Electro-thermal modeling of power LED using SPICE circuit solver

This paper presents a method of multi-domain modeling for power Light Emitting Diodes (LEDs) with the goal of providing the ability for simultaneous simulations of electrical, thermal and optical behavior. This approach enables engineers to have a better insight into LED critical performance parameters in various operating conditions, by considering the main electrical-thermal and optical interactions. Our proposed multi-domain model integrates an electrical model based on typical diode equations, a dynamic thermal model composed of a Cauer type RC network driven by currnet source, and an optical model derived from the forward current and junction temperature variations of the total luminous flux. The presented approach offers three significant advantages over the traditional single-domain modeling: the effects of packaging and board level thermal management can be evaluated in correlation with electrical parameters, the self heating effect of the junction can be analyzed in the time domain, and the variation of luminous flux output can be observed. The model is defined based on SPICE circuit elements and can be used with any conventional SPICE circuit solver, without the need for solver algorithm modification. The inputs necessary for defining the model are based on standard LED measurements and are often specified in the manufacturer´s datasheets. All the necessary algorithms required to obtain the multi-domain model SPICE code were implemented in Matlab.