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

The concept of red-green-blue (RGB) light-emitting-diode (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.