Drive circuit for semiconductor power device and semiconductor switching circuit using the drive circuit

摘要

In the initial stage of the operation of turning off a semiconductor device (Q1), the impedance of a carrier pull out circuit (5) remains low for rapidly pulling out the stored carriers from the control electrode (G) of the device (Q1). When the turn-off transition of the device (Q1) proceeds and becomes close to its completion, the impedance of the carrier pull out circuit (S) is shifted to a higher level for retarding the carrier pull out speed. A detector (4) is provided for detecting a control current developed by pulling out the carriers. When the current measured by the detector (4) drops down to below a predetermined level, it is judged that the turn-off transition is approaching to its end. This permits the turn-off transition to be smoothly finished and can thus prevent unwanted oscillation of the control electrode voltage. More specifically, the device (Q1) can be inhibited from being accidentally turned on by the effect of oscillation of the control electrode voltage and also, the delay time in the turn off transition becomes longer while the storage time is same as the conventional circuitry. <IMAGE>