Investigation on Junction Temperatures of Multichip-on-Board Packaged Light Emitting Diodes with Configurable Electrical Power

The junction temperature of the gallium nitride based light emitting diode (LED) is one of the critical parameters that developed the LED luminaries system with high efficacy, long lifetime, and smart functions. Numerous efforts have been conducted to measure and manage the junction temperature that drove multiple LED array at a steady electrical power during the design stages. However, the emerging functional LED luminaries system needs a dynamic and on-line junction temperature measurement, which makes these successful methods less likely to be applied directly on due to cost and complexity issues. Therefore, the junction temperature analysis of the LED array with configurable electrical power becomes an important topic to simplify the junction temperature estimation. In the present paper, a prototype, built by a 3-chip on board based LED array with pulse-width modulation based constant peak current resources, has been tested initially by thermal infrared imager. Then the junction temperature properties including the non-uniform, nonlinear, and superposed are discussed and modeled using finite element method code COMSOL and the thermal equivalent network method. Finally, a simple and fast junction temperature estimator based on the explored properties is given and validated. The suggested methodology and the analysis results shed light on the estimation and control of the junction temperature of LED arrays in smart solid-state lighting.