SINGLE-STAGE ELECTRONIC BALLAST WITH DIMMING FEATURE AND UNITY POWER-FACTOR

Analysis, design, and practical consideration of a single-stage electr onic ballast with dimming feature and unity power factor are presented in this paper. The proposed single-stage ballast is the combination o f a boost converter and a half-bridge series-resonant parallel-loaded inverter. The boost semistage working in the discontinuous conduction mode functions as a power factor corrector and the inverter semistage operated above resonance are employed to ballast the lamp. Replacing t he lamp with the plasma model, analysis of the ballast is fulfilled. T he dimming feature is carried out by pulse-width modulation (PWM) and variable-frequency controls simultaneously. The proposed single-stage ballast is suitable for applications with moderate power level and low -line voltage while requiring a high-output voltage. It can save a con troller, an active switch and its driver, reduce size, and possibly in crease system reliability while requiring two additional diodes 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.