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 is originated from the integration of two half-wave rectifiers with buck-boost power-factor-correction (PFC) converters and a half-bridge series-resonant parallel-loaded inverter. A high power factor at the input line is assured by operating the buck-boost converters in discontinuous conduction mode (DCM). With symmetrical operation and carefully designed circuit parameters, zero-voltage-switching (ZVS) 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 rapid-start fluorescent lamps is built and tested to verify the analytical predictions. Satisfactory performances are obtained from the experimental results.