Step-stress accelerated testing of high-power LED lamps based on subsystem isolation method

The lifetimes of high-power light-emitting diode (LED) lamps are investigated by step-stress accelerated test. The entire lamp is divided into three subsystems, namely, the LED light source, the driver, and the mechanical fixture. Step-stress accelerated tests are conducted on the LED light source only, which is placed in a thermal chamber and connected to other subsystems outside the aging furnace. Thus, the highest possible stress level can be reached for the LED light source. The reliability characteristics of the LED light source are analyzed based on the step-stress accelerated degradation test model. The fault tree and Monte Carlo algorithm are used to deduce the reliability of the entire LED lamp. The case study shows that the tested samples underwent similar degradation mechanisms under three reasonable stress levels and that the proposed procedure is fast and effective in accelerating the decay process of LED lamps. The predicted LED lamp lifetime is close to the value specified by the LED lamp manufacturer. The proposed subsystem isolation method can overcome the obstacle resulting from the significant difference between the breakdown stress limits of each subsystem. (C) 2015 Elsevier Ltd. All rights reserved.