Patent ID: 6172489
Filing Date: 2001-01-09
Classification: G05F

Abstract:
An AC voltage reduction system for controlling load voltage to a load, said voltage reduction system having an input for coupling to an AC voltage source and having an output for coupling to the load, said voltage reduction system comprising:a controllable switch coupled in series between the input and the output;a capacitor coupled in parallel with the controllable switch;circuitry for turning-on the controllable switch to a conducting state;circuitry for turning-off the controllable switch to a non-conducting state; andswitch control circuitry for generating control signals to control said circuitry for turning-on and said circuitry for turning-off such that the controllable switch is turned on to a conducting state at a selected turn-on time, and is turned off to a non-conducting state at a selected turn-off time prior to a line current zero-crossing point, said switch control circuitry operable to select said turn-off time independent of a measured load voltage or power characteristic; andcircuitry for ensuring that said turn-off time initially occurs just in advance of a line current zero-crossing point.