| 摘要 |
PURPOSE:To reset a latch circuit as soon as a power supply is cut off by connecting the dividing point of a voltage dividing circuit for power supply voltage to a power supply ON/OFF circuit and the latch circuit. CONSTITUTION:In a power supply ON mode, a power supply +VCC is applied to a terminal (d) and the voltage divided by a voltage dividing circuit 2 is applied to a terminal (a) of a latch circuit 1 as well as to a terminal (e) of a power supply ON/OFF detecting circuit 3. While the AC power supply voltage is applied to a terminal (f) of the circuit 3. In this case, a transistor TRQ3 is kept off. when the power supply is cut off during actuation of the circuit 1, the base of the TRQ3 is biased to plus. Thus the TRQ3 is turned on and therefore the voltage of the terminal (e), i.e., the voltage of the terminal (a) of the circut 1 is equal to about zero. As a result, the circuit 1 is reset as soon as the power supply is cut off. |
