JP2017143610A - Driving device for semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a driving device for a semiconductor device capable of preventing a malfunction of a voltage control type semiconductor element without providing a switching element.SOLUTION: The driving device for a semiconductor device including a driving circuit for driving a control electrode of a voltage control type semiconductor element 22b to which a freewheeling diode 24b is connected in reverse parallel includes: a gate voltage control section 30 for controlling a gate voltage applied to the control electrode; and a voltage dependent capacitor 34 connected between the control electrode of the voltage control type semiconductor element and a low potential side electrode.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a driving device for a semiconductor element applied to a power conversion device or the like.

  2. Description of the Related Art Conventionally, a power conversion device using a voltage-driven semiconductor element such as an IGBT (Insulated Gate Bipolar Transistor) or a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) is known (for example, Patent Document 1). In the power conversion device described in Patent Document 1, two main circuit switching elements formed of MOSFETs are connected in series to form a switching arm.

  When the two main circuit switching elements constituting the switching arm are simultaneously turned on, the two main circuit switching elements are connected to the gate, which is a control electrode of the main circuit switching element, in order to suppress an increase in current flowing through the main circuit switching element. A series circuit of a switching element and a capacitor is connected between the sources which are potential side electrodes. A base serving as a control electrode of the switching element is connected to a connection point between the gate resistor and the gate drive circuit.

  Therefore, the switching element connected to the capacitor is turned on when the voltage applied to the gate of the main circuit switching element is low, and the capacitor is connected between the gate and the source of the main circuit switching element. When the gate voltage applied to the gate of the transistor is high, the transistor is turned off, and the gate and the capacitor of the main circuit switch element are disconnected.

  Therefore, for example, when the main circuit switching element on the upper arm side is turned on in a state where the main circuit switching element on the lower arm side is in the off state, the capacitor on the lower arm side is connected to the main circuit switching element via the switching element. Although it is connected between the gate and the source, since a high gate voltage is applied to the gate from the gate drive circuit in order to turn on the main circuit switching element on the upper arm side, the switching element connected to the capacitor is turned off. .

  Then, by turning on the main circuit switching element on the upper arm side, by charging a part of the current flowing into the gate through the feedback capacitance between the drain and gate of the main circuit switching element on the lower arm side, The gate voltage of the gate electrode of the main circuit switching element on the lower arm side is suppressed to prevent the main circuit switching element on the lower arm side from malfunctioning in the on state.

JP 2012-239061 A

However, in the conventional example described in Patent Document 1, when a capacitor for preventing malfunction is connected between the control electrode and the low-potential side electrode of the main circuit switching element, the gate drive during charge / discharge of the capacitor is performed. In order to reduce the load on the circuit, it is necessary to connect the switching element in series with a capacitor.
For this reason, when the other main circuit switching element is turned on, the current flowing into the gate through the feedback capacitance between the drain and gate of the main circuit switching element is charged to the capacitor through the on-resistance of the switching element. For this reason, there is a problem that charging of the capacitor becomes gradual, and quick malfunction prevention cannot be performed.

  Accordingly, the present invention has been made paying attention to the problems of the conventional example described in Patent Document 1 described above, and a semiconductor element capable of preventing malfunction of a voltage-controlled semiconductor element without providing a switching element. It is an object to provide a drive device.

  To achieve the above object, a semiconductor device driving apparatus according to an aspect of the present invention includes a driving circuit for driving a control electrode of a voltage-controlled semiconductor element in which freewheeling diodes are connected in antiparallel. A gate voltage control unit that controls the gate voltage applied to the control electrode, and a voltage-dependent capacitor connected between the control electrode and the low-potential side electrode of the voltage-controlled semiconductor element.

  According to one aspect of the present invention, since a voltage-dependent capacitor is connected between the control electrode and the low-potential side electrode of the voltage-controlled semiconductor element, the current flowing through the feedback resistor can be quickly supplied to the control electrode without providing a switching element. Can be reliably charged, and malfunctions can be reliably prevented.

It is a circuit diagram which shows schematic structure of the inverter provided with the gate drive device of the semiconductor element by this invention. FIG. 2 is a circuit diagram illustrating a first embodiment of the gate driving device of FIG. 1. FIG. 3 is a characteristic diagram illustrating voltage-dependent characteristics of the voltage-dependent capacitor in FIG. 2. It is a signal waveform diagram with which it uses for description of operation | movement of 1st Embodiment. It is a circuit diagram which shows 2nd Embodiment of a gate drive device. FIG. 6 is a characteristic diagram illustrating voltage-dependent characteristics of the voltage-dependent capacitor in FIG. 5. It is a circuit diagram which shows 3rd Embodiment of a gate drive circuit. It is a circuit diagram which shows the modification of a gate voltage control circuit.

Next, an embodiment of the present invention will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals.
Further, the embodiment described below exemplifies an apparatus and a method for embodying the technical idea of the present invention, and the technical idea of the present invention is the material, shape, structure, The layout is not specified as follows. The technical idea of the present invention can be variously modified within the technical scope defined by the claims described in the claims.

Hereinafter, a semiconductor device driving apparatus according to an embodiment of the present invention will be described with reference to the drawings. In the present embodiment, a voltage-driven semiconductor element is taken as an example of a semiconductor element, and a semiconductor element gate drive apparatus is taken as an example of a semiconductor element drive apparatus.
First, a power conversion device 10 including a semiconductor element gate driving device according to the present invention will be described with reference to FIG.

  As shown in FIG. 1, the power conversion device 10 is connected to a three-phase AC power source 11. The power converter 10 includes a rectifier circuit 12 that full-wave rectifies three-phase AC power input from a three-phase AC power supply 11 and a smoothing capacitor 13 that smoothes the power rectified by the rectifier circuit 12. Yes. Although not shown, the rectifier circuit 12 is configured by connecting six diodes in a full bridge, or connecting six switching elements in a full bridge.

A positive electrode side line Lp is connected to the positive electrode output terminal of the rectifier circuit 12, and a negative electrode side line Ln is connected to the negative electrode output terminal. A smoothing capacitor 13 is connected between the positive electrode side line Lp and the negative electrode side line Ln.
Further, the power conversion device 10 includes an inverter circuit 21 that converts a DC voltage applied between the positive electrode side line Lp and the negative electrode side line Ln into a three-phase AC voltage. The inverter circuit 21 includes, for example, insulated gate bipolar transistors (hereinafter referred to as IGBTs) 22a, 22c, and 22e as voltage control type semiconductor elements that constitute the upper arm portion connected to the positive line Lp, and the negative line Ln. IGBT22b, 22d, 22f which comprises the lower arm part connected to this.

  IGBT22a and IGBT22b are connected in series between the positive electrode side line Lp and the negative electrode side line Ln, and comprise the U-phase output arm 23U. The IGBT 22c and the IGBT 22d are connected in series between the positive electrode side line Lp and the negative electrode side line Ln to constitute a V-phase output arm 23V. The IGBT 22e and the IGBT 22f are connected in series between the positive electrode side line Lp and the negative electrode side line Ln to constitute a W-phase output arm 23W.

  Refrigeration diodes 24a to 24f are connected in reverse parallel to the IGBTs 22a to 22f, respectively. That is, the cathodes of the reflux diodes 24a to 24f are respectively connected to the collectors that are the high potential side electrodes of the IGBTs 22a to 22f, and the anodes of the reflux diodes 24a to 24f are respectively connected to the emitters that are the low potential side electrodes of the IGBTs 22a to 22f. ing.

And the connection part of IGBT22a and IGBT22b, the connection part of IGBT22c and IGBT22d, and the connection part of IGBT22e and IGBT22f are each connected to the three-phase alternating current motor 15 used as an inductive load.
Moreover, the power converter device 10 has gate drive units (GDU) 25a to 25f that individually control the switching operations of the IGBTs 22a to 22f, respectively.

The output terminals of the gate driving devices 25a to 25f are connected to gate terminals that are control terminals of the IGBTs 22a to 22f, respectively.
Therefore, the inverter circuit 21 includes a three-phase full bridge circuit in which the U-phase output arm 23U, the V-phase output arm 23V, and the W-phase output arm 23W are connected in parallel, and a gate driving device that controls the switching operation of the U-phase output arm 23U. 25a and 25b, gate drive devices 25c and 25d for controlling the switching operation of the V-phase output arm 23V, and gate drive devices 25e and 25f for controlling the switching operation of the W-phase output arm 23W.

Next, the semiconductor device driving apparatus according to the present embodiment will be described with reference to FIG. 1 and FIG. 2, taking the gate driving apparatus 25b as an example. The gate driving devices 25a, 25c, 25d, 25e, and 25f have the same configuration as the gate driving device 25b.
The gate driving device 25b includes a gate voltage control unit 30 as shown in FIG. The gate voltage control unit 30 includes a forward bias circuit 31, a reverse bias circuit 32, and a bias changeover switch 33.

  The forward bias circuit 31 has a configuration in which a forward bias power supply 31a and a turn-on gate resistor 31b connected in series to the positive electrode side thereof are connected in series. The negative side of the forward bias power supply 31a is connected to the emitter serving as the low potential side electrode of the IGBT 22b. The terminal on the opposite side of the forward bias power supply 31a of the gate resistor 31b at the time of turn-on is connected to one fixed terminal ta of the bias switch 33.

  The reverse bias circuit 32 has a configuration in which a reverse bias power supply 32a and a turn-off gate resistor 32b connected in series to the positive electrode side thereof are connected in series. The negative side of the reverse bias power supply 32a is connected to the emitter which is the low potential side electrode of the IGBT 22b. The terminal opposite to the reverse bias power supply 32a of the gate resistor 32b at the time of turn-off is connected to the other fixed terminal tb of the bias changeover switch 33.

  The bias switch 33 has two fixed terminals ta and tb and a movable terminal tc for selecting the fixed terminals ta and tb. The fixed terminal ta is connected to the forward bias circuit 31, and the fixed terminal tb is connected to the reverse bias circuit 32. The movable terminal tc is connected to the gate of the IGBT 22b, and the selected bias is supplied to the gate of the IGBT 22b. This movable terminal is switched by a switching signal input from the outside.

The gate drive device 25b includes a voltage dependent capacitor 34. One end of the voltage-dependent capacitor 34 is connected to the connection point between the gate voltage control unit 30 and the gate of the IGBT 22b, and the other end is connected to the emitter of the IGBT 22b.
This voltage-dependent capacitor is formed of a ceramic capacitor and has the voltage-dependent characteristics shown in FIG. This voltage-dependent characteristic is such that when the applied voltage Vin applied between the two terminals of the voltage-dependent capacitor is on the horizontal axis and the capacitance is on the vertical axis, the applied voltage Vin is 0 V. The capacitance becomes Cmax, and as the applied voltage is increased from this state, the capacitance becomes a characteristic line L1 that decreases in a quadratic curve. By the way, when a capacitor having no voltage dependency is applied, as shown by a dotted line in FIG. 3, a fixed capacitance Cf for preventing false firing lower than the maximum capacitance Cmax regardless of the change of the applied voltage Vin. To maintain.

  Then, when the voltage-dependent capacitor 34 is set to have a capacitance necessary for preventing false firing, the capacitance of the voltage-dependent capacitor 34 is the capacitance of the capacitor having no voltage dependency near the threshold voltage Vth of the IGBT 22b. The capacitance can be smaller than Cf. Therefore, an increase in switching loss can be suppressed. At this time, since the charge / discharge charge amount of the voltage-dependent capacitor 34 according to the switching operation can be made smaller than when a capacitor having no voltage dependency is used, an increase in gate driving power can be reduced.

Next, the operation of the first embodiment will be described.
Assume that the upper arm IGBT 22a is in an off state and the lower arm IGBT 22b is in an off state. In this state, a reverse bias voltage is applied to the gate of the upper arm IGBT 22a from the reverse bias circuit 32 of the gate voltage control unit 30 of the upper arm IGBT 22a. Similarly, a reverse bias voltage is applied from the reverse bias circuit 32 of the gate voltage control unit 30 of the lower arm IGBT 22b to the gate of the lower arm IGBT 22b.

  In this state, it is assumed that the return current flows to the three-phase AC motor 15 side as the U-phase current Iu through the return diode 24b of the lower arm. From this state, when a forward bias voltage is applied to the gate of the IGBT 22a of the upper arm from the gate voltage control unit 30 to turn it on, the collector current Ic flows through the IGBT 22a when the gate voltage Vge exceeds the threshold voltage Vth of the IGBT 22a. start. Thus, by applying a forward bias voltage to the gate of the IGBT 22a, the gate potential increases, and the capacitance of the voltage-dependent capacitor 34 decreases as the gate potential increases. Therefore, it is possible to reduce an increase in gate driving power when charging the voltage-dependent capacitor 34 when the IGBT 22a is turned on.

  The collector current Ic reversely recovers the lower arm diode 24b, and the collector-emitter voltage Vce of the lower arm IGBT 22b increases from 0V as shown in FIG. For this reason, dv / dt corresponding to the switching time of the IGBT 22a of the upper arm is generated. Since the lower arm IGBT 22b has a feedback capacitance Crss, a current Icrss = Crss × dv / dt shown in FIG. 4B is generated via the feedback capacitance Crss.

At this time, since there is a wiring inductance L at the gate of the IGBT 22b, an induced voltage is generated by the wiring inductance L, and the gate potential is raised as shown by a dotted line in FIG.
However, a voltage-dependent capacitor 34 is connected to the gate of the IGBT 22b, and the electrostatic capacity is the maximum capacity Cmax shown in FIG. 3 because a reverse bias voltage is applied to the gate. For this reason, the current Icrss is shunted to the voltage-dependent capacitor 34 and charged, so that an increase in the gate potential is suppressed as shown by the solid line in FIG. At this time, the current Icrss is directly charged to the voltage-dependent capacitor 34 without passing through the switching element as in the conventional example described in Patent Document 1. For this reason, the voltage-dependent capacitor 34 can be quickly charged without being affected by the on-resistance of the switching element, and the rise in the gate potential can be reliably suppressed.

  As described above, according to the first embodiment, the IGBT 22b malfunctions while suppressing the increase of the driving power at the turn-on of the IGBT 22a only by connecting the voltage-dependent capacitor 34 between the gates and emitters of the IGBTs 22a and 22b. It can be surely prevented. Therefore, since there is no need to arrange a switching element in series with the capacitor as in the conventional example described in Patent Document 1 described above, the current Icrss flowing through the feedback capacitor Crss is not affected by the on-resistance of the switching element. The dependency capacitor 34 can be charged quickly.

Next, a second embodiment of the present invention will be described with reference to FIGS.
In the second embodiment, a parasitic capacitance of a diode is used instead of a ceramic capacitor as a voltage-dependent capacitor.
That is, in the second embodiment, as shown in FIG. 5, a diode 41 is connected as a voltage-dependent capacitor between the gates and emitters of the IGBTs 22a and 22b. Further, the reverse bias power source 32a of the reverse bias circuit 32 is omitted.

The diode 41 has a cathode connected between the gates of the IGBTs 22a and 22b and the gate voltage control unit 30, and an anode connected to the emitter side of the IGBTs 22a and 22b.
The diode 41 has a parasitic capacitance Cd and is used as a voltage-dependent capacitor by utilizing the fact that this parasitic capacitance has voltage dependency.

  Here, the voltage dependence characteristic of the parasitic capacitance of the diode is, as shown in FIG. 6, a maximum capacitance Cdmax when the applied voltage Vin to the parasitic capacitance Cd is low, and a hyperbola as the applied voltage Vin increases. The capacitance is reduced by the characteristic line L2. In this case, the decrease rate of the capacitance with respect to the increase of the applied voltage is larger than that of the ceramic capacitor of the first embodiment, so that it is possible to further reduce the switching loss and the gate drive power.

Since the diode 41 conducts in the forward direction, when a negative voltage is used as the reverse bias, a separate diode may be connected to the diode 41 in reverse series.
Next, a third embodiment of the present invention will be described with reference to FIG.
In the third embodiment, voltage dependency is provided by the series-parallel switching diode and the capacitor.

That is, in the third embodiment, as shown in FIG. 7, the voltage-dependent capacitor 34 in the first embodiment described above is omitted, and instead of this, a malfunction prevention circuit composed of a series-parallel diode and a capacitor. 50 is provided.
The malfunction prevention circuit 50 includes a series circuit of a capacitor 51, a diode 52, and a capacitor 53, one end of which is connected between a connection point between the gate voltage control unit 30 and the gate of the IGBT 22b and the emitter of the IGBT 22b. . Here, the diode 52 has an anode connected to the capacitor 51 and a cathode connected to the capacitor 53.

The malfunction prevention circuit 50 includes a diode 54 connected in antiparallel with the diode 52 and the capacitor 53, and a diode 55 connected in antiparallel with the capacitor 51 and the diode 52.
According to the third embodiment, when the IGBT 22a is turned on from the state where both the IGBTs 22a and 22b are turned off, when the current Icrss flows to the gate of the IGBT 22b through the feedback capacitor Crss, the current Icrss is The capacitor 51, the diode 52 and the capacitor 53 are shunted. The shunted current Icrss is charged in the capacitors 51 and 53, thereby reliably preventing the gate voltage Vge from reaching the threshold voltage Vth.

In this series circuit, since the capacitors 51 and 53 are connected in series via the diode 52, the capacitance C that contributes to prevention of false firing is defined as C1. When the capacitance is C2,
C = C1 / C2 / (C1 + C2) (1)
It becomes.

The malfunction prevention circuit 50 performs three operations with respect to the transition of the gate voltage Vge. First, when the forward bias circuit 31 is selected by the bias changeover switch 33 of the gate voltage control unit 30, the diode 52 is turned on by the forward bias voltage Vfw of the forward bias power supply 31a, and the capacitors 51 and 53 are charged.
The charging voltages Vc1 and Vc2 of the two capacitors 51 and 53 at this time are
Vc1 = Vfw · C2 / (C1 + C2) (2)
Vc2 = Vfw · C1 / (C1 + C2) (3)
It becomes.

  Next, when the bias changeover switch 33 is switched to the reverse bias circuit 32, charges are extracted from the gate capacitance of the IGBT 22b to the reverse bias power source 32b via the gate resistor 32b at the turn-off time. At this time, when the voltage Vc1 of the capacitor 51 is set to be larger than the voltage Vc2 of the capacitor 53, first, the diode 54 becomes conductive when the gate voltage Vge drops to Vc1, and passes through the diode 54 and the capacitor 51. The capacitor 51 is discharged by the current path I2. Further, when the gate voltage Vge decreases to the voltage Vc2 of the capacitor 53, the diode 55 is turned on, and the capacitor 53 is discharged by the current path I3 passing through the capacitor 53 and the diode 55.

At this time, by setting the voltage Vc2 of the capacitor 53 to be smaller than the threshold voltage Vth of the IGBT 22b (Vc2 <Vth), the influence of the discharge of the capacitor 53 on the turn-off operation can be suppressed. For this reason, an increase in turn-off loss can be suppressed.
Since the charging current flows through the capacitors 51 and 53 when the IGBT 22b is turned on, the increase in the gate driving power is about the same as when an ordinary capacitor is connected.

  Thus, according to the third embodiment, the capacitors 51 and 53 of the malfunction prevention circuit 50 are discharged first as the applied voltage, that is, the gate voltage Vge decreases, and then the capacitor 53 starts discharging. Is done. For this reason, the capacitance connected between the gate and the emitter of the IGBT 22b changes depending on the applied voltage, and constitutes a voltage-dependent capacitor.

In the third embodiment, an increase in gate drive power can be suppressed by using at least one of the capacitors 51 and 53 as the voltage-dependent capacitor of the first embodiment.
The first to fourth embodiments of the present invention have been described above, but the present invention is not limited to these, and various changes and improvements can be made.

  For example, as the gate voltage control unit 30, as shown in FIG. 8, a p-channel MOSFET 61 and an n-channel MOSFET 62 connected in series between the positive voltage power supply terminal tp and the negative voltage power supply terminal tn may be provided. Then, an internal control signal output from the interface circuit 63 to which, for example, a pulse width modulation (PWM) signal is input as a control signal from the outside is supplied to the gates of the MOSFETs 61 and 62, and the connection point of the MOSFETs 61 and 62 is connected to the gate of the IGBT 22b. You may make it connect. Reference numeral 64 denotes a gate resistance.

The switching element to be controlled is not limited to the IGBT, and a voltage control type semiconductor element such as a power MOSFET or SiC-MOSFET can be applied.
The switching element to be controlled may be not only a Si-based semiconductor element but also a wide band gap semiconductor element mainly composed of at least one of silicon carbide, gallium nitride, and diamond. The free-wheeling diodes 24a to 24f are not limited to Si-based semiconductor elements, but may be wide-bandgap semiconductor elements mainly composed of at least one of silicon carbide, gallium nitride, and diamond.

  DESCRIPTION OF SYMBOLS 10 ... Power converter, 11 ... Three-phase alternating current power supply, 12 ... Rectifier circuit, 13 ... Smoothing capacitor, 15 ... Three-phase alternating current motor, 21 ... Inverter circuit, 22a-22f ... IGBT, 23U ... U-phase output arm, 23V ... V-phase output arm, 23W ... W-phase output arm, 24a-24f ... freewheeling diode, 25a-25f ... gate drive, 30 ... gate voltage controller, 31 ... forward bias circuit, 32 ... reverse bias circuit, 33 ... bias Changeover switch 34 ... Voltage dependent capacitor 41 ... Diode (voltage dependent capacitor) 50 ... Malfunction prevention circuit 51, 53 ... Capacitor 52, 54, 55 ... Diode

Claims (5)

A drive device for a semiconductor device comprising a drive circuit for driving a control electrode of a voltage controlled semiconductor device in which freewheeling diodes are connected in antiparallel,
A gate voltage controller for controlling a gate voltage applied to the control electrode;
A drive device for a semiconductor element, comprising: a voltage-dependent capacitor connected between a control electrode and a low-potential side electrode of the voltage-controlled semiconductor element.   2. The driving device of a semiconductor device according to claim 1, wherein the voltage-dependent capacitor has a voltage-dependent characteristic in which a capacitance decreases as the gate voltage increases.   3. The semiconductor device driving apparatus according to claim 1, wherein the voltage-dependent capacitor includes a ceramic capacitor.   3. The semiconductor device driving apparatus according to claim 1, wherein the voltage-dependent capacitor includes a parasitic capacitance of the semiconductor element.   3. The semiconductor device driving apparatus according to claim 1, wherein the voltage-dependent capacitor comprises a series-parallel circuit of a diode and a capacitor.

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