LEDs' thermal management aided by infrared thermography

Third International Conference on Solid State Lighting, 2004

Light emitting diodes, LEDs, historically have been used for indicators and produced low amounts of heat. The introduction of high brightness LEDs with white light and monochromatic colors have led to a movement towards general illumination. The increased electrical currents used to drive the LEDs have focused more attention on the thermal paths in the developments of LED power packaging. The luminous efficiency of LEDs is soon expected to reach over 80 lumens/W, this is approximately 6 times the efficiency of a conventional incandescent tungsten bulb. Thermal management for the solid-state lighting applications is a key design parameter for both package and system level. Package and system level thermal management is discussed in separate sections. Effect of chip packages on junction to board thermal resistance was compared for both SiC and Sapphire chips. The higher thermal conductivity of the SiC chip provided about 2 times better thermal performance than the latter, while the under-filled Sapphire chip package can only catch the SiC chip performance. Later, system level thermal management was studied based on established numerical models for a conceptual solid-state lighting system. A conceptual LED illumination system was chosen and CFD models were created to determine the availability and limitations of passive air-cooling.

2016

Thermoelectric model of a light diode was built with a spacial separation of the heat and cold source. The differential equations system was solved, which comprises the stationary equation of the heatconductivity and the equation of Joule thermogeneration. The temperature distribution in the structural elements of LED was calculated and also the temperature of active zone overheating in dependence on the power of LED and the intensity of the heat exchange with the medium. For the numeral estimation a powerful white light diode was chosen-Gree XR7090WHT. It was found out that the light stream can be increased via current increasing, at simultaneous thermal stabilizing of its active zone.

JST: Smart Systems and Devices, 2021

Light Emitting Diodes (LED) shows an important role in replacing traditional lamps due to their longevity, high efficiency, and environment-friendly operation. However, a large portion of the electricity applied on LED converts to heat, raising up the p-n junction working temperature, and lowering the output-light quality and the LED lifetime as well. Therefore, thermal management for LED is one of the key issues in LEDs lighting application. In order to investigate the impact of each component of the LED module on the junction temperature of the LED, we have performed thermal simulations of a typical single LED module by using the finite element method. Effects of thermal conductivity and thickness of each module’s components on junction temperature were analyzed systematically. The results provided a detailed understanding of thermal behavior of a single LED module and established a crucial insight into thermal management design for high-power white LED lamp. Thermal-interface-mat...

Journal of Semiconductors, 2011

Recently, the high-brightness LEDs have begun to be designed for illumination application. The increased electrical currents used to drive LEDs lead to thermal issues. Thermal management for LED module is a key design parameter as high operation temperature directly affects their maximum light output, quality, reliability and life time. In this review, only passive thermal solutions used on LED module will be studied. Moreover, new thermal interface materials and passive thermal solutions applied on electronic equipments are discussed which have high potential to enhance the thermal performance of LED Module.

IEEE Transactions on Power Electronics, 2009

The photometric, electrical, and thermal features of LED systems are highly dependent on one another. By considering all these factors together, it is possible to optimize the design of LED systems. This paper presents a general theory that links the photometric, electrical, and thermal behaviors of an LED system together. The theory shows that the thermal design is an indispensable part of the electrical circuit design and will strongly influence the peak luminous output of LED systems. It can be used to explain why the optimal operating power, at which maximum luminous flux is generated, may not occur at the rated power of the LEDs. This theory can be used to determine the optimal operating point for an LED system so that the maximum luminous flux can be achieved for a given thermal design. The general theory has been verified favorably by experiments using high-brightness LEDs.

International journal of online and biomedical engineering, 2022

This study focuses on LED bulbs where LEDs are typically mounted on a metal core printed circuit board. A sample of LED bulbs having base E27 and a power range between 3.5-11.5 W have been measured. A thermal model will be found using thermal transient testing, infrared thermal measurements, and the Bayesian deconvolution. LED surface temperature will be measured without contact using a low-resolution IR imager. A test facility has been built which automatically switches power on and measures and records samples during the measurement cycle which typically lasts around one hour. This time duration was long enough for reaching the thermal steady-state condition. The procedure uses a measured thermal transient, first calculates the thermal impedance Z th , then the time constant spectrum R ζ (z) using the Bayesian deconvolution. An equivalent thermal network model will be found in Foster-presentation. This can be transformed to Cauer-presentation. The model is a driving point model for thermal impedance and includes thermal resistances and thermal capacitances. FEM simulation gives more detailed information about heat transfer paths and internal temperatures of an LED bulb.

Revista Brasileira de Aplicações de Vácuo, 2020

In this work, we analyze the temperature of the LED lamp of white emission with 9 W with or without the influence of the cooling process using a fan. The investigation was carried out by seven different methods: (1) Analysis of temperature close to LEDs inside the bulb (diffuser); (2) Analysis of temperature on LEDs without bulb; (3) Analysis of temperature on LEDs without bulb with cooling using a fan; (4) Analysis of temperature on LEDs board out of body lamp without bulb; (5) Analysis of temperature on LEDs board out of body lamp without bulb with cooling using a fan. This last analysis 5 exhibited better results, decreasing the significant temperature on the LED surface from ≈130ºC (found in analysis 2) to ≈45ºC. Due to good results exhibited in analysis 5, it was used in the illuminance measurements of the LED lamp without cooling in the analysis 6, and with a fan as analysis 7. Both results compared showed that using a fan had a great influence, and difference on the illuminance values by elapsed time from ≈47,000 lux without a fan (analysis 6) to ≈55,300 lux with fan (analysis 7), and also the use of a fan exhibited the lowest time of stabilization in 1 minute only.

Microelectronics Reliability, 2013

A high brightness LED spot lighting device has been under examination. The device has one multichip LED module which nominal electric power is 15 W. A 3D simulation model has been created and simulated with Comsol Multiphysics software. The temperatures of the LED chip junction, the LED module and the heatsink and have been simulated using a finite-element-method (FEM) software. Simulations have been validated with measurements. Main heat flow paths and the associated thermal resistances in a stationary condition have been resolved. Simulations have been made for the case of external natural and forced external heat convection. Time dependent simulations resolved the time constants of the lamp. The time constants were calculated also by using the thermal resistances and heat capacities of the lamp. Use of thermal grease between the LED module and the heatsink reduces chip temperature. This has also been simulated. Photometric characteristics of the light device, especially luminous flux versus input electrical power and lamp temperature, have been measured. One LED spot light device with a defected LED module was found in photometric measurements and IR-imaging.

2013

High power LED light sources operate mainly in the UV regime. Although the emitted light power is significant, a large amount of heat is generated as a side effect. The increasing temperature degrades the state of the electronic elements of the LED module and decreases the power of the emitted light. This paper discusses the results of the experimental and numerical modelling of the thermal processes inside a module containing a single LED element. Thermal characteristics were investigated for the case with and without forced cooling. Cooling was realized by using air flow induced by a fan. Parameters were identified that govern the main characteristics of the phenomenon.

2015 38th International Spring Seminar on Electronics Technology (ISSE), 2015

A new methodology of infrared thermography (IRT) measurements for quality control of chip on board light emitting diode (COB LED) package is studied and presented. For this goal information measuring system and appropriate additional software is developed and used. COB LED samples are prepared with different kind of defects are prepared. Results from using some suitable IRT methods of passive-, pulsed-, lock in-, FMTWI-thermography are shown and relevant image processing methods are used and discussed.