Dimmable electronic ballast with high power factor SEPIC preregulator, for multiple tubular fluorescent lamps

An electronic ballast for multiple tubular fluorescent lamps is presented in this paper. The proposed structure features high power factor, dimming capability, and soft-switching to the semiconductor devices operated in high frequencies. A zero-current-switching-pulse-width-modulated (ZCS-PWM) SEPIC converter composes the rectifying stage, controlled by the instantaneous average input current technique, performing soft-commutations and high input power factor. Regarding the inverting stage, it is composed by a classical resonant half-bridge converter, associated to series parallel-loaded resonant (SPLR) filters. The dimming control technique employed in this half-bridge inverter is based on the phase-shift in the current processed through the sets of filter + lamp. In addition, experimental results are shown in order to validate the developed analysis.