JPS57154068A - Phase discriminator - Google Patents

Abstract

PURPOSE:To prevent occurrence of an erroneous operation even when waveform distortion is generated in the inputs of a plurality of AC electricity quantities by a method wherein waveform processing after extraction of the condition of phase simultaneity of a plurality of AC electricity quantities is conducted by a combination of an integration circuit with a level detection circuit. CONSTITUTION:AC electricity quantities V1 and V2 supplied to input terminals I1 and I2 are transformed 1, 2 into rectangular waves and sent to an AND circuit A. An output VA of this AND circuit A is sent to an integration circuit S1 and charged when an output signal is logic ''1'', while being discharged when the output signal is ''0''. When the level of an output VS1 of the integration circuit S1 exceeds a threshold levl VL, an output VLD is generated in a level detection circuit LD. An output VLD of this circuit is sent to an on-ready timer T2 through a NOT circuit N1. When instantaneous discontinuation occurs in the waveform of V1, for instance, it occurs also in the output VA and thereby the integration circuit S1 conducts discharge only for a minute time of the instanetanous discontinuation. However, since the charging is continued again, the output of the level detection circuit LD remains as it is only with the pulse width thereof reduced slightly. Thus there is no fear of the output being lost and the erronesous operation is prevented.