| 摘要 |
PROBLEM TO BE SOLVED: To effectively discharge the gate charges of a voltage-driven element (IGBT). SOLUTION: When the pulse outputted from a control circuit 102 shifts from high level to low level, a gate voltage Vg of the IGBT is lower than a reference voltage Vref. When the IGBT starts to turn off from an incompletely turned-on stage, transistors Q2 and Q3 are turned on to cause resistors R1 and R2, to make the gate charges of the IGBT discharged. When the IGBT starts to turn off from a completely turned-on state, the collector voltage Vc of the IGBT is monitored, and when the voltage Vc is lower than a prescribed value, the transistors Q2 and Q3 are turned on, to cause the resistors R1 and R2 to discharge the gate charges. When the collector voltage Vc becomes the prescribed value or higher as the IGBT turns off, the transistor Q2 is turned off, to only cause the resistor R2 to make the gate charged. Consequently, the gate charges can be discharged quickly, regardless of the width of the pulse and, in addition, the occurrence of a surge voltage can be suppressed.
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