Comparison of white LED color shift prediction methods

Supronowicz Robert – Białystok University of Technology – Poland

Nowadays professional and domestic lighting luminaires are being built with LED sources with rated for dozens of thousands operating hours with minimal luminous flux drop by specified time know as lifetime L70. Additionally the LEDs colour consistency is specified in MacAdam’s ellipses tolerance in binning process. Unfortunately pc-W-LED light colour chromaticity are changing during their exploitation time, even before source reaches specified operating time. Such a phenomenon makes live harder for lighting designers at projecting for example museum exhibition or architectural lighting solutions. The ANSI C78.376 and C78.377 presents specifications for the chromaticity of fluorescent lamps and solid-state lighting product respectively. In those document the tolerance of CCT and colour chromaticity points are presented also. The CCT tolerance varies by nominal CCT value and mean sample colour chromaticity is set based MacAdam’s ellipses. According to US DoE ENERGY STAR documents chromaticity stability requirements for LED lamps as after 6.000 hours of lamp operating keep shift for 9 out of 10 samples below 0,007 Δu’v (approx. 7 step-MacAdam).