MULTI-PHASE INPUT BALLAST WITH DIMMING AND METHOD THEREFOR

摘要

An apparatus and method for powering a lamp connected to a ballast circui t. The ballast circuit is connected to a first alternating current (AC) source having a first phase and to a second AC source having a second phase for powering the lamp. A first switching circuit is corrected between the first AC source and a rectifier circuit. A second switching circuit is connected between the second AC source and the rectifier circuit. A control circuit selectively energizes the first and second switching circuits to provide power from one of the first and second AC sources to the lamp load v ia the rectifier circuit and an inverter circuit. A detection circuit connected between the first and second AC sources generates a detection signal indicating whether power is being supplied by each the first and second AC sources. The detection signal is provided to a dimming regulation circuit to generate a dim level command signal for dimmin g the lamp.