An Effective Prediction Method for LED Lumen Maintenance

IES LM-80-08/Energy Star, as an accepted method for LED life testing, requires LED be operated under three temperatures for at least 6000 hours to claim the lifetime of LED by using B50L70, meaning that 50% (B50) of LED's Iwnen output is less than 70% (L70) of initial value. However, it is not acceptable for manufacturers to wait for 6000-hour testing data for lifetime prediction before product launch, as being shortened product design cycle. Therefore, an effective qualification testing is necessary to build for assisting designer in the preliminary verification to eliminate failures and make improvement before product release. This paper demonstrates the trend of lumen maintenance in Wet high temperature operation test (WHTOL) testing, indicating that a prediction method for LED lumen maintenance could be initiated with rather short testing time, which is obviously becoming important for LED release with shortened design cycle.