Balanced Driving System for Multiple Cold-Cathode Fluorescent Lamps

A novel circuit with dual-high-voltage topology to drive cold-cathode fluorescent lamps (CCFLs) for liquid crystal display (LCD) backlight modules is proposed in this paper. In the proposed circuit topology, all the lamps are connected in series to alleviate the influence of parasitic capacitance induced between the lamps and the aluminum backplank. Balance lamp current and uniform light output can be achieved without using any current balancing circuit. The circuit topology is capable of driving arbitrarily even numbers of lamps with same lamp current while achieving significant reduction in size, weight, and cost. The circuit is verified by experimenting on a backlight module with four L-type lamps in a 19-inch LCD. The experimental results demonstrate the effectiveness and feasibility.