High power factor electronic ballast operating at critical conduction mode

A high power factor electronic ballast, that exhibits low switching losses is presented in this paper. The proposed topology is based on a single power processing stage which provides high frequency voltage to the fluorescent lamps and high power factor to the utility line. The lamps are driven by a self-oscillating half-bridge series resonant converter of great simplicity and attendant low cost and increased reliability. High power factor is achieved by using a nonconventional boost converter operating at critical conduction mode. Theoretical analysis and experimental results for two 40 W fluorescent lamps operating at 50 kHz from 127 V utility line have been obtained, which demonstrate the high efficiency and high power factor of this electronic ballast.