Modeling of the Parasitical Capacitance Effect in LCD Panel and Corresponding Elimination Strategy

A mathematical model of parasitical capacitance in LCD panel is conducted to explore the influence of leakage current effect on electric characteristics. First, a class D resonant backlight inverter is employed to act as the main circuit. Next, the phase angle variations caused by the parasitic capacitances is considered as a reference parameter in the proposed control strategy. By using the primary-side control and incorporating the DPLL technique to form a feedback mechanism to track the optimal operating frequency. And then the influence of parasitic capacitance can be reduced so as to eliminate the leakage current effect, hence, the system efficiency and stability will be improved. Complete mathematical analysis and design considerations are detailed. Experimental results agree with the theoretical predictions.

[1]  R.-L. Lin,et al.  Electronic ballast for fluorescent lamps with phase-locked loop control scheme , 2006, IEEE Transactions on Power Electronics.

[2]  Young-Cheol Lim,et al.  An analysis of the backlight inverter by topologies , 2001, ISIE 2001. 2001 IEEE International Symposium on Industrial Electronics Proceedings (Cat. No.01TH8570).

[3]  M. Jordan,et al.  Resonant fluorescent lamp converter provides efficient and compact solution , 1993, Proceedings Eighth Annual Applied Power Electronics Conference and Exposition,.

[4]  S. Kawashima,et al.  Third order longitudinal mode piezoelectric ceramic transformer and its application to high-voltage power inverter , 1994, 1994 Proceedings of IEEE Ultrasonics Symposium.

[5]  Chang-Hua Lin,et al.  DPLL Technique Applied to Backlight Module for Eliminating Temperature Effect in Piezoelectric Transformer , 2005, 2005 International Conference on Power Electronics and Drives Systems.

[6]  Chang-Hua Lin,et al.  The Elimination of the Leakage Current Effect for LCD Backlight Module Based on the Primary-side Control and the DPLL Technique , 2007, 2007 2nd IEEE Conference on Industrial Electronics and Applications.

[7]  M. Kazimierczuk,et al.  Resonant Power Converters , 1995 .

[8]  R.-L. Lin,et al.  PLL control scheme for the electronic ballast with a current-equalization network , 2006, Journal of Display Technology.

[9]  C. S. Moo,et al.  Electronic ballast with piezoelectric transformer for cold cathode fluorescent lamps , 2003 .

[10]  C. S. Moo,et al.  An electronic ballast with piezoelectric transformer for cold cathode fluorescent lamps , 2001, ISIE 2001. 2001 IEEE International Symposium on Industrial Electronics Proceedings (Cat. No.01TH8570).

[11]  Ray-Lee Lin,et al.  Phase-locked-loop-control-based electronic ballast for fluorescent lamps , 2005 .

[12]  Wen-Jung Ho,et al.  A cold-cathode fluorescent lamp driver circuit with synchronous primary-side dimming control , 1998, IEEE Trans. Ind. Electron..