| 摘要 |
PROBLEM TO BE SOLVED: To provide a switching control circuit in which a timer is constituted of the counter having a small number of stages and then a desired brownout operation signal is obtained from the timer by generating a clock signal from an alternating current (AC) input signal and using it for the clock signal to a counter. SOLUTION: When the beginning of a brownout state is detected by detecting that a divided voltage 'a' becomes equal to or lower than a reference voltage 21, a comparator 22 cancels the resetting of the counter 40. After the comparator 22 detects the beginning of the brownout state, the counter 40 counts the clock signal 33 outputted from the comparator 32. Moreover, when it is detected that an 'a' point potential becomes equal to or lower than the reference voltage 31, a pulse signal (rising pulse of the clock signal 33) of a high (H) level is outputted from the comparator 32. An output 25 in the final stage of the counter 40 prevents the passing of a high frequency pulse signal 27 in an AND circuit 26'. COPYRIGHT: (C)2010,JPO&INPIT
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