Revisiting multi-domain empirical modelling of light-emitting diode luminaire

Abstract

In this work, an empirically derived multi-domain model of a light-emitting diode (LED) luminaire is proposed. The optical, electrical, and thermal characteristics of LEDs are obtained from the data sheets provided by manufacturers. Both transient and steady-state performance of LED luminaire were realized theoretically and validated against experimental findings from earlier investigations. The difficulties encountered in creating an ideal LED luminaire are discoursed and examined. Most of the studies on LED luminaires described in prior works ignored the influence of luminaire housing and optics on the thermal management of the luminaire. Knowledge of thermal time constants of LED luminaires is important, as they decide the rate of luminous flux decay when LED lighting systems are used for long periods of operation. Thermal time constants also decide the time taken by the LED junction to reach steady state with its surrounding. From the study it is inferred that the increase in junction temperature and deterioration of luminous flux is controlled by the product of the single most dominant thermal resistance from the junction to a point along the heat conduction path and sum of all the downstream thermal capacitances. This is true as in most cases LED device thermal capacitance is very less related to the thermal capacitance of the heat-sink, hence the product of single most dominant thermal resistance and thermal capacitance of heat-sink decide the rate of rising of junction temperature or luminous flux deterioration.

Keywords:

• Elmore delay
• junction temperature
• LED
• light-emitting diode
• luminaire
• multi-domain
• solid-state lighting
• modelling

Public interest statement

In this work, a method to examine the performance of a light-emitting diode (LED) luminaire using in-situ measurements is discussed. The methodology discussed in this work allows comparing different LED products using a standard metric. LED is a semiconductor device packaged in an integrated circuit. Light is emitted by LEDs from their junction. LED junction is subjected to thermal stress during operation. LEDs convert only a fraction of the applied electrical power to light and the rest needs to be dissipated as heat into the ambient. Hence, the thermal resistance along the heat conduction path from the junction to the ambient must be minimum. Higher the thermal resistance higher will be the operating junction temperature, resulting in derating of device performance and causing accelerated aging and higher failures. Semiconductor manufacturers provide thermal metrics at the device level. For a complete luminaire, the thermal metric needs to be estimated experimentally.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Supplementary material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/23311916.2023.2288423.

Additional information

Notes on contributors

Shailesh K R

Shailesh K R received B.E. degree in Electrical and Electronics engineering from Mangalore University, India, in 1997 and M.Tech. degree in illumination technology from Mangalore University, India, in 1999. He received Ph.D degree for the thesis titled ”Assessment of light-emitting diode luminaire performance using virtual test bench’’ from Manipal Academy of Higher Education, India in 2019. He is the author of more than 40 technical papers published in reputed international journals and international conference proceedings. His notable contributions include a new method of gonio-photometry known as ”Light Sieve Photometry” and a non-invasive method to measures junction temperature of LEDs in a LED luminaire. His research interests are in the area virtual instrumentation for light and light-based technologies. This work brings together the knowledge provided by LED manufacturers, academicians and software developers in creating compact multi-domain models of light-emitting diode luminaires.