PROTECTIVE CIRCUIT AGAINST OVERCURRENT

PROBLEM TO BE SOLVED: To provide a protective circuit against an overcurrent which enables power cut or easy adjustment of the time of automatic return. SOLUTION: This protective circuit detects the abnormal heating accompanying the overcurrent of an external electrical apparatus 3, and a resistance varying element 18a varies its resistance value. The bias voltage outputted from a bias voltage output circuit 18 changes too, according to it. Furthermore, a relay 13 is opened or closed, based on the switching control signal being supplied and controlled by the second transistor element 17, based on the change of this bias voltage. By such control, the power cut at abnormal heating accompanying the overcurrent or the automatic return at vanishing of abnormal heating becomes possible. This protective circuit against an overcurrent having such an automatic return function is not connected serially to a coil 13a unlike a conventional one, but is included in a bias voltage output circuit 18 which supplies a switching control signal for exciting the coil 13a. COPYRIGHT: (C)2003,JPO