采用动态差分模型表征脉冲驱动LED电热特性

为了研究不同驱动方式下LED结温的差异性,依据LED热结构模型,从功率传递角度构建了差分型LED电-热动态模型,利用相同平均功率、不同频率的注入电功率,计算脉冲驱动条件下的LED结温.同时,采用正向电压法测量实际结温,对模型预测结温的准确性进行了分析.研究表明,差分模型能够表征脉冲驱动方式下LED电热特性,其理论预测值与实测值误差约为4℃,基本能够满足工程应用要求.更有意义的是,采用差分模型,能够分析在特定驱动条件下,LED热容、热阻等参数对结温的影响,为不同驱动模式下LED个性化结构设计提供了理论基础.     

关于LED照明驱动电路失效机理的研究

本文介绍一种LED照明驱动电路失效机理的原理和方法。LED灯具失效分为源于电源驱动电路的失效和来源于LED器件本身的失效。在本文研究中,分析了典型LED电源驱动电路原理,并通过从在加入浪涌电压下的仿真实验,测得的LED驱动电路的各项参数指标进行失效分析,从而预测出各种实际工作中的敏感参数对失效的影响。最终,从理论的角度上给出LED器件本身失效的解决方案。     

基于有限元分析的LED肋片散热器非等距排列研究

为了降低LED芯片的结温,国内外的专家和学者主要从改进LED的封装结构,选取合适的LED封装材料等方面来研究。通过对比分析各种散热方法,本论文指出散热器对降低LED芯片的结温有很大的作用,并且散热器的散热面积越大越好,选择合适的散热片来增加散热面积将是一个重点[3]。本文通过有限元软件对模型进行仿真分析。通过改变散热器的肋片的形状,排列方式以及制作材料来比较在不同状况下的温度场分布,对比分析出这些参数对LED芯片结温的影响。     

LED环氧灌封工艺对其可靠性的影响

根据实际工作中分析发光二极管(LED)产品失效问题所获得的经验,探讨环氧树脂灌封工艺对LED可靠性的影响。采用理论结合试验验证的方法,从环氧树脂材料性能、固化工艺条件和改善树脂材料性能等方面,总结出环氧树脂灌封工艺影响LED可靠性的具体因素。环氧树脂材料的性能参数如玻璃化转变温度、热膨胀系数和弹性模量等会影响LED耐焊接热和光衰的能力;降低固化工艺条件会减少LED内应力,防止芯片隐裂;在环氧树脂中添加偶联剂可以提高LED产品气密性,防止水汽渗透,提高LED可靠性。最后建议应当根据不同LED的可靠性要求,选择合适的环氧树脂和固化工艺条件。     

超长LED显示屏驱动方式研究

在研究和分析现有各种LED显示屏控制系统及标准LED单元板的基础上.提出了一种利用LED显示屏单元板排列方式驱动超长LED显示屏的新方法,可最大限度地保证超长LED显示屏显示数据的双向高速输出.在LED显示屏单元板移位时钟给定的情况下,可使超长LED显示屏在水平方向的长度提高1倍.     

LED背光照明系统的设计方案选项

LED正成为中小型彩色显示器背光照明应用的主流器件。LED的选择是决定显示子系统设计最佳性价比的关键因素。此外,LED驱动IC能与较低成本的LED协同工作,通过多种方法提升现有LED的性能。除亮度控制外,这些驱动IC还能实现精确的亮度匹配, 或允许使用一系列具备不同VF特性的LED。本文介绍各种基于LED的背光照明设计方案选项,以及在考虑成本因素和各种设计方法利弊的前提下,如何优化系统性能。LED驱动电路设计人员为便携应用选择LED驱动电路时,一般考虑成本和性能因素。系统设计的一个约束条件是可用电池功率和电压,其它约束条件…     

高压LED球泡灯的设计与分段优化

近年来在解决以开关电源为基础的传统LED驱动效率低、体积大和成本高等问题的过程中,高压线性分段驱动技术应运而生。为了研究高压线性分段驱动LED球泡灯的设计方法,以高压线性分段驱动芯片SM2087为例,通过实测LED效率得到合适的分段比例为8∶4∶3∶1;并根据该分段比例设计了一种高压LED球泡灯,LED采用COB的方式布置在陶瓷环基板上,散热采用太阳花结构,驱动电路置于灯头内,其具有较高的效率、良好的散热与耐高压能力以及较大的发光角度。     

太阳能大功率LED路灯的设计

为积极响应国家节能减排、大力开发利用新能源的号召,以实际应用为目的,围绕太阳能光伏发电技术和LED照明技术,设计了一套太阳能LED路灯照明系统.介绍了太阳能电池功率的选取原则及与蓄电池容量的匹配方法,重点分析研究了基于ATmega128单片机和XLT604驱动器的太阳能照明系统中的太阳能控制器和LED驱动,同时就LED在芯片的功率选取、组合方式等问题上进行了分析.所设计的太阳能LED路灯照明系统照度良好、环保节能,满足太原地区城市道路照明的要求.     

大功率LED照明的驱动和散热设计

对大功率LED光源的驱动电源和散热特性进行了分析。通过对大功率LED驱动电源的应用效率和光源热量产生、热源传导方式及热流特性的研究,提出了优化改进驱动电路设计和结构设计方法,在驱动电路设计中通过升/降压恒流电路、采用工频变压整流设计提高电源的利用率,降低电源耗热;在结构设计中通过优化改进翅片材质及界面材料、改进翅片结构、加装热管和均温板几种方式进一步提高散热效果,从而使产品的质量和性能得到全面提升。     

大功率LED照明驱动匹配方式研究

文章分析了大功率LED的原理和工作特性,LED的特性也决定了驱动电源的性能要求,LED照明适合恒流源驱动。然后具体分析了LED驱动的几种匹配方式,包括全部串联、全部并联、混联、交叉阵列和分布式恒流架构。最后指出,对于大功率LED照明来说,分布式恒流是未来驱动电源的发展方向。     

Lifetime prediction of aluminum electrolytic capacitors in LED drivers considering parameter shifts

The electrolytic capacitor (Al-Cap) is widely considered as one of the reliability-critical components in LED driver applications. A realistic lifetime prediction of Al-Caps would be beneficial to the sizing of capacitors to fulfill a specified design lifetime. This paper investigates the impact of electrolytic capacitor parameter shifts on the LED driver performance and the capacitor reliability. The operation condition, degradation, and tolerance are considered as the main reasons that deviate the parameters from nominal values. A method to model the degradation of Al-Cap parameter is introduced as well. In the case study of a flyback LED driver for street lighting, the contribution of parameter shifts to the electrical performance of LED drivers and Al-Cap core temperature is evaluated based on both theoretical analysis and simulation. A quantitative comparison of the estimated lifetime of Al-Cap in the LED driver is given with and without the consideration of capacitor parameter shifts within the service life. The proposed method enables a more realistic way for electrolytic capacitor lifetime prediction in LED drivers, which would otherwise have the risk of overestimation.     

一种准谐振反激LED驱动电源的设计

针对目前小功率LED驱动电源功率因数不高、效率低、控制复杂,成本高等问题,基于单级BUCK PFC控制器SY5814A设计了一款10 W的LED驱动电源,该电源工作于准谐振模式,通过谐振使开关管在零电流的时刻完成开关转换,又保持了方波开关电源的高能量传输。同时,该电源具有过压保护、开路保护和短路保护等功能。对LED驱动电源关键的电路参数进行了详细设计,并对设计样机进行测试,结果表明,市电输入时,该电源的功率因数和效率可以达到0.94和89.4%。     

基于STM32的多功能LED驱动电源

目前大功率LED照明灯具的驱动电源主要使用集成电路作为电源驱动芯片,其扩展性能差、功能少。针对这些问题,作者基于STM32开发了一种多功能LED驱动电源,通过编程可以实现无级调光与自动温控散热两个扩展功能。测试结果表明：在额定电压为30V、额定电流为3.3A的负载下,输入电压从90V~264V变化时,驱动电源输出电压的波动范围为±1.5V,而输出电流波动范围为±0.11A,恒流特性较好,驱动电源的功率因数均值在0.95以上。     

电流控制模式白光LED驱动电路的频率补偿研究

白光LED由于其工作寿命长和能耗低的特点，为无线通讯产品的应用提供了完美的背光方案，其驱动芯片的设计大部分采用电压模式和电流模式两类控制方案。电流控制型白光LED驱动电路因为线性调整率和负载调整率非常好的优点成为目前设计的热点。基于1 MHz开关频率的电流控制型白光LED驱动芯片，结合相关的研究，对电流控制型白光LED驱动芯片进行了小信号分析，根据得出的回路增益提出了具体的频率补偿方案，并给出了实现频率补偿的方案．必须满足的参数设计方法。补偿方案能有效提高白光LED驱动芯片的小信号稳定性。     

Design and analysis of an integrated LC3–Valley fill passive LED driver

High Brightness Light Emitting Diodes (HBLEDs) replace conventional lamps due to energy savings. LC³ parallel resonance principle is used to reduce the total harmonic distortion (THD) for passive LED drivers. The Valley fill concept is applied to reduce the output voltage ripple of LED driver. This paper presents the design and analysis of an integrated LC³–Valley fill passive LED driver suitable for HBLEDs. Valley fill approach is added with LC³ characteristics to further enhance the performance of the LC³-based LED driver. The proposed LED driver achieves high input power factor, low THD with reduced ripple in the output voltage. The integrated passive LED driver consists of inductors, capacitors and diodes only without using any semiconductor-based switching devices and control circuitry. A 70 W driver circuit using single-phase, 230 V, 50 Hz, ac supply is implemented to verify the theoretical analysis. Performance comparison of the integrated LC³–Valley fill passive LED driver is carried out with the existing passive LED driver topologies. An energy efficiency exceeding 95% is obtained.     

Pulse-driven LED circuit with transformer-based current balance technique

Light emitting diodes (LEDs) have been gradually used for backlight modules for liquid crystal display as a substitute for cold cathode fluorescent lamps. In most of LED applications, it is required to connect several LED strings in parallel to limit the dc voltage level to be applied to the single LED string. Due to considerable current variations through each LED string with inevitable parameter deviations as well as temperature and ageing effects, techniques to balance currents flowing through LED strings are required for LED drivers. This article proposes a pulse-driven LED circuit with transformer-based current balancing scheme, which can simply regulate currents through the LED strings. The transformers are placed in series with the LED strings in such a way that the LED currents are automatically balanced. Since the developed current sharing technique employs no dissipative resistors and no linear-mode transistors, the proposed driver has high efficiency, low power dissipation and reduced thermal problems. In addition, the presented driver with no additional semiconductor devices and no additional controllers can provide a simple and a cost-effective current balancing solution, compared to conventional approaches. Thus, the proposed LED driver can feature a simple, highly efficient, reliable and cost-effective method. The presented LED driver is verified with experimental results.     

高功率密度LED驱动电源的设计

我国目前的照明主要以低效率的照明为主,LED由于其具有高效、节能、环保、可靠、长寿命等优点,正逐渐进入照明领域,对缓解目前环境恶化和能源短缺有重要意义.LED的性能与驱动电源性能和使用环境密切相关,需要开发出高效可靠的LED专用驱动电源与之配套.当前LED驱动电源存在功率密度、功率因数和效率较低等问题,因此开展高功率密度LED驱动电源的研究意义深远.     

Flip Chip Bonding of 68 $times$ 68 MWIR LED Arrays

The flip chip bonding process is optimized by varying the bonding pressure, temperature, and time. The 68times68 mid wave infrared (MWIR) LED array was hybridized onto Si-CMOS driver array with same number of pixels. Each pixel has two indium bumps, one for cathode and another for anode. Both LED array and CMOS drivers have 15-mum-square Indium bump contact pads. We used Karl Suss FC150 flip chip machine for bonding of CMOS driver array onto LED array. From the LED current-voltage characteristics, it is concluded that the optimized flip chip bonding process results in uniform contact and very low contact resistance. Both electrical and optical characteristics of LED array after flip chip bonding are presented.     

利用恒流LED驱动器设计高效率LED照明系统

随着高功率LED的问世,照明产业开始面临新的挑战。LED的使用寿命及电源转换效率成为设计LED照明系统时的主要考虑因素。而为了提供恒流(constantcurrent)以维持LED色彩与亮度的一致性,恒流LED驱动器可作为一个提供恒流输出的开关式转换器。此外,省电或是高效率的电源转换需求更是在LED照明应用上不可缺少的要因,而滞后型脉冲频率调制技术(HystereticPFM)可以大幅提升无论在轻载或重载时的电源转换效率。本文将探讨如何利用恒流LED驱动器设计出高效率、高稳定性的LED照明系统。     

Converter-level FEM simulation for lifetime prediction of an LED driver with improved thermal modelling

Light-emitting diode (LED) drivers are widely regarded as the weakest link in the solid-state lighting systems. This paper proposes an improved thermal modelling process for the mission profile based lifetime prediction of reliability critical components in a LED driver for the outdoor lighting application. A converter-level finite element simulation (FEM) simulation is carried out to obtain the ambient temperature of electrolytic capacitors and power MOSFETs used in the LED driver, which takes into account the impact of the driver enclosure and the thermal coupling among different components. Therefore, the proposed method bridges the link between the global ambient temperature profile outside of the enclosure and the local ambient temperature profiles of the components of interest inside the driver. A quantitative comparison of the estimated annual lifetime consumptions of MOSFETs and capacitors are given based on the proposed thermal modelling process, and the datasheet thermal impedance models and the global ambient temperature.