Enhancing Luminance of CCFL-Based Lighting Systems Using Low-Frequency Driving Techniques

Abstract

This paper proposes the luminance enhancement with low-frequency driving techniques for cold cathode fluorescent lamp (FL) (CCFL)-based lighting systems. The driver architecture features a full-bridge phase-shift inverter with a resonant tank and a three-winding step-up transformer to reduce leakage current, remove parasitic capacitance, enhance optical efficiency, balance and increase lamp uniformity, and achieve two-terminal high-voltage low-frequency driving of CCFLs. The low-frequency control of the driving technique is implemented in a field-programmable gate array controller to achieve luminance enhancement. The control strategy starts igniting the lamp with a high frequency and then reduces to low frequency in order to facilitate the linear increment of lamp brightness. Through the employment of this proposed approach, since the primary current of the transformers is only required, the circuit implementation can be completed with ease. Experimental results show that the proposed technique and control strategy help enhance luminance efficiency and reduce leakage current, demonstrating the practicality for the application considered.