The Elimination of the Leakage Current Effect for LCD Backlight Module Based on the Primary-side Control and the DPLL Technique

A new control method is proposed to eliminate the leakage current effect for backlight module in the LCD housing. First, a class D resonant inverter is employed to assess the system performance. Next, the primary-side control incorporating the DPLL technique is embedded in the backlight system, as a feedback mechanism, to reduce the influence of parasitic capacitance and to track an optimal operating frequency so that the leakage current effect is removed and, hence, the system efficiency and stability is improved. Complete mathematical analysis and design considerations are detailed. Experimental results agree with the theoretical predictions, and the parasitic capacitance in backlight system can be estimated by the derived mathematical models.