【作者】 吕文婷；

【导师】 张驰；

【作者基本信息】 吉林大学 ， 材料加工工程， 2012， 硕士

【摘要】 在能源日益紧张的今天，新型冷光源LED正以高效率、节能环保和寿命长等优势脱颖而出。以大功率LED为光源的照明灯不仅可以大幅度节约能源，还可以缩短响应时间，因此大功率LED被人们视为可以替代白炽灯和荧光灯的第四代光源。随着科技的不断进步，LED自身光通量的提升和散热问题成了阻碍大功率LED照明灯具推广和普及的两个关键性问题。当芯片的亮度不断提高的同时，芯片所承受的温度也在不断提高，过高的温度会使大功率LED灯使用寿命缩短甚至失效。本文就是为了解决由大功率LED照明灯和汽车前大灯散热困难而引起的亮度降低和使用寿命缩短等问题，对大功率LED照明灯及车灯的散热装置进行了深入研究和优化设计。首先本文从LED的国内外发展现状入手，探讨了LED产业和汽车灯具的发展历程，及各自领域中的重大科研成果和目前面临的瓶颈问题。然后深入到理论层面，对LED的发光原理进行了全面的总结，逐步分析了发光二极管的光学特性、电学特性和热学特性，并着重分析了LED的结温和热阻、相关热学模型、目前主流散热方式、翅片效率和翅片的成型方式。其次本文在理论剖析的基础上，与吉林恒光科技有限公司共同合作开发了四种具有相同光源和不同散热装置的大功率LED照明灯。采用的研究方法主要有：1)对已开发的大功率LED灯进行调试，在恒定室温下调试灯具温度，检测其散热效果；2）利用AUTOCAD2004设计散热器二维图，根据二维图纸用CATIA V5R17进行三维建模，将建好的方案导入ANSYS11.0模拟软件后进行仿真。多次改变参数模拟并对比，得到LED照明灯具的散热面积、翅片效率、单位功率面积与PN结导出端温度的关系。通过对四种大功率LED照明灯的热阻计算，得到外部热阻与芯片温度间的关系。同时本文在仿真数值可近似反映实际温度分布情况和影响散热效果因素的基础上，以LEAF前车灯光源为例设计了以翅片对流为主的散热装置和以半导体制冷为主的两种散热装置。通过对两种散热系统的温度场仿真结果对比得出：无论更换何种材料仅以翅片散热都不足以满足汽车前大灯的散热需求；在翅片基础上安置半导体制冷装置后，散热系统可以有效降低LED芯片温度，更换材料可使芯片温度进一步降低，满足汽车前大灯的散热需求。在此基础上本文进一步提出了配合车头设计的气体循环冷却回路，通过高效利用对流来更有效的降低芯片温度的方法。本文最终得出结论：理论分析和实际测量表明，计算机模拟仿真可以较为真实的反映LED灯具实际温度分布情况。在大功率LED照明灯和汽车前大灯散热装置设计过程中，除了改善材料本身特性，还应考虑散热装置翅片排布、散热面积、单位功率面积和翅片效率带来的综合影响。合理的散热系统设计可以大幅度降低芯片温度、提高芯片的寿命。本文所研究的实验和仿真可大幅度缩短工厂研发大功率LED灯具散热装置的时间，提高其工作效率，为LED照明灯及车灯的散热系统设计提供新思路和有力的依据。更多还原

【Abstract】 Along with the increasingly tensing of energy, the new cold light source LED has causedmore and more attention with high efficiency, low power consumption and long life.High-power LED light source not only can save energy, but also can shorten the responsingtime, therefore it be regarded as the fourth-generation light source.Along with the progressingof technology, to enhance the luminous flux of LED chip and heat dissipation become thekey- issues, which hinder the promotion and popularity of high-power LED lights. As thebrightness of the chip is improved, the chip’s temperature will be also improved. Excessivetemperature can shorten the life of the high- power LED lights or even lead to failure. In orderto solve these problems, the paper studied and optimized the design on cooling devices ofhigh-power LED lights and headlamps.The paper start from the development of LED in the world, discussed the develop historyof LED and automotive lights sources, and their significant research results and key issuesrespectivly. In theoretical level of LED, we first summarized the principles of LED, then weanalysis the optical properties, electrical properties and thermal characteristics of LED step bystep, especially on the LED junction temperature and thermal resistance. And we establishedthermal models. Then we discussed cooling means, cooling fins’efficiency and fin’s formingmethod respectivly.On the basis of theoretical analysis, we developed four kinds of high- power LED lightswith HengGuang Technology Co., Ltd., which have the same light sources, but different coolingdevices. The research methods used here were: 1) we regulated the four lights, and detectedthe temperature and thermal effect at a constant room;2)we used AUTO CAD2004 to design 2Ddrawings and use CATIA V5R17 to design 3D models, which can be imported into the ANSYS11.0 software to simulate. After repeatedly changing the material parameters, wecontrasted the results and found the relationships among cooling area, fin efficiency, powerof unit area and PN junction export-side temperatures. Finally, we calculated the thermalresistances of the four high-power LED lights, and we got relationship between externalresistances and chips’temperature.On the basis of the conclusion: the simulation values can reflect the actual temperaturedistribution and the factors,which can affect cooling device design,we used―LEAF‖headlights as the light source to design two kinds of cooling devices: The device with onlycooling fins and the device with cooling fins and semiconductors. After temperaturefield simulations of twocooling systems, which showed that: the cooling device with convectionalone is insufficient to meet the cooling demand of automotive headlamps’high-power LEDchips, but the increased semiconductor cooling device can effectively reduce the temperatureof the LED chips. Then we replaced of the cooling fin material, the heat sink materialand the MCPCB material and resimulated and obtained the relationship among heatsinkmaterial, MCPCB material, cooling fins material and the chip temperatures. On the basisof the conclusions, we designed air circulating cooling loop in front part of automotive, whichcan efficiently use of convection and reduce the chips’temperature more effectively.This paper ultimately concluded that: the computer simulation can in some extent reflectthe actual temperature distribution.In the design process of high-power LED lights and carheadlamps cooling devices, not only should we enhance the characteristics of the material itself,but also should we consider the combined effects of heat sink fins arrangement, the heat coolingarea and the fin efficiency. Rational cooling device design not only can greatly reduce the chiptemperature, but alsocan improve the life of chips. The experiments and simulations in thispaper can significantly reduce the time and improve the factory’s working efficiency, whichwill provide new ideas and a strong theoretical basis to factories.更多还原