A novel two-stage high-power-factor low-frequency HID electronic ballast

A novel two-stage, high-power-factor electronic ballast used to drive high-intensity discharge lamps is proposed in the paper. The ballast consists of a flyback-type input current shaper to achieve power factor correction and a half-bridge-type inverter to supply the lamp with low-frequency square-wave current. Owing to its low-frequency operation, no acoustic resonance occurs. The features of the ballast are cost-effective, low total-harmonic-distortion (THD), high power factor (PF>0.99). Operational principles, design equations and simulated results of one 70-W HID lamp operating at 400 Hz switching frequency with 110 V-rms line input voltage are presented.