A back-plank structure of direct-type backlight module with equal parasitic capacitors

Parasitic capacitors, which occur between cold cathode fluorescent lamps (CCFLs) and the back-plank in backlight modules of liquid crystal display (LCD) panels, are changed by the lamp position. That's the reason why the leakage currents are different from lamps; therefore, the undesirable non-uniform brightness exists. This paper presents a novel structure of backlight module for LCDs, aiming at alleviating the influence of parasitic capacitors in order to attain balanced lamp currents and uniform brightness outputs. By designing a new back-plank, the spaces between the lamps and the back-plank are approximately identical, as a new structure implemented on a direct-type backlight module with 14 CCFL lamps for a 32-inch LCD panel, then experimental results demonstrate that the difference of parasitic capacitors can be reduced to be within 2 %.