Control strategy for eliminating the temperature effect of piezoelectric transformer in the backlight module

A novel control strategy for eliminating the temperature effect of piezoelectric transformer (PT) in the backlight module is proposed in this paper. To overcome the drawbacks of the conventional electromagnetic transformer and miniaturize the backlight module, the PT is adopted for driving the cold cathode fluorescent lamp. In addition, a phase-locked loop (PLL) is incorporated into the original backlight system as a feedback mechanism to track the optimal operating frequency of PT, such that the temperature effect of PT is eliminated, and hence the system efficiency and stability are promoted. The feedback parameter used in the presented system is the phase component instead of the traditionally employed lamp current amplitude. A simple model and design procedure are both constructed by reasonable parameter simplification and combination schemes. Complete analysis and design considerations are discussed in detail in this paper. Experimental results agree with the theoretical prediction.