Thermal analysis of an 80 W light-emitting diode street lamp

Light-emitting diode (LED) street lamps rely heavily on successful thermal management, which strongly affects the optical extraction and the reliability/durability of the LED lamp. A thermal analysis of an 80 W LED street lamp was done. Sixteen thermocouples were used to measure the temperatures at 16 different positions of the street lamp. The results demonstrated that the temperature of the frame and the heat sink of the 80 W LED street lamp remained stable at about 42degC after several hours of lighting at a room temperature of 11degC, and the bulk material resistance of the heat sink could be neglected. Numerical simulation was also used to analyse the temperature distribution of the lamp. The reliability of the numerical model was proven by a comparison of simulation results with the experimental data. Through simulations and the corresponding analyses it was found that the tested 80 W LED street lamp would have poor reliability at an environment temperature of 45degC.     

Analyzing experiments with degradation data for improving reliability and for achieving robust reliability

Statistically designed experiments provide a proactive means for improving reliability; moreover, they can be used to design products that are robust to noise factors which are hard or impossible to control. Traditionally, failure‐time data have been collected; for high‐reliability products, it is unlikely that failures will occur in a reasonable testing period, so the experiment will be uninformative. An alternative, however, is to collect degradation data. Take, for example, fluorescent lamps whose light intensity decreases over time. Observation of light‐intensity degradation paths, given that they are smooth, provides information about the reliability of the lamp, and does not require the lamps to fail. This paper considers experiments with such data for ‘reliability improvement’, as well as for ‘robust reliability achievement’ using Taguchi's robust design paradigm. A two‐stage maximum‐likelihood analysis based on a nonlinear random‐effects model is proposed and illustrated with data from two experiments. One experiment considers the reliability improvement of fluorescent lamps. The other experiment focuses on robust reliability improvement of light‐emitting diodes. Copyright © 2001 John Wiley & Sons, Ltd.     

LED照明的杂散光分析与散热研究

针对LED照明杂散光的形成原因和处理方法,以及LED照明系统散热问题的产生和结温对灯具寿命和发光率的影响,完善LED照明灯具的设计,利用照明灯具的特点,以目前LED照明灯具采用的散热方式和杂散光的处理形式为基准,采用对比测试的方法对灯具样品进行检验测试。通过对检测结果的分析,解决了LED照明的散热设计中涉及到的关键问题。     

Temperature estimation of high-power light emitting diode street lamp by a multi-chip analytical solution

Light emitting diodes (LEDs) are now widely used in many fields including traffic lights, vehicle backlights and liquid crystal display (LCD) displays because of their long life, good illumination efficiency and low energy consumption. At present, LEDs are increasingly replacing the traditional lighting and are being used in general illumination such as the street lamp. For the high-power LED street lamps, good light extraction is the most important thing, but low junction temperature of the LED modules is also critical for achieving a long lifetime and a high optical efficiency. Actually, there have been many reports about early failures of street lamps, called dead lamps that have been regarded as a barrier in the public and administration acceptance of LED street lamps. Therefore temperature estimation is always a crucial issue for LED product development. A multi-chip spreading thermal resistance model was applied to estimate the temperature distribution of LED street lamp. The experiment was first done to obtain temperatures of several locations in a prototype LED street lamp. Then the multi-chip spreading resistance model was established to calculate the full temperature distribution. Comparison between the model calculation and experimental measurement showed a good agreement, which demonstrates that the present model can be used in engineering design to estimate the temperature distribution of high-power LED street lamps.     

New developments and future trends in high-efficiency lighting

There have been several developments in lamp technology and remote lighting systems that promise savings in electrical power consumption and improved quality of the lighting space. This article reviews the developments in fluorescent lamps, metal halide lamps, electrodeless lamps, sulphur lamps, LED lamps, electronic ballasts, and lighting fixtures. Remote lighting systems using hollow light-guides, solid light-guides and reflector based systems are described     

基于Android的智能可调光LED灯节能控制

针对家庭LED灯能源耗电问题,提出了一种智能调光节能控制方法。该方法以安卓操作系统为平台,智能手机作为客户端,利用LM3409HV降压自适应反馈控制机制,通过Wi Fi网络实现无线远程可调光节能LED灯的低功率照明。该系统采用太阳能绿色可再生能源为智能电网供电,结合室外光强,通过光敏传感器和脉宽调制(PWM)技术调节LED灯亮度。在通用输入电压下,可实现高效率、高功率因数调光。与传统的机械式开关LED照明电灯相比,智能调光系统设计的软硬件更为灵活和方便、成本更低、功耗更小,界面和功能都具有良好的通用性、准确性,具有广泛的应用前景。     

道路照明用LED灯具标准对比及趋势分析

LED照明产品的广泛应用和技术的迅猛发展,给LED照明产业标准化研究带来了新的机遇与挑战。本文从技术要求(包括:光通量维持率及寿命、初始光效、显色性)和测试方法(光衰测试方法)的角度对2008～2010年间我国发布的一些代表性国家、行业和地方道路照明用LED灯具标准进行了对比分析,得出如下结论:1)我国各地道路照明用LED灯具标准存在显著差异,急需统一的道路照明用LED灯具标准来有效规范整个行业的发展;2)LED照明技术的不断革新和进步推动着LED照明相关标准的不断更新和改进,已经有并即将有更多符合产业发展要求的标准被逐步推出。可以预见的是,道路照明用LED灯具标准将朝着统一规范化、细致化、全面化的方向发展。鉴于我国道路照明用LED灯具市场的特殊情况,该项标准的制定甚至可能优先于国际标准。     

上海市隧道、道路LED照明应用技术标准研究综述（英文）

The paper summarizes the research on the development of standards for tunnels and roads LED lighting application in Shanghai, analyzes the existing problems on LED road lamps and lighting design, introduces the experiments and testing results, and summarizes current problems of LED street lighting, proposing that LED lighting energy conservation should be "systematic energy saving" throughout the full life cycle based on the integration of products and applications.     

投射式LED汽车前照灯的光学设计

依据GB 4785-1998选择偏蓝成分较少的暖白色LED光源,采用多椭球反射杯、挡光板和非球面透镜的投射式系统,设计出一套LED汽车前照灯.其中每个LED光源都有各自独立的光学系统,设计了消球差的非球面透镜和平面挡光板,模拟分析了多椭球反射杯垂直截面椭圆和水平截面椭圆的最佳焦距.采用3个单个LED光学系统构成近光系统,在近光的基础上增加4个单个LED光学系统构成远光系统,其近光系统明暗截止线很清晰且近光和远光系统配光性能的模拟结果都满足GB 4599-94要求.     

LED灯具光通量的计算方法

LED灯具光通量的计算方法是为了解决LED灯具生产前LED灯芯选用问题。LED灯具生产,LED灯芯的选用是至关重要的,它直接影响LED灯具的产品质量及生产效率。     

Forecasting reliability growth

This paper describes a method for estimating and forecasting reliability from attribute data, using the binomial model, when reliability requirements are very high and test data are limited. Integer data—specifically, numbers of failures — are converted into non-integer data. The rationale is that when engineering corrective action for a failure is implemented, the probability of recurrence of that failure is reduced; therefore, such failures should not be carried as full failures in subsequent reliability estimates. The reduced failure value for each failure mode is the upper limit on the probability of failure based on the number of successes after engineering corrective action has been implemented. Each failure value is less than one and diminishes as test programme successes continue. These numbers replace the integral numbers (of failures) in the binomial estimate. This method of reliability estimation was applied to attribute data from the life history of a previously tested system, and a reliability growth equation was fitted. It was then ‘calibrated’ for a current similar system's ultimate reliability requirements to provide a model for reliability growth over its entire life-cycle. By comparing current estimates of reliability with the expected value computed from the model, the forecast was obtained by extrapolation.     

LED照明产品加速衰减试验方法研究（英文）

With the application of energy-saving, environmental and durable LED lighting products, the reliability testing has become a pivot point for the large scale industrialization and popularization. The paper briefly introduces two methods to be respectively applied in the accelerated depreciation testing for the luminous flex of LED lighting products and the life of outdoor LED-driving power, which can sharply shorten the time for lifetime test, providing references for the LED lighting products' reliability evaluation.     

Integrating run-based preventive maintenance into the capacitated lot sizing problem with reliability constraint

A joint model for integrating run-based preventive maintenance (PM) into the capacitated lot sizing problem (CLSP) is proposed, in which the production system is subject to deterioration with usage and PM operations are implemented to restore the system. In this model, both production and PM operations are restricted by the system's maximum capacity, and the system reliability has to be maintained above a threshold value throughout the planning horizon. By linearisation of the reliability constraints, the problem is formulated as a mixed-integer linear programming. An explanatory example is given to illustrate the advantage of the joint model comparing with the interval-based PM policy in terms of system's overall cost. A three-stage heuristic is proposed to solve this integrated model, which includes a Lagrangian-based heuristic for the CLSP. The numerical experiments are conducted to evaluate the performance of the developed heuristics and the computational results show that the heuristics can provide good feasible solutions for the corresponding models. The discussion of the results is finally given in detail.     

Bridging the Gap between Quantitative and Qualitative Accelerated Life Tests

Test planners have long sought the ability to incorporate the results of highly accelerated life testing (HALT) into an early estimate of system reliability. While case studies attest to the effectiveness of HALT in producing reliable products, the capability to translate the test's limited failure data into a meaningful measure of reliability improvement remains elusive. Further, a review of quality and reliability literature indicates that confusion exists over what defines a HALT and how HALT differs from quantitative accelerated life testing methods. Despite many authors making a clear distinction between qualitative and quantitative accelerated life tests, an explanation as to why this delineation exists cannot be found. In this paper, we consider an exemplary HALT composed of a single stressor to show that the HALT philosophy precludes the estimation of a system's hazard rate function parameters because of the test's fix implementation strategy. Four common accelerated failure data analysis methods are highlighted to show their limitations with respect to estimating reliability from HALT data. Finally, a modified accelerated reliability growth test is proposed as a way forward for future research in HALT scenarios to characterize the risk of attaining a reliability requirement and improve parameter estimation. Copyright © 2014 John Wiley & Sons, Ltd.     

Multivariate Degradation Modeling of Smart Electricity Meter with Multiple Performance Characteristics via Vine Copulas

For smart electricity meter with multiple performance characteristics (PCs) with coupling relationships because of amounts of components experiencing multiple deteriorating processes, we develop a multivariate degradation modeling method via vine copulas to estimate the reliability of products with multiple PCs reflecting degradation states. In the multivariate model, pair‐copula construction and vine graphical representation are used to describe the mutual relationship among PCs to overcome the lack of multivariate copula in high‐dimensional cases. Each PC model of smart electricity meter is built by using drift Brownian motion to describe degradation processes of each PC on the basis of degradation mechanism analysis, and parameters are estimated by using likelihood estimation method. The Pearson correlation coefficient, Kendall's τ and product information are used to analyze correlation among those PCs. Furthermore, on the basis of conditional probability theory, the vine graph is used to construct a multivariate copula which can be decomposed into pair copulas. Akaike information criterion principle is utilized to choose the forms of pair‐copula functions in the correlation model. Finally, the reliability joint distribution of all PCs of smart electricity meter is obtained with combining all PCs' marginal distributions and copula functions. Copyright © 2016 John Wiley & Sons, Ltd.     

LED照明产品设计研究

在现代照明领域, LED被称为第4代光源.由于LED技术特性和设计特点自成一格,具有鲜明特色和品质,因此被业内专家预测将是取代白炽灯、荧光灯等传统灯具的最具有竞争力的新型照明产品.对LED照明产品的设计研究,必将对灯具照明产品的可持续发展以及设计创新将产生积极影响和重要的应用推广价值.     

Electric lamps, past and present

The article traces the story of the electric lamp, which began when, in 1810, Davy demonstrated the now legendary `bright carbon arc' that led, in 1850, to the production of practical arc lamps. Because of the `powerful' intensity of the arc lamp, there was a demand for `the subdivision of light' and this culminated, in 1879, in the invention of the incandescent filament lamp. Gaseous and vapour discharge lamp research began around 1850 and practical lamps were available in the early 1900s. There were carbon dioxide, nitrogen and neon filled tubes giving `daylight', `sunlight' and red light emissions, respectively. Also, and still available, there were high-voltage, mercury vapour, cold-cathode fluorescent tubes. Following research in the early 1930s mains voltage, high- and low-pressure mercury and sodium vapour lamps have been under constant development and they are widely used today. Fluorescent lamps, introduced in 1938, are regularly being improved in design and among the latest are compact energy saving types that are ideally suited, as direct replacements, for GLS lamps. The recent announcement of the QL induction lighting system is the latest milestone in `electric light' invention     

LED电子高效节能冷库专用灯结构设计与应用

冷库传统用灯大多采用白炽灯,金卤灯等,耗能高,灯芯的工作温度要在800度以上,由于内外温差过大,灯泡的玻璃外罩会越来越脆,很容易一碰就破,不仅频繁更换麻烦,而且很不安全。我们舟山浩德光电科技有限公司自主研发、设计的LED电子高效冷库专用照明灯,针对冷库低温环境的特点,可以在零下40度的环境中正常工作,彻底解决冷库照明的难题。本文以我公司生产的LED冷库专用灯为例来剖析LED冷库专用灯的设计特点。     

An economic model for determining the optimal quality and process control policy in a queue-like production system

This paper interrelates and synthesizes the economic design of quality and process control policy and the management of a production system described in terms of an M/G/X queue. A mathematical model is developed to determine the optimal quality and process control policy when both the quality and quantity issues in the production system are considered. The optimal control policy is defined as the one that maximizes the expected profit per unit time over an infinite horizon. Hypothetical data is used to illustrate the impact of on-line control policies on the operating characteristics of the production process.

For a given control policy, it is shown that the expected profit per unit time of the production system can be increased by either improving the reliability of the production system, increasing the arrival rate of incoming jobs, increasing the system's processing rate, or shortening the system's shutdown time. The results also indicate that the larger the performance difference between the in-control and the out-of-control states, the greater the amount of effort should be involved in quality and process control. Finally, it is important for the capacity design of a production system to take into account the requirrments for both quality control and process adjustment.     

Temperature Measurement Technique for Stabilizing the Light Output of RGB LED Lamps

The efficiency of light-emitting-diode (LED) lights approaches that of fluorescent lamps. LED light sources find more applications than conventional light bulbs due to their compactness, lower heat dissipation, and real-time color-changing capability. Stabilizing the colors of red–green–blue (RGB) LED lights is a challenging task, which includes color light intensity control using switching-mode power converters, color point maintenance against LED junction temperature change, and limiting LED device temperature to prolong the LED lifetime. In this paper, we present a LED junction temperature measurement technique for a pulsewidth modulation diode forward current controlled RGB LED lighting system. The technique has been automated and can effectively stabilize the color without the need for using expensive feedback systems that involve light sensors. Performance in terms of chromaticity and luminance stability for a temperature-compensated RGB LED system will be presented.