A novel single-stage high-power-factor electronic ballast with symmetrical topology

This paper proposes a novel single-stage high-power-factor high-efficiency electronic ballast with symmetrical topology for fluorescent lamps. The circuit topology originates from the integration of two half-wave rectifiers with buck-boost power-factor-correction converters and a half-bridge seriesresonant parallel-loaded inverter. A high power factor at the input line is assured by operating the buck-boost converters in discontinuous conduction mode. With symmetrical operation and carefully designed circuit parameters, zero-voltage switching on the active power switches of the inverter can be retained to achieve high circuit efficiency. The design equations are derived from the analyzed results based on fundamental approximation, and then an easy-to-use design tool is provided accordingly under considerations of filament heating and ignition. A prototype circuit designed for two T9-40W rapidstart fluorescent lamps is built and tested to verify the analytical predictions. Satisfactory performance is obtained from the experimental results.