| 摘要 |
PURPOSE:To preclude a deviation from a safe operation area by providing a circuit which puts an output transistor(TR) in an active area and a time-limit element which enables its operation only for a specific time when an IGBT turns on. CONSTITUTION:The circuit which turns on a TR 5 for forward bias voltage application between output TRs 5 and 6 and the time-limit element which operates it only for the specific time are provided. Namely, the emitter of a PNP TR 4 is connected to the plus side of a power source 7, and the collector of the NPN TR 14 is connected to the base of the TR 5 through a constant voltage diode 15; and the differentiating circuit composed of a resistance 12 and a capacitor 11 is interposed as the time-limit element between the collector of the output TR of a photocoupler 1 and the base of the Th 14 and the connection point between the resistance 12 and capacitor 11 is connected to the collector of the output TR of the photocoupler 1 through a resistance 2. Then the output TR 5 is put in operation in the active area under constant conditions in the beginning of turn-on operation to apply a relatively low voltage between the gate and emitter. Consequently, the deviation from the safe operation area is precluded. |
