Low cost, high color rendition, CCT variable lighting system based on W-G-B LED

Abstract

This article proposes a novel approach of tunable correlated color temperature (CCT) lighting system with high color rendition using three component color mixing concept. Using Grassmann’s color mixing theory, phosphor coated warm white LED source (CCT 2800 K) is mixed with the blue (467 nm) and green (527 nm) LED light sources and a detailed mathematical formulation is derived for easy controlling of variable CCT and experimentally validated in this article. As a result, the locus of the blended light source is very close to the Planckian locus on Commission Internationale de l’Eclairage (CIE) 1931 chromaticity diagram. The generated color of the light sources is evaluated by both CIE color rendering index (CRI) method and Illuminating Engineering Society (IES) TM-30-18 method. This proposed system provides a wide range of CCTs starting from 2800 K to 7500 K with a very high CRI (CIE Ra) value of 94, color fidelity index (IES Rf) score of around 85 and color gamut index (IES Rg) of 95. As this system uses only three color component, the cost of this system is comparatively low with respect to other high CRI, tunable CCT lighting system available in market.