System parameters compare between six-phase and improved tweleve-phase PWM dimming control by design rule for backlight inverter

This paper proposes a novel improved twelve-phase with dummy load dimming control for backlight inverter. We adopt six-phase of twelve-phase PWM dimming to control the brightness of twelve lamps. Each of odd phase can control two lamps. The other six even phases are connected to dummy load without lamp current. Circuit architecture is full bridge phase-shift circuit which can improve the total efficiency of the driving circuit. From the experimental results for four-phase and six-phase PWM dimming control, we got a conclusion which power efficiency η (%) is directly proportional to No. of phases and lamp current error E (%) whose range is inversely proportional to No. of phases. We develop a design rule. By the design rule, we compare system parameters between six-phase and improved twelve-phase with dummy load dimming control for backlight inverter. Hence improved twelve-phase with dummy load dimming control achieves optimization output current equalization which also reduces the number of inverters. It possesses the advantage of higher power efficiency η (%) for higher phases dimming and the merit of simplifying inverters for lower phases dimming.