A generalised thermal LED-model and its applications

Abstract Within the last 10 years the illuminants for automotive exterior lighting shifted nearly completely to LEDs. Due to being semiconductor devices, LEDs behave differently compared to incandescent lamps and xenon bulbs. The paper derives a generalized thermal and geometric LED model. This gains advantage because the data provided in data sheets is different from manufacturer to manufacturer and even from one manufacturer the data is not standardized. So the data is not prepared to be included easily in any development process. In this context “model” mainly refers to a calculation procedure. The data provided in data sheets often has to be digitized. Outgoing from this digitized data a model, based on a smart data combination and polynomial regression, is built up. This model is described in detail and an application to simulations by means of computational fluid dynamics (CFD) is discussed. In doing so a geometric simplification is suggested. This simplification is done in a manner to keep the thermal characteristic of the original LED. The model may be used in different applications such as simulations and design. It allows predicting the thermal status and light output during a virtual development phase, because it inherently calculates the thermal power and light output. This may lead to a more precise estimation of temperatures in lighting systems as well as a prediction of hot lumens.