scholarly journals The Effect of Different Filament Arrangements on Thermal and Optical Performances of LED Bulbs

2020 ◽  
Vol 10 (4) ◽  
pp. 1373
Author(s):  
Wei Wang ◽  
Jun Zou ◽  
Qiaoyu Zheng ◽  
Yuefeng Li ◽  
Bobo Yang ◽  
...  
Keyword(s):  
Thermal Cycle ◽  
Gas Flow ◽  
Performance Test ◽  
Light Emitting Diode ◽  
Luminous Flux ◽  
Junction Temperature ◽  
Test Results ◽  
Light Emitting ◽  
Three Samples ◽  
Simulation Results

The influences on thermal and optical performances of light emitting diode (LED) bulbs with three different filament arrangements are investigated in detail. The average junction temperature, temperature of the surface of the bulb, and luminous flux of three samples all increased with increasing power. The thermal performance test results show that between the average junction, temperature and power were linear. The junction temperatures of the three samples at a power of 3.5 W were 102.48, 98.46, and 88.88 °C. The optical performance test results revealed that the luminous flux and efficiency in the two vertical filament arrangements were closely related to each other and higher than that of the horizontal filament arrangement. A numerical model of LED filament bulbs was established by the Floefd 17.2 software for analyzing the temperature distribution of the cross section and the gas flow path inside the bulb. The simulation results illustrated that the average temperatures of three samples were 105.88, 101.83, and 96.12 °C. Additionally, the gas flow inside the bulb of the two vertical filament arrangements was subject to forming a thermal cycle during operation work more than that of the horizontal filament arrangement. As a result, the flexible spiral LED filament bulb is feasible as a new light source.

5mm × 5mm Sized Slug on High Power LED Stress and Junction Temperature Analysis

2013 ◽  
Vol 404 ◽  
pp. 460-464
Author(s):  
Zaliman Sauli ◽  
Vithyacharan Retnasamy ◽  
Fairul Afzal Ahmad Fuad ◽  
Phaklen Ehkan ◽  
Rajendaran Vairavan ◽  
...  
Keyword(s):  
High Power ◽  
Light Emitting Diode ◽  
Input Power ◽  
Junction Temperature ◽  
Temperature Analysis ◽  
Single Chip ◽  
Physical Size ◽  
Light Emitting ◽  
Simulation Results ◽  
Incandescent Lamps

Conventional incandescent lamps are being replaced by high power light emitting diode as a lighting source due to it ascendancy in terms of physical size, performance, output and lifetime. Nevertheless, the reliability and efficiency of the LED is dependent on the junction temperature. This study presents the thermal simulation of single chip LED package with 5mm x5mmx 1mm aluminum heat slug. The junction temperature and stress of LED chip were evaluated using Ansys version 11. Input power of 0.1 W and 1 W were applied to the LED. The simulation results showed that at input power of 1W, the maximum junction temperature and stress of the LED chip is 112.91°C and 263.82Mpa respectively.

scholarly journals LED Rail Signals: Full Hardware Realization of Apparatus with Independent Intensity by Temperature Changes

Electronics ◽  
2021 ◽  
Vol 10 (11) ◽  
pp. 1291
Author(s):  
Giuseppe Schirripa Schirripa Spagnolo ◽  
Fabio Leccese
Keyword(s):  
Temperature Sensor ◽  
Energy Efficient ◽  
Light Emitting Diode ◽  
Junction Temperature ◽  
Light Emitting ◽  
Temperature Changes ◽  
Wide Range ◽  
International Regulations ◽  
Long Lifetime ◽  
Set Up

Nowadays, signal lights are made using light-emitting diode arrays (LEDs). These devices are extremely energy efficient and have a very long lifetime. Unfortunately, especially for yellow/amber LEDs, the intensity of the light is closely related to the junction temperature. This makes it difficult to design signal lights to be used in naval, road, railway, and aeronautical sectors, capable of fully respecting national and international regulations. Furthermore, the limitations prescribed by the standards must be respected in a wide range of temperature variations. In other words, in the signaling apparatuses, a system that varies the light intensity emitted according to the operating temperature is useful/necessary. In this paper, we propose a simple and effective solution. In order to adjust the intensity of the light emitted by the LEDs, we use an LED identical to those used to emit light as a temperature sensor. The proposed system was created and tested in the laboratory. As the same device as the ones to be controlled is used as the temperature sensor, the system is very stable and easy to set up.

Active matrix organic light-emitting diode (AMOLED) performance and life test results

2011 ◽  
Author(s):  
David A. Fellowes ◽  
Michael V. Wood ◽  
Arthur R. Hastings, Jr. ◽  
Russell S. Draper ◽  
Amalkumar Ghosh ◽  
...  
Keyword(s):  
Light Emitting Diode ◽  
Test Results ◽  
Life Test ◽  
Active Matrix ◽  
Light Emitting ◽  
Organic Light Emitting Diode ◽  
Organic Light

Thermal Analysis of High Power Light Emitting Diodes Package

2011 ◽  
Vol 687 ◽  
pp. 215-221
Author(s):  
Yuan Yuan Han ◽  
Hong Guo ◽  
Xi Min Zhang ◽  
Fa Zhang Yin ◽  
Ke Chu ◽  
...  
Keyword(s):  
Finite Element Method ◽  
High Power ◽  
Thermal Field ◽  
Heat Dissipation ◽  
Light Emitting Diode ◽  
Convective Heat Exchange ◽  
Input Power ◽  
Junction Temperature ◽  
Original Structure ◽  
Light Emitting

With increasing of the input power of the chips in light emitting diode (LED)， the thermal accumulation of LEDs package increases. Therefore solving the heat issue has become a precondition of high power LED application. In this paper, finite element method was used to analyze the thermal field of high power LEDs. The effect of the heatsink structure on the junction temperature was also investigated. The results show that the temperature of the chip is 95.8°C which is the highest, and it meets the requirement. The conductivity of each component affects the thermal resistance. Convective heat exchange is connected with the heat dissipation area. In the original structure of LEDs package the heat convected through the substrate is the highest, accounting for 92.58%. Three heatsinks with fin structure are designed to decrease the junction temperature of the LEDs package.

ACCURATE MEASUREMENT OF ULTRAVIOLET LIGHT-EMITTING DIODES

2021 ◽  
Author(s):  
C. Yuqin Zong ◽  
Cameron Miller
Keyword(s):  
Ultraviolet Light ◽  
Light Emitting Diodes ◽  
Luminous Flux ◽  
Junction Temperature ◽  
Integrating Sphere ◽  
Light Emitting ◽  
Type D ◽  
Uv Led ◽  
Uv Leds ◽  
Ultraviolet Light Emitting Diodes

We have developed a new calibration capability for 200 nm to 400 nm ultraviolet light-emitting diodes (UV LEDs) using a Type D gonio-spectroradiometer. The recently-introduced mean differential continuous pulse (M-DCP) method is used to overcome the measurement difficulty associated with the initial forward voltage, VF, anomaly of a UV LED, which makes it impossible to use VF to infer junction temperature, TJ, during pulsed operation. The new measurement facility was validated indirectly by comparing the measured total luminous flux of a white LED with that measured using the NIST’s 2.5 m absolute integrating sphere. The expanded calibration uncertainty for the total radiant flux is approximately 2 % to 3 % (k = 2) depending the wavelength of the UV LED.

Light-emitting diodes as light sources for spectroscopy: Sensitivity to temperature

2017 ◽  
Vol 25 (6) ◽  
pp. 416-422 ◽  
Author(s):  
Clinton J Hayes ◽  
Kerry B Walsh ◽  
Colin V Greensill
Keyword(s):  
Ambient Temperature ◽  
Near Infrared ◽  
Light Emitting Diodes ◽  
Light Emitting Diode ◽  
Junction Temperature ◽  
Effect Of Temperature ◽  
Light Sources ◽  
Spectral Variation ◽  
Light Emitting ◽  
Full Intensity

Understanding of light-emitting diode lamp behaviour is essential to support the use of these devices as illumination sources in near infrared spectroscopy. Spectral variation in light-emitting diode peak output (680, 700, 720, 735, 760, 780, 850, 880 and 940 nm) was assessed over time from power up and with variation in environmental temperature. Initial light-emitting diode power up to full intensity occurred within a measurement cycle (12 ms), then intensity decreased exponentially over approximately 6 min, a result ascribed to an increase in junction temperature as current is passed through the light-emitting diode. Some light-emitting diodes displayed start-up output characteristics on their first use, indicating the need for a short light-emitting diode ‘burn in’ period, which was less than 24 h in all cases. Increasing the ambient temperature produced a logarithmic decrease in overall intensity of the light-emitting diodes and a linear shift to longer wavelength of the peak emission. This behaviour is consistent with the observed decrease in the IAD Index (absorbance difference between 670 nm and 720 nm, A670–A720) with increased ambient temperature, as measured by an instrument utilising light-emitting diode illumination (DA Meter). Instruments using light-emitting diodes should be designed to avoid or accommodate the effect of temperature. If accommodating temperature, as light-emitting diode manufacturer specifications are broad, characterisation is recommended.

Experimental investigation and empirical modelling of thermal and drive current effect on optical performance of commercial LEDs

2020 ◽  
pp. 147715352097693
Author(s):  
AN Padmasali ◽  
SG Kini
Keyword(s):  
Light Emitting Diodes ◽  
Light Emitting Diode ◽  
Operating Conditions ◽  
Junction Temperature ◽  
Optimum Operating ◽  
Current Effect ◽  
Drive Current ◽  
Light Emitting ◽  
Empirical Modelling ◽  
Output Performance

Light-emitting diode is the most dominant lighting technology, and lumen output performance is dependent on junction temperature and operating drive current. An experimental analysis is performed to study the thermal and drive current effect on lumen output, and an empirical model is developed to determine the optimum operating conditions of temperature and drive current so as to obtain a maximum lumen output profile. Three commercially available light-emitting diode down-lighter’s light-emitting diodes are chosen for the study. The investigation reveals that there exists an optimum drive current at which lumen output is maximum, and it has a linear relation with junction temperature. Pulse-soak testing was performed to study the deviations of pulsed and continuous operation of drive current to understand the performance of light-emitting diodes. The work helps light-emitting diode luminaire manufacturers to design a controlled power electronic circuit so as to maximize the lumen output effectively and accurately.

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