A novel dimmable LED driver with soft-start and UVLO circuits

作     者：江金光 谭高建 张泽宇 周细凤 

作者机构：GNSS Research Center Wuhan University School of Physics and Technology Wuhan University Suzhou Institute Wuhan University School of Electronic Information and Electrical Engineering Shanghai Jiao Tong University 

出 版 物：《Journal of Semiconductors》 (半导体学报（英文版）)

年 卷 期：2015年第36卷第2期

页      面：135-143页

核心收录：

学科分类：0810[工学-信息与通信工程] 08[工学] 081001[工学-通信与信息系统] 0803[工学-光学工程] 

基　　金：Project supported by the National Natural Science Foundation of China(No.41274047) the Natural Science Foundation of Jiangsu Province(No.BK2012639) the Changzhou Science and Technology Support(Industrial)Project(No.CE20120074) 

主　　题：LED driver DC-DC converter UVLO soft-start PWM dimming 

摘      要：A fully integrated LED driver based on a current mode PWM boost DC-DC converter with constant output current is proposed. In order to suppress the inrush of current and the overshoot voltage at the start up state, a soft-start circuit is adopted. Additionally, to adjust the LED brightness without color variation over the full dimming range and achieve high efficiency, a PWM dimming circuit is presented. Furthermore, to keep the loop stability of the LED driver, an internal slope compensation network is designed to avoid the sub-harmonic oscillation when the duty cycle exceeds 50%. Finally, a UVLO circuit is adopted to improve the reliability of the LED driver against the input voltage changing. The LED driver has been fabricated with a standard 0.5/xm CMOS process, and only occupies 1.21 × 0.76 mm^2. Experimental results show that the brightness of the LED can be adjusted by an off- chip PWM signal with a wide adjusting range. The inductor current and output current increase smoothly over the whole load range. The chip is in the UVLO condition when the input voltage is below 2.18 V and has achieved about 137 μs typical start-up time.