Patent ID: 6804096
Filing Date: 2004-10-12
Classification: H03K

Abstract:
A circuit for controlling a feed of a power supply voltage of a power supply to a load wherein the circuit has a function of detecting a load driving state, the circuit comprising:a MOSFET connected in series with said power supply and an output terminal connected to the load for effecting an on/off operation; means responsive to a feed control signal given from an external circuit for supplying a driving voltage to said gate to turn said MOSFET on; a resistor connected between said power supply and said output terminal in parallel to said MOSFET, said resistor, if said load is abnormal during off period of the MOSFET, setting a voltage of the output terminal to a predetermined voltage; detection means connected to the output terminal for providing a signal indicative of said load driving state on the basis of a comparison between a predetermined reference voltage and the voltage of the output terminal; protection means connected between a source and a gate of said MOSFET for providing a protection against a reverse bias applied between said source and gate by bypassing; transistor means connected between said source and gate of said MOSFET for discharging a gate capacitance of said MOSFET; and driving means responsive to a non-feed indication by said feed control signal for causing a driving current to flow in a control electrode of said transistor means such that a magnitude of said driving current is enough to operate said transistor means, and a voltage drop in said resistor caused by a flow of said driving current therein is smaller than a difference between said power supply voltage and said predetermined reference voltage.