A Multi-channel High Efficiency Boost LED Backlight Driver with High Dimming Ratio

Abstract

Abstract-In recent years, the screen size and backlight brightness have been increased year by year in portable electronic equipment, which makes much more requirements for LED driver chips. A 3-channel boost LED driver with high efficiency is proposed, and it has 3 channels with 10 LED lights in each channel. The current flow in each channel can reach to 20mA. In order to improve the output efficiency of the chip, the on-resistance of the power MOS sampling method is used here. Thus can achieve powerless sampling. Direct PWM control method is used in the circuit to complete the dimming, which can achieve colorless output of the white light. The use of a dimming MOSFET and LDO in the circuit to further optimize the power consumption. The circuit is designed and simulated in CSMS 0.25um BCD technology. The input voltage range is 2.7V~5V. The maximum dimming output voltage is 36V. The final output efficiency of the chip can achieve 91.4%.The rising time of the LED current in the dimming circuit is about 192ns and the falling time is about 14ns. The maximum dimming ratio is 9000: 1 at 500Hz.