Boost DC-DC Converter With Fast Reference Tracking (FRT) and Charge-Recycling (CR) Techniques for High-Efficiency and Low-Cost LED Driver

An RGB LED driver with the fast reference tracking (FRT) and charge-recycling (CR) techniques is proposed to implement a high-efficiency and low-cost RGB backlight module in color sequential notebook computers' display. The proposed LED driver composed of an asynchronous 1.5 MHz DC/DC boost converter with the FRT and CR techniques was fabricated in TSMC 0.25 mum BCD 40 V technology to generate 16 V for 6-series red (R) LEDs or 21 V for 6-series green (G), or blue (B) LEDs. The FRT technique can speed up the reference tracking performance and effectively improve the up-tracking performance. However, the down-reference tracking depends on the load current and output capacitor. It is difficult to enhance the transient response without reducing the efficiency. Therefore, the CR technique is proposed to store extra energy on the recycling capacitor when the output voltage is switched from high- to low-supplying voltage level and releases the reserved energy back to the output node at next period. Furthermore, the output voltage can be rapidly switched between two different voltage levels by FRT technique without consuming much power owing to the restored energy by the CR technique. Experimental results show that the total power consumption of a notebook computer's 15.4' LCD panel can be reduced from 5 W in cold-cathode fluorescent lamp (CCFL) backlight module to about 2-3 W in RGB LED backlight module with the field color sequential (FCS) algorithm. Furthermore, after the implementation of the LED driver with the FRT and CR techniques, the power loss can be reduced to about 24% of that without the FRT and CR techniques.