JP2002119044A - Gate driving circuit for power semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent increase of a turn-off loss even in a hot temperature state. SOLUTION: The temperature of an IGBT module or IGBT chip as a power semiconductor device is detected by a temperature sensor TS, and this is compared by a comparator CP1. Since it does not matter if the change rate of current di/dt is low, when the temperature is judged to be equal to or higher than a specified temperature, the turn-off loss is reduced by turning a switch S3 on through the use of an AND gate AN1, and making the gate resistance value of the IGBT the parallel resistance value of resistors R2, R3 and lowering the resistance value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gate drive circuit for driving a gate of a power semiconductor device constituting a power converter such as an inverter.

[0002]

2. Description of the Related Art FIG.
A general example of an inverter using T (insulated gate bipolar transistor) will be described. In the figure, 11 is a DC power supply circuit, 12 is an inverter circuit composed of an IGBT and a diode and converts DC to AC, and 13 is an IGBT
Is a snubber capacitor for protecting the IGBT from a surge voltage when the IGBT is turned off, 15 (L) is a wiring inductance between the snubber capacitor 14 and the inverter circuit 12, and 16 is a load such as a motor. The drive circuit 13 is provided for each element.

FIG. 5 shows a specific example of the drive circuit used in FIG. 13A is a power supply for driving the circuit, S1 is IG
A switch element for turning on the BT, and R1 is a gate resistor for turning on. S2 is IGB
A switch element for turning off T, and R2 is a gate resistor for turning off. Switch element S1, S
2 is operated by an ON command signal 13C or an OFF command signal 13D from the control unit 13B.

FIG. 6 shows another example of the drive circuit. This is to switch the gate resistance value according to the collector current value flowing through the IGBT, and reference numeral Id indicates a collector current detection signal. As the collector current detection method,
For example, as shown in FIGS. 8 to 10, an IGBT in which a sense resistor is connected to a second emitter (FIG. 8), an IGBT
Shunt resistor connected to the emitter of FIG.
There is one using the collector-emitter voltage V _CE of the GBT (FIG. 10).

The comparators CP2 to CP4 in FIG. 6 determine the magnitude of the collector current value by comparing the collector current detection value Id with values obtained by dividing the reference voltage E1 by resistance. L1 to L3 are latch circuits, which are OFF command signals 1
The output levels of the comparators CP2 to CP4 are latched in synchronization with 3D. RA to RD are turn-off gate resistors, and an optimum gate resistance value according to the level of the collector current value is selected by the on / off state of the switch elements SA to SD. That is, when the collector current is small, a low resistance value (increase the number of parallel resistances) is selected, and when the collector current is large, a high resistance value (decrease the number of parallel resistances) is selected.

FIG. 7 shows still another example of the drive circuit. This switches the gate resistance value during the turn-off operation of the IGBT, and is provided with a detection circuit DE. This detection circuit DE detects the collector-emitter voltage V _CE of the IGBT, compares its output signal Vs (corresponding to V _CE ) with a reference voltage Vref0, and when it exceeds this, closes the AND gate AN3 and turns off the switch S3. The gate resistance is switched from a low resistance in which R2 and R3 are connected in parallel to a high resistance of only the resistance R2.

[0007]

FIG. 11 shows a turn-off waveform of the IGBT. As shown in the drawing, the lower the chip temperature of the IGBT or the larger the current value to cut off,
The di / dt during the fall period until the current becomes zero increases. Surge voltage (ΔV) generated at turn-off
Is the product (L · di / dt) of the wiring inductance value L (see reference numeral 15 in FIG. 4). Therefore, as di / dt increases, the surge voltage increases. This surge voltage and the DC voltage (Ed) If the sum is equal to or higher than the voltage rating of the IGBT, the IGBT may be broken.

Therefore, when determining the gate resistance for turn-off of the gate drive circuit, the worst case is taken into consideration, and the di / dt at which the surge voltage does not destroy the IGBT even in the low-temperature turn-off operation is taken into consideration. I had to decide. On the other hand, when the transistor is turned off at the normal operating temperature of about 100 ° C. with the gate resistance value determined as described above, the surge voltage has a margin and is suppressed because di / dt is reduced as the characteristic of the IGBT. However, there is a problem that the turn-off loss increases unnecessarily, and furthermore, generally, the gate resistance also has a temperature characteristic. I do. Therefore, an object of the present invention is to prevent the turn-off loss from increasing even when the temperature changes.

[0009]

According to the first aspect of the present invention, there is provided a gate drive circuit for driving a power semiconductor element constituting a power converter.
Providing detection means for detecting the temperature of the module case of the power semiconductor element or the element itself, and a resistance variable circuit for changing the gate resistance value of the element, and it is determined that the detected temperature value has exceeded a certain set value. In this case, the gate resistance value is reduced.

According to a second aspect of the present invention, in a gate drive circuit for driving a power semiconductor element constituting a power conversion device, a detecting means for detecting a temperature of a module case of the power semiconductor element or the element itself; A variable resistor circuit that compares the flowing collector current value with its set value and varies the gate resistance value of the element according to the comparison result, and when it is determined that the detected temperature value is equal to or higher than a certain set value, It is characterized in that the collector current set value is increased.

According to a third aspect of the present invention, in a gate drive circuit for driving a power semiconductor element constituting a power converter, a detecting means for detecting a temperature of a module case of the power semiconductor element or an element itself; A variable resistance circuit for varying the gate resistance value of the element during the turn-off operation, and a control circuit for controlling the variable resistance circuit are provided, and when it is determined that the detected temperature value is equal to or higher than a certain set value, It is characterized in that the control circuit does not switch the gate resistance value in the variable resistance circuit.

That is, according to the present invention, the I
This is made by paying attention to the temperature characteristics of the IGBT and the gate resistance that the di / dt at the time of turn-off differs depending on the temperature of the GBT chip and the gate drive circuit.
Therefore, when the temperature is high and di / dt is low, the transistor is turned off with a low gate resistance value as in the first aspect of the invention, or a current value larger than that in the first aspect as in the second aspect of the invention. The resistance is turned off with a low resistance, or the resistance is not unnecessarily increased during the turn-off operation. That is, by changing the gate resistance value according to the temperature, the semiconductor device is turned off at a constant surge voltage to reduce the loss.

[0013]

FIG. 1 is an explanatory view of a first embodiment of the present invention. FIG. 1 (a) shows a configuration diagram, and FIG. 1 (b) shows a temperature characteristic diagram. That is, FIG. 1A is different from the one shown in FIG. 5 in that the temperature measuring device TS, the comparator CP1, and the AND gate AN are used.
1 is added. In the following, only the differences from the conventional example will be mainly described. The temperature measuring device TS includes, for example, a thermistor or a diode whose electric characteristics change depending on the temperature, and detects the temperature of the IGBT module case or the IGBT chip (element itself). As shown in FIG. 1B, the output characteristic has a characteristic that the output Vt decreases as the temperature value increases.

The comparator CP1 compares the output Vt from the temperature measuring device TS with a set value Vref. If the output Vt is equal to or less than the set value, the comparator CP1 determines that the IGBT is at a high temperature.
The switch S3 is turned on via N1. This allows
Since the turn-off gate resistance value is the parallel value of the resistances R2 and R3, the resistance is lower than in the case where only the resistance R2 is used for driving.

FIG. 2 shows a second embodiment of the present invention. This is different from the conventional example shown in FIG.
S, a comparator CP1, an inverter gate IN1, a switch element SW and the like are added. The comparator CP1 outputs the output Vt from the temperature measuring device TS to the set value V
Compared with ref, if it is equal to or less than the set value, it is determined that the IGBT is at high temperature, and the normally-on switch element SW is turned off via the gate IN1. As a result, the current set value for switching the turn-off gate resistances RA to RD becomes higher than when the switch element SW is turned on, and it is possible to turn off the current to a larger current value with a low resistance. .

FIG. 3 shows a third embodiment of the present invention. This is different from the conventional example shown in FIG.
S, a comparator CP1, an inverter gate IN1, an AND gate AN2, and the like. The comparator CP1 compares the output Vt from the temperature measuring device TS with the set value Vref. If the output Vt is equal to or smaller than the set value, the comparator CP1 determines that the IGBT is at a high temperature, and through the gates IN1 and AN2,
The switch element S3 is prevented from turning off in accordance with the V _CE detection value from the detection circuit DE.

In the above, the comparison of the detected temperature value with the set value is realized by one circuit. However, a plurality of comparison circuits may be provided to switch the resistance for each temperature.

[0018]

According to the present invention, even if the IGBT and the gate drive circuit are in a high temperature state, it is possible to drive the IGBT without increasing the turn-off loss.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a first embodiment of the present invention.

FIG. 2 is a configuration diagram showing a second embodiment of the present invention.

FIG. 3 is a configuration diagram showing a third embodiment of the present invention.

FIG. 4 is a schematic diagram showing a conventional example of an inverter main circuit.

FIG. 5 is a circuit diagram showing a first specific example of a general IGBT drive circuit.

FIG. 6 is a circuit diagram showing a second specific example of a general IGBT drive circuit.

FIG. 7 is a circuit diagram showing a third specific example of a general IGBT drive circuit.

FIG. 8 is an explanatory diagram of a first detection method of a collector current.

FIG. 9 is an explanatory diagram of a second detection method of the collector current.

FIG. 10 is an explanatory diagram of a third detection method of the collector current.

FIG. 11 is an explanatory diagram of an operation when the IGBT is turned off.

[Explanation of symbols]

TS: temperature measuring device, CP1 to CP5: comparator circuit, AN1 to AN3, IN1: gate, S1, S2, S
3, SW: switch element, R1 to R7, RA to RD: resistor, L1 to L3: latch circuit, DE: detection circuit, 11:
DC power supply circuit, 12 inverter circuit, 13 drive circuit, 13A power supply, 13B control unit, 13C on command, 13D off command, 14 snubber capacitor, 15
... wiring inductance, 16 ... load (motor).

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5H007 CA01 CC07 DB03 DB09 FA01 FA13 5H740 BA11 BB07 BB08 HH05 JA01 KK01 LL01 MM01 MM08 5J055 AX15 AX56 AX64 BX16 CX20 DX09 EX06 EY01 EZ10 EZ25 EZ31 FX61 FX06 FX12

Claims (3)

[Claims] 1. A gate drive circuit for driving a power semiconductor element constituting a power conversion device, comprising: detecting means for detecting a temperature of a module case of the power semiconductor element or an element itself; and varying a gate resistance value of the element. A gate drive circuit for a power semiconductor device, characterized in that a gate resistance value is reduced when it is determined that the detected temperature value has exceeded a certain set value. 2. A gate drive circuit for driving a power semiconductor device constituting a power conversion device, comprising: detecting means for detecting the temperature of a module case of the power semiconductor device or the device itself; A resistance variable circuit that compares the set temperature with the set value and varies the gate resistance value of the element according to the comparison result, and when it is determined that the detected temperature value is equal to or greater than a certain set value, the collector current set value A gate drive circuit for a power semiconductor device, wherein 3. A gate drive circuit for driving a power semiconductor device constituting a power conversion device, comprising: a detecting means for detecting a temperature of a module case of the power semiconductor device or the temperature of the device itself; A variable resistance circuit for varying the gate resistance value of
And a control circuit for controlling the variable resistance circuit, and when it is determined that the detected temperature value has exceeded a certain set value, the control circuit does not switch the gate resistance value in the variable resistance circuit. A gate drive circuit for a power semiconductor device, characterized in that: