Primary-side charge-pump dimming controller for the cold-cathode fluorescent lamp ballast

A primary-side charge-pump controller built into a cold-cathode fluorescent lamp (CCFL) ballast is presented for widening the dimmer range while stabilizing the dynamic feedback regulation for the lamp luminance in uniform distribution without thermometer effect. The proposed controller consists of a linear error amplifier for dynamic feedback control regulation and a shunt amplifier for dimmer control. A dimming strategy is explored for extending the dimming range above 1:50 far higher than the conventional 1:10. Besides, floating the CCFL alone at the secondary side also raises the lamp efficiency without parasitic effect.