SAMPLING METHOD AND DETECTING CIRCUIT FOR AMPLITUDE OF AC SIGNAL

摘要

PROBLEM TO BE SOLVED: To provide an amplitude detecting circuit capable of precisely detecting the amplitude of an AC signal fluctuated in period with a slight time delay. SOLUTION: The AC signal S fluctuated in period is passed through two all-pass filters 11 and 12 differed in central frequency of transfer phase, whereby phase correction signals S1 and S2 shifted in phase by 90 deg. are generated. The zero cross detection of the phase signal S2 is performed by a pulse generator 22 to generate a sampling pulse Sp. The phase correction signal S1 is full-wave rectified by a full-wave rectifier 21, and the resulting output is put in a sampling circuit 23 to extract the amplitude value with the sampling pulse Sp.