Illumination and Color Control in Red-Green-Blue Light-Emitting Diode

Abstract

The concept of red-green-blue (RGB) light-emittingdiode (LED) lighting has gained wide attention during recent years and is now one of the targets for future lighting solutions. However, the self-heating of LEDs and environmental temperature variation lead to luminous intensity droop and lighting color drift. The main purpose of this research is to investigate a novel flux feedback and temperature feed-forward (FFB&TFF) control structure for RGB LED lighting control system, in order to provide a wide color range of input commands and regulation of both luminous and color outputs. The work in this paper was carried out in three main steps. First, a thermal-electrical-luminous-chromatic model was derived and identified for RGB LED luminaire. Second, a converter and a compensator were derived and applied to input command conversion and temperature compensation, respectively. Finally, a diagonal proportional-integral controller designed by the decentralized control approach was implemented to regulate the lighting outputs of luminous intensity and chromaticity coordinates in CIE 1976 Uniform Chromaticity Space (UCS) diagram. The results of transient and steady-state experiments showed that the proposed control system was effective.Index Terms-Decentralized control approach, flux feedback and temperature feed-forward (FFB&TFF), red-green-blue (RGB) light-emitting-diodes (LEDs), system identification, thermalelectrical-luminous-chromatic model. I. INTRODUCTIONL IGHT-EMITTING diodes (LEDs) are a highly effective lighting technology. Energy saving and long lifetimes are the main advantages in lighting applications. Red-green-blue (RGB) LED lighting is one of the most popular techniques for white light in the application of LCD backlighting, video projection and general lighting. Its chromatic changeability and wide color range can provide unique lighting experiences [1]. However, the luminous and color outputs are easily affected by self-heating of LEDs as well as environmental temperature variations [2], [3]. Thus, a control system for RGB LEDs is called for to regulate both luminous and color outputs. The key issue of effective regulation is a proper control structure design.

An Estimation Method for the Efficiency of Light-Emitting Diode (LED) Devices

“…(4) and heat power equation in Equ. (8) are related to device properties. For various types of LED devices, these coefficients differ.…”

“…For various types of LED devices, these coefficients differ. When adopting the efficiency model (4) and heat power model (8) to evaluate LED performance, the coefficients in the two equations should be determined in advance.…”

“…The variation of peak wavelength with junction temperature was studied, and the sensitive factor between peak wavelength and junction temperature was identified in [5], [6]. The relationship between chromaticity coordinates and junction temperature was determined in [7], [8]. The mathematical model of forward voltage as a function of junction temperature [9], [10], [11] is widely applied in the industry.…”

Power quality improvement using bridgeless‐Landsman converter for LED driver

“…There are other requirements for LED drivers as constant current, small form factor, LED junction cooling, high efficiency, efficient dimming, no flicker etc. [3][4][5][6][7][8][9][10]. There are different LED drivers which are proposed to fulfil different requirements [6].…”

Repetitive Learning Control Design for LED Light Tracking

“…with a robust control algorithm in [26] and its modifications in [23]. Although the aforementioned papers constitute relevant solutions to general light control problems, when tracking of desired luminous color and intensity reference signals is repeatedly considered in the presence of completely uncertain dynamics-with the aim of reproducing a lighting profile similar to the one corresponding to a day cycle (in real world or even in virtual set scenarios) or, more interestingly, with the aim of benefiting from chromotherapy repetitive lighting profiles-possibly complex periodic output reference signals (with known period) naturally arise and repetitive learning control techniques 2 can be successfully used (see [8], [19] for recent theoretical results and [6], [7], [20], [21] for recent significant applications).…”