Parametric Compact Thermal Models of Power LEDs

Abstract

Light-emitting diodes are nowadays the most dynamically developing type of light sources. Considering that temperature is the main factor affecting the electrical and lighting parameters of these devices, thermal models are essential subcomponents of the multidomain models commonly used for simulation of their operation. The authors investigated white power light-emitting diodes soldered to Metal Core Printed Circuit Boards (MCPCBs). The tested devices were placed in a light-tight box on a cold plate and their cooling curves were registered for different diode heating current values and various preset cold plate temperatures. These data allowed the computation of optical and real heating power values and consequently the generation of compact thermal models in the form of Foster and Cauer RC ladders. This also rendered possible the analysis of the influence of the considered factors on the compact model element values and their parametrization. The resulting models yield accurate values of diode junction temperature in most realistic operating conditions and they can be easily included in multidomain compact models of power light emitting diodes.

Influence of a Thermal Pad on Selected Parameters of Power LEDs

“…This set-up consists of a transient thermal tester, a water-cooling system with a cold plate, a light-tight chamber, a luxmeter, and a radiometer. The interior of the light-tight chamber with the cold plate are shown in Figure 1b [28]. The cold plate with a tested power LED is placed inside the light-tight chamber.…”

Understanding multi-domain compact modeling of light-emitting diodes

“…There exists need for standardized compact multi-domain models of LEDs, which need to be implemented by integrating models of other electronic and mechanical components to establish a more unified software-based design for complete LED luminaires as well as their performance analysis. The method suggested by Delphi4LED is to model the multi-domain characteristics of the LEDs such that it can be used at module and system levels (Bornoff et al, 2016;Janicki et al, 2019;Poppe et al, 2019). When an accurate thermal model of an LED is used conforming to the actual application environment, performance can be accurately analyzed.…”

Compact Thermal Modeling of Modules Containing Multiple Power LEDs

“…According to the JEDEC standards [30,31], all thermal analyses should be always carried out using the real heating power as the input quantity, which can be found by subtracting from the measured electrical power the value of the optical power emitted in the form of light. Thus, it was also necessary to determine the value of the LED optical power, which could be computed using the method described in [32], based on the knowledge of the measured light intensity at a known distance directly over the diode and the spatial light distribution curve provided by the manufacturer in the datasheet. For the LED heating current considered here, the measured optical and real heating power values were equal to 0.4 W and 1.8 W. Unfortunately, without the information concerning the internal diode structure, it was not possible to evaluate how much heat was dissipated in the semiconductor structure itself and how much was dissipated during the wavelength conversion in phosphorus.…”