Patent ID: 8427802
Filing Date: 2013-04-23
Classification: H02H

Abstract:
1. An overvoltage protection circuit that prevents an overvoltage from flowing into a system and thereby protects the system, comprising: a first switch to function as a switch disposed between an input circuit and the system, the input circuit being configured to supply an input voltage, and the first switch being constructed of a semiconductor transistor; a comparator that determines an occurrence of an overvoltage by comparing the input voltage with a predetermined reference voltage, and when no overvoltage is detected, outputs an operation signal; a soft switching control circuit that starts up by using the operation signal from the comparator as an enable signal, and turns on the first switch gradually by gradually increasing a voltage between a source and a gate of the first switch; and a second switch provided between the soft switching control circuit and the input circuit, the second switch being configured to cutoff a current path between the input circuit and the soft switching control circuit in response to an overvoltage detection signal output from the comparator.