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Lin C.,Xiamen University | Lin C.,Xiamen Hualian Electronics Co.
Journal of Applied Optics

Recently, high power multi-chip chip on board (COB) LED has become the industrial trends, duo to its advantages, such as higher packaging density, higher thermal stability, wider irritation angle and etc. However, low light extraction efficiency of COB LED restricts its application and development. In order to improve the light extraction efficiency of LED, the models of COB LED packaged by cone arrays, half-ellipsoid arrays, rectangular pyramid arrays and hemisphere array were established and investigated by applying stimulation software. The stimulation result showed that under optimal conditions, the luminous flux of COB LED with 0.9 mm height and 0.5 mm diameter cone array lens increased from 67 lm to 84.3 lm, that is, light extraction efficiency increased by 25.8%. Finally, LED samples with RGB multi-chips were packaged by 1 mm diameter hemisphere array, and the light extraction efficiency increased by 18.8%. ©, 2014, The No.205 Research Institute of China Ordnance Industry. All right reserved. Source

Chen J.,Xiamen University | Chen Z.,Xiamen University | Chen J.,Xiamen Hualian Electronics Co. | Li X.H.,Xiamen Hualian Electronics Co. | And 3 more authors.
Advanced Materials Research

In order to solve the heat dissipation problem of LED (light-emitting diode) downlight, CFD thermal simulation software was used to establish LED downlight dissipation model. Material's thermal conductivity, thermal resistance, thermal emissive values, heat load forms and other factors were all taken in considered, and then numerical simulation combined with laboratory measurement methods was used to analysis the lamp's dissipation. Based on this method, focused on the dissipation effect with different LED quantities and LED ring distances, and then optimized light source layout of current LED downlight products. After experimental verification, LED working temperatures were more ideal after the light source layout optimized, and it can improve the LED lamp lifetime effectively, this result also has important practice significance in the future LED downlight design process. © (2013) Trans Tech Publications, Switzerland. Source

Xiao H.,Xiamen University | Lv Y.-J.,Xiamen University | Zhu L.-H.,Xiamen University | Wang Y.-X.,Xiamen Hualian Electronics Co. | And 4 more authors.
Guangzi Xuebao/Acta Photonica Sinica

The luminous properties of sphere-like remote phosphor white LEDs with high Correlated Color Temperature(CCT) and low CCT were studied under different drive currents and heat sink temperatures. The result shown that the quantum efficiency and luminous efficacy of both LEDs raise with the increase of heat sink temperatures; the high-CCT LED's quantum efficiency and luminous efficacy decrease with rising currents. However, the low-CCT LED shows a reverse trend. The reason is attributed to the quantum confinement stark effect in the active region, which makes the wavelength move towards short-wavelength so as to deviate from the optimum stimulation wavelength of the high-CCT phosphor, but close to the optimum stimulation wavelength of the low-CCT phosphor. The CCT of the high-CCT LED increase with rising currents, again, the low-CCT LED shows a reverse trend with rising currents. This trend is mainly related to the drifting of color coordinates caused by quantum efficiency changing. To sum up, the high-CCT LED possesses better optical properties but inferior color properties than the low-CCT LED. Source

Shen Y.,Xiamen Hualian Electronics Co.
Bandaoti Guangdian/Semiconductor Optoelectronics

The fluid finite element thermal analysis software (CFD) is often used in LED thermal modeling and simulation, and the analysis, calculation and setting of relevant cooling parameters are key factors affecting the simulation precision. A comprehensive research on the key problems including boundary condition setting, thermal resistance calculation and heat load analysis was carried out. Then, laboratory temperature measurement was combined with this research to validate the accuracy of the simulation method. The results show that the method can be used for accurate thermal analysis of indoor LED lighting, with the temperature error less than 4°C and the simulation result is of a great reference value for LED design. Source

Chen J.,Xiamen University | Chen J.,Xiamen Hualian Electronics Co. | Li X.,Xiamen Hualian Electronics Co. | Chen Z.,Xiamen University | And 2 more authors.
Bandaoti Guangdian/Semiconductor Optoelectronics

In order to reduce the manufacturing cost (radiator quality) of high power LED downlight and ensure the heat dissipation ability, the orthogonal experimental method was used to optimize the design of radiator. The effects of 6 key factors, such as radiator substrate diameter, substrate thickness, fin thickness, fin pitch, fin height and fin profile diameter, on the radiator weight and LED temperature were analyzed. Then the modeling and heat dissipation simulation of the LED downlight were carried out with CFD thermal simulation software, and finally a relatively ideal optimization result was achieved. Simulation and experimental results show that, although LED temperature decrease slightly using the optimized LED downlight radiator, the radiator quality decreases more than 30%, realizing the optimization target very well. Source

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