| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a power supply board protection circuit in which an apparatus connected to the power supply output side is hard to malfunction even when sudden variation occurs in power supply voltage due to a lightning surge. <P>SOLUTION: When sudden voltage variation occurs in the power supply input 10 due to a lightning surge, a lightning surge protection circuit 1 suppresses overvoltage of a predetermined level or above in case of overvoltage. When voltage drop occurs, the power supply output 11 is turned off for a predetermined time or more so that the voltage drops below a level at which an apparatus connected with the power supply output 11 can operate normally and the apparatus does not malfunction on a halfway voltage but stops power supply normally and performs reset operation. A time duration extension circuit 4 processes a control signal to turn the power supply output 11 on/off surely even if the time duration of voltage drop is short. <P>COPYRIGHT: (C)2008,JPO&INPIT |
