A Novel Single-Stage High-Power-Factor Electronic Ballast with Symmetrical Half-Bridge Topology

This paper proposes a novel single-stage high-power-factor electronic ballast with symmetrical half-bridge topology for fluorescent lamps. The proposed electronic ballast only uses a symmetrical half-bridge topology to procure the functions of a boost power-factor-correction converter and a half-bridge series parallel-loaded inverter. In spite of its simplicity, an excellent performance concerning load and supply is achieved, ensuring a sinusoidal and in phase supply current. The conventional electronic ballast circuit has larger conduction losses because its power factor correction (PFC) power flow path circuit always includes two diode losses from the front-end bridge rectifier and one power switch loss. The PFC power flow path of the proposed circuit has only two conduction drops in the current flow paths. Therefore, it can provide lower conduction loss than the conventional one. 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 one 40-W fluorescent lamps operating at 40-kHz switching frequency and 110-V line voltage is built and tested to verify the analytical predictions