| 摘要 |
PROBLEM TO BE SOLVED: To provide a power failure detection circuit having a highly accurate power failure detection voltage and high reliability. SOLUTION: This power failure detection circuit is equipped with a primary side circuit wherein a resistance 2 is connected to an input power source 1, and a secondary side circuit comprising the first photocoupler 4 composed of the first light emitting diode 4a connected in parallel to a resistance 3 for emitting light corresponding to the current quantity and the first phototransistor 4b for short circuiting the input end with the output end by light emission therefrom, a gate IC 8 connected to the output end of the first phototransistor 4b, and a direct current power source 5 connected between the output end and the gate IC 8 through a resistance 6. A power failure and a voltage drop of the input power source 1 are detected by the magnitude of a current of the first light emitting diode 4a. This circuit is also provided with the second photocoupler 10 comprising the second phototransistor 10b provided in parallel with the first light emitting diode 4a through a resistance 9 and the second light emitting diode 10a connected to an output circuit branched from the output end of the gate IC 8. COPYRIGHT: (C)2005,JPO&NCIPI
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