A Novel Single-Stage High-Power-Factor Electronic Ballast for Metal-Halide Lamps Free of Acoustic Resonance

This paper proposes a novel single-stage high-power-factor electronic ballast for metal-halide lamps. By integrating two buck-boost converters, a full-bridge inverter and a bidirectional buck converter, a single-stage electronic ballast with symmetrical circuit topology is derived. The circuit component count can be effectively reduced and circuit energy-conversion efficiency is improved. With a tactful control scheme, the proposed electronic ballast can output a low-frequency square-wave voltage to drive metal-halide lamps. The problematic phenomena of acoustic resonance can be eliminated. Both the buck-boost converters serve as power-factor correction (PFC) circuits, which are operated at discontinuous conduction mode (DCM) to obtain a unity power factor at the input line. The operation modes, design equations, and design steps for the circuit parameters are proposed. A prototype circuit designed for a 70-W metal-halide lamp was built and tested to verify the analytical predictions. Satisfactory performances are obtained from the experimental results.