Applying grey model to predict the useful lifetime for high-power white LEDs

An accelerated degradation test has been widely used to analyze the useful lifetime of high-power white light-emitting diodes (HPWLEDs). A two-stage method is proposed to predict the useful lifetime of HPWLEDs. In the first stage, an exponential model first fits the degradation data. In the second stage, a response model based on an inverse power (exponential) law under different stresses is derived for predicting the useful lifetime under normal operating conditions. To improve the fitting accuracy for the degradation data, we consider the grey model. The useful lifetimes based on the exponential and grey models using the two-stage method are obtained as 192,317 and 184,538 h, respectively.