AC INPUT VOLTAGE INTERRUPTION DETECTION METHOD AND CIRCUIT

摘要

A selector selects either a class upper-limit voltage or class lower-limit voltage as the reference voltage of a comparator. A control logic controls the selector and generates a count-up signal or a count-down signal according to the output of the comparator. An up/down counter counts up in response to the reception of the count-up signal from the control logic and counts down in response to the reception of the count-down signal. A digital-analog converter outputs the class upper-limit voltage and class lower-limit voltage according to the digital value output from the up/down counter. A timer is configured so as to be reset by the count-up signal output from the control logic to the up/down counter.