| 摘要 |
An overcurrent protective circuit for a modulated conductivity type MOSFET, i.e., a BIFET, which has a voltage detection circuit for detecting a voltage between the drain and source of the BIFET and a main switching circuit for lowering a voltage between the gate ad source of the BIFET and preventing the failure of the BIFET and delay of turn-on of the BIFET according to the output of the voltage detection circuit. The protective circuit produces a constant time delay before the main switching circuit becomes turned on during the initial turn-on period of the BIFET upon application of an ON-gate signal to the gate of the BIFET. The protection circuit thereby prevents, during the initial turn period of the BIFET, a situation where the main switching circuit is turned on but the BIFET is not turned on. The protective circuit further assures that after detection of an overvoltage across the source and drain of the BIFET as may be caused by a load failure, the BIFET gate is maintained at such a low voltage to assure at most a small current conduction through the BIFET even if a ringing voltage occurs across the BIFET. |
