Thermal and optical characterization of white and blue multi-chip LED light engines

Abstract

A clear understanding of thermal characteristics for light emitting diodes (LEDs) is at the center of attention for lighting industry. Especially accurate evaluation of the junction temperature of various light engines is the subject matter for last two decades. Nonetheless, viability of the priorly offered solutions is still an argument and only a few of them are practical enough for the extensive practices. Therefore, in this research, utilization of a new multi-LED chip junction temperature measurement technique is studied through thermal characterization of a commercially available MR16 solid-state light lamp. In order to increase the precision of junction temperature measurement for complex LED structures, a newly proposed methodology is applied simultaneously for each LED chip and temperatures of the multi-LED system at each location are determined. Experimental analysis conducted using an advanced junction temperature measurement device that practices the inverse relationship between Forward Voltage (FV) and Junction Temperature (Tj) considering the three-dimensional heat flow from the p-n junction region. Validation of the above-stated measurement device is performed via local temperature maps captured by using an Infrared (IR) thermal camera and detailed CFD numerical models of each LED package is built with commercially available softwares. Optical measurements are then performed, and relevant thermo-optical relationships are established. Findings presented in this paper shown that augmented multi-chip junction temperature measurement method is a promising solution to measure temperature of complex multi-LED devices. In virtue of the established approach, thermal degradation and optical performance assessments of different types of light engines can be accomplished extensively. In future studies, junction temperature data gathered from various multi-LED light engines can be optimized to form a temperature predictive analytical models that can offer a new perspective for the advanced technological applications.