| 摘要 |
PURPOSE:To prevent the effect of fluctuation in a power voltage by detecting early the generation of power failure so as to inhibit the counting of a counter circuit. CONSTITUTION:A voltage level detection circuit 10 detecting the output voltage of a rectifier circuit 4 connected sequentially to an AC power supply, a timer circuit 50 giving an inhibition signal by the output of the circuit 10 or resetting the inhibition signal and inhibition circuits 60a, 60b operated by the inhibition signal and inhibiting the counting of counter circuits 20, 30 respectively are provided. Then a DC voltage before being rectified and smoothed by the rectifier circuit 4 to detect the power failure quickly is detected by the circuit 10 and the inhibition circuit is operated via the timer circuit by the output of the circuit 10. Since the inhibition operating period is independent of the state of power consumption of the internal circuit, the possibility of malfunction due to an error signal from a peripheral equipment is precluded. Since the operation of the output circuit is inhibited at power failure, the power consumption is less. |
