Multi-Domain Modelling of LEDs for Supporting Virtual Prototyping of Luminaires

Abstract

This paper presents our approaches to chip level multi-domain LED (light emitting diode) modelling, targeting luminaire design in the Industry 4.0 era, to support virtual prototyping of LED luminaires through luminaire level multi-domain simulations. The primary goal of such virtual prototypes is to predict the light output characteristics of LED luminaires under different operating conditions. The key component in such digital twins of a luminaire is an appropriate multi-domain model for packaged LED devices that captures the electrical, thermal, and light output characteristics and their mutual dependence simultaneously and consistently. We developed two such models with this goal in mind that are presented in detail in this paper. The first model is a semi analytical, quasi black-box model that can be implemented on the basis of the built-in diode models of spice-like circuit simulators and a few added controlled sources. Our second presented model is derived from the physics of the operation of today’s power LEDs realized with multiple quantum well heterojunction structures. Both models have been implemented in the form of visual basic macros as well as circuit models suitable for usual spice circuit simulators. The primary test bench for the two circuit models was an LTspice simulation environment. Then, to support the design of different demonstrator luminaires of the Delphi4LED project, a spreadsheet application was developed, which ensured seamless integration of the two models with additional models representing the LED chips’ thermal environment in a luminaire. The usability of our proposed models is demonstrated by real design case studies during which simulated light output characteristics (such as hot lumens) were confirmed by luminaire level physical tests.

Luminaire Digital Design Flow with Multi-Domain Digital Twins of LEDs

“…Figure 5 provides the major steps of creating the multi-domain compact models of LED packages. The LED package (multi-domain) compact model is comprised of; (1) a boundary condition-independent compact thermal model of the physical LED package and (2) a multi-domain, so called Spice-like, model that describes the LED operation at the chip level [7]. The former can be created with the help of the measured real thermal impedance, ( ) of the LED package in question while the parameters of a chip level LED model can be identified from the so called isothermal current-voltage-flux characteristics of the LED device (see later).…”

“…First a detailed thermal model of the LED package structure is set up and "calibrated" with the help of structure functions derived from the measured thermal impedance, ( ) of the package and then, in a subsequent step, thermal capacitance and thermal resistance values of a thermal RC network model of the package are optimized to best represent the thermal properties of the LED package under any boundary conditions at the package footprints and the LED's dome (lens) [8]. (1) a boundary condition-independent compact thermal model of the physical LED package and (2) a multi-domain, so called Spice-like, model that describes the LED operation at the chip level [7]. The former can be created with the help of the measured real thermal impedance, Z th (t) of the LED package in question while the parameters of a chip level LED model can be identified from the so called isothermal current-voltage-flux characteristics of the LED device (see later).…”

Thermal Analysis of the Factors Influencing Junction Temperature of LED Panel Sources

“…The increase of temperature T j causes a drop in the value of the emitted light stream Φ, a change in the dominant wave length, as well as a decrease in the LED light source lifetime. Exceeding the maximum junction temperature T j declared by the producers may irreversibly damage a semi-conductive light source [8][9][10][11][12][13].…”

Research on Luminance Distributions of Chip-On-Board Light-Emitting Diodes

“…According to the latest research, limiting the Tj junction temperature is of key importance to the life of light-emitting diodes [34]. Exceeding the maximum Tj junction temperature set by producers can irreversibly damage a LED [35,36]. For each optical system designer, knowing the luminance level and luminance distribution (including its gradient) on the light source surface is critical regardless of the type of light source used.…”