Malfunction detection circuit null of entry section for alternating voltage detection

摘要

PROBLEM TO BE SOLVED: To detect the abnormality of an input part including an A/D converter for AC voltage detection, at a high speed and accurately. ;SOLUTION: In a detecting circuit of abnormality of an input part for AC voltage detection which is provided for subjecting an AC input voltage to A/D conversion and taking it in CPU 7, a frequency-dividing counter 2 which divides the frequency of a sampling pulse of A/D conversion into that of a pulse having (n) ((n) is an integer, 2 or above) time the period of a fundamental wave of the AC input voltage, an adder which adds this pulse to the AC input voltage, a Fourier operation means 8 which receives an output of this adder and subjects it to Fourier transform continuously, a fluctuation amount determining means 9 which detects noncoincidence of the period of a DC term component outputted from the Fourier operation means 8 with that of the pulse and detects the abnormality of the input part and a timer 10 are provided.;COPYRIGHT: (C)1998,JPO