The design and implementation of a new digital dimming controller for the backlight resonant inverter

This paper presents a new digital dimming controller (DDC) for the backlight resonant inverter to improve the ignition behavior of the cold cathode fluorescent lamp (CCFL) and, hence, to increase the CCFL´s lifespan. The DDC using a soft-starting technique (DDC-SST) is designed and developed to reduce the high ignition voltage and to eliminate the ignition current spikes. A full-bridge resonant inverter is adopted in the backlight system. The design considerations along with a complete analysis for said controller are detailed. Encouraging experimental results in close agreement with the theoretical analysis are also exhibited. The overall system power efficiency is approximately 85%. The ignition voltage is reduced by around 30% without any lamp current spike occurring during the dimming control operation. The apparent advantages of the proposed dimmer are listed in the conclusion.