A High Accuracy Weak Voltage LED Analog Dimming Method

Jiang-Ping He; Bo Zhang; Xin Gao; Chang-Dong Wu; Zhao-Ji Li; Jiang-Yun Zhou

doi:10.1109/ACCESS.2019.2935013

IEEE Access (Jan 2019)

A High Accuracy Weak Voltage LED Analog Dimming Method

Jiang-Ping He,
Bo Zhang,
Xin Gao,
Chang-Dong Wu,
Zhao-Ji Li,
Jiang-Yun Zhou

Affiliations

Jiang-Ping He: ORCiD; School of Electrical Engineering and Electronic Information, Xihua University, Chengdu, China
Bo Zhang: State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, China
Xin Gao: Electrical Engineering Department, Chengdu Technological University, Chengdu, China
Chang-Dong Wu: School of Electrical Engineering and Electronic Information, Xihua University, Chengdu, China
Zhao-Ji Li: State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, China
Jiang-Yun Zhou: ConvenientPower Semiconductor Corporation, Chengdu, China

DOI: https://doi.org/10.1109/ACCESS.2019.2935013
Journal volume & issue: Vol. 7
pp. 172362 – 172373

Abstract

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A weak voltage analog dimming method for high precision light emitting diode (LED) current control with N-Bits analog static offset calibration (N-Bits ASOC), dynamic offset cancellation (DOC) and K-times dimming duty to voltage (KD2V) conversion is presented. The N-Bits ASOC circuit decreases the analog dimming error to VOSMAX/2N - 1 by pre-calibrating the error amplifier offset. Moreover, through a smart combination of KD2V circuits and DOC amplifier, the KD2V and DOC operational amplifier magnify the dimming reference and LED current sense voltage K-times, respectively, which reduces the residual dimming error K-times without any modification to the LED current sampling resistor. Based on the 0.18μm 5V/40V Bipolar-CMOS-DMOS (BCD) process, experimental results for a cell phone backlighting driver show that the analog dimming ILED error reduces to 30μA at maximum 200mV LED current feedback voltage. This deviation mostly keeps constant through a dimming duty range of 0.5% to 100% and VIN range of 2.7V to 5.5V. Furthermore, a 200-sample measurement data suggests that this method is effective even when dimming duty is smaller than 0.5% for mass production.

Published in IEEE Access

ISSN: 2169-3536 (Online)
Publisher: IEEE
Country of publisher: United States
LCC subjects: Technology: Electrical engineering. Electronics. Nuclear engineering
Website: https://ieeexplore.ieee.org/xpl/RecentIssue.jsp?punumber=6287639

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