| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an AC power supply detecting circuit which prevents a power interruption detection signal from being wrongly output when an AC power is applied. <P>SOLUTION: The AC power supply detecting circuit includes: an amplification circuit for receiving an input voltage obtained by rectifying a voltage from the AC power supply and dividing the voltage, and then outputting a voltage corresponding to the input voltage, a voltage comparing circuit; and a low-voltage detection circuit. The AC power supply detection circuit detects AC power interruption and outputs a signal. The circuit includes: time constant circuits I1, C1 connected to an output node are provided on an output stage of the amplification circuit; and a pull-up transistor M8 connected between the power supply voltage terminal and a control terminal of an output stage transistor, or a pull-down transistor M9 connected between the output node of the output stage and a grounding point is provided. When the power supply voltage is low, the pull-up and pull-down transistors are turned on by a signal from the low-voltage detection circuit to prevent the output of the amplification circuit from rising when the power is applied. <P>COPYRIGHT: (C)2010,JPO&INPIT |
