| 摘要 |
PURPOSE:To detect latch-up phenomenon without fail, by monitoring the state by the use of the voltage across and the current between the gate and the emitter of an insulated gate bipolar transistor. CONSTITUTION:In a power converter, etc., such as an inverter for driving an AC motor, the abnormal state of an insulated gate bipolar transistor (hereinafter referred to as IGBT) 1 is detected. For this purpose, a state monitoring circuit 2 connected to a gate drive circuit 3 of an IGBT 1, a current detector 4 and an exclusive OR (EOR) gate 5 are provided. The abovementioned detector 4 outputs logical '1' when the collector current of the IGBT 1 is 0, while the monitoring circuit 2 outputs logical '1' when the gate is 0. Thus, since no collector (emitter) current will be reduced even if the latched-up IGBT 1 sets up the gate voltage for 0. it can be easily detected by logical operation.
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