| 摘要 |
PURPOSE:To detect the abnormality of a power supply exceeding an allowable value by connecting a hit and power failure detecting circuit for a commercial AC power supply and a continuous reduction detecting circuit for the commercial AC power supply and sending detecting signals of both circuits to a control circuit of an apparatus through respective prescribed diodes. CONSTITUTION:The commercial AC power supply is applied to diodes D1-D4 through a transformer T and supplied with full-wave rectification. The rectified voltage is divided by resistors R1, R2 and supplied to a voltage comparator 1 to be compared with reference voltage VREF1. When the voltage VREF1 is higher than the divided voltage, a capacitor C1 is charged by a time constant C1R4, and when lower than the divided voltage, the charge of the C1 is discharged by a time constant C1R3. The voltage of the C1 is supplied to a voltage comparator 2, and when the voltage exceeds a reference voltage VREF2, hit and power failure can be detected through a D6. A full wave rectified voltage is smoothed by the D, R5, R6, and C2 and the smoothed voltage is supplied to a voltage comparator 3. When the smoothed voltage is dropped lower than a reference voltage VREF3, continuous reduction of the AC power supply can be detected through the D1.
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