A High-Efficiency Single-Inductor Multiple-Output Buck-Type LED Driver With Average Current Correction Technique

Abstract

The state-of-the-art topology of a single-inductor multiple-output light emission diode (LED) driver employs time-multiplexing (TM) control multiple parallel LED strings. The TM control technology provides large output current but the inductor current is separated to several parts and unable to be used simultaneously. The limitation of TM control also results in low dimming frequency and low color resolution. Thus, a single-inductor multiple-floating-output (SIMFO) LED driver with the average current correction (ACC) technique is proposed to solve these problems, so the inductor current is simultaneously utilized by every LED in series, with enhancement of luminous efficiency. Furthermore, the proposed ACC technique adaptively adjusts the average current to eliminate the current cross-regulation effect occurring in different dimming patterns, so each different color LED has its own dimming ratio. The test chip is fabricated in a 0.5-mu m high voltage (HV) process with an active area of 15 mm(2), and experimental results show the proposed LED driver achieves 24-b color resolution with 12 W output power and maintains 96% high efficiency in the RGBW LED applications.