A novel method of using second-order lamp model to design dimmable fluorescent lamps electronic ballast

A novel method for designing half-bridge series-parallel resonant inverters suitable for driving various fluorescent lamps with dimming feature is introduced. The analysis of the proposed method is especially concerned with the second-order high frequency equivalent model of fluorescent lamps. To ensure zero-voltage-switching, the L6569-driven power stage is set to operate above the resonant frequency. A design example is presented for a 40 W fluorescent lamp operating at a 30 kHz switching frequency and 110 V-rms utility line voltage. Quasi-sinusoidal waveforms are obtained and the crest factor of lamp current is smaller than 1.7, resulting in longer lamp life. Lamps of various powers and brands are tested. All show good performance, verifying the functionality of the proposed procedure.