Hot Junction Temperature Evaluation of Array LED Using Thermal Dynamic Model

Abstract

LED (Light-Emitting Diode) has superior luminescence characteristics and reliability, durability compared with conventional lighting, and copes with lighting for all life from indoor lighting to automotive head lamp. In this study, the junction and surface temperature, which have the greatest influence on the LED performance, are measured accurately by considering the emissivity change depending on whether or not the LED phosphor emits light. For this purpose, the LED junction temperature is measured and compared by taking into consideration both the non contact measurement using the IR camera and the contact method using the thermocouple. It also generates thermal models of the LED package, which uses the thermal structure function method and the measured light efficiency of the LED itself, and the radiation type thermocouple, which is a contact temperature sensor. By comparing the temperature obtained from the thermal dynamic model of the LED and the thermocouple thus obtained with the experimentally obtained temperature, the temperature of the surface and the junction of the LED phosphor are accurately evaluated.