Three-way dimming CFL ballast

摘要

A three-way dimming CFL ballast operates at a single high bus voltage while varying switching frequency to control lamp current. The ballast accepts three different light level input switch command positions and an off position to provide three different light output levels. A closed loop current feedback control maintains a precise switching frequency for the ballast to produce accurate light output levels based on the light output switch selection. A reference value is provided to the feedback loop based on the selected light output level to drive the switching frequency at the appropriate value. The ballast circuit provides a sufficient CFL control for three-way dimming as adapted to be used with a standard Edison screw base.