Design and analysis for backlight inverter with six-phase PWM dimming control circuit

This paper proposes a novel dimming control scheme which possesses six-phase PWM dimming control for backlight inverter. We adopt six-phase PWM dimming control circuit to control the brightness of twelve lamps. Each phase driving circuit can control two lamps. Circuit architecture is full bridge circuit which can improve the total efficiency of driving circuit. Due to single-phase PWM dimming consumes large input current Iin(A) Iin(A) than six -phase PWM dimming at the same PDIM. So, it causes that single-phase dimming presents larger percent error range (-6.36 ~ +9.8%) and six-phase dimming presents smaller percent error range(-1.26~+1.98%)in average lamp current Ioavg (mA) comparing with lamp currents Io(mA). Hence the six-phase dimming achieves uniform output lamp currents which is called current equalization. From the experimental results, We verify that six-phase dimming is better than conventional single-phase dimming in the performance and in power efficiency η. We use twelve CCFLs(300-mm/2.4-mm) inside of a 24 inch LCDTV.