A novel dimmable LED driver with soft-start and UVLO circuits. (1st February 2015)

• Record Type: Journal Article
• Authors: Jiang, Jinguang; Tan, Gaojian; Zhang, Zeyu; Zhou, Xifeng
• Is Part Of: Journal of semiconductors. Volume 36:Number 2(2015:Feb.)
• Page Start: 025004
• Publication Date: 2015-02-01
• Subjects: Semiconductors -- Periodicals; 621.38152
• DOI: 10.1088/1674-4926/36/2/025004
• Languages: English
• ISSNs: 1674-4926

Abstract

<abstract xml:lang="en"> <title>Abstract</title> <p>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 μm CMOS process, and only occupies 1.21 × 0.76 mm². 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.</p> </abstract>