A Novel Dimming Technique for Cold Cathode Fluorescent Lamp

In this paper, a simple dimming control is presented herein and applied to the cold cathode fluorescent lamp (CCFL). Conventionally, there are two types of dimming of CCFL, analog and digital. However, performance of analog dimming is poor due to parasitic capacitance existing between the CCFL and the ground, thereby causing a large error in the sensed current of the CCFL and hence reducing the performance of dimming, whereas the digital dimming takes back-and-fro start and cut-off of the CCFL, thereby causing surge current and voltage spike and hence reducing the life of the CCFL. Consequently, to overcome these problems, a novel dimming strategy is presented according to frequency shift. Also, a full-bridge phase-shift resonant inverter is used to power the CCFL. Some experimental results are provided to demonstrate the effectiveness of the proposed scheme.