An Improved Digital-Dimming Controller for Back-light Module Applying Frequency-Shift Technique

A novel simple control method to improve the ignition behavior of cold cathode fluorescent lamp in digital-dimming mode is proposed in this paper. The half-bridge resonant inverter is employed in the presented back-light system. To extend the lamp life, we realize a digital-dimming controller with frequency-shift technique (DDC-FST) to reduce the high ignition voltage and to eliminate the ignition current spike. Complete analysis and design considerations are discussed in detail in this paper. Simulation and experimental results are close to the theoretical prediction. The overall efficiency of the system achieved at the rated power is over 91%. The ignition voltage is reduced about 30% without any lamp current spike occurred under digital-dimming operation.