Novel high-power-factor isolated electronic ballast for multiple tubular fluorescent lamps

This paper presents a novel isolated electronic ballast for multiple fluorescent lamps, featuring high power-factor, and high efficiency. Two stages compose this new electronic ballast, namely, a new voltage step-down isolated Sepic rectifier, and a classical resonant half-bridge inverter. The new isolated Sepic rectifier is obtained from a zero-current-switching (ZCS) pulse-width-modulated (PWM) soft-commutation cell. The average-current control technique is used in this preregulator stage in order to provide low phase displacement and low total-harmonic-distortion (THD) at input current, resulting in high power-factor, and accordance with IEC 61000-3-2 standards. The resonant half-bridge inverter performs zero-voltage-switching (ZVS), providing conditions for the obtaining of overall high efficiency. A design example is developed for the new isolated electronic ballast rated at 200 W output power, 220 V/sub RMS/ input voltage, 115 V/sub DC/ DC link voltage, with rectifier and inverter stages operating at 50 kHz. Finally, experimental results are presented in order to verify the developed analysis. The THD at input current is equal to 5.25%, for an input voltage THD equal to 1.63%, and the measured overall efficiency is about 88.25%, at rated load.