Patent ID: 8040650

Claim:
An excess-current protection circuit comprising: an outer input terminal; an outer output terminal; a driver transistor, connected between the outer input terminal and the outer output terminal, to control an excess current; and an excess-current control circuit the excess-current control circuit comprising a first sense transistor connected in parallel to the driver transistor to flow a current in accordance with a predetermined ratio through the driver transistor, a sense resistor connected between the first sense transistor and the outer input terminal, a first comparator to compare a predetermined first bias voltage with a voltage obtained by a current flowing through the first sense transistor multiplied by a resistance value of the sense resistor and output an output signal based on a comparison result, and a control member to control a gate voltage of the driver transistor in accordance with the output signal from the first comparator; an excess-current detection circuit to compare voltage between the drain-source of the driver transistor and a predetermined second bias voltage, the excess-current detection circuit including an output transistor to control the gate voltage of the driver transistor in accordance with a comparison result; and a supplementary circuit configured to connect the gate of the output transistor to ground and prevent the excess-current detection circuit from controlling the gate voltage of the driver transistor, in a case that a voltage at the outer output terminal approaches or equals zero.