Integrated Magnetics for Dimmable Electronic Ballasts

This paper presents an integrated inductor structure for a typical configuration of dimmable electronic ballasts, consisting of two power processing stages. The inductor used in the front-stage power factor corrector is integrated with the resonant inductor in the output-stage of the ballast inverter, so that the overall size and cost can be reduced. Existing circuit designs can be retained without requiring any circuit modification. Most importantly, the ballast performance is similar to the original two-inductor design. Based on using z-parameter gyrator-capacitor model, the modeling, design, and analysis of the ballast operation is presented. A comparative study of the two-inductor and integrated-inductor designs on the core volume, conduction and hysteresis losses is discussed. Simplified design procedures are given. The structure has been successfully applied to a 36 W prototype