| 摘要 |
PURPOSE:To attain the operation of an IGBT (Insulated Gate Bipolar Mode Transistor) within its safe operating region by providing a voltage reduction circuit decreasing its gate voltage to a prescribed limit value if a prescribed value or over of voltage is applied between the collector and emitter when the IGBT is turned on. CONSTITUTION:Resistors 22b, 22c are connected between the collector and emitter of the IGBT 3 and a base of a transistor (TR) 23 is connected to a connecting point P of the resistors 22b, 22c and since the potential of the connecting point P is low when the IGBT 3 is turned on, the TR 23 is not conductive. On the other hand, if short-circuiting the like takes place and a prescribed value of the voltage or over is applied between the collector-emitter of the IGBT, since the potential at the point P rises, the TR 23 is conductive. Thus, a Zener diode 24 is inserted between the gate and emitter of the IGBT 3 via the TR 23 and the gate-emitter voltage (gate voltage) is limited to a prescribed level decided by the Zener voltage. |
