IGBT grid resistor variable circuit

Abstract

he invention discloses an IGBT grid resistor variable circuit comprising an IGBT drive circuit, a first resistor, a second resistor, a first diode, a second diode, a field-effect transistor, and an IGBT. The first resistor is an IGBT grid resistor and the field-effect transistor is an N channel enhanced type one. The IGBT drive circuit outputs drive voltages through positive and negative wiring terminals; and the drive voltages are in positive use for turning on the IGBT and are in negative use for turning off the IGBT; a positive electrode of the IGBT drive circuit is connected with one end of the first resistor and a source electrode of the field-effect transistor; a negative electrode of the IGBT drive circuit is connected with an emitter of the IGBT, one end of the second resistor, and a cathode of the second diode; a grid electrode of the field-effect transistor is connected with the other end of the second resistor and an anode of the second diode; the other end of the first resistor is connected with a grid electrode of the IGBT and an anode of first diode; and a drain electrode of the field-effect transistor is connected with a cathode of the first diode. Compared with the prior art, the circuit has the following advantage: the turn-off state of the IGBT is not affected by the high-frequency voltage component between a collector and an emitter.

Description

technical field [0001] The invention relates to switching power supply technology, in particular to a variable resistance circuit connected in series between an IGBT driving circuit and an IGBT grid. The IGBT refers to an insulated gate bipolar transistor. [0002] technical background [0003] IGBTs are widely used in various switching power supplies. Usually, a resistor, the gate resistor, is connected in series between the IGBT drive circuit and the IGBT gate to adjust the switching characteristics of the IGBT, such as figure 1 The Rg shown is the gate resistance, but the existence of this resistance is not conducive to the reliable shutdown of the IGBT: when the IGBT drive circuit outputs a negative voltage, that is, when the IGBT gate voltage is lower than the emitter voltage through the gate resistor, the IGBT should be in the shutdown state. state, but at this time the voltage borne by the IGBT, that is, the voltage between the collector and the emitter of the IGBT is ...

AI Technical Summary

Problems solved by technology

[0003] IGBTs are widely used in various switching power supplies. Usually, a resistor, the gate resistor, is connected in series between the IGBT drive circuit and the IGBT gate to adjust the switching characteristics of the IGBT, such as figure 1 The Rg shown is the gate resistance, but the existence of this resistance is not conducive to the reliable shutdown of the IGBT: when the IGBT drive circuit outputs a negative voltage, that is, when the IGBT gate voltage is lower than the emitter voltage through the gate resistor, the IGBT should be in the shutdown state. state, but at this time the voltage borne by the IGBT, that is, the voltage between the collector and the emitter of the IGBT is generally not stable, and often contains high-frequency components. Due to the Miller effect, the high-frequency voltage will be transmitted to the gate of the IGBT Pole, and because the gate resistance has a certain isolation effect on the output of the IGBT drive circuit, the voltage between the IGBT gate and the emitter may change from negative to positive, resulting in the IGBT turning from off to on

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