| 摘要 |
PURPOSE:To detect the service interruption of an AC power supply surely by combining a zero-cross comparator, an arbitrary frequency oscillator and an oscillator transmitting a frequency differing somewhat from the frequency of said frequency oscillator. CONSTITUTION:A pulse signal from (60+alpha).NHz oscillator 22 is given to the clock input of a counter (CT)17 and a pulse signal from 60.NHz oscillator 23 is given to the clock input of CT19 to perform counting. The signal of a zero-cross comparator ZC16 obtained from a power supply ES clears the CT17, 19 for every zero-cross. When the power supply ES is normal, a difference alphain the number of oscillations is ignored and judged to be in-phase and a multi-vibrator (MB)21 outputs L signal. When the power supply ES stops, a signal from the ZC16 is not inputted to the CT17, 19, which continue counting. Said difference alpha in the number of oscillations increases every cycle, and the MB21 detects a service interruption and brings the output to H. |
