| 摘要 |
PURPOSE:To remove the necessity of static current consumption in a time when no voltage is detected and improve detecting accuracy by operating a second voltage detecting circuit which is accurate and consumes current only in operation by the detecting signal of a first voltage detecting circuit. CONSTITUTION:A first voltage detecting circuit 5 outputs a first detecting signal 7 when the voltage of input signal exceeds a power supply voltage by a first prescribed amount in the same direction as that of the voltage characteristics of a power supply. The circuit 5 requires no current consumption when no input signal is detected. When inputted with the signal 7, a second voltage detecting circuit 6 becomes operative and, when input signal voltage exceeds the power supply voltage by a second prescribed amount not smaller than the first prescribed amount in the same direction as that of the voltage polarity of the power supply, outputs a second detection signal 8. When the signal 7 is not inputted, the circuit 6 falls in nonoperating condition wherein no current consumption is required. Thus, by connecting the circuit 6 whose activation/ nonactivation is controlled by the output of the circuit 5 and which requires no static power consumption in an inoperative condition and setting such that the circuit 5 becomes a detecting condition before the circuit 6, accurate detection can be performed with minimum current consumption.
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