JP6299416B2 - Drive circuit system - Google Patents

Description

  The present invention relates to a drive circuit system.

  Conventionally, a drive circuit that suppresses erroneous turn-on of a switching element is known (see Patent Document 1). Patent Document 1 controls the on / off of the switching element while controlling the voltage applied to the gate during the dead time.

JP 2008-278552 A

  However, as in Patent Document 1, when controlling on / off of two switching elements, when one switching element is turned on, the drain-source voltage of the other switching element that is in the off state rapidly changes. May turn on accidentally.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a drive circuit system capable of suppressing erroneous turn-on when the drain-source voltage of a switching element in an off state fluctuates. That is.

A driving circuit system according to one embodiment of the present invention controls on / off of a switching element having a gate electrode, a drain electrode, and a source electrode, applies a first voltage to the gate electrode, drives the switching element to an off state, and drives A drive circuit that applies a second voltage lower than the first voltage to the gate electrode by switching on and off the element, and when the switching element is in an off state, the drain-source voltage of the switching element is detected, and the detected switching A control device that drives the drive element according to the amount of time variation of the drain-source voltage of the element, and a second switching element having a second gate electrode, a second drain electrode, and a second source electrode . The drive circuit includes a drive element, and includes a second drive circuit that applies a second voltage lower than the first voltage to the gate electrode by switching on and off of the drive element. The drive element is driven to an ON state in accordance with the amount of time change in the drain-source voltage. The second switching element is connected in series with the switching element. The control device detects the voltage value or time variation of the drain-source voltage of the second switching element when the switching element is in the OFF state, and from the detected time variation of the drain-source voltage of the second switching element. The time variation of the drain-source voltage of the switching element is predicted, and the drive element is driven to the on state according to the predicted time variation of the drain-source voltage of the switching element.

  According to the present invention, it is possible to suppress erroneous turn-on when the drain-source voltage of the switching element in the off state varies.

FIG. 1 is a circuit diagram showing a configuration of a drive circuit system according to the first embodiment of the present invention. FIG. 2A is a timing chart showing a signal waveform of the gate-source voltage Vgs1 of the switching element Q1 during operation of the drive circuit system according to the first embodiment of the present invention. FIG. 2B is a timing chart showing a signal waveform of the drain-source voltage Vds1 of the switching element Q1 during operation of the drive circuit system according to the first embodiment of the present invention. FIG. 2C is a timing chart showing a signal waveform of the gate-source voltage Vgs2 of the switching element Q2 during operation of the drive circuit system according to the first embodiment of the present invention. FIG. 2D is a timing chart showing the signal waveform of the drive signal of the signal generator 11 when the drive circuit system according to the first embodiment of the present invention is in operation. FIG. 3 is a circuit diagram showing a configuration of a drive circuit system according to the second embodiment of the present invention. FIG. 4A is a timing chart showing a signal waveform of the gate-source voltage Vgs1 of the switching element Q1 during the operation of the drive circuit system according to the second embodiment of the present invention. FIG. 4B is a timing chart showing a signal waveform of the gate-source voltage Vgs2 of the switching element Q2 during the operation of the drive circuit system according to the second embodiment of the present invention. FIG. 5 is a circuit diagram showing a configuration of a drive circuit system according to the third embodiment of the present invention. FIG. 6A is a timing chart showing a signal waveform of the gate-source voltage Vgs1 of the switching element Q1 during the operation of the drive circuit system according to the third embodiment of the present invention. FIG. 6B is a timing chart showing the signal waveform of the drive signal of the signal generator 11 during the operation of the drive circuit system according to the third embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the description of the drawings, the same portions are denoted by the same reference numerals, and description thereof is omitted.

[First Embodiment]
The configuration of the drive circuit system according to the first embodiment will be described with reference to FIG.
The drive circuit system includes two drive circuits, two switching elements, and two control devices. More specifically, the drive circuit system includes a high-side drive circuit 1, a switching element Q1 and a control device 20 connected to the drive circuit 1, a low-side drive circuit 2, and a switching element Q2 connected to the drive circuit 2. And a control device 21. The drive circuits 1 and 2 output a drive signal to the gate electrodes G of the switching elements Q1 and Q2, and control on / off of the switching elements Q1 and Q2.

  The switching elements Q1 and Q2 are high-voltage / high-current power semiconductors having a drain electrode D that is a high-potential side electrode, a source electrode S that is a low-potential side electrode, and a gate electrode G that is a control electrode. A wide band gap semiconductor such as silicon (SiC) or diamond (C) can be used. The switching element Q1 and the switching element Q2 are connected in series. More specifically, the source electrode S of the switching element Q1 and the drain electrode D of the switching element Q2 are connected. Further, a load circuit (not shown) is connected to the switching elements Q1 and Q2, and the switching elements Q1 and Q2 drive the load by alternately turning on and off. Switching elements Q1, Q2 may be unipolar or bipolar.

  The drive circuit 1 includes an NPN transistor T1 that is a drive element for driving the switching element Q1 from the off state to the on state, and a PNP type that is a drive element for driving the switching element Q1 from the on state to the off state. A push-pull circuit comprising a transistor T2, a diode D1, a diode D2, a resistor R1, a resistor R2, a drive power supply E1, a drive power supply E2, and a drive signal for driving the transistors T1 and T2. Signal generator 10, a transistor T3, and a voltage variable power source E3.

Next, each configuration of the drive circuit 1, the connection relationship between the switching element Q1 and the control device 20 will be described.
The positive side of the drive power supply E1 is connected to the collector C of the transistor T1. The emitter E of the transistor T1 is connected to the gate electrode G of the switching element Q1 via the diode D1 and the resistor R1. The emitter E of the transistor T1 is connected to the emitter E of the transistor T2. The emitter E of the transistor T2 is connected to the gate electrode G of the switching element Q1 through the diode D2 and the resistor R2. The emitter E of the transistor T3 is connected to the gate electrode G of the switching element Q1, the collector C of the transistor T3 is connected to the negative side of the voltage variable power supply E3, and the base B of the transistor T3 is connected to the control device 20. Yes. That is, the transistor T3 and the voltage variable power source E3 are connected in series to the gate electrode G of the switching element Q1. The control device 20 is connected to the drain electrode D and the source electrode S of the switching element Q1. The base B of the transistor T1 and the base B of the transistor T2 are connected to the signal generator 10. Further, the negative side of the driving power source E1, the positive side of the driving power source E2, the positive side of the voltage variable power source E3, and the source electrode S of the switching element Q1 are connected to the signal generator 10. The control device 20 and the voltage variable power source E3 are connected by a signal line.

  The control device 20 includes a voltage sensor and a current sensor, and can detect the drain-source voltage Vds1 of the switching element Q1 and the current flowing through the drain electrode D. In addition, the control device 20 can output a drive signal to the base B of the transistor T3 to switch the on / off operation of the transistor T3. In addition, the control device 20 can increase or decrease the voltage output from the voltage variable power supply E3.

  The drive circuit 2 includes an NPN transistor T4 that is a drive element for driving the switching element Q2 from the off state to the on state, and a PNP type that is a drive element for driving the switching element Q2 from the on state to the off state. A push-pull circuit comprising a transistor T5, a diode D3, a diode D4, a resistor R3, a resistor R4, a drive power supply E4, a drive power supply E5, and a drive signal for driving the transistors T4 and T5 Signal generator 11, a transistor T6, and a voltage variable power supply E6.

Next, each configuration of the drive circuit 2, the connection relationship between the switching element Q2 and the control device 21 will be described.
The positive side of the drive power supply E4 is connected to the collector C of the transistor T4. The emitter E of the transistor T4 is connected to the gate electrode G of the switching element Q2 via the diode D3 and the resistor R3. The emitter E of the transistor T4 is connected to the emitter E of the transistor T5. The emitter E of the transistor T5 is connected to the gate electrode G of the switching element Q2 via the diode D4 and the resistor R4. The emitter E of the transistor T6 is connected to the gate electrode G of the switching element Q2, the collector C of the transistor T6 is connected to the negative side of the voltage variable power supply E6, and the base B of the transistor T6 is connected to the control device 21. Yes. That is, the transistor T6 and the voltage variable power source E6 are connected in series to the gate electrode G of the switching element Q2. The control device 21 is connected to the drain electrode D and the source electrode S of the switching element Q2. The base B of the transistor T4 and the base B of the transistor T5 are connected to the signal generator 11. Further, the negative electrode side of the drive power supply E4, the positive electrode side of the drive power supply E5, the positive electrode side of the voltage variable power supply E6, and the source electrode S of the switching element Q2 are connected to the signal generator 11. The control device 21 and the voltage variable power source E6 are connected by a signal line.

  The control device 21 includes a voltage sensor and a current sensor, and can detect the drain-source voltage Vds2 of the switching element Q2 and the current flowing through the drain electrode D. Further, the control device 21 can output a drive signal to the base B of the transistor T6 to switch the on / off operation of the transistor T6. Further, the control device 21 can increase or decrease the voltage output from the voltage variable power supply E6.

  The control devices 20 and 21 are configured as an integrated computer including storage means such as a CPU, RAM, ROM, and hard disk.

  The drive power supply E1 and the drive power supply E4 are power supplies that apply a voltage Vg1 higher than the threshold voltages Vth1 and Vth2 to the gate electrodes G of the switching elements Q1 and Q2 to turn on the switching elements Q1 and Q2. The drive power supply E2 and the drive power supply E5 are power supplies that apply a voltage Vg2 lower than the threshold voltages Vth1 and Vth2 to the gate electrodes G of the switching elements Q1 and Q2 in order to turn off the switching elements Q1 and Q2. . The voltages applied by the drive power supply E2 and the drive power supply E5 may be positive or negative as long as the voltages are lower than the threshold voltages Vth1 and Vth2 of the switching elements Q1 and Q2.

  For the transistors T1 to T6, a wide band gap semiconductor such as silicon carbide (SiC) or diamond (C) can be used. The transistors T1 to T6 are described as bipolar transistors, but unipolar transistors capable of the same operation may be used.

  Next, the operation of the drive circuit system according to the first embodiment will be described with reference to the timing chart of FIG.

  When the drive signal from the signal generator 10 is switched off at time t1, the gate-source voltage Vgs1 of the switching element Q1 is lowered from the voltage Vg1 to the voltage Vg2, and the switching element Q1 is turned off.

  When the drive signal from the signal generator 11 is turned on at time t2, the transistor T4 is turned on and the transistor T5 is turned off, and the gate of the switching element Q2 is connected via the drive power supply E4, transistor T4, diode D3, and resistor R3. A current flows through the electrode G.

  At time t3, the gate-source voltage Vgs2 of the switching element Q2 rises from the voltage Vg2 to the voltage Vg1. Thereby, the switching element Q2 is turned on.

  When the switching element Q2 is turned on, the voltage at the contact point between the switching element Q1 and the switching element Q2 increases. Thereby, at time t4, the drain-source voltage Vds1 of the switching element Q1 in the off state increases from the low level to the high level.

  Here, the influence of the rise of the drain-source voltage Vds1 of the switching element Q1 will be described. A parasitic capacitance (hereinafter referred to as gate-source capacitance) exists between the gate and source of the switching element Q1. When the drain-source voltage Vds1 of the switching element Q1 increases, a current flows through the gate-source capacitance of the switching element Q1 along with this voltage change. As a result, the gate-source voltage Vgs1 of the switching element Q1 increases. When the gate-source voltage Vgs1 exceeds the threshold voltage Vth1, the switching element Q1 is erroneously turned on. Further, a large through current flows from the switching element Q2 to the switching element Q1, and the switching element Q1 may be destroyed.

  Therefore, when detecting an increase in the drain-source voltage Vds1 of the switching element Q1, the control device 20 outputs a drive signal for turning on the transistor T3. Here, detecting the rise of the drain-source voltage Vds1 means detecting that the temporal change amount of the drain-source voltage Vds1 is equal to or greater than a predetermined value. The predetermined value can be obtained in advance from experiments or simulations. Further, the control device 20 performs control so that the output voltage of the voltage variable power supply E3 becomes a voltage Vg3 lower than the voltage Vg2. Thereby, the transistor T3 is turned on, and the voltage Vg3 is applied to the gate electrode G of the switching element Q1 only at the moment when the transistor T3 is turned on. As a result, at time t4, the gate-source voltage Vgs1 of the switching element Q1 falls to a voltage Vg3 lower than the voltage Vg2. Thereby, the rise of the gate-source voltage Vgs1 due to the rise of the drain-source voltage Vds1 of the switching element Q1 is suppressed, and the erroneous turn-on of the switching element Q1 is suppressed.

  At time t5, the drain-source voltage Vds1 of the switching element Q1 becomes high level, and the voltage increase stops. When detecting that the rise of the drain-source voltage Vds1 has stopped, the control device 20 outputs a drive signal for turning off the transistor T3. As a result, the transistor T3 is turned off.

  At time t6, when the drive signal from the signal generator 11 is switched off, the transistor T4 is turned off and the transistor T5 is turned on, so that the charge stored in the gate-source capacitance of the switching element Q2 is discharged, and the resistor R4, A current flows through the transistor T5 via the diode D4.

  At time t7, when the gate-source voltage Vgs2 of the switching element Q2 falls from the voltage Vg1 to the voltage Vg2, the switching element Q2 is turned off. As a result, the voltage at the contact point between the switching element Q1 and the switching element Q2 drops, and the drain-source voltage Vds1 of the switching element Q1 starts to drop from the high level to the low level.

  When the drive signal from the signal generator 10 is turned on at time t8, the transistor T1 is turned on and the transistor T2 is turned off, and the gate of the switching element Q1 is connected via the drive power supply E1, the transistor T1, the diode D1, and the resistor R1. A current flows through the electrode G. Then, the gate-source voltage Vgs1 of the switching element Q1 rises from the voltage Vg2 to the voltage Vg1, and the switching element Q1 is turned on.

  When the switching element Q1 is turned on, the voltage at the contact point between the switching element Q1 and the switching element Q2 increases. As a result, the drain-source voltage Vds2 of the switching element Q2 in the off state rises, and along with this voltage change, a current flows through the gate-source capacity via the drain-gate capacity of the switching element Q2. As a result, the gate-source voltage Vgs2 of the switching element Q2 increases. When the gate-source voltage Vgs2 exceeds the threshold voltage Vth2, the switching element Q2 is erroneously turned on. Further, a large through current flows from the switching element Q1 to the switching element Q2, and the switching element Q2 may be destroyed.

  Therefore, when detecting an increase in the drain-source voltage Vds2 of the switching element Q2, the control device 21 outputs a drive signal for turning on the transistor T6. Here, detecting the rise of the drain-source voltage Vds2 means detecting that the temporal change amount of the drain-source voltage Vds2 is equal to or greater than a predetermined value. The predetermined value can be obtained in advance from experiments or simulations. Further, the control device 21 performs control so that the output voltage of the voltage variable power supply E6 becomes a voltage Vg3 lower than the voltage Vg2. Thereby, the transistor T6 is turned on, and the voltage Vg3 is applied to the gate electrode G of the switching element Q2 only at the moment when the transistor T6 is turned on. Thereby, at time t9, the gate-source voltage Vgs2 of the switching element Q2 falls to the voltage Vg3 lower than the voltage Vg2. Thereby, the rise of the gate-source voltage Vgs2 due to the rise of the drain-source voltage Vds1 of the switching element Q2 is suppressed, and the erroneous turn-on of the switching element Q2 is suppressed.

  Further, the control device 20 changes the voltage Vg3, which is the output of the voltage variable power supply E3, according to the voltage value or the time change amount of the drain-source voltage Vds1 of the switching element Q1 detected from time t4 to time t5. Can be adjusted. For example, the control device 20 can adjust the voltage Vg3 to be lower as the detected voltage value or time change amount of the drain-source voltage Vds1 is larger. Thereby, the transient response of the voltage change of the gate-source voltage Vgs1 with respect to the voltage change of the drain-source voltage Vds1 becomes good.

  As described above, the drive circuit system according to the first embodiment detects the drain-source voltage Vds1 of the switching element Q1 in the off state, and changes the transistor according to the amount of time change of the detected drain-source voltage Vds1. T3 is driven to an ON state, and a voltage Vg3 lower than the voltage Vg2 is applied to the gate electrode G of the switching element Q1. As a result, the drive circuit system suppresses the increase in the gate-source voltage Vgs1 of the switching element Q1 due to the increase in the drain-source voltage Vds1 of the switching element Q1 that occurs when the switching element Q2 is turned on. Thus, erroneous turn-on of the switching element Q1 can be suppressed.

  Further, the drive circuit system according to the first embodiment can adjust the voltage Vg3, which is the output of the voltage variable power supply E3, according to the detected voltage value or time change amount of the drain-source voltage Vds1 of the switching element Q1. it can.

  Specifically, the drive circuit system according to the first embodiment can be adjusted so that the voltage Vg3 decreases as the voltage value or time change amount of the detected drain-source voltage Vds1 of the switching element Q1 increases. . Thereby, the transient response of the voltage change of the gate-source voltage Vgs1 with respect to the voltage change of the drain-source voltage Vds1 becomes good.

  Further, the current value of the drain electrode D of the switching element Q1 or the time change amount of the current value is detected, and the voltage Vg3 that is the output of the voltage variable power supply E3 is adjusted according to the detected current value or the time change amount of the current value. May be.

  For example, the drive circuit system according to the first embodiment can be adjusted so that the voltage Vg3 becomes lower as the detected current value of the drain electrode D of the switching element Q1 or the time change amount of the current value is larger.

[Second Embodiment]
Next, a drive circuit system according to the second embodiment will be described with reference to FIG. The second embodiment differs from the first embodiment in that the control device 20 is further connected to the gate electrode G and the source electrode S of the switching element Q2, and the control device 21 is connected to the gate electrode G of the switching element Q1. To be further connected. Thereby, the control apparatus 20 can detect the drain-source voltage Vds2 and the gate-source voltage Vgs2 of the switching element Q2. Further, the control device 21 can detect the gate-source voltage Vgs1 of the switching element Q1.

  Next, the operation of the drive circuit system according to the second embodiment will be described with reference to the timing chart of FIG. Since operations at times t1, t3, t5, t7, t8, and t9 are the same as those in the first embodiment, detailed description thereof is omitted.

  At time t3, when detecting the time change amount of gate-source voltage Vgs2 of switching element Q2, control device 20 predicts the time change amount of drain-source voltage Vds1 of switching element Q1 generated after time t3. . The time change amount of the drain-source voltage Vds1 of the switching element Q1 generated after the time t3 can be obtained in advance from experiments or simulations. When the control device 20 determines that the predicted amount of change in the drain-source voltage Vds1 over time is equal to or greater than a predetermined value, the control device 20 drives to turn on the transistor T3 at time t10 between time t3 and time t5. A signal is output and a voltage Vg3 is applied to the gate electrode G of the switching element Q1. As a result, the gate-source voltage Vgs1 of the switching element Q1 falls to a voltage Vg3 lower than the voltage Vg2. Thereby, the rise of the gate-source voltage Vgs1 due to the rise of the drain-source voltage Vds1 of the switching element Q1 is suppressed, and the erroneous turn-on of the switching element Q1 is suppressed.

  Further, the control device 20 can adjust the voltage Vg3, which is the output of the voltage variable power supply E3, according to the detected voltage value or time change amount of the gate-source voltage Vgs2 of the switching element Q2. For example, the control device 20 can adjust the voltage Vg3 to be lower as the detected voltage value or time change amount of the gate-source voltage Vgs2 is larger. Thereby, the transient response of the voltage change of the gate-source voltage Vgs1 of the switching element Q1 to the voltage change of the gate-source voltage Vgs2 of the switching element Q2 becomes good.

  As described above, the drive circuit system according to the second embodiment detects the amount of time change of the gate-source voltage Vgs2 of the switching element Q2, and the switching element Q2 is turned on from the detected gate-source voltage Vgs2. The time change amount of the drain-source voltage Vds1 of the switching element Q1 in the off state that occurs when the switching state is reached is predicted, and the transistor T3 is driven to the on state based on this prediction, and the voltage Vg3 lower than the voltage Vg2 Is applied to the gate electrode G of the switching element Q1. Thereby, the drive circuit system can suppress the rise of the gate-source voltage Vgs1 of the switching element Q1 due to the rise of the drain-source voltage Vds1 of the switching element Q1, and suppress the erroneous turn-on of the switching element Q1. can do.

  Further, the drive circuit system according to the second embodiment can adjust the voltage Vg3, which is the output of the voltage variable power supply E3, in accordance with the detected voltage value or time change amount of the gate-source voltage Vgs2 of the switching element Q2. it can.

  Specifically, the drive circuit system according to the second embodiment can be adjusted such that the voltage Vg3 decreases as the voltage value or time change amount of the detected gate-source voltage Vgs2 of the switching element Q2 increases. . Thereby, the transient response of the voltage change of the gate-source voltage Vgs1 of the switching element Q1 to the voltage change of the gate-source voltage Vgs2 of the switching element Q2 becomes good.

  In the second embodiment, the time change amount of the drain-source voltage Vds1 of the switching element Q1 is predicted from the time change amount of the gate-source voltage Vgs2 of the switching element Q2. Instead of the voltage Vgs2, the time change amount of the drain-source voltage Vds2 of the switching element Q2 is detected, and the time change of the drain-source voltage Vds1 of the switching element Q1 is detected from the detected time change amount of the drain-source voltage Vds2. The amount may be predicted.

  Further, when the time variation of the drain-source voltage Vds1 of the switching element Q1 is predicted from the detected time variation of the drain-source voltage Vds2 of the switching element Q2, the detected drain-source voltage Vds2 of the switching element Q2 is detected. The voltage Vg3 that is the output of the voltage variable power supply E3 may be adjusted according to the voltage value or the amount of time change.

  Specifically, the drive circuit system according to the second embodiment can be adjusted such that the voltage Vg3 decreases as the voltage value or time change amount of the detected drain-source voltage Vds2 of the switching element Q2 increases. .

  Further, the current value of the drain electrode D of the switching element Q2 or the time change amount of the current value is detected, and the voltage Vg3 that is the output of the voltage variable power supply E3 is adjusted according to the detected current value or the time change amount of the current value. May be.

  For example, the drive circuit system according to the second embodiment can be adjusted such that the voltage Vg3 is lower as the detected current value of the drain electrode D of the switching element Q2 or the time variation of the current value is larger.

  The control device 21 is connected to the drain electrode D of the switching element Q1, and the control device 21 detects the drain-source voltage Vds1 of the switching element Q1, or the current of the drain electrode D of the switching element Q1. You may make it do. Further, the control device 20 may be connected to the drain electrode D of the switching element Q1, and the control device 20 may detect the current of the drain electrode D of the switching element Q1.

[Third Embodiment]
Next, a drive circuit system according to the third embodiment will be described with reference to FIG. The third embodiment differs from the first embodiment in that the control device 20 is further connected to the signal generator 11 and the control device 21 is further connected to the signal generator 10. As a result, the control device 20 can receive the drive signal from the signal generator 11. Further, the control device 21 can receive a drive signal from the signal generator 10.

  Next, the operation of the drive circuit system according to the third embodiment will be described with reference to the timing chart of FIG. Since operations at times t1, t2, t5, t6, and t8 are the same as those in the first embodiment, detailed description thereof is omitted.

  At time t2, when receiving the drive signal (ON) from the signal generator 11, the control device 20 predicts a time change amount of the drain-source voltage Vds1 of the switching element Q1 generated after the time t2. The time change amount of the drain-source voltage Vds1 of the switching element Q1 generated after the time t2 can be obtained in advance from experiments or simulations. When the control device 20 determines that the predicted amount of time change of the drain-source voltage Vds1 is greater than or equal to a predetermined value, the control device 20 drives to turn on the transistor T3 at time t11 between time t2 and time t5. A signal is output and a voltage Vg3 is applied to the gate electrode G of the switching element Q1. As a result, the gate-source voltage Vgs1 of the switching element Q1 falls to a voltage Vg3 lower than the voltage Vg2. Thereby, the rise of the gate-source voltage Vgs1 of the switching element Q1 due to the rise of the drain-source voltage Vds1 of the switching element Q1 is suppressed, and the erroneous turn-on of the switching element Q1 is suppressed.

  As described above, the drive circuit system according to the third embodiment is based on the received drive signal (ON) of the signal generator 11 and is generated when the switching element Q2 is turned on. The time change amount of the drain-source voltage Vds1 is predicted, the transistor T3 is driven to the ON state based on this prediction, and the voltage Vg3 lower than the voltage Vg2 is applied to the gate electrode G of the switching element Q1. Thereby, the drive circuit system can suppress the increase of the switching element Q1 gate-source voltage Vgs1 due to the increase of the drain-source voltage Vds1 of the switching element Q1, and suppress the erroneous turn-on of the switching element Q1. be able to.

  Although the embodiments of the present invention have been described as described above, it should not be understood that the descriptions and drawings constituting a part of this disclosure limit the present invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

1, 2 Drive circuits 10, 11 Signal generators 20, 21 Control devices Q1, Q2 Switching elements T1, T2, T3, T4, T5, T6 Transistors R1, R2, R3, R4 Resistors D1, D2, D3, D4 Diode E1 , E2, E4, E5 Drive power supply E3, E6 Voltage variable power supply

Claims (10)

A drive circuit for controlling on / off of a switching element having a gate electrode, a drain electrode, and a source electrode, and applying a first voltage to the gate electrode to drive the switching element in an off state;
A control device for detecting a voltage value or a time change amount of a drain-source voltage of the switching element when the switching element is in an off state;
A second switching element having a second gate electrode, a second drain electrode, and a second source electrode ,
The drive circuit includes a drive element, and includes a second drive circuit that applies a second voltage lower than the first voltage to the gate electrode by switching on and off the drive element,
The control device drives the driving element to an on state according to the detected amount of time change in the drain-source voltage of the switching element ,
The second switching element is connected in series to the switching element;
The control device detects a voltage value or a temporal change amount of a drain-source voltage of the second switching element when the switching element is in an OFF state, and detects the detected drain-source voltage of the second switching element. Predicting a time change amount of the drain-source voltage of the switching element from the time change amount, and driving the driving element in an ON state according to the predicted time change amount of the drain-source voltage of the switching element; A drive circuit system characterized by the above.   A drive circuit for controlling on / off of a switching element having a gate electrode, a drain electrode, and a source electrode, and applying a first voltage to the gate electrode to drive the switching element in an off state;
  A control device for detecting a voltage value or a time change amount of a drain-source voltage of the switching element when the switching element is in an off state;
  A second switching element having a second gate electrode, a second drain electrode, and a second source electrode,
  The drive circuit includes a drive element, and includes a second drive circuit that applies a second voltage lower than the first voltage to the gate electrode by switching on and off the drive element,
  The control device drives the driving element to an on state according to the detected amount of time change in the drain-source voltage of the switching element,
  The second switching element is connected in series to the switching element;
  The control device detects a voltage value or a time change amount of the gate-source voltage of the second switching element when the switching element is in an OFF state, and detects the detected gate-source voltage of the second switching element. A time change amount of the drain-source voltage of the switching element is predicted from the time change amount, and the driving element is driven to an ON state according to the predicted time change amount of the drain-source voltage of the switching element.
  A drive circuit system characterized by that. 3. The drive circuit system according to claim 1, wherein the control device adjusts the second voltage in accordance with a detected voltage value or a temporal change amount of a drain-source voltage of the switching element. 2. The drive circuit system according to claim 1 , wherein the control device adjusts the second voltage according to a detected voltage value or a temporal change amount of a drain-source voltage of the second switching element. The control device detects a current value flowing through the drain electrode of the switching element or a time change amount of the current value, and according to the detected current value flowing through the drain electrode of the switching element or a time change amount of the current value. driving circuit system according to claim 1 or 2, characterized in that adjusting the second voltage. The control device detects a current value flowing through the second drain electrode of the second switching element or a time change amount of the current value, and detects the detected current value or current flowing through the second drain electrode of the second switching element. 3. The drive circuit system according to claim 1, wherein the second voltage is adjusted according to a time change amount of the value. 4. The drive circuit system according to claim 3 , wherein the control device lowers the second voltage as the detected voltage value or time change amount of the drain-source voltage of the switching element is larger. 5. The drive circuit system according to claim 4 , wherein the control device lowers the second voltage as the detected voltage value or time change amount of the drain-source voltage of the second switching element is larger. . 6. The drive circuit system according to claim 5 , wherein the control device lowers the second voltage as the detected current value flowing through the drain electrode of the switching element or the time variation of the current value increases. . The control device according to claim 6, wherein as the time change amount of the current value or the current value flowing through the second drain electrode of the detected said second switching element is large, to lower the second voltage Drive circuit system.

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