Single-stage dimmable electronic ballast with high power factor and low EMI

A novel fixed-frequency electronic ballast that consists of a single-stage balanced type asymmetrical half-bridge inverter, a load resonant tank and a switched-capacitor dimming control circuit is proposed for driving fluorescent lamps. High efficiency and unity power factor are achieved by the proposed single-stage topology. The switched-capacitor dimming control technique and the balanced topology in the studied high-frequency electronic ballast provide better EMI features. The steady-state operating principle and design procedure for the proposed single-stage dimmable electronic ballast are analysed and discussed in detail. A ballast prototype has been implemented in the laboratory. The experimental results verify the feasibility of the proposed method.