Improving Current Crest Factor of Fluorescent Lamp with Valley-Fill Filter Using Pulse Width Modulation

In this paper, a pulse width modulation(PWM) method to reduce the fluorescent lamp current crest factor of the valley-filled power factor corrected(PFC) electronic ballast is presented. The proposed method controls switching duty cycle by feeding forward the dc-link voltage waveform of valley-filled PFC, restraining the lamp peak current and improving the lamp current crest factor. The control block diagram and basic theory are introduced to improve the current crest factor. Computer simulations are used to verify the proposed theory and obtain a minimum crest factor. Experimental results indicate that the lamp current crest factor is minimized to about 1.58. Additionally, the fixed switching frequency operation results in a satisfactory power quality. The ac line power factor is about 96%, and the input current THD is about 29.3%.