| 摘要 |
PURPOSE:To obtain the synchronism between a power-failure detection signal and a sequence control circuit by stopping the operation of the sequence control circuit on detecting a power failure. CONSTITUTION:When an AC voltage (a) is interrupted momentarily, a smoothed voltage (b) drops gradually. Then, a photocoupler 5 turns off when the voltage drops below the Zener voltage of a Zener diode 4. An input voltage (c) to a comparator 7, therefore, rises. The output signal (d) of the comparator 7 goes up to a high level. The voltage at a terminal CK of a D-type flip-flop 14 rises with the time constant determined by a resistance 12 and a capacitor 13 after a transistor (TR) 9 turns on and TR10 turns off. The Q output of the flip-flop rises to the high level a certain time later and currents flowing through relays 18-20 are ceased to stop the operation of the sequence controller. |
