LED点阵显示-外文文献及翻译

LED点阵书写显示屏摘要本设计运用了基于 Nios II 嵌入式处理器的 SOPC 技术。

系统以 ALTERA 公司的 Cyclone II 系列 FPGA 为数字平台，将微处理器、Avalon 总线、LED 点阵扫描控制器、存储器和人机接口控制器等硬件设备集中在一片 FPGA 上，利用片内硬件来实现 LED 点阵的带地址扫描，降低系统总功耗和简化 CPU 编程的同时，提高了系统的精确度、稳定性和抗干扰性能。

关键词：SOPC FPGA 带地址扫描AbstractThis design using the Nios II based on embedded processor SOPC technology.ALTERA system to the company for the Cyclone II FPGA digital platform、 series、Will microprocessor、 Avalon bus of LED dot matrix scanning controller、memory and human-computer interface controller hardware device focused on such a FPGA,Using the piece of hardware to achieve inside of LED dot matrix with address scanning, reduce the total power of the programming and simplify the CPU, improve the precision and stability of the system and the anti-jamming performance.Keyword: SOPC FPGA Address scanning１目录1 引言 (3)2 系统方案 (3)2.1主控器选择方案论证 (3)2.2点阵驱动方案论证 (3)3 理论分析与计算 (4)3.1 光笔选取与参数设计 (5)3.2 LED点阵屏驱动参数设计........................................ (5)3.3 屏亮自动调节设计 (6)3.4 超时关显示节电设计 (6)4 系统电路设计 (7)4.1 系统工作原理 (7)4.2 系统工作时序 (7)5 系统程序设计 (8)5.1 系统流程概述 (8)5.2系统总流程图 (8)6 系统测试与结果 (9)7 结论 (9)参考文献 (10)附录: (10)附1:电路原理图 (10)附2:扫描电路硬件描述 (11)附2:软核NIOS II程序 (17)附4:完整的测试结果 (47)２1 引言LED点阵显示屏被用到很多领域，随着电子技术的发展，LED点阵书写显示屏的广泛应用是一种趋势。

LED 的发展与应用随着显示器件与技术的进一步发展，屏幕显示系统在国民经济中得到了广泛的应用，LED 显示屏是信息显示的重要传媒之一。

LED 显示屏是利用发光二极管点阵模块或像素单元组成的显示屏幕。

伴随着计算机技术的发展，使得LED 数码管能够在减少驱动器的情况下能够直接被驱动。

而且它具有可靠性高、使用寿命长、性能价格比高、使用成本低、环境适应能力强等特点，所以一直在平板显示领域扮演着重要的角色，并且在今后相当长的一段时期内还有相当大的发展空间。

所以被广泛应用于金融市场、医院、体育场馆、机场、码头、车站、高速公路等公共场所的信息显示和广告宣传。

一LED概述LED （Light Emitting Diode），发光二极管，是一种固态的半导体器件，它可以直接把电转化为光。

LED 的心脏是一个半导体的晶片，晶片的一端附在一个支架上，一端是负极，另一端连接电源的正极，使整个晶片被环氧树脂封装起来。

半导体晶片由两部分组成，一部分是P 型半导体，在它里面空穴占主导地位，另一端是N 型半导体，在这边主要是电子。

但这两种半导体连接起来的时候，它们之间就形成一个“P-N 结”。

当电流通过导线作用于这个晶片的时候，电子就会被推向P 区，在P 区里电子跟空穴复合，然后就会以光子的形式发出能量，这就是LED 发光的原理。

而光的波长也就是光的颜色，是由形成P-N 结的材料决定的。

二 LED发展现状LED 显示屏的发展可分为以下几个阶段：第一阶段为1990年到1995年，主要是单色和16级双色图文屏。

用于显示文字和简单图片，主要用在车站、金融证券、银行、邮局等公共场所，作为公共信息显示工具。

第二阶段是1995年到1999年，出现了64级、256级灰度的双基色视频屏。

视频控制技术、图像处理技术、光纤通信技术等的应用将LED 显示屏提升到了一个新的台阶。

LED 显示屏控制专用大规模集成电路芯片也在此时由国内企业开发出来并得以应用。

摘要伴随当今高度发展的信息时代，涉及半导体技术光电器件、电子电路、集成电路、信息图像处理、信息传输、计算机网络以及电子产品制造和电子产品安装工程等相关技术的LED显示屏在信息领域显得尤为活跃，在各行业的应用及普及方面也取得了长足的进步。

从LED材料的不断更新，灰度控制技术的发展，真彩色图像的展现；到驱动电路的灵活、高效，控制系统技术的提高无不体现了LED行业技术的飞跃发展。

另外，随着计算机网络技术的发展，LED显示屏在网络环境下的使用情况越来越多，在多媒体、多种显示设备组成的信息显示系统中，采用智能化网络控制，联网控制多屏技术也在实际中得到应用。

现存显示屏的控制系统包括了输入接口电路、信号的控制、转换和数字化处理电路、输出接口电路等，涉及的具体技术很多，其中为关注并研究开发和应用的关键技术包括：串行传输与并行传输、动态扫描与静态锁存、输入接口技术、自动检测、远程控制技术等。

本文以4个8×8点阵显示器为例，单片机AT89C52作为控制器，探讨简单的汉字、数字显示技术。

硬件模块设计方面，主控制系统采用单片机控制方式，实现点阵 LED显示屏的驱动及信息的保存与显示。

具体包括：（1）LED显示点阵：主要由LED、固定板及其电路构成。

通过单片机的控制驱动电路，采用扫描方式进行显示时，每行有一个行驱动器，各行的同名列共用一个列驱动器，由行译码器给出的列选通信号，从第一列开始，按顺序依次对个行进行扫描，实现LED的发光功能。

（2）主控制系统：采用AT89C52单片机控制整个硬件模块的工作，系统可以和PC 机进行通信，实现数据刷新。

综上所述，基于系统的分析设计方案以及硬件设备的支持，对整个系统做了深入浅出的分析，本文以8×8LED点阵显示器为例，采用ATMEL公司的高性能8位单片机，探讨简单的汉字、数字显示技术，并为大型系统的研发和生产提供思路。

关键词：LED点阵显示器；单片机AT89C52； 74LS154 4-16线译码器； MAX232电平转换芯片；铁电存储器FM24C16ABSTRACTWith the high development of communication in our society,LED large screen include so many kinds of technique such as semiconductor technology, electrocircuit, integrate circuit,image manipulation, information transfers, computer network and electronic manufacture technology and engineering has become more and more active in the information field, and also make a great progress with application and populaziration in every walk of life.From the development of the material of LED, the technique of ash-degree control, the clearly multicolor image’s displaying to the active and high efficient drive electrocircuit, also the improving skill of control system are all incarnate the great progress of the LED-industry. In addition , with the development of network LED large screen is more and more in used ,intelligentize net control and net-join control technology are also bu used in practice under the multimedia and information display system composed with multi-device environment. Taking four 8 ×8 LED matrix with the controller of single-chip minicomputer AT89C52 as an example, we discuss the display technology of Chinese character, number.The hardware-model is under the single-chip’s control, achieve saving the information and driving the LED. Including :1.Led-field-array display: it is consist of LED, fixation and driving electrocircuit. At last through the control of single-chip accomplish the word and picture display.2. Center control system: under transfer data to the hardware system SMC, The system may carry on the communication with PC machine, realizes the data revolution. Information preservation in poss ferroelectric random access memory FM24C16 According to the analysis and design of the system, arithmetic, program and support of hardware device. This article take 8×8 the LED matrix as an example, uses ATMEL Corporation the high performance 8 monolithic integrated circuits, discusses the simple Chinese character, the digital demonstration technology, and provides the mentality for the large-scale system research and development and the production.Key words:LEDmatrix; Single-chip microcomputerAT89C52; 4-Line to 16-Line Decoder/Demultiplexer; Poss ferroelectric random access memory FM24C16；MAX232 level transformation chip目录绪论 (1)1.1 LED显示屏的研究背景及意义 (1)1.2 LED显示屏的技术现状及发展趋势 (2)1.3 论文主要研究内容及要考虑问题 (4)2．直流电源设计介绍 (5)2.1 桥式整流电路 (6)2.2 滤波电路 (6)2.3 三端集成稳压器 (7)3． PC机与单片机串口通信接口设 (8)3.1 串行通信接口标准RS－232C (8)3.2 RS-232C与TTL\COMS逻辑电平的比较和转换 (9)3.3 MAX232电平转换芯片 (9)3.4 PC机与单片机的串行通信接电路 (10)4． LED显示屏结构功能介绍 (11)4.1 屏体部分结构与功能 (11)4.2 控制器结构与功能 (12)4.2.1 单片机功能电路 (12)4.2.2 驱动电路 (13)5．硬件模块的设计与实现 (14)5.1 总体设计 (14)5.2 主要元件介绍 (15)5.2.1 单片AT89C52 (15)5.2.2 8*8点阵显示器 (17)5.2.3 4线-16线译玛器74LS154 (24)5.2.4 大功率2SC8050NPN三极管 (28)5.2.5 大功率2SC8550PNP三极管 (31)5.2.6 铁电存储器FM24C16及其应用 (31)5.3 LED点阵显示系统的硬件设计 (34)5.3.1 单片机的晶阵电路 (34)5.3.2 单片机的复位电路 (35)5.3.3 AT89C52的最小应用系统 (36)5.3.4 显示器及接口设计 (37)5.3.5 驱动电路的原理与设计 (38)总结与展望致谢参考文献附录绪论LED显示屏是八十年代后期在全球迅速发展起来的新型信息显示媒体，是集微电子技术、光电子技术、计算机技术、信息处理技术于一体的大型显示系统。

（要求翻译与毕业设计（论文）相关的外文文献两篇，且3000单词以上/ 篇，将译文附在原文之后）第一篇：[ 所译外文资料：①作者：Taeil Jung②书名（或论文题目）：Nano-structured InGaN Light-Emitting Diodesfor Solid-State Lighting③出版社（或刊物名称或可获得地址）：All Rights Reserved.④出版时间（或卷期号）：2009.⑤所译起止页码：Nano-structured InGaN Light-Emitting Diodesfor Solid-State LightingSolid-state lighting can potentially reduce the electricity consumption by 25%. It requires high efficiency light-emitting diodes across the visible spectrum. GaN and related materials have direct band gap across the entire visible spectrum and are ideal for future solid-state lighting applications. However, materials defects, polarization charges, and total internal reflection have thus far limited the efficiencies of InGaN LEDs, in particular InGaN LEDs in the green/yellow wavelength range, which are critical in achieving highly efficient LED luminaries with an excellent color-rendering indexIn this Thesis, we have developed and demonstrated that novel in situ nanostructured GaN processes in MOCVD are effective in improving the efficiencies of InGaN LEDs. InGaN LEDs grown on quasi-planar semi-polar GaN templates were proven to exhibit three times higher internal quantum efficiencies and negligible quantum confined Stark effect using selective area epitaxy. InGaN LEDs grown on nanostructured semi-polar GaN templates are also effective to improve the internal quantum efficiency by 31%. The same in situ processes are also effective in reducing the defect density by an order of magnitude and increasing the photon extraction efficiency as a factor of two.The in situ processes include in situ silane treatment and high temperature overgrowth. Both processes require only standard MOCVD tools and hence are cost effective and suitable for mass-production. In situ silane treatment treatsc-plane GaN samples with silane under ammonia environment, generating nano-scale truncated cone structures with up to 200 nm scale. These truncated cone structures can be subsequently transformed into pyramidal nanostructures comprising of only (10-11) and (11-22) semipolar planes using high temperature overgrowth. These processes were applied to both InGaN active region and the LED surface to improve the internal quantum efficiency and the photon extraction efficiency, respectively. Extensive materials, device, and optical characterizations have been carried out in this research.1.1 Gallium Nitride Materials for Optoelectronic ApplicationsGallium nitride based materials, including GaN, AlN, InN, and their alloys, are excellent candidates for short-wavelength optoelectronic applications. Their direct bandgaps extend from ultraviolet to near-infrared. In addition, they exhibit high mechanical and thermal stabilities compared to other III-Vsemi-conductors, making them especially suitable for high-power andhigh-temperature operations. In recent years, breakthroughs in p-type doping and defect reduction have led to the commercialization of GaN based laser diodes, light-emitting diodes (LEDs), high electron mobility transistors (HEMT) and hydrogen detectors. Despite these advances, many technological challenges such as green gap and substrate growths still remain.Perhaps one of the most important applications for GaN based materials is solidstate lighting (SSL). Worldwide, lighting constitutes 20% of electricity consumption while its efficiency is much lower than 25%. In contrast, efficiency of space heating has exceeded 90%. To this end, the development of highly efficient and reliable LEDs for solid-state lighting has been very active in both industry and academia in the past few years. It is projected by the US Department of Energy that by 2015, if successful, solidstate lighting can reduce the overall electricity consumption by 25%.Unlike GaAs and InP based semi-conductors, GaN based materials have suffered from a high density of defects due to very limited availability of lattice-matched GaN substrates. Up to now, most GaN based optoelectronic devices have been fabricated using hetero-epitaxy on foreign substrates such as sapphire (Al2O3), silicon carbide (SiC), and aluminum nitride (AlN), and in a very small percentage on silicon. Because of large lattice mismatch, GaN grown on these substrates often exhibits a high density of threading dislocations, typically on the order of 108 – 1010 /cm2. These defects are still one of the major limiting factors for the performance of GaN based optoelectronic devices, acting as non-radiative recombination and scattering centers. Achievement of lower defect density would also improve device reliability, resulting in a longer lifetime. Various defect reduction approaches, such as epitaxial lateral over-growth (ELOG), have been demonstrated and some of the details will be discussed in Chap.1.3.1. As part of this thesis, we have explored a novel approach to using nano-structured GaN to effectively lower the threading dislocation density.Among various epitaxial techniques that have been developed for GaN based materials, metal-organic chemical vapor deposition (MOCVD) is the leading technology. The typical growth temperature for GaN materials is around 1000 to 1200°C. This high growth temperature is necessary to improve the crystal quality and is a result of low cracking efficiency of the nitrogen source, ammonia (NH3), at a low temperature. In Chapter 2, I will summarize my contributions to successfully ramp up an MOCVD tool for the epitaxial growth of GaN LEDs for this research.1.2 InGaN LEDs for Solid-State LightingThe basic component for SSL is a white-light LED. As shown in Figure 1-1, itcan be achieved by mixing various color components, which can be generated either from the direct output of individual LEDs or from color-conversion materials, such as phosphor. To date, commercially available white-light LEDs usually consist of a blue emitter and a yellow phosphor plate. It has been shown that InGaN based blue LEDs could achieve external quantum efficiency in excess of 70% [1, 2]. However, this di-chromatic configuration typically has a poor color rendering index due to the lack of green and red components. The phosphor conversion process also limits the overall luminous efficiency due to energy loss during downconversion. To achieve luminous efficiency in excess of 200 lm/W and a color rendering index (CRI) in excess of 90, which is required for general illumination, a further improvement in blue LED efficiency and the use of tetra-chromatic configuration (blue + green + yellow + red) is necessary [3].* Unfortunately, the efficiency of both InGaN and AlInGaP LEDs decreases significantly in the green-yellow (500 - 580 nm) range. This efficiency gap is also known as “green gap”. Because AlInGaP materials have indirect bandgaps in this wavelength range, to achieve high-efficiency SSL, it is crucial to significantly improve the luminousNote that a trichromatic (e.g. blue + green + red) source cannot achieve a CRI > 90. efficiency of green and yellow InGaN LEDs. In this thesis, we will address these challenges using nano-structured GaN.Figure 1-1. Illustration of various potential white-light LEDs configurations (after Ref. [4]).1.3Limiting Factors for InGaN LEDs EfficiencyTo date, the efficiencies of InGaN LEDs are still limited by materials defects, polarization charges, and photon trapping. In this Section, we will briefly review the state of theart and overview how this research helps address these limitations.1.3.1 Materials DefectsAs mentioned before, the high defect density in GaN based materials grown on foreignsubstrates increases the non-radiative recombination rate and lowers the radiative efficiency. To date, several techniques have been demonstrated to improve the crystal quality and reduce the threading dislocation (TD) density of the GaN layer. Substrate pretreatmentat the growth temperature in an ammonia environment, also known as nitridation [5-7], has been shown to be critical for high quality GaN epilayers. The TD density of a typical GaN layer grown on c-plane sapphire substrate can be reduced to 108/cm2 [8] by employing the combination of a low temperature (LT; 450 - 600 °C)nucleation layer (NL) and a short annealing at the growth temperature to change the phase of the as-grown NL from cubic to hexagonal [9-11]. As will be discussed in Chapter 2, careful optimization of these low temperature growth sequences can significantly alter the subsequent GaN template growth. To this end, a home-made optical in situ monitoring tool (reflectometry) was established and will be discussed extensively in Chapter 2.In addition low temperature buffer growth, epitaxial lateral overgrowth (ELOG) which is a variation of selective area epitaxy (SAE) has been introduced [12, 13] to further lower the TD density by an order of magnitude to below 107/cm2. Variations of ELOG including pendeo- (from the Latin : hang on or suspended from) epitaxy (PE) [14] and multi-step ELOG are also effective to further reduce the TD density. Additional techniques such as TiN nano-porous network [15] and anodic aluminum oxide nano-mask [16] have also been proposed and demonstrated. All these methods, however, require ex situ processing and hence will add complexity and cost to the manufacturing. In this thesis, we will explore and generalize an in situ silane treatment approach to effectively lowering the TD density by an order of magnitude.1.3.2 Polarization ChargesDue to the non-cubic symmetry of GaN materials, compressively-strained active regions in InGaN LEDs exhibit both spontaneous and piezoelectric polarization charges. These polarization charges induce a strong internal electric field (IEF), typically on the order of MV/cm, in the active region, resulting in both efficiency droop at a high injection current density and the decrease of radiative efficiency with an increasing emission wavelength. The IEF can separate electrons from holes and increase electron leakage, resulting in low internal quantum efficiency (IQE) and efficiency droop [17], respectively. The suppression of the IEF, which is expected to increase IQE and the current density at which efficiency droop occurs, can be achieved by reducing the lattice mismatch in hetero-structures or growing them on semi-polar (e.g. {10-11} and {11-22}) and non-polar (e.g. a-plane and m-plane) surfaces. Because indium incorporation is more difficult on non-polar planes than on semi-polar planes, it is more advantageous to fabricate long-wavelength green-yellow LEDs on semi-polar planes to suppress the IEF.At least three approaches to fabricating semi-polar InGaN LEDs have been reported thus far. These include the growth of a GaN epilayer on spinel substrates [18], on bulk GaN substrates [19-27], and on the sidewalls of pyramidal or ridge GaN structures created on planar polar GaN surfaces using SAE [28-35]. GaN grown on spinel substrates have so far exhibited a high density of threading dislocations and stacking faults, thereby compromising the potential improvement of efficiency from the lowering of IEF. The use of bulk semi-polar GaN substrates has demonstrated the advantage of a lower IEF for the enhanced efficiency of green and yellow LEDs [25, 26]. However, limitations such as prohibitively high wafer cost and small substrate size need to be resolved before this approach can become more practical. On the other hand, the SAE technique can create semi-polar planes on polar GaN surfaces.High quality polar GaN films have been fabricated from a variety of substrates including sapphire, 6H-SiC, and bulk GaN by MOCVD. Using growth rate anisotropy and three-dimensional growth, different semi-polar and non-polar GaN planes can be generated on c-plane GaN [13]. In Chapter 3, we will show that high quality InGaN multiple quantum wells (MQWs) which exhibit IQE as large as a factor of three compared to polar MQWs can be grown on pyramidal GaN microstructures. This approach, however, requires ex situ patterning processes and does not easily produce a planar structure for electrical contacts. In this thesis, a new semi-polar LED structure is investigated, which is enabled by a novel epitaxial nanostructure, namely the nanostructured semi-polar (NSSP) GaN, which can be fabricated directly on c-plane GaN but without the issues of the SAE technique mentioned above [36]. NSSP GaN also eliminates the issues of excessive defects for GaN grown on spinel substrates and lowers the cost of using bulk semi-polar GaN substrates. As we will show later, the surface of NSSP GaN consists of two different semi-polar planes: (10-11) and (11-22). Therefore it is expected that InGaN active regions fabricated on NSSP GaN can exhibit a low IEF, and hence much improved IQE.1.3.3 Photon ExtractionAfter photons are generated from the active region in LEDs, they need to escape the device in order to be useful. When light travels from a medium with a higher refractive index to a medium with a lower refractive index, total internal reflection (TIR) occurs at the interface. In InGaN LEDs, photons experiencing TIR at LED surfaces can be re-absorbed by the active region or trapped in the device due to a wave-guiding effect as shown in Figure 1-2. In a simple InGaN LED, only 4% of photons generated from the active region can escape from each device surface. It has been shown that surface textures on LED surfaces can greatly reduce TIR and improve photon extraction efficiency as illustrated in Figure 1-2. To date, many surface texturing techniques such as photonic crystal structures [37] and photo-electrochemical etching of GaN surfaces [38] have been introduced. Notably, the photo-electrochemical etching of nitrogen-terminated GaN surface has been successfully implemented into commercial blue LEDs [2]. However, these approaches all require additional ex situ patterning processes which add significant costs.In this thesis, we investigate an in situ process to fabricate nano-structured GaN surfaces on LEDs which effectively improves the photon extraction efficiency. Figure 1-2. Light traveling within waveguides (left) with a smooth interface and (right) with a rough interface (after [39]).1.4 Organization of the ThesisThe objective of this thesis is to investigate cost-effective nanofabrication techniques that can significantly improve the efficiency of the state-of-the-art InGaN LEDs in both blue and green/yellow ranges for high performance solid-state lighting. The organization of this thesis is as follows.In Chapter 2, a summary of the MOCVD techniques for InGaN LEDs is given. In Chapter 3, we study the dependence of InGaN LED IQE on {10-11} semi-polar planes using SAE. In Chapter 4, fabrication and characterization of novel andcost-effective nano-structured GaN templates will be described. Using in situ silane treatment (ISST) and high temperature overgrowth (HTO), the formation of nano-scale inverted cone structures and nano-structured semi-polar (NSSP) templates has been obtained. In Chapter 5, we study InGaN semi-polar LEDs based on NSSP templates. An improvement of internal quantum efficiency is demonstrated.A green semi-polar InGaN LED grown on a c-plane substrate is also demonstrated. In Chapter 6, current spreading in NSSP InGaN LEDs will be discussed. In Chapter 7, the application of ISST for theimprovement of photon extraction efficiency of an InGaN LED will be discussed. In Chapter 8, we will summarize and make suggestions for future work.2.1 Gallium Nitride GrowthAs mentioned in the Introduction, gallium nitride (GaN) and related alloys are excellent candidates for future solid-state lighting. To date, III-nitride epitaxial growth has been limited by the lack of sufficiently large single crystal substrate for homoepitaxial growth. Therefore, the growth of GaN and related materials has been largely based on hetero-epitaxy using hydride vapor phase epitaxy (HVPE), metal organic chemical vapor deposition (MOCVD), and molecular beam epitaxy (MBE). Among these techniques, MOCVD is the leading technology due to the advantages on material quality, scalability, and cost [40]. The material quality of GaN grown by MOCVD has been excellent owing to its relatively high growth temperature (1000 - 1200°C) [41, 42].To date, various substrate materials including sapphire (Al2O3), silicon carbide (SiC), and silicon have been studied for GaN growth (Table 2-1). Although GaN substrates have been recently introduced in markets through bulk material growth on foreign substrates using HVPE and laser cutting along specific crystal planes, the cost has been prohibitively high. On the other hand, GaN grown on c-plane (0001) sapphire substrate exhibits stable growth over a wide range of growth conditions despite high dislocation density at the interface between thesubstrate and epitaxial layer. In this research, I have helped ramping up an MOCVD system together with Dr. Hongbo Yu. In this Chapter, I will summarize the MOCVD technologies and defect reduction strategies for InGaN light-emitting diodes (LEDs) epitaxy that will be used throughout this Thesis.2.1.1 GaN Growth Using MOCVDDue to a large lattice mismatch between GaN and sapphire, it is important to contain the defects near the GaN/sapphire interface such that the defect density can be minimized in the device region. Such optimization is achieved using in situ reflectometry [44, 45]. A home-made reflectometry system shown in Figure 2-1 was established in our 3 x 2” Thomas-Swan Close-Coupled Showerhead (CCS) MOCVD system. White light is reflected from the sample surface and monitored by a spectrometer during the growth. The reflectivity is sensitive to both the surface morphology and the epitaxial layer structure.Figure 2-1. Illustration of a home-made in situ reflectometry system integrated into the MOCVD system.Figure 2-2. Typical growth conditions for GaN templates used in this research.Typical growth conditions for GaN templates used in this research are summarized in Figure 2-2 and Table 2-2. Unless otherwise mentioned, c-plane sapphire substrates were used. The five steps outlined in Table 2-2, including high temperature (HT) cleaning, nitridation, low temperature (LT) nucleation, annealing of LT nucleation layer, and HT GaN growth, are crucial for high quality GaN epilayer.Figure 2-3 and Table 2-3 show the corresponding in situ reflectometry signal.In the following, we will describe how the reflectometry signal can be used to optimize the GaN template growth. Unless otherwise mentioned, we will refer to the reflectometry signal shown in Figure 2-3.Figure 2-3. In situ reflectometry trace of GaN template growth (Sample ID : UM-S07- 254). The highlighted areas correspond to important sub-steps during the epitaxy.2.1.1.1 High Temperature CleaningInitially, as the sample temperature is ramped up, the reflectivity increases due to the increase of the refractive index of the sample. Kim et al. has thoroughly studied the effect of initial thermal cleaning on the sapphire substrate andexperimentally demonstrated that this thermal treatment can effectively reduce the surface roughness of the substrate [46]. Generally, the flat surface is preferred for the GaN nuclei to be formed uniformly, which is critical to the crystal quality of the final GaN epilayer. The specific condition for the HT cleaning should be optimized by examining the treatment temperature and time. In our GaN growth, the optimal treatment temperature and time were set to be 1075 °C and 5 minutes, respectively. Moreover, HT surface annealing can effectively eliminate surface moisture.2.1.1.2 NitridationNitridation [5, 7] is the process of NH3 preflow under hydrogen (H2) ambient to prepare the surface for growth. During nitridation, NH3 reacts with the surface oxygen atoms on the sapphire substrate. Due to the replacement of the oxygen atoms by the nitrogen atoms and the diffusion of the nitrogen atoms into a certain depth, the exposed surface becomes a smooth amorphous state. Because this change of surface morphology is on the order of tens of angstrom, the corresponding reflectivity change is not significant. It has been shown that with a proper nitridation condition, GaN epilayers with lower dislocation density and better electrical and optical properties can be achieved [7]. However, as mentioned above, suitable combination of reactor conditions such as temperature, treatment time, and NH3 flow rate must be considered. In our GaN growth, the nitridation was optimized at 530 °C for a total of 210 seconds under 3 slm of NH3 flow.2.1.1.3 Low Temperature NucleationAs mentioned in Section 1.3.1, several approaches have been introduced to reduce the threading dislocation (TD) density in growing the GaN template. Specifically, the use of low temperature nucleation layer (LT NL) has been shown to be simple yet effective. A threading dislocation density as low as 108/cm2 has been reported [8].As GaN is nucleated on sapphire, the cubic phase islands are first formed at a temperature of 450 - 600 °C. These islands are subsequently transformed into the wurtzite phase [8]. The increase of the reflectivity during the LT NL growth is attributed to the increase of reflection from the flat top surfaces of nuclei. Basically, we know that the reflection from GaN is about twice stronger than that from sapphire due to the difference in refractive indices. As the islands become denser (i.e. the growth time of LT NL becomes longer), total reflection from the top surface of nuclei becomes up to 200% of reflection from sapphire substrate assuming that the entire surface is covered by GaN islands. Even though the islands are not coalesced completely to form a crystalline layer, this is still possible because the distances between the adjacent islands are too small compared to the optical wavelength. Once the reflectance exceeds twice that of the sapphire (as shown in Figure 2-3), the islands continue to coalesce further, which results in larger GaN grains and a thicker NL. Here, the size of the nucleation islands and the thickness of the NL are critical to obtain high quality GaN epilayer. To show that, we have compared a series of GaN templates with different NL conditions. All conditions were kept the same† except the growth time of the LT NL was varied,resulting in different LT NL thicknesses. The thickness of the LT NL was extrapolated by analyzing the reflectometry data as the reflection ratio at the end of LT NL growth to the sapphire substrate (RLT NL / RSapphire). The qualities of the GaN templates were characterized using photoluminescence (PL) and x-ray diffraction (XRD). From these results, the best GaN template quality can be obtained when RLT NL / RSapphire is around 2.6 which corresponds to a 40nm thick NL, at the given growth conditions.† LT NL growth temperature = 530°C, V/III = 9140, LT NL annealing time = 420 seconds, HT GaN growth temperature = 1040°C, V/III = 1230, growth time = 4300 seconds.Figure 2-4. The comparison of GaN template qualities with respect to the reflection ratio between the LT NL surface and the sapphire substrate.2.1.1.4 Annealing of Low Temperature Nucleation LayerIn GaN hetero-epitaxy with a large lattice mismatch, the initial growth on the surface follows the Volmer Weber model [47], i.e. GaN island growth dominates. In order to obtain smooth GaN templates, these islands need to be transformed into the layer-by-layer growth mode using an NL annealing process. During annealing, the substrate temperature is gradually increased up to around 1030 - 1050 °C under NH3 overpressure. Temperature ramping rate, reactor pressure, and NH3 flow can control the NL decomposition rate, which determines the surface roughness at the end of the annealing process [48, 49]. In Figure 2-3, after point (h) at which LT NL annealing begins, slight increase of reflectance is normally observed. The increase continues until around 800 °C at which GaN decomposition process starts to occur. Once the reflection intensity peaks, it begins to drop due to the increase in surface roughness. Initially randomly distributed islands start to be transformed into relatively uniform islands due to the decomposition of the NL and the migration of the gallium ad-atoms.During the annealing process, the reflectivity first decreases due to the increase of surface roughness. Further annealing results in a slight increase of reflectivity because at a higher temperature, the surface morphology becomes smoother. However, if we anneal the surface even further, the surface roughness increases again, which results in the decrease of reflection intensity [48, 49]. This phenomenon can be explained by considering the volume of the GaN islands. At the transition point ((k) in Figure 2-3), the volume of the islands per unit area becomes the highest which is preferable for the subsequent HT GaN growth. As a rule of thumb, the position of this (reflectometry trace) shoulder is dominated by the highest temperature of the annealing process [50]. In summary, the goal of the low temperature nucleation and the subsequent annealing is to achieve a surface morphology with proper density and sizes of the islands for the following HT GaN growth.As shown in Figure 2-5, even a slight change of the island distribution caused by a slight difference of the NL thickness and temperature ramping rate (Table 2-4) can result in a significant difference in the following HT GaN growth under the same conditions. In general, it takes longer for an NL with a rougher surface and smaller islands to be transformed into the 2D growth mode. The conditions to achieve high crystal quality GaN on sapphire are mostly related to the growth and annealing of the LT NL.2.1.1.5 HT GaN GrowthAs soon as the sapphire surface is covered with suitable volume, uniformity, thickness, and density of GaN islands, HT GaN growth can be followed. This HT GaN itself can be divided into two parts (Figure 2-6). Part I corresponds to the initial stage of HT GaN growth when the growth mode is transitioned from 3D to 2D, which affects the crystal quality significantly. In part II, GaN epilayer becomes thicker because the growth mode as well as growth condition is stabilized for 2Dmode. Several strategies to control the GaN growth in each regime will be briefly discussed in the following.The growth in part I is a buffer step to prepare a surface suitable for HT GaN growth. During this step, the oscillation of the reflectometry signal becomes increasingly obvious. Initially, the reflectivity continues to drop due to the increase of surface roughness induced by the coagulations of the islands, i.e. 3D growth. As time goes by, the 3D growth mode is suppressed and the 2D growth mode is enhanced. Once the surface becomes flattened due to the enhanced 2D growth, layer by layer growth of GaN begins, which causes the reflectivity to increase. The duration of this part of growth can be optimized by tweaking the reactor pressure, V/III ratio, and growth rate [51, 52]. For example, in the case of a low V/III ratio, it takes longer to recover the reflection intensity, which implies that the change of the growth mode (3D 2D) occurs more slowly. The reflectivity recovery time is critical to oscillation amplitude in part II. In general, a larger oscillation amplitude corresponds to a better crystal quality.The part II of the HT GaN growth is stable in a wide range of growth conditions because the growth occurs in a mass transfer limited region. Nevertheless, several key factors will still affect the crystalline structure, including the growth temperature, trimethyl-gallium (TMG) flow, NH3 flow, V/III ratio, and reactor pressure. As shown in Figure 2-7, the growth rate increases as the group III flow increases but decreases as the V/III ratio and growth temperature increase. The。

期末电子设计论文16×32点阵LED电子显示屏的设计The 16×32 lattice LED electron display monitor design论文书组长姓名：学号：指导教师；所在院系：计算机科学与技术所学专业：电子信息科学与技术山东财经大学中国·济南2013年6月一、课题名称16×32点阵LED电子显示屏的设计二、课题内容设计一个室内用的16×32点阵LED图文显示屏。

三、课题任务要求在目测条件下16×32点阵LED显示屏各点亮度均匀、充足，可显示图形和文字，显示图形或文字应稳定、清晰无串扰。

图形或文字显示有静止、移入移出等显示方式。

四、主要参考文献[1] 郭天祥主编：《51单片机C语言教程》北京：电子工业出版社，2013[2]张毅刚主编：《单片机原理及应用》．北京：高等教育出版社，2006指导教师签字教研室主任签字年月日摘要本设计是一16×32点阵LED电子显示屏的设计。

整机以美国ATMEL 公司生产的40脚单片机AT89C52为核心，介绍了以它为控制系统的LED点阵电子显示屏的动态设计和开发过程。

通过该芯片控制两个个行驱动器74HC138和两个列驱动器74HC595来驱动显示屏显示。

该电子显示屏可以显示各种文字或单色图像，全屏能显示2个汉字，采用8块8×8点阵LED显示模块来组成16×32点阵显示模式。

显示采用动态显示，使得图形或文字能够实现静止、移入移出等多种显示方式。

文中详细介绍了LED点阵显示的硬件设计思路、硬件电路各个部分的功能及原理、相应软件的程序设计，以及使用说明等。

单片机控制系统程序采用单片机C语言进行编辑，通过编程控制各显示点对应LED阳极和阴极端的电平，就可以有效的控制各显示点的亮灭。

所显示字符的点阵数据可以自行编写（即直接点阵画图）。

LED显示以其组构方式灵活、显示稳定、功耗低、寿命长、技术成熟、成本低廉等特点在车站、证券所、运动场馆、交通干道及各种室内/外显示场合的信息发布，公益宣传，环境参数实时，重大活动倒计时等等得到广泛的应用。

目录摘要 (1)1绪论 (2)1.1 LED显示屏的研究背景及意义 (2)2 LED电子显示屏的介绍 (2)2.1 LED显示屏简介 (2)2.2 LED显示屏的分类 (3)3 LED显示屏的组成 (4)3.1 LED显示模块结构 (4)3.2 LED显示系统的构成 (5)3.3 LED显示屏的硬件原理 (6)4 LED显示屏的设计 (7)4.1 LED点阵显示屏驱动设计 (7)4.2 LED显示屏的控制模式 (8)4.3 LED显示屏的主控电路 (8)4.4 LED显示屏的实现技术 (9)5 LED显示屏的应用 (10)5.1 LED显示屏的应用 (10)5.2成果展示与总结 (11)5.3 LED显示屏的术语解释 (13)参考文献 (15)致谢 (16)LED显示屏设计与制作摘要：LED就是light emitting diode （发光二极管）的英文缩写,它是一种能发光的二极管。

LED显示屏（LED display），又叫电子显示屏或者飘字屏幕，是由LED点阵组成，通过红色或绿色灯珠的亮灭来显示文字、图片、动画、视频等各种信息的显示屏幕，内容可以随时更换，各部分组件都是模块化结构，通常由显示模块、控制系统及电源组成。

显示模块由LED灯组成的点阵构成，负责发光显示；控制系统通过控制相应区域的亮灭，可以让屏幕显示文字、图片、视频等内容，恒舞动卡主要是播放动画的；电源系统负责将输入电压或电流转为显示屏需要的电压电流。

关键词：LED；数据传输；信息发布系统；单片机1 绪论1.1 LED显示屏的研究背景及意义发光二极管(LED)，是一种把电能变成光能的特种器件，主要由PN结芯片、电极和光学系统构成。

当系统受到外界激发后，会从稳定的低能态跃迁到不稳定的高能态，当系统由不稳定的高能态重新回到稳定的低能态时，能量差以光的形式辐射出来，就会产生发光现象。

当在PN结上加以正向电压之后，P区的空穴注入至N区，N区的电子注入至P区，相互注入的电子与空穴相遇后即产生复合，这些多数载流子在结的注入和复合中产生辐射而发光。

目录摘要 (1)前言 (2)1 概述 (2)1.1 LED电子显示屏的分类 (2)1。

2 LED显示屏的应用示例 (2)1。

3 设计任务 (2)2 显示原理及控制方式分析 (3)2.1 LED点阵模块结构 (3)2。

2 LED 动态显示原理 (3)2.3 LED常见的控制方式 (5)3 总体方案设计与分析 (6)3.1显示单元的考虑 (6)3。

2 滚屏的实现 (6)3。

3 关于可扩展性 (6)3。

4 微控制器的考虑 (6)3.5 总体电路结构及工作原理 (6)3.5。

1 硬件电路框图 (6)3.5。

2 工作原理 (7)4 硬件电路设计 (7)4。

1 显示单元电路设计 (7)4。

1。

1 LED点阵模块的选择 (8)4.1.2 列驱动电路设计 (8)4。

1。

3 行驱动电路设计 (9)4.2 单片机控制系统电路设计 (10)4.2.1单片机的选型 (10)4。

3对于系统电源及通信电缆的选择 (11)4。

4 其它元件的选择 (11)5 单片机软件设计与仿真 (12)5.1 开发工具及语言 (12)5。

2 单片机软件流程 (13)5。

3 单片机软件中算法的实现 (14)5.4 调试及仿真结果 (15)6 PCB设计及硬件调试 (16)6。

1 PCB设计平台 (16)6.2元件布局及PCB整体结构工艺 (16)6。

3 布线工艺与准则 (16)7 总结 (17)谢辞............................................................................................ 错误!未定义书签。

参考文献. (18)附录 (19)LED点阵电子显示屏系统的设计xxx摘要:本设计使用STC系列高速单片机作为主控制模块，利用简单的外围电路来驱动16×64的点阵LED显示屏。

本LED显示屏能够以动态扫描的方式同时显示特定的四个16×16点阵汉字。

文献综述电气工程及其自动化LED点阵全彩屏的设计前言LED灯也就是发光二极管已经成为我们生活的必须品了，现如今我们晚上出门就会被那些多彩的LED灯照的眼花缭乱，无论走到哪里那些五彩的小灯都会进入我们的眼眶，从一出家门锁门的指示灯，到开车时中控台上的LED屏幕，然后去餐厅，公司，车站，医院，学校等各钟LED屏，还有很多，现在我们的生活已经渐渐的离不开那些一点点的发着微弱的光的LED灯了。

正文1 LED的发展概况发光二极管（LED）是一种电致发光的光电器件。

早在1907年开始，人们就发现某些半导体材料制成的二极管在正向导通时有发光的物理现象，但生产出有一定发光效率的红光LED 已是1969年了。

到今天，LED已生产了30多年，回顾过去，它已茁壮成长。

各种类型的LED、利用LED作二次开发的产品及与LED配套的产品（如白光LED驱动器）发展迅速，新产品不断上市，已发展成不少新型产业。

展望将来，还期望更进一步地提高。

早期的LED 主要用于做指示灯。

它的发光强度不高，一般小于1mcd，高的也仅几个mcd；另外，发光效率也不高，一般小于0.2lm/W；其功率仅几十mW到上百个mW（属于小功率LED）。

作为指示灯方面的应用，有几个mcd的发光强度也可以了，但由LED组成的数码管或字符管则显得亮度不足，若要用于户外作信号或标志显示，则其亮度太低，不能满足使用的要求。

所以LED 的主要发展方向是提高发光强度（也就是一般所指的提高亮度）。

随着半导体材料及半导体工艺技术、设备的发展，LED的亮度不断提高，开发出高亮度及超高亮度LED，并且不断创造新记录。

2 LED照明与应用该文从 LED的有关发光原理、特点、LED的驱动、LED的调光控制和LED的世界新产品推出与性能改进等方面进行了讨论,由于 LED照明技术的一系列优点,LED照明进展非常快 , LED照明有很好的应用前景。

1963年2月, LED的发明者N. HOLONY AK在《读者文摘》(美)上发表了“我们坚信LED 会发展成实用的白色光源”一文 ,并作了明确的预言:“将来的灯可以是铅笔尖大小的一块合金 ,它实用且不易破碎、决不烧毁 ,比起今天通用的灯泡来说,其转换效率至少大10倍。

XXXXXXXX大学专业文献综述LED点阵电子显示屏系统的设计xxx 指导教师：xxx摘要：本设计拟采用一种由单片机控制的8*8点阵发光模块组成的16*64发光点阵，探讨简单的汉字、英文字母和动态图象显示技术，以及实时的温度测量显示。

该系统具有设计简单、字符清晰、可靠性高等特点。

关键词：LED；单片机；点阵；Design of LED Dot Matrix Electronic Display SystemAuthor: Song Jian-lei Instruct teacher: Li Xue-lianAbstract：The paper introduces a kind of 16*64 dot matrix consists of 8*8 dot matrix module, we discuss the display technology of Chinese character, English letter, dynamic image and real time temperature. It is simple in design, cheap in cost and high in reliability.Key words: LED；Single Chip Microcomputer；Dot Matrix；引言LED(Light Emitting Diode，LED)电子显示屏是随着计算机及相关的微电子、光电子技术的迅速开展而形成的一种新型信息显示媒体。

LED点阵显示器作为一种新兴的显示器件，它是由多个独立的LED发光二极管封装而成。

发光二极管LED具有体积小、抗冲击和抗震性能好、高可靠性、寿命长、工作电压低、功耗小及响应速度等优点[1]。

由于电子显示屏具有显示内容信息量大，外形美观大方，操作使用方便灵活，用户可随时任意自行编辑修改显示内容，显示方式图文并茂等优点，因此被广泛应用于商场、学校、银行、邮局、机场、车站、码头、金融证券市场、文化中心、信息中心休息设施等公共场所[2]。

译文：大屏幕显示系统的研究LED的发展随着计算机技术的高速发展，LED屏幕显示系统作为继电视、广播、报纸、杂志之后的“第五大媒体”正快速步入社会生活的各个方面.它集微电子技术、计算机技术、信息处理技术于一体，可以将信息通过文字、图案、动画及视频四种形式显示出来。

与电视墙、磁翻板等媒体相比，LED大屏幕显示系统具有图案美观、色彩亮丽；图案、色彩变化丰富、快速；低功耗、长寿命、使用成本低、工作稳定可靠等特点。

它显示的图文视角大、视距远，因而已广泛应用于大型广场、商业广告、体育场馆、信息传播、新闻发布、证券交易；它还应用于工业控制和工业调动系统,便于把各种参数、报警点、工艺流程显示得更加清晰完美，可以满足不同环境的需要。

LED显示屏是一种利用计算机和复杂数字信号处理的电子广告宣传屏。

它的屏体部分由微处理器（主要是单片机）和驱动电路控制运行，显示的图像或文字由计算机编辑软件编辑获得。

由于LED显示屏这种新一代信息显示设备具有显示图案稳定、功耗低、寿命长等特点，而且它综合了各种信息显示设备的长处，并且克服了自身的不足，特别是由于一幅显示屏可以显示不同的内容，显示方式丰富.所以在公共场合,它具有强烈的广告宣传和信息传递效果，日趋在固体显示中占主导地位。

LED显示屏的发展前景极为广阔，目前正朝着更高亮度、更高耐气候性、更高的发光密度、更高的发光均匀性、可靠性、全色化方向发展。

由不同材料的半导体组成能发出不同色彩的LED晶点。

目前应用最广的是红色、绿色、黄色LED。

而蓝色和纯绿色LED的开发已经达到了实用阶段。

LED显示屏的分类LED显示屏是多种技术综合应用的产品，涉及光电子学、半导体器件、数字电子电路、大规模集成电路、单片机及微机等各个方面，既有硬件又有软件。

LED 显示屏是作为广播、电视、报纸、杂志之后的又一新传播媒体。

目前LED显示屏根据使用场所不同,可以分为室外屏和室内屏两种，其主要区别是发光管的发光亮度不同。