Single-stage electronic ballast with unity power factor

A single-stage electronic ballast with unity power factor is proposed. A saturable transformer constituting the self-oscillating drive limits the lamp current and dominates the switching frequency of the ballast. The proposed ballast has high energy efficiency: low cost and high reliability compared to conventional high-power-factor (HPF) electronic ballasts. Experimental results obtained on two 40 W fluorescent lamps are discussed.