Analysis of Balancing Driver for Multiple Cold Cathode Fluorescent Lamps

This paper proposes a novel topology to drive the cold cathode fluorescent lamps (CCFLs) for liquid crystal displays (LCDs) in a direct-type backlight module. The topology is capable of driving an even number of lamps with identical current without additional balancing circuits, thereby significantly reducing the display's size, weight, and cost. Aiming at alleviating the influence of parasitic capacitance and thus balancing the lamp currents and light output, the proposed topology comprises series CCFLs and the secondary sides of transformers, takes the leakage inductances of the transformer and the parasitic capacitances of the metal back-plank as a resonance tank, and provides both ends of lamps the voltages of equal magnitude and opposite phase. A prototype of the multi-CCFLs driver is designed and built for a backlight module with 14 lamps in a 32-in LCD. Experimental results demonstrate the effectiveness and feasibility of the current balance topology.