Single-stage single-switch high-rower-factor electronic ballast for fluorescent lamps

This paper presents an efficient, small-sized, and cost-effective single-switch power-factor-correction (PFC) scheme for high-frequency electronic ballasts. The circuit topology originates from the integration of a buck-boost PFC converter and class-E electronic ballast. Only one active power switch is commonly used by both power stages to save the cost of active switches and control circuits. The active switch is controlled by pulsewidth modulation at a fixed switching frequency and constant duty cycle. The electronic ballast can achieve nearly unity power factor by operating the buck-boost converter at discontinuous conduction mode. With carefully designed circuit parameters, the active power switch can be operated at zero-voltage switching, leading to high circuit efficiency. A prototype circuit designed for a PL-27-W compact fluorescent lamp is built and tested to verify the theoretical predictions. Satisfactory performance is obtained from the experimental results.