OVERCURRENT PROTECTION APPARATUS

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PROBLEM TO BE SOLVED : To provide an overcurrent protection apparatus for protecting a load circuit by shutting off the circuit in accordance with each of situations when a rare short circuit or a dead short circuit occurs in the load circuit. SOLUTION : The apparatus includes : a counter-electromotive force detection circuit 6 for detecting a counter-electromotive force that is generated in power supply wiring 5; and a voltage detection circuit 4 for detecting that a load current ID flowing to a load circuit 10 becomes an overcurrent on the basis of voltages generated at both terminals of a semiconductor switch T11 provided in the load circuit 10. Furthermore, the apparatus includes a filter circuit 7 which outputs a filter output signal for a first delay time when the overcurrent is detected by a first overcurrent detecting means, and outputs the filter output signal for a second delay time shorter than the first delay time when the overcurrent is detected by a second overcurrent detecting means. In this configuration, the load circuit 10 can be shut off at the first delay time when the rare short circuit occurs, and the load circuit 10 can be shut off at the second delay time when the dead short circuit occurs. COPYRIGHT : (C)2009, JPO&INPIT