Analysis and design of a high power factor, single-stage electronic ballast with dimming feature

The analysis, design and practical consideration of a single-stage electronic ballast with a dimming feature and unity power factor are presented in this paper. The proposed single-stage ballast is the combination of a boost power converter and a half-bridge series-resonant parallel-loaded inverter. The boost semi-stage, working in the discontinuous conduction mode, functions as a power factor corrector and the inverter semi-stage, operated above resonance, is employed to ballast the lamp. Replacing the lamp with a plasma model, analysis of the ballast is fulfilled. The dimming feature is carried out by using pulse-width modulation and variable-frequency controls simultaneously. The proposed ballast can save a controller, reduce size and possibly increase system reliability over a conventional two-stage system. A prototype was implemented to verify the theoretical discussion. The hardware measurements have shown that the desired performance can be achieved feasibly.