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Appl. Sci. 2017, 7(2), 206; doi:10.3390/app7020206

LED Current Balance Using a Variable Voltage Regulator with Low Dropout vDS Control

Department of Electrical Engineering, National Chiayi University, Chiayi City 60004, Taiwan
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Author to whom correspondence should be addressed.
Academic Editor: Eric Ka-wai Cheng
Received: 26 December 2016 / Accepted: 14 February 2017 / Published: 20 February 2017
(This article belongs to the Special Issue Energy Saving)
View Full-Text   |   Download PDF [2168 KB, uploaded 21 February 2017]   |  

Abstract

A cost-effective light-emitting diode (LED) current balance strategy using a variable voltage regulator (VVR) with low dropout vDS control is proposed. This can regulate the multiple metal-oxide-semiconductor field-effect transistors (MOSFETs) of the linear current regulators (LCR), maintaining low dropout vDS on the flat vGS-characteristic curves and making all drain currents almost the same. Simple group LCRs respectively loaded with a string LED are employed to implement the theme. The voltage VVdc from a VVR is synthesized by a string LED voltage NvD, source voltage vR, and a specified low dropout vDS = VQ. The VVdc updates instantly, through the control loop of the master LCR, which means that all slave MOSFETs have almost the same biases on their flat vGS-characteristic curves. This leads to all of the string LED currents being equal to each other, producing an almost even luminance. An experimental setup with microchip control is built to verify the estimations. Experimental results show that the luminance of all of the string LEDs are almost equal to one another, with a maximum deviation below 1% during a wide dimming range, while keeping all vDS of the MOSFETs at a low dropout voltage, as expected. View Full-Text
Keywords: linear current regulator; variable voltage regulator; LED; low dropout voltage linear current regulator; variable voltage regulator; LED; low dropout voltage
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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Hsieh, H.-I.; Wang, H. LED Current Balance Using a Variable Voltage Regulator with Low Dropout vDS Control. Appl. Sci. 2017, 7, 206.

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