on operation or off operation when the gate threshold voltages (the gate voltage at which the voltage-driven semiconductor element starts to turn on) of the voltage-driven semiconductor elements are the same, but the effect is small when the gate threshold voltages are different. In many cases, the gate threshold voltage varies depending on the voltage-driven semiconductor element, so the effect of matching the switching timing of the on operation and the off operation is small, and the imbalance of the applied voltage during the on operation and the off operation becomes large.

[0007] For example, by applying a technique for setting the gate voltage of an element that turns on slowly, as in the invention described in Patent Document 2 (JP Patent Publication No. 4449190), to the invention described in Patent Document 1, it is possible to synchronize the switching timing of the on-operation of each of a plurality of voltage-driven semiconductor elements, but it is not possible to synchronize the switching timing of the off-operation of each of a plurality of power semiconductor elements. Also, if the gate voltage is set high, the on-operation of the voltage-driven semiconductor elements that operate slowly can be accelerated due to a delay in the gate voltage signal, and the switching timing can be synchronized, but the off-operation is delayed compared to when the gate voltage is not high, so the switching timing of each of the voltage-driven semiconductor elements when they are turned off is significantly shifted, and the imbalance of the applied voltage becomes large.

[0008] Therefore, in a gate drive device for multiple power semiconductor elements connected in series and a power conversion device equipped with the same, there is a demand for technology that can align the switching timing for the on and off operations of each of the power semiconductor elements, even if there is variation in the transmission time of the gate signal and the characteristics of the power semiconductor elements, and suppress imbalances in the voltages applied to the power semiconductor elements. [Means for solving the problem]

[0009] According to one aspect of the present disclosure, a gate drive device for a plurality of power semiconductor elements connected in series includes a gate drive voltage variable unit provided corresponding to each power semiconductor element and outputting a variable gate drive voltage, gate lines supplying the gate drive voltage output from the gate drive voltage variable unit to each gate terminal of the corresponding power semiconductor element, and a magnetic coupling unit magnetically coupling each of the gate lines to each other.

[0010] Here, in the gate drive device, the gate drive voltage variable section may vary the potential of the gate drive voltage to be output in accordance with a difference in electrical characteristics between the power semiconductor elements.

[0011] In addition, in the above gate drive device, the gate drive voltage variable section corresponding to the power semiconductor element having the first gate threshold voltage may output positive and negative potentials of a gate drive voltage that are lower than the positive and negative potentials of a gate drive voltage output by a gate drive voltage variable section corresponding to a power semiconductor element having a second gate threshold voltage higher than the first gate threshold voltage.

[0012] Moreover, in the above gate drive device, each of the gate drive voltage variable sections includes a positive potential output section that outputs a positive potential of the gate drive voltage, and a negative potential output section that is connected in series to the positive potential output section and outputs a negative potential of the gate drive voltage, and in each of the gate drive voltage variable sections, a potential at an intermediate terminal that is a connection point between the positive potential output section and the negative potential output section is the same as a potential at an output terminal of a power semiconductor element corresponding to the gate drive voltage variable section, and a potential difference between the positive potential output by the gate drive voltage variable section corresponding to the power semiconductor element having the second gate threshold voltage and the potential at the intermediate terminal may be greater than a potential difference between the positive potential output by the gate drive voltage variable section corresponding to the power semiconductor element having the first gate threshold voltage and the potential at the intermediate terminal.

[0013] Moreover, in the above gate drive device, each of the gate drive voltage variable sections has a positive potential output section that outputs a positive potential of the gate drive voltage, and a negative potential output section that is connected in series to the positive potential output section and outputs a negative potential of the gate drive voltage, and in each of the gate drive voltage variable sections, the potential at an intermediate terminal that is a connection point between the positive potential output section and the negative potential output section is the same as the potential at an output terminal of the power semiconductor element corresponding to the gate drive voltage variable section, and a potential difference between the potential at the intermediate terminal of the gate drive voltage variable section corresponding to the power semiconductor element having the second gate threshold voltage and the negative potential output by the gate drive voltage variable section may be smaller than a potential difference between the potential at the intermediate terminal of the gate drive voltage variable section corresponding to the power semiconductor element having the first gate threshold voltage and the negative potential output by the gate drive voltage variable section.

[0014] In addition, in the above gate drive device, the gate drive voltage variable section corresponding to the power semiconductor element having the first gate threshold voltage may output positive and negative potentials of a gate drive voltage that are higher than the positive and negative potentials of the gate drive voltage output by the gate drive voltage variable section corresponding to the power semiconductor element having a third gate threshold voltage lower than the first gate threshold voltage.

[0015] Moreover, in the above gate drive device, each of the gate drive voltage variable sections has a positive potential output section that outputs a positive potential of the gate drive voltage, and a negative potential output section that is connected in series to the positive potential output section and outputs a negative potential of the gate drive voltage, and in each of the gate drive voltage variable sections, a potential at an intermediate terminal that is a connection point between the positive potential output section and the negative potential output section is the same as a potential at an output terminal of a power semiconductor element corresponding to the gate drive voltage variable section, and a potential difference between the positive potential output by the gate drive voltage variable section corresponding to the power semiconductor element having the third gate threshold voltage and the potential at the intermediate terminal may be smaller than a potential difference between the positive potential output by the gate drive voltage variable section corresponding to the power semiconductor element having the first gate threshold voltage and the potential at the intermediate terminal.

[0016] Moreover, in the above gate drive device, each of the gate drive voltage variable sections has a positive potential output section that outputs a positive potential of the gate drive voltage, and a negative potential output section that is connected in series to the positive potential output section and outputs a negative potential of the gate drive voltage, and in each of the gate drive voltage variable sections, the potential at an intermediate terminal that is a connection point between the positive potential output section and the negative potential output section is the same as the potential at an output terminal of the power semiconductor element corresponding to the gate drive voltage variable section, and the potential difference between the potential at the intermediate terminal of the gate drive voltage variable section corresponding to the power semiconductor element having the third gate threshold voltage and the negative potential output by the gate drive voltage variable section may be larger than the potential difference between the potential at the intermediate terminal of the gate drive voltage variable section corresponding to the power semiconductor element having the first gate threshold voltage and the negative potential output by the gate drive voltage variable section.

[0017] In addition, the gate drive device may further include a temperature sensor provided corresponding to each of the power semiconductor elements, and each of the gate drive voltage variable sections may change the positive side potential and the negative side potential of the gate drive voltage in accordance with the temperature of the power semiconductor element detected by the corresponding temperature sensor.

[0018] In the above gate drive device, each of the positive and negative potentials of the gate drive voltage output from the gate drive voltage variable section corresponding to the power semiconductor element corresponding to the temperature sensor that detected the first temperature may be lower than each of the positive and negative potentials of the gate drive voltage output from the gate drive voltage variable section corresponding to the power semiconductor element corresponding to the temperature sensor that detected a second temperature lower than the first temperature.

[0019] In the above gate drive device, the gate drive voltage variable section corresponding to the power semiconductor element corresponding to the temperature sensor that detected the first temperature may output positive and negative potentials of a gate drive voltage that are higher than the positive and negative potentials of the gate drive voltage output by the gate drive voltage variable section corresponding to the power semiconductor element corresponding to the temperature sensor that detected a third temperature higher than the first temperature.

[0020] Moreover, according to one aspect of the present disclosure, a power conversion device includes the above-mentioned gate drive device, a power conversion circuit unit having an arm provided with a plurality of power semiconductor elements connected in series and performing power conversion operation in response to the on / off operation of the power semiconductor elements, and a power conversion control unit that controls the power conversion operation of the power conversion circuit unit.

[0021] Here, in the above power conversion device, each of the gate drive voltage variable sections may change the positive side potential and the negative side potential of the gate drive voltage in accordance with the value of the current output from the power conversion circuit section.

[0022] In addition, in the above power conversion device, each of the gate drive voltage variable sections may change the positive side potential and the negative side potential of the gate drive voltage according to the value of a current command generated by the power conversion control section to control the on / off operation of the power conversion circuit section. Effect of the Invention

[0023] According to one aspect of the present disclosure, in a gate drive device for multiple power semiconductor elements connected in series and a power conversion device including the same, even if there is variation in the transmission time of the gate signal or the characteristics of the power semiconductor elements, it is possible to align the switching timing for the on and off operations of each of the power semiconductor elements, and suppress imbalances in the voltages applied to the power semiconductor elements. [Brief description of the drawings]

[0024] [Figure 1] FIG. 2 is a circuit diagram illustrating a gate driver according to one embodiment of the present disclosure. [Diagram 2] 13 is a circuit diagram showing a modified example of a gate drive voltage variable section in the gate drive device according to the embodiment of the present disclosure. FIG. [Diagram 3] FIG. 2 illustrates a magnetic coupling portion in a gate drive device according to an embodiment of the present disclosure. [Figure 4] FIG. 1 illustrates a power converter including a gate drive according to one embodiment of the present disclosure. [Diagram 5] 5 is a circuit diagram showing an arm provided in the power conversion device shown in FIG. 4. [Figure 6] FIG. 1 is a diagram for explaining the definition of the gate voltage imbalance degree when two power semiconductor elements have different characteristics, where (A) shows the definition of the gate voltage imbalance degree during off operation, and (B) shows the definition of the gate voltage imbalance degree during on operation. [Figure 7] FIG. 13 is a diagram illustrating simulation results of the degree of imbalance when there is a magnetic coupling of gate lines in Patent Document 1 (Japanese Patent No. 4396036) and when there is a variation in the characteristics of power semiconductor elements. [Figure 8] 11A and 11B are diagrams illustrating simulation results of imbalance in an embodiment of the present disclosure when there is variation in the characteristics of power semiconductor elements; [Figure 9]1 is a circuit diagram showing a gate driver for turning on and off three power semiconductor devices connected in series according to an embodiment of the present disclosure. [Figure 10] FIG. 2 is a circuit diagram showing a gate driver according to a first modified example of an embodiment of the present disclosure. [Figure 11] FIG. 13 is a diagram illustrating a simulation result of the degree of imbalance in a first modified example of an embodiment of the present disclosure when there is variation in the characteristics of power semiconductor elements. [Figure 12] 1 is a diagram illustrating an example of the relationship between the temperature, the gate-source voltage, and the drain current of a power semiconductor device. [Figure 13] FIG. 11 is a circuit diagram showing a gate driver according to a second modified example of an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] The gate driver and the power converter for power semiconductor devices will be described below with reference to the drawings. In each drawing, the same components are given the same reference symbols. In addition, the scale of these drawings is appropriately changed to facilitate understanding. The illustrated embodiment is one example for carrying out the present invention, and the present invention is not limited to these embodiments.

[0026] The gate driver according to each embodiment of the present disclosure drives a plurality of power semiconductor elements connected in series to turn on and off. Examples of the power semiconductor elements include MOSFETs, IGBTs, thyristors, GTOs, and transistors. A MOSFET has a gate terminal, a drain terminal, and a source terminal as its terminals. An IGBT has a gate terminal, an emitter terminal, and a collector terminal as its terminals. A transistor has a base terminal, an emitter terminal, and a collector terminal as its terminals. A thyristor and a GTO have a gate terminal, an anode terminal, and a cathode terminal as its terminals. Hereinafter, as an example, a case where the power semiconductor element is configured by a MOSFET will be described, but each embodiment of the present disclosure is applicable even if the power semiconductor element is configured by an IGBT, a thyristor, a GTO, or a transistor. In addition, when the power semiconductor element is configured by an IGBT, the "drain" is replaced with the "collector" and the "source" is replaced with the "emitter", and each embodiment of the present disclosure is applied. Furthermore, when the power semiconductor element is configured with a transistor, the "gate" is replaced with the "base", the "drain" is replaced with the "collector", and the "source" is replaced with the "emitter" in each embodiment of the present disclosure. Furthermore, when the power semiconductor element is configured with a thyristor or a GTO, the "gate" is replaced with the "base", the "drain" is replaced with the "anode", and the "source" is replaced with the "cathode" in each embodiment of the present disclosure. Furthermore, the "output terminal of the power semiconductor element" corresponds to the "source terminal" of a MOSFET, the "emitter terminal" of an IGBT and a transistor, and the "cathode terminal" of a thyristor and a GTO.

[0027] 1 is a circuit diagram showing a gate driver according to an embodiment of the present disclosure. Hereinafter, components with the same reference numerals in different drawings have the same functions.

[0028] The gate driver 1 according to an embodiment of the present disclosure drives a plurality of power semiconductor elements connected in series to be turned on and off. Here, as an example, a gate driver 1 is used that drives two power semiconductor elements Q A and Q BAn example of on / off driving will be described.

[0029] Power semiconductor device Q A Diode D A are connected in inverse parallel. Similarly, the power semiconductor element Q B Diode D B are connected in inverse parallel.

[0030] The gate drive device 1 includes gate drive voltage variable units 11-A and 11-B, gate lines 12-A and 12-B, and a magnetic coupling unit 13.

[0031] The gate drive voltage variable unit 11-A is a power semiconductor element Q A The gate drive voltage variable unit 11-B is provided corresponding to the power semiconductor element Q B One or both of the gate drive voltage variable units 11-A and 11-B output a variable gate drive voltage according to the difference in electrical characteristics between the power semiconductor elements, particularly the difference in gate threshold voltage. The details of the gate drive voltage variable units 11-A and 11-B will be described later.

[0032] The gate line 12-A supplies the gate drive voltage output from the gate drive voltage variable unit 11-A to the corresponding power semiconductor element Q A The gate line 12-B supplies the gate driving voltage output from the gate driving voltage variable unit 11-B to the gate terminal of the corresponding power semiconductor element Q. B The voltage is supplied to the gate terminal of the

[0033] The magnetic coupling unit 13 magnetically couples the gate line 12-A and the gate line 12-B. FIG. 3 is a diagram illustrating a magnetic coupling unit in a gate driver according to an embodiment of the present disclosure. The magnetic coupling unit 13 has a magnetic body 30. The gate lines 12-A and 12-B are wound around the magnetic body 30. For example, as shown in FIG. 3, when a gate current Ig1 flows, a magnetic flux Φ1 is generated in the magnetic body 30 and crosses the gate line 12-B. Similarly, when a gate current Ig2 flows, a magnetic flux Φ2 is generated in the magnetic body 30 and crosses the gate line 12-A. This magnetically couples the gate lines 12-A and 12-B. The number of turns N1 of the gate line 12-A around the magnetic body 30 is the same as the number of turns N2 of the gate line 12-B around the magnetic body 30, and when the gate currents Ig1 and Ig2 are equal, |Φ1|=|Φ2|. Ig2 When Φ1 and Φ2 have opposite polarities, Φ2 and Φ3 have opposite polarities.

[0034] For example, power semiconductor element Q A and power semiconductor element Q B The timing of the off operation of the power semiconductor element Q A Q is a power semiconductor device B If the gate current Ig1 is turned off before the gate current Ig2, the magnetic flux Φ1 and the magnetic flux Φ2 will not be equal when the gate current Ig1 flows out before the gate current Ig2, so that a magnetic flux of |Φ1-Φ2| is generated in the magnetic body 30 and they are magnetically coupled. At this time, an inductance L1 is generated in the gate line 12-A and an inductance L2 is generated in the gate line 12-B, and these inductances L1 and L2 are proportional to |Φ1-Φ2|. The greater the imbalance between the gate current Ig1 and the gate current Ig2, the greater the inductances L1 and L2. Also, the greater the inductances L1 and L2, the greater the impedance of the gate lines 12-A and 12-B, so that the gate currents Ig1 and Ig2 become less likely to flow. This changes the impedance of the gate lines 12-A and 12-B according to the imbalance between the gate current Ig1 and the gate current Ig2, and the gate currents Ig1 and Ig2 can be operated so as to match each other.

[0035] Next, the gate drive voltage variable section 11-A and the gate drive voltage variable section 11-B will be described in detail.

[0036] One or both of the gate drive voltage variable sections 11-A and 11-B output a variable gate drive voltage.

[0037] The gate drive voltage variable unit 11-A controls the positive potential VP A A positive potential output section 21P-A that outputs a negative potential VN of the gate drive voltage is connected in series to the positive potential output section 21P-A. A The gate drive voltage variable section 11-B has a negative side potential output section 21N-A that outputs a positive side potential VP B and a positive side potential output section 21P-B that outputs a negative side potential VN of the gate drive voltage. B The negative side potential output unit 21N-B outputs a positive potential, a positive side switch 23P-B, and a negative side switch 23N-B.

[0038] The positive-side switch 23P-A in the gate drive voltage variable unit 11-A and the positive-side switch 23P-B in the gate drive voltage variable unit 11-B perform on and off operations in synchronization, i.e., the on and off timings of these positive-side switches 23P-A and 23P-B are consistent. Similarly, the negative-side switch 23N-A in the gate drive voltage variable unit 11-A and the negative-side switch 23N-B in the gate drive voltage variable unit 11-B perform on and off operations in synchronization, i.e., the on and off timings of these negative-side switches 23N-A and 23N-B are consistent. In one embodiment of the present disclosure, the gate drive voltage variable unit 11-A and the gate drive voltage variable unit 11-B each generate a variable gate drive voltage as described below, and then turn on and off the positive-side switches 23P-A and 23P-B and the negative-side switches 23N-A and 23N-B to generate a variable gate drive voltage. A and Q B The voltage applied to the gate terminal of the transistor is controlled.

[0039] In the gate drive voltage variable unit 11-A, the positive potential VP A and the negative potential VN output by the negative potential output unit 21N-A. A The potential difference between A -VN A " is controlled to be constant, while controlling the potential VR at the intermediate terminal 22-A which is the connection point between the positive potential output section 21P-A and the negative potential output section 21N-A. A and a power semiconductor element Q corresponding to the gate drive voltage variable unit 11-A. A The potential VQ at the source terminal, which is the output terminal of A For example, the intermediate terminal 22-A and the power semiconductor element Q A By connecting the source terminal of A =VQ A After realizing the above, the positive potential VP A and the negative potential VN output by the negative potential output unit 21N-A. A The potential difference between A -VN A " is kept constant, the positive potential VP output by the positive potential output unit 21P-A is A and the potential VR at the intermediate terminal 22-A A The potential difference between A -VR A " and the potential VR at the intermediate terminal 22-A A and the negative potential VN output by the negative potential output unit 21N-A. A The potential difference between the A -VN A " or both of them may be variable.

[0040] In the gate drive voltage variable unit 11-B, the positive potential VP B and the negative potential VN output by the negative potential output unit 21N-B B The potential difference between B -VN B " is controlled to be constant, while controlling the potential VR at the intermediate terminal 22-B, which is the connection point between the positive potential output section 21P-B and the negative potential output section 21N-B. Band a power semiconductor element Q corresponding to the gate drive voltage variable unit 11-B. B The potential VQ at the source terminal, which is the output terminal of B For example, the intermediate terminal 22-B and the power semiconductor element Q B By connecting the source terminal of B =VQ B After realizing the above, the positive potential VP B and the negative potential VN output by the negative potential output unit 21N-B B The potential difference between B -VN B " is kept constant, the positive potential VP output by the positive potential output unit 21P-B is B and the potential VR at the intermediate terminal 22-B B The potential difference between B -VR B " and the potential VR at the intermediate terminal 22-B B and the negative potential VN output by the negative potential output unit 21N-B B The potential difference between the B -VN B " or both of them may be variable.

[0041] Also, for example, the power semiconductor element Q A is the first gate threshold voltage V thA A power semiconductor element Q B A second gate threshold voltage V is higher than the first gate threshold voltage. thB (i.e., V thA <V thB ) is the first gate threshold voltage V thA A power semiconductor element Q having A The positive potential VP of the gate drive voltage output from the gate drive voltage variable unit 11-A corresponding to A and negative potential VN A Each of the second gate drive voltages V thB A power semiconductor element Q having B The positive potential VP of the gate drive voltage output from the gate drive voltage variable unit 11-B corresponding to B and negative potential VN Bbe lower than each of the above.

[0042] For more information, see V thA <V thB For example, if the gate threshold voltage V thA A power semiconductor element Q having A The positive side potential output section 21P-A of the gate drive voltage variable section 11-A corresponding to the gate threshold voltage V thB A power semiconductor element Q having B The positive potential VP of the gate drive voltage output by the positive potential output unit 21P-B of the gate drive voltage variable unit 11-B corresponding to B The positive potential of the gate drive voltage VP A The negative potential output unit 21N-A of the gate drive voltage variable unit 11-A outputs the gate threshold voltage V thB A power semiconductor element Q having B The negative potential VN of the gate drive voltage output by the negative potential output unit 21N-B of the gate drive voltage variable unit 11-B corresponding to B The negative potential VN of the gate drive voltage is lower than A where the gate threshold voltage V thB A power semiconductor element Q having B The positive potential VP output by the positive potential output unit 21P-B of the gate drive voltage variable unit 11-B corresponding to B and the potential VR at the intermediate terminal 22-B B The potential difference between B -VR B " is the gate threshold voltage V thA A power semiconductor element Q having A The positive potential VP output by the positive potential output unit 21P-A of the gate drive voltage variable unit 11-A corresponding to A and the potential difference at intermediate terminal 22-A, "VP A -VR A " and / or the gate threshold voltage V thB A power semiconductor element Q having B The potential VR at the intermediate terminal 22-B of the gate drive voltage variable unit 11-B corresponding to Band the negative potential VN output by the negative potential output unit 21N-B of the gate drive voltage variable unit 11-B. B The potential difference between the B -VN B " is the gate threshold voltage V thA A power semiconductor element Q having A The potential VR at the intermediate terminal 22-A of the gate drive voltage variable unit 11-A corresponds to A and the negative potential VN output by the negative potential output unit 21N-A of the gate drive voltage variable unit 11-A. A The potential difference between the A -VN A " should be smaller than "

[0043] Also, for example, the power semiconductor element Q A is the first gate threshold voltage V thA A power semiconductor element Q B a third gate threshold voltage V that is lower than the first gate threshold voltage thB (i.e., V thA >V thB ) is the first gate threshold voltage V thA A power semiconductor element Q having A The positive potential VP of the gate drive voltage output from the gate drive voltage variable unit 11-A corresponding to A and negative potential VN A Each of the third gate drive voltages V thB A power semiconductor element Q having B The positive potential VP of the gate drive voltage output from the gate drive voltage variable unit 11-B corresponding to B and negative potential VN B be higher than each of the above.

[0044] That is, V thA >V thB For example, if the gate threshold voltage V thA A power semiconductor element Q having A The positive side potential output section 21P-A of the gate drive voltage variable section 11-A corresponding to the gate threshold voltage V thB A power semiconductor element Q having BThe positive potential VP of the gate drive voltage output by the positive potential output unit 21P-B of the gate drive voltage variable unit 11-B corresponding to B The positive potential of the gate drive voltage VP A The negative potential output unit 21N-A of the gate drive voltage variable unit 11-A outputs the gate threshold voltage V thB A power semiconductor element Q having B The negative potential VN of the gate drive voltage output by the negative potential output unit 21N-B of the gate drive voltage variable unit 11-B corresponding to B The negative potential of the gate drive voltage VN A where the gate threshold voltage V thB A power semiconductor element Q having B The positive potential VP output by the positive potential output unit 21P-B of the gate drive voltage variable unit 11-B corresponding to B and the potential VR at the intermediate terminal 22-B B The potential difference between B -VR B " is the gate threshold voltage V thA A power semiconductor element Q having A The positive potential VP output by the positive potential output unit 21P-A of the gate drive voltage variable unit 11-A corresponding to A and the potential VR at the intermediate terminal 22-A A The potential difference between A -VR A " and / or the gate threshold voltage V thB A power semiconductor element Q having B The potential VR at the intermediate terminal 22-B of the gate drive voltage variable unit 11-B corresponding to B and the negative potential VN output by the negative potential output unit 21N-B of the gate drive voltage variable unit 11-B. B The potential difference between the B -VN B " is the gate threshold voltage V thA A power semiconductor element Q having A The potential VR at the intermediate terminal 22-A of the gate drive voltage variable unit 11-A corresponds to A and the negative potential VN output by the negative potential output unit 21N-A of the gate drive voltage variable unit 11-A. A The potential difference between theA -VN A " should be greater than "

[0045] In this way, one or both of the gate drive voltage variable units 11-A and 11-B output a variable gate drive voltage. When both the gate drive voltage variable units 11-A and 11-B output a variable gate drive voltage, the voltage width to be changed can be made smaller, and the absolute values ​​of the positive and negative potentials of the gate drive voltage of the power semiconductor element become smaller, which has the advantage of reducing the burden on the power semiconductor element.

[0046] 2 is a circuit diagram showing a modified example of a gate drive voltage variable unit in a gate drive device according to an embodiment of the present disclosure. A and Q B is omitted in the illustration.

[0047] The gate drive voltage variable unit 11-A has a plurality of DC power supplies 21-A connected in series and a changeover switch 26-A. Intermediate taps are provided between the DC power supplies, and the changeover switch 26-A is connected to one of the intermediate taps to adjust the positive side potential VP A and the potential VR of the changeover switch 26-A A (The potential VR at the intermediate terminal 22-A in FIG. 1 A (corresponding to VP A -VR A " and the potential VR of the change-over switch 26-A. A and the negative potential VN A The potential difference between the A -VN A " changes.

[0048] Similarly, the gate drive voltage variable unit 11-B has a plurality of DC power supplies 21-B connected in series and a changeover switch 26-B. Intermediate taps are provided between the DC power supplies, and the changeover switch 26-B is connected to one of the intermediate taps to adjust the positive side potential VP B and the potential VR of the changeover switch 26-B B(The potential VR at the intermediate terminal 22-B in FIG. 1 B (corresponding to VP B -VR B " and the potential VR of the change-over switch 26-B. B and the negative potential VN B The potential difference between the B -VN B " changes.

[0049] In this way, the gate drive voltage variable units 11-A and 11-B shown in FIG. 2 also generate the potential VP A , VR B , V.N. A , V.P. B , VR B and VN B Each gate threshold voltage V thA and V thB and the potential difference "VP A -VR A ", "VR A -VN A ", V.P. B -VR B " and "VR B -VN B " and each power semiconductor element Q A and Q B The potential VQ at the source terminal of A and VQ B and potential VR A and VR B The relationship between them is the same as that described with reference to FIG.

[0050] The above-described gate driver 1 can also drive the power semiconductor elements on and off in a power conversion device configured by connecting a plurality of arms in series, each arm having a plurality of power semiconductor elements connected in series thereon.

[0051] FIG. 4 is a diagram showing a power conversion device including a gate driver according to an embodiment of the present disclosure. FIG. 5 is a circuit diagram showing an arm provided in the power conversion device shown in FIG. 4. Here, as an example, two power semiconductor elements Q A and QB An example of the configuration of the arm 50 will be described.

[0052] A power conversion device 100 according to an embodiment of the present disclosure includes the above-mentioned gate drive device 1, a power conversion circuit unit 2 having an arm 50 provided with a plurality of power semiconductor elements connected in series and performing power conversion operation in response to the on / off operation of the power semiconductor elements, and a power conversion control unit 3 controlling the power conversion operation of the power conversion circuit unit 2.

[0053] As shown in FIG. 5, the arm 50 is, for example, a power semiconductor element Q A and Q B Power semiconductor element Q A The drain terminal of the power semiconductor element Q B A terminal P2 is drawn out from the source terminal of the arm 50. In the power conversion circuit unit 2, the terminal P2 of one arm 50 is connected to the terminal P1 of the other arm 50, and the connection point is connected to one terminal of the load. In the example shown in Fig. 4, two arms 50 are connected in series to form one leg 60, and the power conversion circuit unit 2 is formed by the two legs 60.

[0054] A DC power supply 200 is connected to a leg 60 formed of the arms 50 connected in series. A load 300 is connected between a terminal T1 between the arms 50 connected in series in one leg 60 and a terminal T2 between the arms 50 connected in series in the other leg 60.

[0055] A gate driver 1 is provided corresponding to each arm 50. A and power semiconductor element Q B are turned on and off by the corresponding gate drive device 1. That is, the gate drive voltage variable unit 11-A and the gate drive voltage variable unit 11-B generate variable gate drive voltages as described above, and then turn on and off the positive side switches 23P-A and 23P-B and the negative side switches 23N-A and 23N-B to generate the power semiconductor element Q A and QB The voltage applied to the gate terminal of the transistor is controlled.

[0056] The power conversion control unit 3 controls the on and off operations of the positive side switches 23P-A and 23P-B and the negative side switches 23N-A and 23N-B in each gate drive device 1. That is, the power conversion control unit 3 controls the on and off operations of the positive side switches 23P-A and 23P-B and the negative side switches 23N-A and 23N-B in each gate drive device 1, thereby controlling the power semiconductor element Q A and Q B This controls the voltage applied to the gate terminal of the power semiconductor element Q A and Q B The power conversion circuit unit 2 performs an ON operation and an OFF operation. As a result, the power conversion circuit unit 2 performs a power conversion operation of converting the DC power supplied from the DC power source 200 into a desired power and supplying it to the load 300. The power conversion control unit 3 converts, for example, a detection value i of a current flowing from the positive terminal T1 to the load 300 and a current command i which is a control target value. * The gate driver 1 generates gate command signals for controlling the ON and OFF operations of the positive-side switches 23P-A and 23P-B and the negative-side switches 23N-A and 23N-B in each gate driver 1 so as to eliminate any deviation from the reference voltage Vcc.

[0057] An arithmetic processing device (processor) is provided in the power conversion device 100. This arithmetic processing device has a power conversion control unit 3. The power conversion control unit 3 of the arithmetic processing device is, for example, a functional module realized by a computer program executed on the processor. For example, when the power conversion control unit 3 is constructed in the form of a computer program, the arithmetic processing device can be operated according to the computer program to realize the corresponding function. The computer program for executing the processing of the power conversion control unit 3 may be provided in a form recorded on a computer-readable recording medium such as a semiconductor memory, a magnetic recording medium, or an optical recording medium. Alternatively, the power conversion control unit 3 may be realized as a semiconductor integrated circuit in which a computer program for realizing the corresponding function is written.

[0058] Next, two power semiconductor elements Q A and Q B The degree of imbalance in gate voltage during on-operation and off-operation when the characteristics of the gate electrodes are different will now be described.

[0059] FIG. 6 is a diagram for explaining the definition of the gate voltage imbalance degree when the characteristics of two power semiconductor elements are different, where (A) shows the definition of the gate voltage imbalance degree during off-state operation, and (B) shows the definition of the gate voltage imbalance degree during on-state operation. As an example, the power semiconductor element Q A is the first gate threshold voltage V thA A power semiconductor element Q B A second gate threshold voltage V is higher than the first gate threshold voltage. thB (i.e., V thA <V thB This section explains what may be the case.

[0060] As shown in FIG. 6(A), a power semiconductor element Q A and Q B As a phenomenon that occurs when the power semiconductor element Q A When the gate potential of the power semiconductor element Q is changed from a positive potential to a negative potential, A The drain-source voltage of A [V], and the power semiconductor element Q B When the gate potential of the power semiconductor element Q is changed from a positive potential to a negative potential, B The drain-source voltage of B [V]. At this time, the imbalance of the gate voltage during off operation is ΔVds off [%] is defined as in Equation 1.

[0061]

number

[0062] Also, as shown in FIG. 6(B), a power semiconductor element Q A and Q BWhen the gate potential of a power semiconductor element Q is negative, A and Q B The average drain-source voltage in the off state is Vds ave [V], and the power semiconductor element Q A and Q B The gate potential of the power semiconductor element Q is changed from a negative potential to a positive potential. A and Q B The maximum voltage rise that occurs when either of the power semiconductor elements is turned on and Vds ave When the difference between the gate voltage and the on-state voltage is Vp [V], the imbalance of the gate voltage during on-state operation is ΔVds on [%] is defined as in Equation 2.

[0063]

number

[0064] FIG. 7 is a diagram illustrating simulation results of the degree of imbalance when there is a magnetic coupling of the gate lines in Patent Document 1 (Japanese Patent No. 4396036) and when there is a variation in the characteristics of the power semiconductor elements.

[0065] As shown in FIG. 7, according to the invention described in Patent Document 1, a power semiconductor element Q A and Q B If the characteristics of (V thA <V thB ), the degree of imbalance is high whether or not there is magnetic coupling of the gate lines. Even if there is magnetic coupling of the gate lines, the imbalance is high. A and power semiconductor element Q B Therefore, the effect of aligning the timing of the ON operation and the timing of the OFF operation is small.

[0066] FIG. 8 is a diagram illustrating a simulation result of the degree of imbalance in an embodiment of the present disclosure when there is variation in the characteristics of power semiconductor elements.

[0067] 3.3kV SiC-MOSFET power semiconductor device Q with different characteristics A and Q B (V thA <V thB The simulation was performed assuming that when a voltage of 3.6 kV is applied to a series-connected positive potential VP A and the negative potential VN A Difference with "VP A -VN A " is fixed at 28 V, and the positive side potential VP B and the negative potential VN B Difference with "VP B -VN B " is fixed at 28 V, and the positive potential VP B is kept constant at 17V, and the negative potential VN B is constant at −11 V. Under these conditions, the positive side potential VP A / Negative side potential VN A When a simulation was performed in which the voltage was changed to "17V / -11V", "16.75V / -11.25V", "16.5V / -11.5V", and "16.25V / -11.75V", the imbalance degree at ON and OFF time was obtained as shown in Fig. 8. From Fig. 8, the power semiconductor element Q A Positive voltage VP A / Negative voltage VN A It can be seen that by setting between 16.5V / -11.5V and 16.25V / -11.75V, the imbalance between the on-state and the off-state can be reduced.

[0068] As described above, an example of turning on and off two power semiconductor elements connected in series has been described, but the gate drive device 1 according to an embodiment of the present disclosure can also turn on and off three or more power semiconductor elements connected in series.

[0069] 9 is a circuit diagram showing a gate driver for turning on and off three power semiconductor devices connected in series according to an embodiment of the present disclosure. As an example, A , Q B and Q C An example of on / off driving will be described.

[0070] Power semiconductor device Q A Diode D A are connected in inverse parallel. Similarly, the power semiconductor element Q B Diode D B are connected in inverse parallel, and the power semiconductor element Q C Diode D C are connected in inverse parallel.

[0071] The gate driver 1 includes gate drive voltage variable units 11-A, 11-B, and 11-C, gate lines 12-A, 12-B, and 12-C, and a magnetic coupling unit 13.

[0072] The gate drive voltage variable unit 11-A is a power semiconductor element Q A The gate drive voltage variable unit 11-B is provided corresponding to the power semiconductor element Q B The gate drive voltage variable unit 11-C is provided corresponding to the power semiconductor element Q C Some or all of the gate drive voltage variable units 11-A, 11-B, and 11-C each output a variable gate drive voltage.

[0073] The gate drive voltage variable unit 11-A controls the positive potential VP A A positive potential output section 21P-A that outputs a negative potential VN of the gate drive voltage is connected in series to the positive potential output section 21P-A. A The gate drive voltage variable section 11-B has a negative side potential output section 21N-A that outputs a positive side potential VP Band a positive side potential output section 21P-B that outputs a negative side potential VN of the gate drive voltage. B The gate drive voltage variable section 11-C has a negative side potential output section 21N-B that outputs a positive side potential VP C and a positive side potential output section 21P-C that outputs a negative side potential VN of the gate drive voltage. C The negative-side potential output unit 21N-C outputs a positive-side potential output signal, a positive-side switch 23P-C, and a negative-side switch 23N-C.

[0074] The positive-side switch 23P-A in the gate drive voltage variable unit 11-A, the positive-side switch 23P-B in the gate drive voltage variable unit 11-B, and the positive-side switch 23P-C in the gate drive voltage variable unit 11-C perform on and off operations in synchronization, i.e., the on and off timings of these positive-side switches 23P-A, 23P-B, and 23P-C are consistent. Similarly, the negative-side switch 23N-A in the gate drive voltage variable unit 11-A, the negative-side switch 23N-B in the gate drive voltage variable unit 11-B, and the negative-side switch 23N-C in the gate drive voltage variable unit 11-C perform on and off operations in synchronization, i.e., the on and off timings of these negative-side switches 23N-A, 23N-B, and 23N-C are consistent. In one embodiment of the present disclosure, the gate drive voltage variable units 11-A, 11-B, and 11-C each generate a variable gate drive voltage as described below, and then turn on and off the positive-side switches 23P-A, 23P-B, and 23P-C and the negative-side switches 23N-A, 23N-B, and 23N-C to control the power semiconductor element Q A , Q B and Q C The voltage applied to the gate terminal of the transistor is controlled.

[0075] In the gate drive voltage variable unit 11-A, the positive potential VP A and the negative potential VN output by the negative potential output unit 21N-A. AThe potential difference between A -VN A " is controlled to be constant, while controlling the potential VR at the intermediate terminal 22-A which is the connection point between the positive potential output section 21P-A and the negative potential output section 21N-A. A and a power semiconductor element Q corresponding to the gate drive voltage variable unit 11-A. A The potential VQ at the source terminal, which is the output terminal of A For example, the intermediate terminal 22-A and the power semiconductor element Q A By connecting the source terminal of A =VQ A After realizing the above, the positive potential VP A and the negative potential VN output by the negative potential output unit 21N-A. A The potential difference between A -VN A " is kept constant, the positive potential VP output by the positive potential output unit 21P-A is A and the potential VR at the intermediate terminal 22-A A The potential difference between A -VR A " and the potential VR at the intermediate terminal 22-A A and the negative potential VN output by the negative potential output unit 21N-A. A The potential difference between the A -VN A " or both of them may be variable.

[0076] In the gate drive voltage variable unit 11-B, the positive potential VP B and the negative potential VN output by the negative potential output unit 21N-B B The potential difference between B -VN B " is controlled to be constant, while controlling the potential VR at the intermediate terminal 22-B, which is the connection point between the positive potential output section 21P-B and the negative potential output section 21N-B. B and a power semiconductor element Q corresponding to the gate drive voltage variable unit 11-B. B The potential VQ at the source terminal, which is the output terminal of BFor example, the intermediate terminal 22-B and the power semiconductor element Q B By connecting the source terminal of B =VQ B After realizing the above, the positive potential VP B and the negative potential VN output by the negative potential output unit 21N-B B The potential difference between B -VN B " is kept constant, the positive potential VP output by the positive potential output unit 21P-B is B and the potential VR at the intermediate terminal 22-B B The potential difference between B -VR B " and the potential VR at the intermediate terminal 22-B B and the negative potential VN output by the negative potential output unit 21N-B B The potential difference between the B -VN B " or both of them may be variable.

[0077] In the gate drive voltage variable unit 11-C, the positive potential VP C and the negative potential VN outputted by the negative potential output unit 21N-C C The potential difference between C -VN C " is controlled to be constant, while controlling the potential VR at the intermediate terminal 22-C which is the connection point between the positive potential output section 21P-C and the negative potential output section 21N-C. C and a power semiconductor element Q corresponding to the gate drive voltage variable unit 11-C. C The potential VQ at the source terminal, which is the output terminal of C For example, the intermediate terminal 22-C and the power semiconductor element Q C By connecting the source terminal of C =VQ C After realizing the above, the positive potential VP C and the negative potential VN outputted by the negative potential output unit 21N-C C The potential difference between C -VN C" is kept constant, the positive potential VP output from the positive potential output unit 21P-C is C and the potential VR at the intermediate terminal 22-C C The potential difference between C -VR C " and the potential VR at the intermediate terminal 22-C C and the negative potential VN outputted by the negative potential output unit 21N-C C The potential difference between the C -VN C " or both of them may be variable.

[0078] Also, for example, the power semiconductor element Q A Gate threshold voltage V thA , power semiconductor element Q B Gate threshold voltage V thB , and power semiconductor element Q C Gate threshold voltage V thC V thA <V thB <V thC If the magnitude relationship between the gate threshold voltage V thA A power semiconductor element Q having A The positive potential VP of the gate drive voltage output from the gate drive voltage variable unit 11-A corresponding to A and negative potential VN A Each of these is the gate drive voltage V thB A power semiconductor element Q having B The positive potential VP of the gate drive voltage output from the gate drive voltage variable unit 11-B corresponding to B and negative potential VN B Additionally / alternatively, the gate threshold voltage V thB A power semiconductor element Q having B The positive potential VP of the gate drive voltage output from the gate drive voltage variable unit 11-B corresponding to B and negative potential VN B Each of these is the gate drive voltage V thC A power semiconductor element Q having C The positive potential VP of the gate drive voltage output from the gate drive voltage variable unit 11-C corresponding to C and negative potential VN Cbe lower than each of the above.

[0079] For more information, see V thA <V thB <V thC If the gate threshold voltage V thA A power semiconductor element Q having A The positive side potential output section 21P-A of the gate drive voltage variable section 11-A corresponding to the gate threshold voltage V thB A power semiconductor element Q having B The positive potential VP of the gate drive voltage output by the positive potential output unit 21P-B of the gate drive voltage variable unit 11-B corresponding to B The positive potential of the gate drive voltage VP A The negative potential output unit 21N-A of the gate drive voltage variable unit 11-A outputs the gate threshold voltage V thB A power semiconductor element Q having B The negative potential VN of the gate drive voltage output by the negative potential output unit 21N-B of the gate drive voltage variable unit 11-B corresponding to B The negative potential of the gate drive voltage VN A where the gate threshold voltage V thB A power semiconductor element Q having B The positive potential VP output by the positive potential output unit 21P-B of the gate drive voltage variable unit 11-B corresponding to B and the potential VR at the intermediate terminal 22-B B The potential difference between B -VR B " is the gate threshold voltage V thA A power semiconductor element Q having A The positive potential VP output by the positive potential output unit 21P-A of the gate drive voltage variable unit 11-A corresponding to A and the potential difference at intermediate terminal 22-A, "VP A -VR A " and / or the gate threshold voltage V thB A power semiconductor element Q having B The potential VR at the intermediate terminal 22-B of the gate drive voltage variable unit 11-B corresponding to Band the negative potential VN output by the negative potential output unit 21N-B of the gate drive voltage variable unit 11-B. B The potential difference between the B -VN B " is the gate threshold voltage V thA A power semiconductor element Q having A The potential VR at the intermediate terminal 22-A of the gate drive voltage variable unit 11-A corresponds to A and the negative potential VN output by the negative potential output unit 21N-A of the gate drive voltage variable unit 11-A. A The potential difference between the A -VN A " should be smaller than "

[0080] Similarly, V thA <V thB <V thC If the gate threshold voltage V thB A power semiconductor element Q having B The positive side potential output section 21P-B of the gate drive voltage variable section 11-B corresponding to the gate threshold voltage V thC A power semiconductor element Q having C The positive potential VP of the gate drive voltage output by the positive potential output unit 21P-C of the gate drive voltage variable unit 11-C corresponding to C The positive potential of the gate drive voltage VP B The negative potential output unit 21N-B of the gate drive voltage variable unit 11-B outputs the gate threshold voltage V thC A power semiconductor element Q having C The negative potential VN of the gate drive voltage output by the negative potential output unit 21N-C of the gate drive voltage variable unit 11-C corresponding to C The negative potential VN of the gate drive voltage is lower than B where the gate threshold voltage V thC A power semiconductor element Q having C The positive potential VP output by the positive potential output unit 21P-C of the gate drive voltage variable unit 11-C corresponding to C and the potential VR at the intermediate terminal 22-C C The potential difference between C -VR C " is the gate threshold voltage V thBA power semiconductor element Q having B The positive potential VP output by the positive potential output unit 21P-B of the gate drive voltage variable unit 11-B corresponding to B and the potential difference at intermediate terminal 22-B, "VP B -VR B " and / or the gate threshold voltage V thC A power semiconductor element Q having C The potential VR at the intermediate terminal 22-C of the gate drive voltage variable unit 11-C corresponds to C and the negative potential VN output by the negative potential output unit 21N-C of the gate drive voltage variable unit 11-C. C The potential difference between the C -VN C " is the gate threshold voltage V thB A power semiconductor element Q having B The potential VR at the intermediate terminal 22-B of the gate drive voltage variable unit 11-B corresponding to B and the negative potential VN output by the negative potential output unit 21N-B of the gate drive voltage variable unit 11-B. B The potential difference between the B -VN B " should be smaller than "

[0081] Also, for example, the power semiconductor element Q A Gate threshold voltage V thA , power semiconductor element Q B Gate threshold voltage V thB , and power semiconductor element Q C Gate threshold voltage V thC V thA >V thB >V thC If the magnitude relationship between the gate threshold voltage V thA A power semiconductor element Q having A The positive potential VP of the gate drive voltage output from the gate drive voltage variable unit 11-A corresponding to A and negative potential VN A Each of these is the gate drive voltage V thB A power semiconductor element Q having B The positive potential VP of the gate drive voltage output from the gate drive voltage variable unit 11-B corresponding toB and negative potential VN B and / or the gate threshold voltage V thB A power semiconductor element Q having B The positive potential VP of the gate drive voltage output from the gate drive voltage variable unit 11-B corresponding to B and negative potential VN B Each of these is the gate drive voltage V thC A power semiconductor element Q having C The positive potential VP of the gate drive voltage output from the gate drive voltage variable unit 11-C corresponding to C and negative potential VN C be higher than each of the above.

[0082] That is, V thA >V thB >V thC For example, if the gate threshold voltage V thA A power semiconductor element Q having A The positive side potential output section 21P-A of the gate drive voltage variable section 11-A corresponding to the gate threshold voltage V thB A power semiconductor element Q having B The positive potential VP of the gate drive voltage output by the positive potential output unit 21P-B of the gate drive voltage variable unit 11-B corresponding to B The positive potential of the gate drive voltage VP A The negative potential output unit 21N-A of the gate drive voltage variable unit 11-A outputs the gate threshold voltage V thB A power semiconductor element Q having B The negative potential VN of the gate drive voltage output by the negative potential output unit 21N-B of the gate drive voltage variable unit 11-B corresponding to B The negative potential of the gate drive voltage VN A where the gate threshold voltage V thB A power semiconductor element Q having B The positive potential VP output by the positive potential output unit 21P-B of the gate drive voltage variable unit 11-B corresponding to B and the potential VR at the intermediate terminal 22-B B The potential difference between B -VR B" is the gate threshold voltage V thA A power semiconductor element Q having A The positive potential VP output by the positive potential output unit 21P-A of the gate drive voltage variable unit 11-A corresponding to A and the potential VR at the intermediate terminal 22-A A The potential difference between A -VR A " and / or the gate threshold voltage V thB A power semiconductor element Q having B The potential VR at the intermediate terminal 22-B of the gate drive voltage variable unit 11-B corresponding to B and the negative potential VN output by the negative potential output unit 21N-B of the gate drive voltage variable unit 11-B. B The potential difference between the B -VN B " is the gate threshold voltage V thA A power semiconductor element Q having A The potential VR at the intermediate terminal 22-A of the gate drive voltage variable unit 11-A corresponds to A and the negative potential VN output by the negative potential output unit 21N-A of the gate drive voltage variable unit 11-A. A The potential difference between the A -VN A " should be greater than "

[0083] Similarly, V thA >V thB >V thC For example, if the gate threshold voltage V thB A power semiconductor element Q having B The positive side potential output section 21P-B of the gate drive voltage variable section 11-B corresponding to the gate threshold voltage V thC A power semiconductor element Q having C The positive potential VP of the gate drive voltage output by the positive potential output unit 21P-C of the gate drive voltage variable unit 11-C corresponding to C The positive potential of the gate drive voltage VP B The negative potential output unit 21N-B of the gate drive voltage variable unit 11-B outputs the gate threshold voltage V thC A power semiconductor element Q having CThe negative potential VN of the gate drive voltage output by the negative potential output unit 21N-C of the gate drive voltage variable unit 11-C corresponding to C The negative potential of the gate drive voltage VN C where the gate threshold voltage V thC A power semiconductor element Q having C The positive potential VP output by the positive potential output unit 21P-C of the gate drive voltage variable unit 11-C corresponding to C and the potential VR at the intermediate terminal 22-C C The potential difference between C -VR C " is the gate threshold voltage V thB A power semiconductor element Q having B The positive potential VP output by the positive potential output unit 21P-B of the gate drive voltage variable unit 11-B corresponding to B and the potential VR at the intermediate terminal 22-B B The potential difference between B -VR B " and / or the gate threshold voltage V thC A power semiconductor element Q having C The potential VR at the intermediate terminal 22-C of the gate drive voltage variable unit 11-C corresponds to C and the negative potential VN output by the negative potential output unit 21N-C of the gate drive voltage variable unit 11-C. C The potential difference between the C -VN C " is the gate threshold voltage V thB A power semiconductor element Q having B The potential VR at the intermediate terminal 22-B of the gate drive voltage variable unit 11-B corresponding to B and the negative potential VN output by the negative potential output unit 21N-B of the gate drive voltage variable unit 11-B. B The potential difference between the B -VN B " should be greater than "

[0084] The gate line 12-A supplies the gate drive voltage output from the gate drive voltage variable unit 11-A to the corresponding power semiconductor element Q AThe gate line 12-B supplies the gate driving voltage output from the gate driving voltage variable unit 11-B to the gate terminal of the corresponding power semiconductor element Q. B The gate line 12-C supplies the gate driving voltage output from the gate driving voltage variable unit 11-C to the gate terminal of the corresponding power semiconductor element Q. C The voltage is supplied to the gate terminal of the

[0085] The magnetic coupling portion 13 magnetically couples the gate line 12-A to the gate line 12-B, and magnetically couples the gate line 12-B to the gate line 12-C.

[0086] In this way, the gate driver 1 according to an embodiment of the present disclosure has a configuration in which the same number of gate drive voltage variable units and gate lines as the number of power semiconductor elements connected in series are provided, and the gate lines are magnetically coupled to each other at the magnetic coupling units. According to the embodiment of the present disclosure, even if there is variation in the transmission time of the gate signal for the power semiconductor elements or the characteristics of the power semiconductor elements, it is possible to align the switching timing for the on and off operations of each of the power semiconductor elements and suppress imbalances in the voltages applied to the power semiconductor elements.

[0087] Next, a first modified example of the embodiment of the present disclosure will be described.

[0088] 10 is a circuit diagram showing a gate driver according to a first modification of an embodiment of the present disclosure. As an example, two power semiconductor elements Q A and Q B An example in which the gate drive voltage variable units 11-A and 11-B are turned on and off will be described, but the first modified example can also be applied to a case in which three or more power semiconductor elements connected in series are turned on and off. Also, as an example, a case in which the gate drive voltage variable units 11-A and 11-B have the configuration shown in Fig. 2 will be described, but the first modified example can also be applied to a case in which the gate drive voltage variable units 11-A and 11-B have the configuration shown in Fig. 1.

[0089] 4 and 5, for the power conversion circuit section 2 configured with the arm 50 having a plurality of power semiconductor elements connected in series, the gate drive device 1 can drive the power semiconductor elements in the arm 50 to turn on and off. Since the characteristics of the power semiconductor elements change depending on the magnitude of the current flowing between the drain and source, the gate drive device 1 according to the first modified example changes the positive and negative potentials of the gate drive voltage according to the current flowing between the drain and source, and even if the characteristics of each of the power semiconductor elements change depending on the magnitude of the current flowing between the drain and source, the switching timing for the on and off operations of each of the power semiconductor elements is aligned, thereby suppressing imbalance in the voltage applied to the power semiconductor elements.

[0090] The power conversion control unit 3 receives, as information about the current, a value i of the current output from the power conversion circuit unit 2 or a value i of a current command generated by the power conversion control unit 3 to control the power conversion operation of the power conversion circuit unit 2. * Each of the gate drive voltage variable units 11-A and 11-B holds a current value i output from the power conversion circuit unit 2 or a current command value i generated by the power conversion control unit 3 to control the power conversion operation of the power conversion circuit unit 2. * 10, the gate drive voltage variable section 11-A further includes a selector circuit 24-A, and the gate drive voltage variable section 11-B further includes a selector circuit 24-B.

[0091] A center tap is provided between each of the multiple DC power supplies 21-A connected in series, and each center tap is connected to an intermediate terminal 22-A via a switch unit composed of a MOSFET. The on / off of the MOSFET of each switch unit is controlled by a selector circuit 24-A. The selector circuit 24-A selects a current value i output from the power conversion circuit unit 2 or a current command value i generated by the power conversion control unit 3 to control the power conversion operation of the power conversion circuit unit 2. * Depending on the voltage, one of the multiple MOSFETs is turned on to supply the positive side potential VP Aand the potential VR of the intermediate terminal 22-A A The potential difference between A -VR A " and the potential VR of the intermediate terminal 22-A. A and the negative potential VN A The potential difference between the A -VN A " Changes the

[0092] Similarly, an intermediate tap is provided between each of the multiple DC power supplies 21-B connected in series, and each intermediate tap is connected to an intermediate terminal 22-B via a switch unit composed of a MOSFET. The on / off of the MOSFET of each switch unit is controlled by a selector circuit 24-B. The selector circuit 24-B selects a current value i output from the power conversion circuit unit 2 or a current command value i generated by the power conversion control unit 3 to control the power conversion operation of the power conversion circuit unit 2. * Depending on the voltage, one of the multiple MOSFETs is turned on to supply the positive side potential VP B and the potential VR of the intermediate terminal 22-B B The potential difference between B -VR B " and the potential VR of the intermediate terminal 22-B. B and the negative potential VN B The potential difference between the B -VN B " Changes the

[0093] FIG. 11 is a diagram illustrating a simulation result regarding the degree of imbalance in the first modified example of the embodiment of the present disclosure when there is variation in the characteristics of the power semiconductor elements.

[0094] 3.3kV SiC-MOSFET power semiconductor device Q with different characteristics A and Q B (V thA <V thB) connected in series and a voltage of 3.6 kV was applied, the current flowing between the drain and source was set to 750 A, 500 A, and 50 A. In this simulation, it was assumed that there was no delay in each gate signal, and the positive potential VP A and the negative potential VN A Difference with "VP A -VN A " is fixed at 28 V, and the positive potential VP B and the negative potential VN B Difference with "VP B -VN B " is fixed at 28 V, and the positive potential VP B is kept constant at 17V, and the negative potential VN B Under these conditions, the positive potential VP output from the gate drive voltage variable unit 11-A for drain-source currents of 750 A, 500 A, and 50 A is A / Negative side potential VN A When a simulation was performed in which the voltage was changed to "17V / -11V", "16.75V / -11.25V", "16.5V / -11.5V", and "16.25V / -11.75V", the imbalance degree at ON and OFF was obtained as shown in Figure 11. From Figure 11, when the current flowing between the drain and source is 750A, the positive side potential VP A / Negative side potential VN A When the drain-source current is 300A, the positive potential VP A / Negative side potential VN A When the drain-source current is 50A, the positive potential VP A / Negative side potential VN A When the voltage is "17V / -11V", the imbalance ΔVds when the off It can be seen that it is possible to reduce

[0095] Next, a second modified example of the embodiment of the present disclosure will be described.

[0096] FIG. 12 is a diagram illustrating the relationship between the temperature, the gate-source voltage, and the drain current of a power semiconductor device.

[0097] The temperature of the power semiconductor element rises due to self-heating during on / off operation. Therefore, for example, due to design constraints or the arrangement position of the power semiconductor element, a temperature difference may occur for each power semiconductor element in the power conversion device. FIG. 12 shows, as an example, the relationship between the gate-source voltage Vgs [V] and the drain current Id [A] when the temperature of the power semiconductor element made of SiC-MOSFET is 25° C. and 175° C. As can be seen from FIG. 12, the gate threshold voltage decreases when the temperature of the power semiconductor element increases. In this way, the temperature difference between the power semiconductor elements causes variations in the gate threshold voltage, and the imbalance of the applied voltage during on operation and off operation increases. Therefore, in a second example of an embodiment of the present disclosure, the positive side potential and the negative side potential of the gate drive voltage are changed according to the temperature of the power semiconductor element, and even if the characteristics change due to the heat generation of each power semiconductor element, the switching timing for the on operation and the off operation of each power semiconductor element is aligned, thereby suppressing the imbalance of the voltage applied to the power semiconductor element.

[0098] 13 is a circuit diagram showing a gate driver according to a second modification of an embodiment of the present disclosure. As an example, two power semiconductor elements Q A and Q B However, the second modification can be applied even when three or more power semiconductor elements connected in series are turned on and off. Also, as an example, the gate drive voltage variable units 11-A and 11-B have the configuration shown in Fig. 2, but the second modification can be applied even when the gate drive voltage variable units 11-A and 11-B have the configuration shown in Fig. 1.

[0099] The gate driver 1 includes a power semiconductor element QA and Q B The temperature sensors 25-A and 25-B are provided corresponding to the power semiconductor element Q. A and Q B It is preferable that each of the gate drive voltage variable units 11-A and 11-B is installed at a portion that generates the most heat. Each of the gate drive voltage variable units 11-A and 11-B changes the positive side potential and the negative side potential of the gate drive voltage according to the temperature of the power semiconductor element detected by the corresponding temperature sensor 25-A or 25-B. For this reason, as shown in Fig. 13, the gate drive voltage variable unit 11-A further includes a selector circuit 24-A, and the gate drive voltage variable unit 11-B further includes a selector circuit 24-B.

[0100] A center tap is provided between each of the multiple DC power supplies 21-A connected in series, and each center tap is connected to an intermediate terminal 22-A via a conductor provided with a MOSFET. The on / off of the MOSFET on each conductor is controlled by a selector circuit 24-A. The selector circuit 24-A selects the temperature of the power semiconductor element Q detected by a temperature sensor 25-A. A Depending on the temperature, one of the multiple MOSFETs is turned on to maintain the positive potential VP A and the potential VR of the intermediate terminal 22-A A The potential difference between A -VR A " and the potential VR of the intermediate terminal 22-A. A and the negative potential VN A The potential difference between the A -VN A " Changes the

[0101] Similarly, a center tap is provided between each of the multiple DC power supplies 21-B connected in series, and each center tap is connected to an intermediate terminal 22-B via a conductor provided with a MOSFET. The on / off of the MOSFET on each conductor is controlled by a selector circuit 24-B. The selector circuit 24-B is connected to the power semiconductor element Q B Depending on the temperature, one of the multiple MOSFETs is turned on to maintain the positive potential VPB and the potential VR of the intermediate terminal 22-B B The potential difference between B -VR B " and the potential VR of the intermediate terminal 22-B. B and the negative potential VN B The potential difference between the B -VN B " Changes the

[0102] For example, the temperature of the power semiconductor element Q detected by the temperature sensor 25-A A is the first temperature Temp A The temperature of the power semiconductor element Q detected by the temperature sensor 25-B is B is the first temperature Temp A Lower Second Temperature Temp B If (i.e. Temp A >Temp B If so, the first temperature Temp A The power semiconductor element Q corresponding to the temperature sensor 25-A that detected A The positive potential VP of the gate drive voltage output from the gate drive voltage variable unit 11-A corresponding to A and negative potential VN B Each of the second temperatures Temp B The power semiconductor element Q corresponding to the temperature sensor 25-B that detected B The positive potential VP of the gate drive voltage output from the gate drive voltage variable unit 11-B corresponding to B and negative potential VN B be lower than each of the above.

[0103] For more information, see Temp A >Temp B For example, if the temperature A A power semiconductor element Q having A The positive side potential output section 21P-A of the gate drive voltage variable section 11-A corresponding to the temperature Temp B A power semiconductor element Q having B The positive potential VP of the gate drive voltage output by the positive potential output unit 21P-B of the gate drive voltage variable unit 11-B corresponding to BThe positive potential of the gate drive voltage VP A The negative potential output section 21N-A of the gate drive voltage variable section 11-A outputs a temperature Temp B A power semiconductor element Q having B The negative potential VN of the gate drive voltage output by the negative potential output unit 21N-B of the gate drive voltage variable unit 11-B corresponding to B The negative potential VN of the gate drive voltage is lower than A Here, the temperature Temp B A power semiconductor element Q having B The positive potential VP output by the positive potential output unit 21P-B of the gate drive voltage variable unit 11-B corresponding to B and the potential VR at the intermediate terminal 22-B B The potential difference between B -VR B " is the temperature A A power semiconductor element Q having A The positive potential VP output by the positive potential output unit 21P-A of the gate drive voltage variable unit 11-A corresponding to A and the potential difference at intermediate terminal 22-A, "VP A -VR A " and / or the temperature Temp B A power semiconductor element Q having B The potential VR at the intermediate terminal 22-B of the gate drive voltage variable unit 11-B corresponding to B and the negative potential VN output by the negative potential output unit 21N-B of the gate drive voltage variable unit 11-B. B The potential difference between the B -VN B " is the temperature A A power semiconductor element Q having A The potential VR at the intermediate terminal 22-A of the gate drive voltage variable unit 11-A corresponds to A and the negative potential VN output by the negative potential output unit 21N-A of the gate drive voltage variable unit 11-A. A The potential difference between the A -VN A " should be smaller than "

[0104] In addition, for example, the power semiconductor element Q detected by the temperature sensor 25-A A is the first temperature Temp A The temperature of the power semiconductor element Q detected by the temperature sensor 25-B is B is the first temperature Temp A Higher third temperature Temp B If (i.e. Temp A <Temp B If so, the first temperature Temp A The power semiconductor element Q corresponding to the temperature sensor 25-A that detected A The positive potential VP of the gate drive voltage output from the gate drive voltage variable unit 11-A corresponding to A and negative potential VN A Each of the third temperatures Temp B The power semiconductor element Q corresponding to the temperature sensor 25-B that detected B The positive potential VP of the gate drive voltage output from the gate drive voltage variable unit 11-B corresponding to B and negative potential VN B be higher than each of the above.

[0105] For more information, see Temp A <Temp B For example, if the temperature A A power semiconductor element Q having A The positive side potential output section 21P-A of the gate drive voltage variable section 11-A corresponding to the temperature Temp B A power semiconductor element Q having B The positive potential VP of the gate drive voltage output by the positive potential output unit 21P-B of the gate drive voltage variable unit 11-B corresponding to B The positive potential of the gate drive voltage VP A The negative potential output section 21N-A of the gate drive voltage variable section 11-A outputs a temperature Temp B A power semiconductor element Q having B The negative potential VN of the gate drive voltage output by the negative potential output unit 21N-B of the gate drive voltage variable unit 11-B corresponding to B The negative potential VN of the gate drive voltage is higher than AHere, the temperature Temp B A power semiconductor element Q having B The positive potential VP output by the positive potential output unit 21P-B of the gate drive voltage variable unit 11-B corresponding to B and the potential VR at the intermediate terminal 22-B B The potential difference between B -VR B " is the temperature A A power semiconductor element Q having A The positive potential VP output by the positive potential output unit 21P-A of the gate drive voltage variable unit 11-A corresponding to A and the potential difference at intermediate terminal 22-A, "VP A -VR A " and / or the temperature Temp B A power semiconductor element Q having B The potential VR at the intermediate terminal 22-B of the gate drive voltage variable unit 11-B corresponding to B and the negative potential VN output by the negative potential output unit 21N-B of the gate drive voltage variable unit 11-B. B The potential difference between the B -VN B " is the temperature A A power semiconductor element Q having A The potential VR at the intermediate terminal 22-A of the gate drive voltage variable unit 11-A corresponds to A and the negative potential VN output by the negative potential output unit 21N-A of the gate drive voltage variable unit 11-A. A The potential difference between the A -VN A " should be greater than "

[0106] The first and second modified examples described above may be implemented in combination. In this case, the positive and negative potentials of the gate drive voltage are changed according to the value of the current output from the power conversion circuit unit 2 or the value of the current command generated by the power conversion control unit 3 to control the power conversion operation of the power conversion circuit unit 2, and the temperature of the power semiconductor element detected by the temperature sensor.

[0107] As described above, according to one embodiment and each of the modified examples of the present disclosure, even if there is variation in the transmission time of the gate signal on the gate line or in the characteristics of the power semiconductor elements, it is possible to align the switching timing for the on and off operations of each of the power semiconductor elements, and to suppress imbalances in the voltages applied to the power semiconductor elements. [Explanation of symbols]

[0108] 1 Gate driver 2 Power conversion circuit section 3 Power conversion control section 11-A, 11-B, 11-C Gate drive voltage variable section 12-A, 12-B, 12-C gate lines 13 Magnetic coupling section 21-A, 21-B DC power supply 21P-A, 21P-B, 21P-C Positive side potential output section 21N-A, 21N-B, 21N-C Negative side potential output section 22-A, 22-B, 22-C intermediate terminal 23P-A, 23P-B, 23P-C Positive switch 23N-A, 23N-B, 23N-C Negative switch 24-A, 24-B selector circuit 25-A, 25-B Temperature Sensor 26-A, 26-B, 26-C changeover switch 30 Magnetic material 50 Arm 60 Legs 100 Power conversion device 200 DC power supply 300 Load C Capacitor D A , D B , D C diode P1, P2 terminals Q A , Q B , Q C Power Semiconductor Devices T1 terminal T2 terminal

Claims

1. A gate driver for a plurality of power semiconductor devices connected in series, comprising: a gate drive voltage variable unit provided corresponding to the power semiconductor element and outputting a variable gate drive voltage, the gate drive voltage variable unit varying a potential of the gate drive voltage to be output in response to a difference in electrical characteristics between the power semiconductor elements; a gate line for supplying the gate driving voltage output from the gate driving voltage variable unit to a gate terminal of each of the corresponding power semiconductor devices; a magnetic coupling portion that magnetically couples each of the gate lines to each other; Equipped with the gate drive voltage variable section corresponding to the power semiconductor element having a first gate threshold voltage outputs a positive side potential and a negative side potential of the gate drive voltage that are lower than the positive side potential and the negative side potential of the gate drive voltage output by the gate drive voltage variable section corresponding to the power semiconductor element having a second gate threshold voltage higher than the first gate threshold voltage, Each of the gate drive voltage variable sections includes a positive potential output section that outputs a positive potential of the gate drive voltage, and a negative potential output section that is connected in series to the positive potential output section and outputs a negative potential of the gate drive voltage, a gate drive device in which, in each of the gate drive voltage variable sections, a potential at an intermediate terminal which is a connection point between the positive potential output section and the negative potential output section and a potential at an output terminal of the power semiconductor element corresponding to the gate drive voltage variable section are the same potential.

2. A gate drive device as described in claim 1, wherein a potential difference between the positive side potential output by the gate drive voltage variable unit corresponding to the power semiconductor element having the second gate threshold voltage and the potential at the intermediate terminal is greater than a potential difference between the positive side potential output by the gate drive voltage variable unit corresponding to the power semiconductor element having the first gate threshold voltage and the potential at the intermediate terminal.

3. Each of the gate drive voltage variable sections includes a positive potential output section that outputs a positive potential of the gate drive voltage, and a negative potential output section that is connected in series to the positive potential output section and outputs a negative potential of the gate drive voltage, in each of the gate drive voltage variable sections, a potential at an intermediate terminal which is a connection point between the positive potential output section and the negative potential output section is the same as a potential at an output terminal of the power semiconductor element corresponding to the gate drive voltage variable section, 3. The gate drive device according to claim 1, wherein a potential difference between a potential at the intermediate terminal of the gate drive voltage variable section corresponding to the power semiconductor element having the second gate threshold voltage and the negative potential output by the gate drive voltage variable section is smaller than a potential difference between a potential at the intermediate terminal of the gate drive voltage variable section corresponding to the power semiconductor element having the first gate threshold voltage and the negative potential output by the gate drive voltage variable section.

4. 2. The gate drive device according to claim 1, wherein the gate drive voltage variable section corresponding to the power semiconductor element having a first gate threshold voltage outputs a positive side potential and a negative side potential of the gate drive voltage that are higher than the positive side potential and the negative side potential of the gate drive voltage output by the gate drive voltage variable section corresponding to the power semiconductor element having a third gate threshold voltage that is lower than the first gate threshold voltage.

5. Each of the gate drive voltage variable sections includes a positive potential output section that outputs a positive potential of the gate drive voltage, and a negative potential output section that is connected in series to the positive potential output section and outputs a negative potential of the gate drive voltage, in each of the gate drive voltage variable sections, a potential at an intermediate terminal which is a connection point between the positive potential output section and the negative potential output section is the same as a potential at an output terminal of the power semiconductor element corresponding to the gate drive voltage variable section, 5. The gate drive device according to claim 4, wherein a potential difference between the positive side potential output by the gate drive voltage variable section corresponding to the power semiconductor element having the third gate threshold voltage and a potential at the intermediate terminal is smaller than a potential difference between the positive side potential output by the gate drive voltage variable section corresponding to the power semiconductor element having the first gate threshold voltage and a potential at the intermediate terminal.

6. Each of the gate drive voltage variable sections includes a positive potential output section that outputs a positive potential of the gate drive voltage, and a negative potential output section that is connected in series to the positive potential output section and outputs a negative potential of the gate drive voltage, in each of the gate drive voltage variable sections, a potential at an intermediate terminal which is a connection point between the positive potential output section and the negative potential output section is the same as a potential at an output terminal of the power semiconductor element corresponding to the gate drive voltage variable section, 6. The gate drive device according to claim 4, wherein a potential difference between a potential at the intermediate terminal of the gate drive voltage variable section corresponding to the power semiconductor element having the third gate threshold voltage and the negative potential output by the gate drive voltage variable section is greater than a potential difference between a potential at the intermediate terminal of the gate drive voltage variable section corresponding to the power semiconductor element having the first gate threshold voltage and the negative potential output by the gate drive voltage variable section.

7. a temperature sensor provided corresponding to each of the power semiconductor elements; 7. The gate drive device according to claim 1, wherein each of the gate drive voltage variable sections changes a positive side potential and a negative side potential of the gate drive voltage in response to a temperature of the power semiconductor element detected by the corresponding temperature sensor.

8. 8. The gate drive device according to claim 7, wherein the gate drive voltage variable section corresponding to the power semiconductor element corresponding to the temperature sensor that detected a first temperature outputs a positive side potential and a negative side potential of the gate drive voltage that are lower than the positive side potential and the negative side potential of the gate drive voltage output by the gate drive voltage variable section corresponding to the power semiconductor element corresponding to the temperature sensor that detected a second temperature that is lower than the first temperature.

9. 9. The gate drive device according to claim 7, wherein the gate drive voltage variable section corresponding to the power semiconductor element corresponding to the temperature sensor that detected a first temperature outputs a positive side potential and a negative side potential of the gate drive voltage that are higher than the positive side potential and the negative side potential of the gate drive voltage output by the gate drive voltage variable section corresponding to the power semiconductor element corresponding to the temperature sensor that detected a third temperature higher than the first temperature.

10. A gate drive device according to any one of claims 1 to 9; a power conversion circuit section having an arm on which a plurality of the power semiconductor elements connected in series are provided, the power conversion circuit section performing a power conversion operation in response to an on / off operation of the power semiconductor elements; a power conversion control unit that controls a power conversion operation of the power conversion circuit unit; A power conversion device comprising:

11. The power conversion device according to claim 10 , wherein each of the gate drive voltage variable sections changes a positive side potential and a negative side potential of the gate drive voltage in accordance with a value of a current output from the power conversion circuit section.

12. 11. The power conversion device according to claim 10, wherein each of the gate drive voltage variable units changes a positive side potential and a negative side potential of the gate drive voltage according to a value of a current command generated by the power conversion control unit to control a power conversion operation of the power conversion circuit unit.

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