JP5460272B2 - Voltage-driven semiconductor device gate drive device - Google Patents

Description

  The present invention relates to a gate drive device for a voltage-driven semiconductor element having an insulated gate structure such as IGBT or MOSFET.

  Since semiconductor switching elements having an insulated gate structure such as IGBT and MOSFET are voltage driven elements, they have a lower driving power than current driven elements such as bipolar transistors and are widely used in a wide range of fields.

  In these insulated gate type elements, the gate is insulated from other terminals, and a capacitor is equivalently formed when viewed from the gate terminal. The gate drive circuit is a circuit for charging and discharging these gate capacitors.

  FIG. 2 is a general configuration diagram of an IGBT drive circuit. In FIG. 2, the IGBT drive circuit comprises an IGBT 1 to be driven, a series circuit of an on power supply 6 and an on transistor 8, a series circuit of an off power supply 7 and an off transistor 9, and a transistor on / off signal source 10. Has been. An IGBT drive signal is output as a gate signal from the connection point of both transistors, but a resistor 5 is inserted between the IGBT drive signal and the IGBT gate terminal, and it charges and discharges the gate capacity of the IGBT both when it is turned on and off. It works as a gate resistance.

  Conventional gate drive devices are driven both on and off with a single resistor. However, when used for a high-speed switching element such as an IGBT, an excessive surge voltage may be generated due to stray inductance such as circuit wiring when the element is switched, and the element may be destroyed.

Here, if the gate capacitance is gradually charged / discharged, the IGBT switching operation will be moderated accordingly, so intentionally setting the gate resistance to slow the IGBT switching slow and suppress the surge voltage. Done. (For example, see Non-Patent Document 1)
FIG. 3 shows an example of a waveform when the gate resistance of the IGBT gate drive device is increased to suppress the surge during IGBT turn-off. VGE represents the gate-emitter voltage of IGBT1, and VCE represents the collector-emitter voltage of IGBT1. When the gate resistance is increased, both VGE and VCE in FIG. 3 change from a solid line to a broken line. When attention is paid to VGE, it can be seen that when an off signal is input before improvement, the gate voltage quickly decreases and the IGBT starts to turn off. I understand that. Since the gate voltage changes gently, the IGBT 1 is also cut off gradually. As a result, the turn-off surge voltage can be lowered by increasing the gate resistance value.

JP 2004-15675 A

Fuji IGBT Module Application Manual February 2004 RH984 Chapter 7 Gate Drive Circuit Design Method

However, as described above, in the method of suppressing the switching surge of the IGBT by increasing the gate resistance to moderate the charge / discharge of the gate capacitance and suppressing the switching surge of the IGBT, the IGBT is actually connected after the on / off signal is input to the drive circuit. The delay time until the start of the off operation until the operation is started increases as shown by the arrows in FIG. This is nothing but the actual operation being delayed from the originally required OFF timing, and the output voltage width required for control of the converter using the IGBT, for example, is undesirably widened. As a result, there is a possibility of deteriorating the performance of the conversion device.
In general, the ON operation is unlikely to cause problems such as an excessive surge voltage in the switching waveform. Therefore, the gate resistance on the ON side does not need to be set too large to suppress the surge voltage. In addition, the increase in loss due to the increase in on-side gate resistance appears significantly more significantly than the increase in loss when the off-side gate resistance is increased. Here, the ON operation and the OFF operation cannot be individually adjusted with a single gate resistor as in the conventional example.
The present invention provides a gate driving device for solving the above problems.

According to the invention of claim 1,
A voltage-driven semiconductor element, a first switching circuit composed of a series circuit of a power supply for on and an on transistor, and a second switching circuit composed of a power supply for off and a transistor for off. In a gate drive device having a circuit, the first switching circuit and the second switching circuit are connected in series, and an on / off command signal source and an on / off signal supplied from the on / off command signal source are A parallel body of a diode and a capacitor, provided in series with the parallel body, between the first and second switching circuit outputs and the gate terminal of the voltage-driven semiconductor element, provided to the first and second transistors. series body by connecting the first resistor to a further comprising a connected in parallel with the series body and the second resistor is a value larger than the first resistor The gate drive of that voltage-driven semiconductor element.

According to the invention of claim 2,
2. The gate driving device according to claim 1, wherein the resistance value of the second resistor is 8 to 15 times the resistance value of the first resistor.

In the present invention, in order to solve the above-mentioned problem, in the gate drive device for a voltage-driven semiconductor element according to the present invention, an on-state circuit comprising a voltage-driven semiconductor element, a series circuit of an on-state power source and an on-state transistor. In the gate drive device having the first switching circuit and the second switching circuit for turning off that is a series circuit of the power source for turning off and the transistor for turning off, the first switching circuit and the second switching circuit Are connected in series, and an on / off command signal source and an on / off signal given from the on / off command signal source are given to the first and second transistors, and the first and second switching between the gate terminal of the circuit output and the voltage driven type semiconductor element, parallel body diode and a capacitor, straight by connecting a first resistor in series with said parallel bodies Body, connected in parallel with the series body and than the first resistor constituting than the second resistor is a large value.

When the gate resistance of the gate driving circuit is increased in order to reduce the surge voltage between elements generated by wiring inductance during switching of the voltage driven semiconductor element, the switching operation delay time becomes longer.
When the gate charge is discharged by the off signal when the voltage driven semiconductor element is turned off, the first resistor and the capacitor are quickly discharged at the beginning of the off signal application to prevent an increase in switching operation time delay, and thereafter The surge voltage between elements is reduced by reducing the gate current by switching to the second resistor. In addition, when the voltage-driven semiconductor element is turned on, the diode is turned on, so that the first resistor and the second resistor are configured in parallel. Therefore, depending on the resistance value of the first resistor The gate charge can be quickly charged.
According to the present invention, the gate resistance can be set large without increasing the delay time especially when the IGBT is turned off to suppress the switching surge voltage, and the on and off gate resistance can be individually adjusted. Become.

It is the circuit diagram which showed the gate drive device of IGBT as an Example of this invention. It is a circuit diagram which showed the gate drive device of IGBT as a prior art example. It is a wave form diagram for demonstrating the gate drive circuit operation | movement of the conventional IGBT. It is a wave form diagram for demonstrating operation | movement of the gate drive apparatus of IGBT of the Example of this invention.

  By adding a few circuits to the conventional gate drive circuit, the turn-off delay time can be reduced and the operation adjustment by the gate resistance can be performed separately for turn-on and turn-off.

  FIG. 1 is a diagram showing an embodiment of an IGBT gate driving apparatus according to claim 1 of the present invention. The circuit of FIG. 1 includes resistors 4, 5 provided between an IGBT 1 to be driven, a series body of an on power source 6 and an on transistor 8, and a series body of an off power source 7 and an off transistor 9. A combination of the capacitor 2 and the diode 3 is used. Specifically, the capacitor 2 and the diode 3 are connected in parallel, and the resistor 4 is connected in series to the parallel body. Finally, the resistor 5 is connected in parallel to the series body. When a signal is input from the on / off signal source 10 to each of the transistors 8 and 9, the voltages of the on power supply 6 and the off power supply 7 are applied to the gate terminal of the IGBT 1 via the gate resistance accordingly. . As will be described later, the resistor 4 functions mainly at the time of turn-on and the resistor 5 at the time of turn-off. A smaller value is set.

At the time of turn-off at this time, first, the charge of the gate of the IGBT 1 is quickly discharged by the series circuit of the resistor 4 and the capacitor 2. This action shortens the turn-off delay time. In the series circuit of the capacitor 2 and the resistor 4, due to the time constant of CR, when the impedance of the capacitor 2 becomes very large and close to the insulation state, no current flows through the resistor 4 with the backflow prevention function of the diode 3. The gate voltage of the IGBT 1 gradually changes through the resistor 5 and the turn-off operation becomes gentle. Then, the turn-off delay time of the IGBT 1 is shortened, and the surge voltage at the turn-off is suppressed.
At turn-on, the diode 3 is biased in the forward direction and becomes conductive, so that the current passes through the resistor 4 and is turned on with a gate resistance appropriate for turn-on. As described above, the resistor 4 functions as a gate resistance at the time of turn-on, and also provides a rapid gate charge discharging operation at the time of turn-off and also a function of limiting a drawing current by the capacitor at this time.

  The recommended gate resistance on the device manufacturer's data sheet is almost the same value for both on and off, but as described above, the off-side resistance value is large, and the on-side resistance value is close to the manufacturer's recommended value. It was confirmed that by setting to 3.9 [Ω] and off-side 33 [Ω], the surge voltage at the turn-off was reduced while suppressing an increase in turn-on loss. The relationship between the on-side and off-side resistance values differs depending on the element characteristics and the situation of the peripheral circuit. By taking the resistance ratio from 1: 8 to 1:15 on: off, It was confirmed that the effect was exerted. In addition, when it deviates from these values (1) When the ON-side resistance value becomes low, the reverse recovery current of the flywheel diode of the reverse side arm becomes high, and there is a risk that the semiconductor element is destroyed. is there. (2) When the resistance value on the off side is too high, an operation delay is caused, resulting in an increase in switching loss. From the above, the most suitable set value is the ratio of the resistance values from 1: 8 to 1:15.

  The solid line in FIG. 4 shows the waveform when the gate resistance is only increased as is conventionally done. The solid line in FIG. 4 represents the same as the broken line in FIG. When the present invention is applied here, it becomes as shown by a broken line in FIG. The surge voltage at the time of turn-off remains the same as before, and the time from when the off signal is input to the drive circuit until the IGBT actually turns off is shortened.

  By applying it for driving a switching element such as an inverter, it is possible to reduce the switching surge, especially at the time of turn-off, reduce the operation delay time, and individually set the gate resistance value at the time of turn-on and turn-off.

  The description of the present invention has been given by taking an IGBT as an example. However, the present invention can be applied to a voltage-driven semiconductor element such as a MOSFET other than the IGBT.

1 IGBT
2 Capacitor 3 Diode 4, 5 Resistor 6 ON power supply 7 OFF power supply 8 ON transistor 9 OFF transistor 10 ON / OFF signal source

Claims (2)

A voltage-driven semiconductor element, a first switching circuit composed of a series circuit of a power supply for on and an on transistor, and a second switching circuit composed of a power supply for off and a transistor for off. In a gate drive device having a circuit, the first switching circuit and the second switching circuit are connected in series, and an on / off command signal source and an on / off signal supplied from the on / off command signal source are A parallel body of a diode and a capacitor, provided in series with the parallel body, between the first and second switching circuit outputs and the gate terminal of the voltage-driven semiconductor element, provided to the first and second transistors. series body by connecting the first resistor to a further comprising a connected in parallel with the series body and the second resistor is a value larger than the first resistor The gate drive of that voltage-driven semiconductor element. 2. The gate driving device according to claim 1, wherein the resistance value of the second resistor is 8 to 15 times the resistance value of the first resistor.

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