A high efficiency boost white LED driver for portable electronics applications

Power efficiency is a very important issue for portable electronic devices since it determines the battery life. The backlight module usually accounts for the major part of power dissipation in a portable device. Thus, to extend the operation time of a portable device, a high efficiency backlight module should be employed. White light-emitting diodes (WLEDs) have replaced cold cathode fluorescent lamps as backlight modules in portable electronics in recently years due to their superior power efficiency. This paper presents a high efficiency WLED driver with an integrated boost DC-DC converter that can drive a series of WLEDs using a single lithium-ion battery, which is the most popular power source for portable devices. As unexpected operation conditions can result in the failure of the driver, battery, or inductor, the driver integrates protection circuits for over current, over voltage, and under voltage. The driver was fabricated in the TSMC 0.25-μm 60-V bipolar-CMOS-DMOS process. The over current protection level is set to 2 A. The over voltage protection is set to 50 V, allowing the boost converter to drive 12 WLEDs in series connection. The under voltage protection circuit turns off the converter when it detects an input voltage below 2.5 V to protect the battery.