A Statistical Method Analyzing LED Lumen Depreciation and Projecting LED Life

There is a strong need for a method to represent the potential life of LED products as a critical part of design decisions including cost-effectiveness analysis. The IES LM-80 test method is in place to collect lumen depreciation data but it does not provide for estimation of future long term depreciation. Separate estimation methods are being considered (TM-21) and this paper describes the analysis of a series of LED degradation models and subsequent development of an estimation method. The work involves analysis of a set of engineering models to determine their applicability and define a structure for their use in LED lumen output life based on a lumen output level such as the L70 metric. The analysis has provided valuable information on methods effectively estimating LED life time, and impacts of measurement uncertainties, test duration, interval and other test conditions on selecting degradation models and LED life time projection. A set of guidelines are recommended to estimate LED life from data obtained using the current LM-80 test method.