JP5503427B2 - Gate drive circuit - Google Patents

Description

  The present invention relates to a gate drive circuit for driving a power semiconductor such as an IGBT.

When a power semiconductor such as an insulated gate bipolar transistor (IGBT) is driven by a totem pole gate driving circuit using a bipolar transistor, a protection circuit capable of blocking even if an overcurrent / short circuit occurs is required.
The IGBT is a power semiconductor that can reduce the short-circuit current by reducing the gate voltage, and the conventional protection circuit is known to detect an overcurrent / short-circuit and directly reduce the gate potential of the IGBT with an independent circuit. (For example, see Patent Documents 1 and 2). Further, at the time of overcurrent / short circuit, the protection circuit lowers the gate potential and at the same time the operation of stopping the drive circuit is performed.

Japanese Patent Publication No. 8-10821 Japanese Patent No. 3039092

However, especially when a short circuit occurs, the Vce potential, which is the collector-emitter voltage of the IGBT, drops, the charge (carrier) between the collector and gate flows into the IGBT gate, and the gate potential rises above the base potential (power supply voltage). It is said that.
When the gate potential rises above the base potential of the transistor, charge is supplied from the emitter of the NPN transistor to the base, the base potential of the transistor does not drop, and even if the protection circuit tries to stop the drive circuit, the transistor is removed until the charge is completely removed. As a result, a short circuit interruption delay occurs.

  The present invention has been made in view of the above-described circumstances, and an object of the present invention is to provide a gate drive circuit that can suppress a transistor cutoff delay and improve the protection operation of an insulated gate transistor (IGBT).

In order to achieve the above object, the present invention provides a gate drive circuit for connecting a complementary pair of transistors to the gate of an insulated gate transistor and driving the insulated gate transistor by controlling the current of the base line of the pair of transistors. in, the baseline of the transistor, and a capacitor which is charged during the turn at baseline current, the transistor, the gate potential rises before Symbol insulated gate transistor to co consuming the electric charge charged in the capacitor at turn-off base Rutotomoni a charge dissipation circuit and a resistor connected in parallel to consume electric charge supplied to said provided connected by a current limiting resistor in the charge dissipation circuit in series, the charge dissipation circuit, than the current limiting resistor It is arranged on the transistor side of the complementary pair .

According to this arrangement the, the baseline of the transistor, and a capacitor that is charged by the turn-on to the baseline current, the gate potential rises before Symbol insulated gate transistor to co Consuming the electric charge charged in the capacitor at turn-off Since a charge consuming circuit is connected in parallel with the resistor that consumes the charge supplied to the base of the transistor, the charge charged in the capacitor at turn-off is consumed by the resistor in the charge consuming circuit and causes a short circuit The charges injected due to the rise in the gate potential are also consumed by the resistance. For this reason, even when there is an increase in the gate potential at the time of abnormality, the delay in shutting off the transistor can be suppressed, the turn-off performance can be improved, and the protection operation of the insulated gate transistor can be improved.
In addition, since the charge charged in the capacitor at the time of turn-off is instantaneously consumed by the resistance in the charge consuming circuit, the switching speed to OFF can be increased, so that IGBT switching loss can be reduced.

In addition, a current limiting resistor connected in series with the charge consuming circuit is provided, and the charge consuming circuit is arranged on the complementary pair of transistors side of the current limiting resistor, so that the current to the base of the transistor Can be reliably suppressed within an appropriate range. Further, the gate drive circuit is used in an inverter circuit that converts a DC voltage supplied from an in-vehicle battery into an AC voltage that drives the motor for driving a vehicle by switching the insulated gate transistors connected in series. It is a gate drive circuit of an insulated gate transistor.

  In the present invention, a capacitor charged with a baseline current at the time of turn-on is consumed in the base line of the transistor, and a charge charged in the capacitor at the time of turn-off is consumed, and the base of the transistor is increased due to a rise in gate potential of the insulated gate transistor. Since a charge consuming circuit in which a resistor for consuming the supplied charge is connected in parallel is provided, it is possible to suppress the transistor blocking delay and improve the protection operation of the insulated gate transistor (IGBT).

1 is a schematic configuration diagram of a motor drive device to which an embodiment of the present invention is applied. It is a figure which shows a gate drive circuit. It is a figure which shows a gate drive circuit simply. It is a figure which shows a comparative example. (A) is a characteristic curve figure which shows the IGBT short circuit waveform of the circuit of a comparative example, (B) is a characteristic curve figure which shows the IGBT short circuit waveform of this circuit.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram of a motor drive device to which an embodiment of the present invention is applied.
The motor drive device 100 is an in-vehicle device mounted on an electric vehicle or a hybrid vehicle, and uses electric power from an external power source 12 that is an in-vehicle battery as driving electric power for driving a vehicle driving motor 30 as a load. A power conversion device 10 for conversion is provided.

The power conversion device 10 is a power conversion device using insulated gate transistors (Insulated Gate Bipolar Transistors: hereinafter referred to as “IGBTs”) 31H and 31L, which are power semiconductors. An external power supply 12 is connected to the input terminal 14, and a three-phase AC motor 30 is connected to the U-phase output terminal 15, V-phase output terminal 16, and W-phase output terminal 17 on the output side.
This power conversion device 10 operates under the control of the controller 23, and converts a DC voltage supplied from the external power supply 12 into a three-phase AC voltage using a plurality of (six in this configuration) switching elements (IGBTs 31H and 31L). And the three-phase AC motor 30 is rotationally driven by outputting the output signals from the output terminals 15 to 17 to the three-phase AC motor 30 for driving the vehicle.

The power converter 10 is provided between the high-voltage side input terminal 13 and the low-voltage side input terminal 14, and smoothing capacitors 22 that smooth the DC power supplied from the external power supply 12, and a plurality (six) of IGBTs 31 </ b> H. , 31L, and a gate drive substrate 26 provided with a gate drive circuit 25 for driving the IGBTs 31H, 31L of the inverter circuit 24, respectively.
The inverter circuit 24 includes IGBT series circuits 24U, 24V, and 24W corresponding to the U-phase output terminal 15, the V-phase output terminal 16, and the W-phase output terminal 17, and the IGBT series circuits 24U, 24V, and 24W are respectively A pair of IGBTs 31H and 31L connected in series is provided.

The gates of the IGBTs 31 </ b> H and 31 </ b> L of the inverter circuit 24 are connected to the gate drive circuit 25. The gate drive circuit 25 can supply a gate voltage to each of the IGBTs 31H and 31L, and switches the IGBTs 31H and 31L by controlling the gate voltage to the IGBTs 31H and 31L to be on (Hi level) / off (Low level). Let
The IGBT 31H of the IGBT series circuit 24U is connected between the high-voltage side input terminal 13 and the U-phase output terminal 15, and the IGBT 32L is connected between the U-phase output terminal 15 and the low-voltage side input terminal 14, and these IGBTs 31H, 31L Outputs a U-phase current.

The IGBT 31H of the IGBT series circuit 24V is connected between the high-voltage side input terminal 13 and the V-phase output terminal 16, and the IGBT 31L is connected between the V-phase output terminal 16 and the low-voltage side input terminal 14. The V-phase current is output by these IGBTs 31H and 31L. The IGBT 31H of the IGBT series circuit 24W is connected between the high-voltage side input terminal 13 and the W-phase output terminal 17, and the IGBT 31L is connected between the W-phase output terminal 17 and the low-voltage side input terminal 14, and the IGBTs 31H and 31L As a result, a W-phase current is output.
A commutation diode 32H is connected between the collectors and emitters of the IGBTs 31H and 31L. A current flows through the commutation diode 32H from the emitter side to the collector side of the IGBTs 31H and 31L while the IGBTs 31H and 31L are off.

  The controller 23 functions as a microcomputer that controls each part of the motor driving device 100, and the signal lines UH and UL connected to the U-phase gate driving circuit 25 and the signal lines VH and VL connected to the V-phase gate driving circuit 25, respectively. Then, an operation such as outputting a motor drive signal to the signal lines WH and WL respectively connected to the W-phase gate drive circuit 25 is performed.

Next, the gate drive circuit 25 will be described. Since the gate drive circuit 25 has the same configuration as the gate drive circuits 25 of the IGBTs 31H and 31L, a single gate drive circuit 25 will be described below. Further, in the following description, the IGBTs 31H and 31L are denoted as IGBT 31 when it is not necessary to distinguish between them.
FIG. 2 is a diagram illustrating the gate drive circuit 25, and FIG. 3 illustrates the gate drive circuit 25 in a simplified manner. As shown in FIG. 2, the gate drive circuit 25 is configured by a totem pole gate drive circuit, and includes a drive circuit unit 41 having a pair of complementary transistors 41A and 41B constituting a push-pull circuit, and a drive circuit unit. 41 detects a short circuit or an overcurrent of the base line circuit unit 43 provided in the base line 42 commonly connected to the bases of the transistors 41A and 41B, the gate driver (gate IC) 44 connected to the base line 42, and the IGBT 31. The detection circuit unit 45 is provided. The gate driver 44 is provided with a terminal for inputting a motor drive signal from the controller 23, a terminal for outputting an error to the controller 23, and the like.

The transistor 41A is an NPN bipolar transistor. The emitter of the transistor 41A is connected to the gate of the IGBT 31, and the collector is connected to a power supply line (a line connected to the high-voltage side input terminal 13) HL to which the power supply voltage VDD is applied. A high gate current is supplied in the on state. In FIG. 2 and FIG. 3, the gate line of the IGBT 31 is indicated by reference numeral 31G.
The transistor 41B is a PNP-type bipolar transistor. The collector of the transistor 41B is connected to the gate of the IGBT 31, and the emitter is connected to the earth line (line (GND) connected to the low-voltage side input terminal 14) LL. Provides a gate discharge path.

  In FIG. 2, a resistor 41 </ b> C is a resistor for adjusting the turn-on speed of the IGBT 31. Since both transistors 41A and 41B are bipolar transistors, there is an advantage that they can be driven at a low voltage. Under this configuration, to turn on the IGBT 31, charges are supplied to the common base line 42 in both transistors 41A and 41B (= the base line 42 is set to the Hi level), the transistor 41A is turned on, and the transistor 41B Is turned off. On the other hand, when the transistor 41A is turned off and the transistor 41B is turned on, the IGBT 31 is turned off.

  The detection circuit unit 45 is a circuit that detects an overcurrent or a short circuit of the IGBT 31 and outputs a detection result to the gate driver 44. The detection circuit unit 45 of this configuration shows a configuration that detects an overcurrent or a short circuit based on a minute current (sense current) output from a sense terminal provided in the IGBT 31. However, the present invention is not limited to this configuration, and other known circuit configurations may be applied.

By the way, in this gate drive circuit 25, when an overcurrent or a short circuit is detected by the detection circuit unit 45, the gate driver 44 operates to lower the gate potential by setting the base line 42 to the low level (including the case of setting the impedance to Hi). Do. At this time, particularly when a short circuit occurs, the Vce potential, which is the collector-emitter voltage of the IGBT 31L, drops, and the charge (carrier) between the collector and gate flows into the gate of the IGBT 31, causing the gate potential to be higher than the base potential (power supply voltage VDD). There is a possibility that the phenomenon of lifting, that is, the gate potential rises.
This rise in gate potential leads to a situation in which charge is supplied from the emitter of the transistor (NPN transistor) 41A to the base and the base potential of the transistor 41A does not drop. The transistor 41A is not switched off until the charge is removed. Short circuit interruption will be delayed.

In order to eliminate this short-circuit interruption delay, it is desirable to provide a circuit that forcibly consumes the charge injected into the base of the transistor 41A when it is assumed that the gate potential is increased due to a short circuit or the like. In addition, the circuit is desirably a circuit that does not adversely affect normal turn-on / off (a circuit that contributes in a better direction).
Therefore, in this configuration, as shown in FIGS. 2 and 3, the current limit resistor Rb1, the resistor Rb2, and the capacitor Cs are connected in parallel to the baseline circuit portion 43 provided in the base line 42 of the transistors 41A and 41B. The circuit configuration is such that a circuit (charge consuming circuit) 43A is connected in series.

Next, the operation of the gate drive circuit 25 will be described.
First, a case where the IGBT 31 is switched on will be described. When switching from OFF to ON, the gate driver 44 sets the base line 42 to the Hi level and supplies current to the bases of the transistors 41A and 41B. In this case, the through current flows through the capacitor Cs through the current limiting resistor Rb1, and the capacitor Cs is charged with electric charge. Therefore, the reduction in the IGBT on-speed due to the addition of the capacitor Cs is almost eliminated.

  Next, a case where the IGBT 31 is switched off will be described. In addition, when switching to off, there are a normal switching operation (switching operation for normally driving the rotation of the motor 30) and a case where the detection circuit unit 45 detects an overcurrent or a short circuit, Both are common in that the gate driver 44 lowers the base potential (extracts the base charge), and will be described together. When an overcurrent or a short circuit is detected, an operation of stopping various circuits at the same time as lowering the gate potential is also performed.

  When switching from on to off, the gate driver 44 sets the baseline 42 to a low level (including the case of setting the impedance to Hi). In this case, a closed circuit (see symbol α in FIG. 3) in which the electric charge charged in the capacitor Cs is consumed via the resistor Rb2 is formed, which causes a delay in extracting the electric charge by the current limiting resistor Rb1. Even if there is, the base potential can be lowered quickly by offsetting this factor. Therefore, both transistors 41A and 41B can be switched quickly, and the IGBT 31 can be switched off quickly.

Further, during the switching from on to off, that is, at the time of turn-off, when the gate potential rises due to a short circuit or the like and charges are injected from the emitter of the transistor 41A to the base (in FIG. 3, reference numeral This injected charge flows into the closed circuit α and is instantaneously consumed by the resistor Rb2. For this reason, even if the gate potential rises, the base potential is rapidly lowered, and the IGBT 31 can be quickly switched off. Therefore, even when the gate potential rises, the delay of switching to OFF can be suppressed, and the short circuit can be cut off quickly.
Therefore, the charge consuming circuit 43A in the gate drive circuit 25 can function as a circuit for forcibly consuming the remaining charge of the base line 42 without adversely affecting normal turn-on / off.

FIG. 4 shows a comparative example. This comparative example is a circuit obtained by removing the charge consuming circuit 43A from the gate drive circuit 25 shown in FIG. FIG. 5A is a characteristic curve diagram showing an IGBT short-circuit waveform in the circuit of this comparative example, and FIG. 5B is a characteristic curve diagram showing an IGBT short-circuit waveform in this gate drive circuit.
5A and 5B, the horizontal axis indicates the time (Time [μsec]), the vertical axis indicates the voltage value or the current value, and the on-time of the transistor 41A at the time of the short circuit is represented by a symbol T1. Each is shown.
In FIG. 5, the symbol Vge is a gate potential that is a gate-emitter voltage of the IGBT 31, the symbol Ic is a collector current of the IGBT 31, and a symbol Vce is a collector-emitter voltage of the IGBT 31.

As shown in FIGS. 5A and 5B, the on-time T1 of the transistor 41A of this configuration is less than half that of the comparative example (about 3 μsec in this configuration and about 7 μsec in the comparative example). It can be seen that the delay of the short circuit interruption can be effectively suppressed.
If the on-time T1 of the transistor 41A is short, as shown in FIGS. 5A and 5B, the time during which the gate potential Vge is high and the time during which the collector current Ic is continuously supplied (collector current application time) are shortened. It can be seen that it is possible to effectively avoid the situation where the tolerance of the IGBT 31 is exceeded.

  As described above, in this embodiment, the base line 42 of the transistors 41A and 41B consumes the capacitor Cs charged with the baseline current at the time of turn-on and the charge charged in the capacitor Cs at the time of turn-off, and the IGBT 31. Since the charge consuming circuit 43A is provided in parallel with the resistor Rb2 that consumes the charge supplied to the base of the transistor 41A due to the rise in the gate potential of the transistor 41A, the transistor 41A is cut off even if the gate potential rises during an abnormality such as a short Delay can be suppressed. For this reason, it is possible to prevent the on state of the transistor 41A from continuing when a protective function such as a short-circuit protective function is activated, thereby improving turn-off performance and improving the protective operation of the IGBT 31.

Further, even during normal turn-off, since the charge charged in the capacitor Cs is instantaneously consumed via the resistor Rb2, the base potential is rapidly lowered, and the switching speed from on to off can be increased. There is also an effect.
As a result, in this configuration, in addition to the effect that the delay of the cutoff time can be suppressed and the cutoff time can be shortened even if there is carrier injection due to the rise in gate potential at the time of abnormality, the turn-off speed in normal switching is improved. Especially, the off-time performance is improved by improving the transistor storage time, and the IGBT loss is also reduced.

Further, in this configuration, since the current limiting resistor Rb1 connected in series with the charge consuming circuit 43A is provided in the base line 42, the current to the bases of the transistors 41A and 41B can be reliably suppressed within an appropriate range.
In this configuration, since the power consumption circuit 43A is used in the power conversion device 10 of the motor drive device 100 that drives the vehicle drive motor 30, the vehicle fuel consumption is improved by improving the turn-off speed and the motor control. This is advantageous for shortening the time lag.

  In addition, embodiment mentioned above shows the one aspect | mode of this invention to the last, and can change arbitrarily within the scope of the present invention. For example, in the above-described embodiment, the case where the current limiting resistor Rb1 is provided has been described. However, the current limiting resistor Rb1 may not be provided. In the above-described embodiment, the case where the present invention is applied to the gate driving circuit 25 used in the power conversion device 10 of the motor driving device 100 has been described. However, the present invention is applied to the gate driving circuit used in other devices. The invention may be applied.

DESCRIPTION OF SYMBOLS 10 Power converter 25 Gate drive circuit 31, 31H, 31L Insulated gate type transistor (IGBT)
41A, 41B Transistor 42 Baseline 43A Charge consuming circuit 44 Gate driver Cs Capacitor Rb1 Current limiting resistor Rb2 Resistor

Claims (2)

In a gate drive circuit that connects a complementary pair of transistors to the gate of an insulated gate transistor and drives the insulated gate transistor by controlling the current of the base line of the pair of transistors,
To the base line of the transistor, and a capacitor which is charged during the turn at baseline current, the gate potential rises before Symbol insulated gate transistor to co If consumes charged in the capacitor during turn-off charge to the base of said transistor been Rutotomoni a charge dissipation circuit and a resistor connected in parallel to consume charge, a current limiting resistor on which is connected to a charge dissipation circuit in series is provided,
The gate drive circuit according to claim 1, wherein the charge consuming circuit is disposed on the side of the complementary pair of transistors with respect to the current limiting resistor . The gate drive circuit uses the insulated gate used in an inverter circuit that converts a DC voltage supplied from an in-vehicle battery into an AC voltage that drives the motor for driving a vehicle by switching the insulated gate transistors connected in series. 2. The gate drive circuit according to claim 1, wherein the gate drive circuit is a gate drive circuit of a type transistor.

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