. Various CCFL leak current Measurement at the LCD Module free download

File name CCFL leak current Measurement at the LCD Module.pdf

CCFL leak current at the LCD Module (2) By reducing the stray capacitance Cs How to reduce the leak current Cs = S/d It is impossible to eliminate the leak current perfectly. There is an effect that a stray capacitance decreases the lighting start voltage. Widen the distance "d" between the high voltage wiring / lamp Therefore, it is recommended to decrease the leak current to the and the conductor portion (reflector, chassis etc.). possible level in consideration of matching with Inverter. For example, a non-conductive reflector should be reviewed. It is to be noted, however, that the metallic reflector has an Leak current Is = 2 f CsVL effect of lowering the lighting start voltage. (1) By lowering the driving frequency f If the driving frequency f is made too low, electric discharge (3) By reducing the Lamp Voltage VL becomes unstable and the luminance is decreased. In consideration (Reducing the lamp impedance) of the luminance efficiency of the lamp, 50-60 kHz is currently The lamp voltage depends on the CCFL characteristics. prevalent. As the lamp diameter is smaller, it is necessary to raise As the CCFL is thinner and longer, the lamp voltage becomes the frequency for stable lighting. higher. As the gas pressure is higher, the impedance tends to be higher. [Appendix] How to measure leak current As a measuring method of the lamp current, please see "Case The measurement point of current is shown. A" which is recommendable and "Case B" (not recommendable) as follows. Case A: recommended Case B: not recommendable LCD panel LCD Panel FG FG Lo Hi Lo Hi Lamp Lamp Current probe Current probe