| 摘要 |
PROBLEM TO BE SOLVED: To achieve downsizing and the reduction of electric power and cost by carrying out protection against an overvoltage and a reverse voltage. SOLUTION: A protection circuit 1 includes: a transistor 2, whose emitter is connected to an input side terminal; an FET element Q1, whose gate is connected to the collector of the transistor 2 and whose drain is connected to the input side terminal; another FET element Q2, whose gate is connected to the collector of the transistor 2 and whose drain is connected to an output side terminal; and an error detection portion 3, which is connected to the base of the transistor 2 and compares a divided voltage of the output side terminal with a reference voltage. When the divided voltage of the output side terminal is higher than the reference voltage, the FET element Q1 decreases a drain voltage based on the rise of the gate voltage arising from the increase of a collector current of the transistor 2 caused by a current supplied from an error detection portion 3. When the reverse voltage is applied between the input side terminal and the output side one, the FET elements Q1, Q2 are put into a non-conduction state. COPYRIGHT: (C)2009,JPO&INPIT
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