| 摘要 |
PROBLEM TO BE SOLVED: To realize an overvoltage protection circuit capable of using an appropriate switch device and fuse without any influence of the magnitude of a serge current, in the overvoltage protection circuit of a power supply unit in which measures against the serge are performed at an input part. SOLUTION: This is the overvoltage protection circuit of the power supply unit in which the measures against serge are performed at the input part for more detail. This protection circuit includes a first overcurrent cut-off device which is provided at an input line and cuts off the input line when a predetermined current flows; an overvoltage restriction device which is connected between the input lines and restricts to a predetermined voltage by flowing a continuity current when the voltage reaches a predetermined restriction voltage or higher; a second overcurrent cut-off device which is provided at input line at a rear stage of the first overcurrent cut-off device and the overvoltage restriction device and cuts off the input line when the predetermined current flows; an overvoltage detection device which detects the overvoltage at least either on the input voltage or the output voltage; and an opening/closing device which is connected between the input lines at the rear stage of the second overcurrent cut-off device, and is opened/closed in accordance with the detected voltage of the overvoltage detection device. COPYRIGHT: (C)2007,JPO&INPIT
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