Modeling LED driver lifespan through capacitor degradation due to thermal cycling

This paper proposes a life test method and a model to predict the time to failure of LED drivers with electrolytic capacitors at the output stage that experience cycled power/thermal conditions. Based on failure rate estimation methods and field studies, degradation of aluminum electrolytic capacitors can be considered a potential point of failure in LED drivers and other power electronic applications. It is essential to identify failure modes, causes, and precursors of failure of electrolytic capacitors to design reliable power electronic circuits and estimate the useful lifetime of the designed drivers for a given application. LED drivers are exposed to elevated temperatures, on-off switching, and cycled thermal conditions like other power electronic converters. Past studies have investigated the parametric degradation of electrolytic capacitors under constant thermal stresses but not under cycled thermal conditions commonly found in lighting applications. Therefore, temperature and thermal cycling were selected as acceleration factors to study the effects of power/thermal cycling on the life of electrolytic capacitors in LED drivers. The accelerated life test showed that the LED driver's useful life had an inverse exponential relationship to the operating temperature of the output capacitor. The thermally cycled conditions did not indicate additional failure mechanisms introduced due to thermal cycling within the tested temperature range. Based on the experimental results, we developed a mathematical modeling technique to estimate the time to failure of LED drivers due to the electrolytic capacitor's parametric degradation with different operating profiles.