Accurate thermal characterization and optimization of high lumen led array fixtures

Abstract

High lumen light emitting diode (LED) arrays have been preferred in di erent applications due to their low energy consumption. To maintain the performance of LEDs, heat generated by the LED chips should be removed e ectively. Junction temperature can be estimated by thermal models utilizing constant thermal resistances provided in LED datasheets. However, constant thermal resistance used in simulations often neglect the temperature and thickness dependent thermal conductivity of chip layers, which becomes more important at higher temperatures. To include this e ect, a multiscale thermal model will be built via COMSOL. First step will include important package features such as LED array and the heat sink and the second step will include the detailed analysis of an LED chip by including temperature and thickness dependent thermal conductivity of chip. The model will be used to analyze junction temperature sensitivity. Today, heat sinks that provide passive thermal management with n structures are commonly used for e ective heat removal from LEDs. Optimization of the heat sink based on thermal needs is crucial for better design of LED arrays. The optimization model will be used to optimize the LED structure by using only three di erent inputs such as width and length of the n, and the heat that is desired to spread. And the result of these optimization are applied to the multiscale thermal model to see the real e ect of these optimizations on the junction temperature. The results of this study show that the junction temperature values with multiscale model are higher than using constant thermal resistance values from the product datasheet. In addition, to design a high lumen LED array, di erent priorities can be used according to user demand and di erent initial LED array designs are obtained from the optimization result.