scholarly journals Compact Thermal Modeling of Modules Containing Multiple Power LEDs

Energies ◽  
2020 ◽  
Vol 13 (12) ◽  
pp. 3130
Author(s):  
Marcin Janicki ◽  
Przemysław Ptak ◽  
Tomasz Torzewicz ◽  
Krzysztof Górecki
Keyword(s):  
Thermal Coupling ◽  
Essential Factor ◽  
Thermal Models ◽  
Light Emitting ◽  
Heating Effects ◽  
Network Identification ◽  
Multiple Devices ◽  
Convection Cooling ◽  
Multiple Power ◽  
Compact Thermal Modeling

Temperature is an essential factor affecting the operation of light-emitting diodes (LEDs), which are often used in circuits containing multiple devices influencing each other. Therefore, the thermal models of such circuits should take into account not only the self-heating effects, but also the mutual thermal influences among devices. This problem is illustrated here based on the example of a module containing six LEDs forming on the substrate a hexagon. This module is supposed to operate without any heat sink in the natural convection cooling conditions, hence it has been proposed to increase the thermal pad area in order to lower the device-operating temperature. In the experimental part of the paper, the recorded diode-heating curves are processed using the network identification by deconvolution method. This allows for the computation of the thermal time constant spectra and the generation of device-compact thermal models. Moreover, the influence of the thermal pad surface area on the device temperature and the thermal coupling between LEDs is investigated.

Self-heating effects at high pump currents in deep ultraviolet light-emitting diodes at 324 nm

2002 ◽  
Vol 81 (18) ◽  
pp. 3491-3493 ◽  
Author(s):  
A. Chitnis ◽  
J. Sun ◽  
V. Mandavilli ◽  
R. Pachipulusu ◽  
S. Wu ◽  
...  
Keyword(s):  
Ultraviolet Light ◽  
Light Emitting Diodes ◽  
Light Emitting ◽  
Self Heating ◽  
Heating Effects ◽  
High Pump ◽  
Deep Ultraviolet ◽  
Ultraviolet Light Emitting Diodes

scholarly journals OLEDs: light-emitting thin film thermistors revealing advanced self-heating effects

2015 ◽  
Author(s):  
Axel Fischer ◽  
Thomas Koprucki ◽  
Annegret Glitzky ◽  
Matthias Liero ◽  
Klaus Gärtner ◽  
...  
Keyword(s):  
Thin Film ◽  
Light Emitting ◽  
Self Heating ◽  
Heating Effects

Modelling mutual thermal coupling in LED modules

2015 ◽  
Vol 32 (3) ◽  
pp. 152-157 ◽  
Author(s):  
Krzysztof Górecki ◽  
Przemysław Ptak
Keyword(s):  
Thermal Characteristics ◽  
Thermal Inertia ◽  
Thermal Coupling ◽  
Cooling Systems ◽  
Content Type ◽  
Light Emitting ◽  
Common Base ◽  
The Common ◽  
Practical Implications ◽  
Good Agreement

Purpose – The purpose of this paper is to present an electrothermal model of the module containing power light emitting diodes (LEDs) situated on a common base. Design/methodology/approach – The electrothermal model of this device, which takes into account both self-heating and mutual thermal coupling between the diodes situated in this module, is described. Findings – The correctness of the presented model is verified experimentally, and a good agreement of the calculated and measured optical and thermal characteristics of the considered module is obtained. Research limitations/implications – The presented model can be used for different structures of the LED module, but electrical inertia in the diodes is omitted. Practical implications – The presented model was used to calculate electrical, thermal and optical waveforms of the module OSPR3XW1 containing three power LED situated on the common base. Originality/value – The presented model takes into account thermal inertia in the considered LED module and its cooling systems with mutual thermal coupling between all the diodes situated in the same module.

scholarly journals Circuit-free, optoelectronic sensing of electrodermal activities based on photon recycling of a micro-LED

2020 ◽  
Author(s):  
He Ding ◽  
Guoqing Lv ◽  
Zhao Shi ◽  
Dali Cheng ◽  
Yunxiang Huang ◽  
...  
Keyword(s):  
Data Transmission ◽  
Light Emitting Diode ◽  
External Resistance ◽  
Power Harvesting ◽  
Light Emitting ◽  
Skin Response ◽  
Multiple Power ◽  
Pl Emission ◽  
Photon Recycling ◽  
Unique Mechanism

AbstractConventional epidermal electronics integrate multiple power harvesting, signal amplification and data transmission components for wireless biophysical and biochemical signal detection. This paper reports the real-time electrodermal activities can be optically captured using a microscale light-emitting diode (micro-LED), eliminating the need for complicated sensing circuit. Owing to its strong photon-recycling effects, the micro-LED’s photoluminescence (PL) emission exhibits a superlinear dependence on the external resistance. Taking advantage of this unique mechanism, the galvanic skin response (GSR) of a human subject is optically monitored, and it demonstrates that such an optoelectronic sensing technique outperforms a traditional tethered, electrically based GSR sensing circuit, in terms of its footprint, accuracy and sensitivity. This presented optoelectronic sensing approach could establish promising routes to advanced biological sensors.

Improved Radial Plane Fins Heat Sink for Light-Emitting Diode Lamps Cooling

2019 ◽  
Vol 12 (4) ◽  
Author(s):  
António M. G. Lopes ◽  
Vítor A. F. Costa
Keyword(s):  
Heat Sink ◽  
Numerical Study ◽  
Light Emitting Diode ◽  
Heat Sinks ◽  
Electronic Components ◽  
Turning Operation ◽  
Light Emitting ◽  
Radial Plane ◽  
Convection Cooling ◽  
Main Ideas

Abstract A numerical study is conducted concerning the improvement of radial plane fins heat sinks for natural convection cooling of light-emitting diode (LED) lamps. The main objective is to maintain the temperature of the heat sink base below a prescribed threshold for a given released heat flux at the heat sink, minimizing its mass and maintaining at a reasonably simple level the manufacturing processes and operations required for its production. Starting from a previously optimized heat sink for the same purpose, constituted by complete rectangular radial plane fins, the present study aims at further improvements by considering incomplete rectangular radial plane fins. The main objective of this study is to find the best profile for the turning operation to obtain the radial plane fins lighter configuration. It is found that this can be achieved by removing part of the upper internal corners of the rectangular fins, more specifically shaping a curved cut, leading to heat sink mass reduction up to 32.4%. The geometry of the improved heat sink is of cylindrical nature, obtained from cutting an aluminum extruded bar comprising a cylindrical central core and a number of uniformly distributed rectangular radial plane fins, followed by a simple turning operation to remove their upper internal corners. Even if results concern a particular LED lamp, the main ideas and approach prevail to improve other types of heat sinks for general light and/or electronic components cooling.

scholarly journals Experimental proof of Joule heating-induced switched-back regions in OLEDs

2020 ◽  
Vol 9 (1) ◽  
Author(s):  
Anton Kirch ◽  
Axel Fischer ◽  
Matthias Liero ◽  
Jürgen Fuhrmann ◽  
Annegret Glitzky ◽  
...  
Keyword(s):  
Current Density ◽  
Electrical Potential ◽  
Thermal Coupling ◽  
Large Area ◽  
Experimental Proof ◽  
High Brightness ◽  
Light Emitting ◽  
Term Operation ◽  
Ohmic Resistance

AbstractOrganic light-emitting diodes (OLEDs) have become a major pixel technology in the display sector, with products spanning the entire range of current panel sizes. The ability to freely scale the active area to large and random surfaces paired with flexible substrates provides additional application scenarios for OLEDs in the general lighting, automotive, and signage sectors. These applications require higher brightness and, thus, current density operation compared to the specifications needed for general displays. As extended transparent electrodes pose a significant ohmic resistance, OLEDs suffering from Joule self-heating exhibit spatial inhomogeneities in electrical potential, current density, and hence luminance. In this article, we provide experimental proof of the theoretical prediction that OLEDs will display regions of decreasing luminance with increasing driving current. With a two-dimensional OLED model, we can conclude that these regions are switched back locally in voltage as well as current due to insufficient lateral thermal coupling. Experimentally, we demonstrate this effect in lab-scale devices and derive that it becomes more severe with increasing pixel size, which implies its significance for large-area, high-brightness use cases of OLEDs. Equally, these non-linear switching effects cannot be ignored with respect to the long-term operation and stability of OLEDs; in particular, they might be important for the understanding of sudden-death scenarios.

Micro-Raman Spectroscopy: Self-Heating Effects In Deep UV Light Emitting Diodes

2002 ◽  
Vol 743 ◽  
Author(s):  
A. Sarua ◽  
M. Kuball ◽  
M. J. Uren ◽  
A. Chitnis ◽  
J. P. Zhang ◽  
...  
Keyword(s):  
Raman Spectroscopy ◽  
Heat Dissipation ◽  
Light Emitting Diodes ◽  
Light Output ◽  
Multiple Quantum ◽  
Light Emitting ◽  
Self Heating ◽  
Micro Raman Spectroscopy ◽  
Heating Effects ◽  
Heat Sinking

ABSTRACTUltraviolet light emitting diodes (LED) based on GaN and its ternary alloy AlGaN are key devices for applications such as solid state white lighting and chemical sensing. Ultraviolet LEDs are prone to self-heating effects, i.e., temperature rises during operation, contributing significantly to the commonly observed saturation of light output power at relatively low input currents. Rather little, however, is known about the actual device temperature of an operating ultraviolet LED. Using micro-Raman spectroscopy temperature measurements were performed as a function of input current on 325nm-Al0.18Ga0.82N/Al0.12Ga0.88N multiple quantum wells LEDs grown on sapphire substrates, flip-chip mounted on SiC for heat-sinking. Temperature maps were recorded over the active device area. Temperature rises of about 65 °C were measured at input currents as low as 50mA (at 8V) for 200 μm x 200 μm size LEDs despite flipchip mounting the devices. Temperature rises at the device edges were found to be higher than in the device center, due to combined heat sinking and current crowding effects. Finite difference heat dissipation simulations were performed and compared to the experimental results.

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