A Color-Theory-Based Chromaticity Coordinates Tracking Strategy for LED Color-Mixing System

Based on the color theory, a precise chromaticity coordinates tracking strategy for the LED color-mixing system is proposed. The relationship between the resulting mixing color and the flux ratio of primary colors is derived according to the center of gravity rule on the CIE1931 chromaticity diagram. Based on this, the hysteresis control is introduced to minimize the color shift caused by aging and temperature effects without requiring any temperature sensor. A prototype with red-green-blue (RGB) strings has been built and evaluated. The experimental results show that the luminous output can be controlled between 100 and 600 lm with an error within ±2%. Any chromaticity coordinate within the triangle enclosed by the points corresponding to RGB can be controlled accurately and the color distance between the output coordinate and the reference coordinate in CIE1976 is less than 0.007 over the whole color gamut.