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

Abstract

This paper proposes a novel twelve-phase PWM dimming control for backlight inverter. We adopt twelve-phase or six-phase PWM dimming to control the brightness of twelve lamps. Each phase can control one or two lamps. 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. By the design rule, we compare system parameters between twelve-phase and six-phase dimming control for backlight inverter. Hence higher phases dimming will achieve uniform output lamp currents which is called current equalization. Higher phases dimming possesses higher power efficiency η (%). We develop the design rule that it also can apply for twelve-phase PWM dimming control.