A reliability analysis method for LED luminaires based on step stress accelerated degradation test

To consider the complex system integration of LED luminaires, a novel analysis method combined with reliability test is presented. Initially, the whole system is divided into three subsystems (Drive, fixture and LED light source) so that reliability test can be conducted on the objective subsystem with a stress level as high as possible. And further step stress accelerated degradation test (SSADT) is implemented on the light source subsystem, with a goal to achieve its reliability distribution function. Only the light source subsystem is accelerated inside the thermal chamber, and connected with other subsystems outside the chamber. And then the reliability of LED light source subsystem is extrapolated with the methodology model of SSADT. Finally, the whole LED system reliability is integrated reasonably with the help of Fault Tree and Monte Carlos Algorithm. The proposed method considers the stresslimit difference of subsystems, and solves the difficulty to assess the system reliability of LED luminaire with complex system integration. The result of an example case shows that the SSADT method is very effective based on the subsystem-isolation acceleration way, and that the whole LED system lifetime meets closely the lifetime remarked by vendor. The proposed method is expected to be very useful in future LED luminaire fast qualification test.