Light degradation prediction of high-power light-emitting diode lighting modules

Abstract

Light-emitting diode (LED), generally used for indicator light, has been developed for the past 50 years. Recently, LED has attracted many industries in the research and design of their products. However, its low electro-optical conversion efficiency causes redundant heat leading to increased junction temperature and decreased LED luminosity. In this research, a detailed finite element method (FEM) model of a LED module with a proper estimated thermal power and boundary conditions is established using an ANSYS <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">®</sup> finite element analysis software. Electrical test method (ETM) and thermocouple measurement are utilized to estimate junction temperature and heat sink temperature, as well as to validate the simulation results. Results from simulation agree with experiment results at a 5% deviation. In the life test of high-power LED modules, the six tested devices had different junction temperatures were conducted in this experiment. Luminosity variations are measured by the integral sphere measurement system. Experiment results show different junction temperatures will influence the light degradation mode. Therefore, it is important to predict and control the junction temperature to improve the LED performance. A detailed FEM model of a LED module is established to simulate the junction temperature. Then, the light degradation mode of this LED module is predicted by the simulation result. This method could rapidly predict the light degradation mode of high power LED lighting modules.