Computer Modeling and Simulation Evaluation of High Power LED Sources for Secondary Optical Design

Proposed and demonstrated is a novel computer modeling method for high power light emitting diodes(LEDs). It contains geometrical structure and optical property of high power LED as well as LED dies definition with its spatial and angular distribution. Merits and non-merits of traditional modeling methods when applied to high power LEDs based on secondary optical design are discussed. Two commercial high power LEDs are simulated using the proposed computer modeling method. Correlation coefficient is proposed to compare and analyze the simulation results and manufacturing specifications. The source model is precisely demonstrated by obtaining above 99% in correlation coefficient with different surface incident angle intervals.

Thermal Resistance Testing Technology Research of Integration High Power-LED

In this paper,high-power LED with many integrated chips is used as thermal resistance analysis research object, and we do thermal resistance testing technology research on it. We put forward the thermocouple point contact test method. According to the principle that LED forward voltage changes with temperature,LED heat sink to surface temperature distribution is studied directly in the test,and then we analyze the thermal resistance of high-power LED with many integrated chips when its secondary packaging is introduced. This method makes the measurement of thermal resistance of LED more rapid and convenient. It provides an effective assessment method for the analysis of high power LED device design and engineering application.

Spacing optimization of high power LED arrays for solid state lighting

This paper provides an analytical approach to determine the optimum pitch by utilizing a thermal resistance network, under the assumption of constant luminous efficiency. This work allows an LED array design which is mounted on a printed circuit board （PCB） attached with a heat sink subject to the natural convection cooling. Being validated by finite element （FE） models, the current approach can be shown as an effective method for the determination of optimal component spacing in an LED array assembly for SSL.

基于光效和BP神经网络的LED结温预测研究

提出了一种发光效率结合BP神经网络的大功率LED结温预测方法。实验中发现LED的发光效率在结温升高至80℃左右将急剧下降,光效与结温的函数关系发生改变,进而影响了测量精度。针对这一问题,基于发光效率与结温的函数关系,构建实验平台,获取发光效率和相应结温的数据,然后通过BP神经网络建立LED结温预测模型。模型所得数据与正向电压法进行对比实验,最大误差为2.1℃,验证了所提方法的可行性,同时所提方法无需考虑LED的内部结构,能够简便,准确地预测大功率LED结温。

Experimental and numerical study on a micro jet cooling solution for high power LEDs

An active cooling solution based on close-looped micro impinging jet is proposed for high power light emitting diodes (LEDs). In this system, a micro pump is utilized to enable the fluid circulation, impinging jet is used for heat exchange between LED chips and the present system. To check the feasibility of the present cooling system, the preliminary experiments are conducted without the intention of parameter opti-mization on micro jet device and other system components. The experiment results demonstrate that the present cooling system can achieve good cooling effect. For a 16.4 W input power, the surface temperature of 2 by 2 LED array is just 44.2℃ after 10 min operation, much lower than 112.2℃, which is measured without any active cool-ing techniques at the same input power. Experimental results also show that increase in the flow rate of micro pump will greatly enhance the heat transfer efficiency, how-ever, it will increase power consumption. Therefore, it should have a trade-off be-tween the flow rate and the power consumption. To find a suitable numerical model for next step parameter optimization, numerical simulation on the above experiment system is also conducted in this paper. The comparison between numerical and ex-periment results is presented. For two by two chip array, when the input power is 4 W, the surface average temperature achieved by a steady numerical simulation is 34℃, which is close to the value of 32.8℃ obtained by surface experiment test. The simu-lation results also demonstrate that the micro jet device in the present cooling sys-tem needs parameter optimization.

Analysis of heat transfer of loop heat pipe used to cool high power LED

A novel loop heat pipe(LHP)cooling device for high power LED is developed.The thermal capabilities, including startup performance,temperature uniformity and thermal resistance of the loop heat pipe under different heat loads and incline angles have been investigated experimentally.The obtained results indicate that the thermal resistance of the heat pipe heat sink is in the range of 0.19―3.1 K/W,the temperature uniformity in the evaporator is controlled within 1.5℃,and the junction temperature of high power LED can be controlled steadily under 100℃for a heat load of 100 W.

Design and Simulation of High-power LED Array Packaging

Thermal management is one of the key technologies for high-power Light emitting diode(LED)entering into the general illuminating field.Successful thermal management depends on optimal packaging structure and selected packaging materials.In this paper,the aluminum is employed as a substrate of LED,3×3 array chips are placed on the substrate,heat dissipation performance is simulated using finite element analysis(FEA)software,analyzed are the influences on the temperature of the chip with different convection coefficient,and optical properties are simulated using optical analysis software.The results show that the packaging structure can not only effectually improve the thermal performance of high-power LED array but also increase the light extraction efficiency.

Study on High-power LED Heat Dissipation Based on Printed Circuit Board

In order to study the role of printed circuit board(PCB)in high-power LED heat dissipation,a simple model of high-power LED lamp was designed.According to this lamp model,some thermal performances such as thermal resistances of four types of PCB and the changes of LED junction temperature were tested under three different working currents.The obtained results indicate that LED junction temperature can not be lowered significantly with the decreasing thermal resistance of PCB.However,PCB with low thermal resistance can be matched with smaller volume heat sink,so it is hopeful to reduce the size,weight and cost of LED lamp.

Ceramic-metal package for high power LED lighting

灯光的轻射出的二极管(LEDs ) 在最近的年里在街光系统的地里画了大兴趣的高力量。分别地，为在商业市场的带的街光的成功的发射的关键参数是价格和轻效率，他们被材料极大地影响，尽最大努力使用的设计因素带了包裹。这篇文章介绍一个新图案和材料处理技术认识到包装带与的解决方案在价格和性能有益。合算的材料和处理技术能经由厚电影被认识到眼镜陶器的绝缘层和银售票员。用到在带的包裹的热水池的直接的热驱散的高度有效的热设计被表明。

Fabrication of High-power White LEDs and White Light Uniformity Testing

As the blue and yellow lights are complementary colors, a blue InGaN LED chip is coated by a yellow phosphor film to generate white light based on luminescence conversion mechanism. The emitted light of a blue LED is used as the primary source for exciting fluorescent material such as cerium doped yttrium aluminum garnet with the formula Y3Al5O12∶Ce3+(in short: YAG∶Ce3+). The matching of the spectrum of the blue LED chips and the YAG∶Ce3+ yellow phosphor is studied to improve the conversion efficiency. The packaging methods and manufacturing processes for high-power single-chip-white-LEDs are introduced. The uniformity of the output white light is investigated. Based on the characteristics of the high-power white LEDs, some approaches and processes are suggested to improve the light uniformity when they are fabricated. The effectiveness of those approaches on the improvement of LEDs is discussed in detail and some interesting conclusions are also presented.

A Cooling System with a Fan for Thermal Management of High-Power LEDs

To improve the heat dissipation of high-power light-emitting diodes (LEDs), a cooling system with a fan is proposed. In the experiment, the LEDs array of 18 W composed of 6 LEDs of 3 W is used and the room temperature is 26oC. Results show that the temperature of the substrate of LEDs reaches 62oC without the fan, however, it reaches only 32oC when the best cooling condition appears. The temperature of the LEDs decreases by 30oC since the heat produced by LEDs is transferred rapidly by the fan. The experiment demonstrates that the cooling system with the fan has good performance.

一种无桥高增益单级LED驱动电路及其混合控制策略

中小功率的LED驱动电源中,传统两级LED驱动电源存在体积大、成本高以及传统Boost PFC电路在低压输入时导通损耗大等问题。为此提出一种由无桥二次型Boost PFC电路和DC-DC LLC电路集成的无桥高增益单级LED驱动电路,实现了高电压增益、功率开关器件软开关、一套控制电路和高电路转换效率。针对单级电路在电网输入电压变化引起直流母线电压变动范围大等问题,设计一种适用于所提电路的APWM-PFM混合控制策略,并对混合控制原理和控制过程进行详细分析。最后设计一台200 W的实验样机,在输入电压80~120 Vrms范围内,占空比最大为0.5,最大电压增益为6.7,直流母线电压基于网侧特性和LLC电路特性设计在700 V以内,样机的功率因数值均高于0.990,THD均低于15%。在满载条件下,110 Vrms输入时,样机效率为93.20%,相比于传统无桥PFC,电压增益提高了2.21倍,实现了高电压增益和软开关,有效提升了在低压输入条件下的电路转换效率。仿真和实验结果验证了所提出电路和控制方法的有效性。

大功率LED灯干冰喷射散热数值分析

【目的】解决大功率LED灯具高效散热问题。【方法】以干冰为冷却介质,设计出干冰喷射散热器,通过COMSOL软件研究干冰喷射对功率为300 W LED灯的散热特性。【结果】仿真试验结果表明,增大干冰流量能明显改善传热效果,流量由7.85 mL/s增至23.55 mL/s,散热器相同位置处干冰固相分数由0.04增至0.34。增大干冰流速可显著降低基板表面温度,流速由0.1 m/s增至0.3 m/s,温度约降低26.4%,且随着流速增大,降温效果逐渐减弱。【结论】与自然对流和水微喷射阵列冷却方式相比,以干冰为冷却介质的基板表面温度分别降低44.71%和23.44%;与单相射流方式相比,温度降低24.1%。干冰喷射冷却效果明显提升,温度更加均匀。

大功率LED芯片直接固晶热电制冷器主动散热

发光二极管(LED)作为新一代绿色固态照明光源,已广泛应用于照明和显示等领域,但散热问题一直是大功率LED封装的关键技术瓶颈。采用大功率LED芯片直接固晶热电制冷器(TEC)的主动散热方法,可增强大功率LED的热耗散,提升大功率LED的发光性能和长期可靠性。利用高精度陶瓷基板和纳米银膏材料制备出高性能TEC,TEC冷端温度最低可达-22.2℃。将LED芯片直接固晶于TEC冷端的陶瓷基板焊盘上,实现LED芯片与TEC的集成封装,制备出LED-TEC主动散热模块。在芯片电流为1.0 A时,由于热电制冷的珀尔帖效应,LED-TEC模块可将LED芯片的工作温度从232℃降低到123℃(降温幅度为109℃),且可使其输出光功率从1087 mW提升到1479 mW,光功率提升幅度达到36.1%。

一种采用降压补偿的大功率LED结温动态测量法

提出了一种新型的采用降压补偿的大功率LED结温动态预测法。文章分析了常规FVM法过程中的测量误差,同时利用反向电流降低电压加速光注入非平衡载流子的复合过程,并通过LabVIEW程序控制电源实现所需补偿电流波形。最后通过与传统方法测试结果进行对比,验证了该方法的有效性。

大功率UV-LED散热与纳米TiO_(2)光催化酸性红26耦合系统性能

设计了大功率UV-LED散热和纳米TiO_(2)光催化酸性红26耦合系统,采用污水循环冷却UV-LED提高灯珠工作效率的同时实现污水光催化降解脱色,将污水循环系统与紫外光源冷却耦合是创新点。采用模拟优化UV-LED灯珠排布,以污水脱色为探针反应,发现污水冷却能使UV-LED结温降低41.2%,平均辐照度和污水脱色效率分别提高11.03%和1.68倍。环境因素对污水降解性能影响结果表明,光催化活性与污染物浓度成反比,与催化剂初始浓度成正比,达0.75g/L后趋于稳定;考虑吸附和氧化基团对降解速率影响,最优pH为2。本设计与传统环隙式反应器对比,表观量子产率和脱色效率分别是后者的2.3倍和4.3倍,能耗仅为后者的9.1%。该耦合系统在UV-LED的温度控制和废水处理领域具有潜在应用价值。

An Improved Non-isolated LED Converter with Power Factor Correction and Average Current Mode Control

A new type of high power LED drivers is proposed by adopting an improved two-stages non-isolated configuration. In order to improve power factor and achieve accurate average current control under universal input voltages ranging from 100 Vrms to 240 Vrms, the power factor correction and average current mode control methods operating in continuous current conduction mode are designed and implemented. With the LUMILEDS emitter type LEDs, a laboratory prototype is built and measured. And from the measured results, it could be concluded that the proposed driver has many better performances such as high power factor, low current harmonic, accurate average current control and switch protection.

大功率智能控制LED温室补光灯的设计与功能分析

大功率LED温室补光灯为设施园艺补光所必需,但LED灯具设计是实现高效补光的难点。本文介绍了一种新型大功率LED温室园艺补光灯的系统组成和结构设计,通过列举国内外市场上常见的大功率LED温室园艺补光灯的产品实例,提炼总结新型大功率LED需具备:(1)针对性优化设计的高效散热能力;(2)具备IP65及以上防水;(3)恒流电源驱动;(4)多通道等智能控制技术实现光强光谱可控;(5)适合植物生长的灯珠配比设计;(6)科学的配光设计,并针对上述关键技术进行了剖析。同时,以荷兰市场为例,展示大功率LED补光灯在温室园艺中的应用实例,说明了其在节能效果显著、产量提升明显和生长调控作用突出的效果。最后,对大功率LED补光灯在设计中所面临的技术挑战和应用中的注意事项进行讨论分析,以期为今后大功率LED温室补光灯具的设计与实际应用提供参考。

用于大功率紫外LED的圆柱扰流散热器设计仿真

如何降低芯片结温成为大功率紫外LED应用的关键。本文提出了一种新型圆柱扰流水冷散热器,对光源模块进行高效热管理。采用COMSOL软件对散热系统进行热场和流场分析,分别从散热器盖板厚度、扰流柱直径、增加档板结构、流速设置四个方面进行优化仿真,有效改善流动均匀性、提高换热效果,将功率密度643 W/cm^(2)的串联紫外LED光源模块的芯片结温由120℃降至95℃。

基于LED光源的色温可调摄影灯设计

为了解决传统镝灯类影视灯具色温不可调和发光效率低等问题,设计可变色温的大功率摄影灯,主要由LED光源模组、智能控制模块、LED驱动模块和灯具支架组成。LED光源模组包括大功率CSP-LED光源和与之配套的散热器等,智能控制模块则采用Wi-Fi、蓝牙和DMX512三种控制方式结合的形式,整个灯具依据程序指令对影视灯具的参数诸如色温、亮度等进行调节,实现影视灯具的智能化工作。