Patent ID: 6614217
Filing Date: 2003-09-02
Classification: H02H

Abstract:
A power supply negative-phase detecting circuit for electronic equipment using a three-phase AC power supply source, characterized by comprising: a pulse generator for generating a first pulse indicating a phase difference between any pair of two phases of three-phase AC power to be supplied to said electronic equipment, and a second pulse indicating the phase difference between another pair of two phases of the three-phase AC power; a differentiating circuit for generating a third pulse from the second pulse in synchronism with the rise-up of the second pulse so that the third pulse has a pulse width smaller than the phase difference between the first and second pulses; and a power supply switching unit for subjecting the first pulse and the third pulse to AND operation and turning on/off the power supply to said electronic equipment on the basis of the AND operation result of the first and third pulses.