| 摘要 |
PURPOSE:To protect an element safely by decreasing a voltage fed to a gate when a detection voltage between a collector and an emitter of a static induction type self-extinction element exceeds a prescribed value and at a prescribed time after an ON signal is fed to the gate of the element. CONSTITUTION:A transistor (TR) 14 of a gate drive circuit of the static induction type self-extinction element BIFET 1 detects a voltage VCE between the emitter and collector of the BIFET 1. The light emitting side 13a of a photocoupler is connected to the TR 14, the reception signal of the light emitting side 13a of the photocoupler is connected to the 2nd latch circuit 23 of the circuit and a AND circuit 24 is connected to the circuit 23. The 2nd circuit includes a differentiation circuit comprising a capacitor 18 and a resistor 19. When the detection voltage of the BIFET 1 exceeds a prescribed voltage and a gate voltage Vg fed to the BIFET 1 via the circuit 24 is lower than the voltage fed to the gate from the 2nd circuit after a prescribed time, the overcurrent is reduced quickly at short-circuit. |
