Product level accelerated lifetime test for indoor LED luminaires

A 2-stage acceleration theory for luminous flux depreciation testing at LED lamp/luminaire level is developed to reduce the test time from 6,000 hours to less than 2,000 hours. Such an acceleration theory is based on the exponential decay model and Arrhenius acceleration equation. Three key parameters, namely, activation energy, operating junction temperature, and accelerated testing junction temperature are obtained from massive proven LM80 data sets, nominal junction design temperature, and maximum allowed ambient temperature in operating conditions. A 'master curve' that describes the minimum requirement of the luminous decay is defined, and the curve is associated with a certain design junction temperature. Such a design junction temperature matches the maximum junction temperature where LM80 data are enveloped in the master curve. The corresponding acceleration test procedures have been established by considering the currently available measurement capabilities. Considerable amount of representative lamp/luminaire samples, which directly came from market, have been tested to validate the theory. The results show that the proposed accelerated lifetime test is equivalent to the current 6000h test. In addition, the newly developed accelerated test can eliminate those products with either poor LED sources, or poor system thermal design, or poor electronics system (including driver system) that cannot sustain sufficient temperature storage period.