| 摘要 |
PROBLEM TO BE SOLVED: To provide a power supply circuit with a function for detecting interruption of input of an AC power supply quickly through a circuit having only one detection terminal even when a relatively large filter capacity is provided on the power supply line. SOLUTION: The power supply circuit comprises a summing circuit (21) generating a voltage compounding the one half period voltage of an AC power supply inputted to a first power supply line and the other half period voltage of the AC power supply inputted to a second power supply line out of a plurality of power supply lines (La, Lb) to which the AC power supply is inputted, and circuits (17, 18) for detecting interruption of input of the AC power supply based on the output voltage from the summing circuit. COPYRIGHT: (C)2008,JPO&INPIT
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