《IESNA LM-80-08 and TM-21-11》.pdf

IESNA LM-80-08 and TM-21-11 Mark Hodapp, CRE Senior Application Engineer Philips Lumileds 370 West Trimble Road San Jose, CA 95131 What is lumen maintenance? Well understood that LEDs are very long life light sources. However, the light output of SSL products gradually goes down over time. Rated lumen maintenance life of the LED (Lp) is the elapsed operating time over which the LED light source will maintain the percentage, p, of its initial light output L70 (hours) = time to 70% lumen maintenance L50 (hours) = time to 50% lumen maintenance Lumen maintenance and EPA EPA is using a simple exponential model for lumen maintenance until TM-21 is published: ( ) ( ) φ time exp −alpha time ( ) ln 0.7 alpha − time ( ) alpha (25,000 hour ) −ln 0.7 1.4267 e −5 25,000 ( ) [ ( )( )] EPA limit LM 25,000 exp − 1.467 e −5 6,000 0.918 Lumen maintenance and EPA Lumen Maintenance Projection for White 3500°K LXML-PWx1 LUXEON Rebel under these conditions 85°C, 0.35A (Tjunction ≅ 98°C) Normalized to 1 at 0 hours 1.2 Ta within –5°C of Ts, in accordance with LM80. 1.1 t u p 1.0 t u O