INSTANTANEOUS VOLTAGE LOWERING DETECTION DEVICE

摘要

An instantaneous voltage lowering detection device includes: an all-pass filter (2) for phase-shifting a power source voltage waveform (11) by a 90-degree angle; a comparator (7) for outputting a signal when the power source voltage waveform (11) is smaller than its threshold value (12) in pi/4 to 3pi/4 and 5pi/4 to 7pi/4; a comparator (8) for outputting a signal when the phase-shifted voltage waveform (13) is smaller than its threshold value (14) in 0 to pi/4, 3pi/4 to 5pi/4, and 7pi/4 to 2pi; an OR circuit (9) supplied with signals from the comparators (7, 8); and means (10) for generating a voltage lowering detection signal in accordance with the output from the OR circuit (9).