单片CCFL控制器改善大屏幕LCD TV的图像质量

虽然LCD背光有多种方式,例如LED、EL、CCFL等,但对于大尺寸LCD屏来说,由于CCFL发光效率高而成为主流背光光源。传统的LCD屏主要用于笔记本电脑或台式电脑,背光组件在有一定亮度的前提下,还要尺寸小和重量轻等,大多采用侧面背光方式(CCFL灯管安装在屏的二边或四周,通过导光板将光漫射到整个屏幕后面);而LCD TV特别是大尺寸LCD TV,由于对显示亮度(450cd/m2)、视角广度(170°)、图像对比度(500:1)等有更高的要求,因而需要采用光源利用率更高的垂直背光技术。1垂直背光垂直背光,顾名思义,是将CCFL灯管直接安装在LCD屏后面,并…     

背光/照明

飞兆推出CCFL背光逆变器驱动IC;奥地利微电子发布LED驱动器AS1112;研诺推出升压转换器AAT1239-1。     

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…     

为背光LCD和电视选择LED驱动IC

发光二极管(LED)的内在品质使它能够替代冷阴极荧光灯管(CCFL)成为下一代电视机、台式机和笔记本显示器的背光解决方案.LED的功耗远小于CCFL,寿命比后者长5倍,效率更高,显示器厚度更薄,亮度调节的精细度更小,使用低电压驱动器,而且本身就更加环保,因为LED与CCFL不同,它不含有汞或其他有害物质.     

LCD背光：电视用量过半CCFL，LED并存

液晶显示器，尤其TFT—LCD显示器仍然是当前发展势头最好的平板显示器。大尺寸TFT—LCD显示器，特别是液晶电视用显示器成为发展重点。由于液晶器件本身不发光，背光模块就成为液晶器件不可缺少的关键元件，其在液晶成本构成中占有重要地位。冷阴极荧光灯（CCFL）是目前的主流产品，除手机等少数小尺寸产品之外，其在其他产品领域占有绝对多数的市场份额，在近几年仍然有发展空间。     

飞兆半导体特为LCD背光系统推出业界最高集成度CCFL背光逆变器驱动IC

飞兆半导体公司日前推出业界最高集成度CCFL背光逆变器驱动电路FAN7316和FAN7317,它们针对N—N半桥、推挽式和P—N全桥LCD背光逆变器设计,能够节省空间和成本,同时提供出色的系统可靠性及简化设计。FAN7316和FAN7317具有宽泛的输入电压范围,并内置灯管开路保护和灯管开路调节电路,与市场上类似的器件相比,可在四个灯管的逆变器设计中省去多达30个外部元件。这些高度集成的CCFL背光逆变器驱动IC具有可选择的亮度调节极性,以及模拟和间歇式亮度调节功能,能够简化设计及加快产品上市。     

LCD背光驱动电荷泵的原理及应用

介绍广泛用于手机、PDA等便携电子产品的LCD背光驱动电荷泵的原理、分类，并给出AAT3110LCD背光驱动电荷泵的性能及应用电路。     

低成本LCD驱动控制的ASIC实现方案

LCD驱动控制是显示驱动信号,进而驱动LCD显示器的核心部件。在驱动LCD设计的过程中首要的是配置LCD控制器,直接控制影响LCD产品的质量。本文就该驱动IC的一种实现方法进行讨论。文中将以带键盘扫描接口的LCD驱动控制专用电路为重点,简述内部集成的MCU数字接口、数据锁存器、LCD驱动、键盘扫描、幻彩背光驱动等电路。其特点与同类设计相比,无须更改解码板底层指令,完全兼容现有的LED驱动IC的指令集,并可以直接外接LCD显示前面板,不需要外加单片机进行按键扫描(或通过解码板扫描按键),不需要另外用PT2222作按键扫描,同时支持P…     

Synthesis and analysis for a novel single-stage isolated high power factor correction converter

A novel single-stage isolated high power factor correction (HPFC) converter operating in the discontinuous conduction mode is proposed in this paper. It is an integration of a buck-boost converter with a flyback converter by means of components placement and synchronous switching technology. It can achieve HPFC, tight output voltage regulation and lower voltage stress of the bulk capacitor, which is independent of the loads. The small-signal mathematical model for the proposed converter is derived separately by the averaging method and the current injected equivalent circuit approach. The IsSpice simulations and experimental results successfully verify the dynamics and performances of the proposed converter.     

A fuzzy-logic-controlled single-stage converter for PV-poweredlighting system applications

This paper presents a fuzzy-logic-controlled single-stage power converter (SSC) for photovoltaic (PV)-powered lighting system applications. The SSC is the integration of a bidirectional buck-boost charger/discharger and a class-D series resonant parallel loaded inverter. The designed fuzzy logic controller (FLC) can control both the charging and discharging current, and can improve its dynamic and steady-state performance. Furthermore, a maximum power point tracker (MPPT) based on a perturb-and-observe method is also realized to effectively draw power from PV arrays. Both the FLC and the MPPT are implemented on a single-chip microprocessor. Simulated and experimental results obtained from the proposed circuit with an FLC have verified the adaptivity, robustness and feasibility     

A single-stage quasi-resonant flyback converter using a synchronous rectifier

A single-stage quasi-resonant flyback converter using the synchronous rectifier (SR) is proposed for improving power factor and system efficiency. This converter operates at the critical conduction mode with the variable frequency (VF) control to reduce the switching loss of the primary switch. The bulk capacitor voltage can be independent of the output load and kept within a practical range for the universal line input. Therefore, the problem of high-voltage stress across the bulk capacitor is reduced. The proposed converter features relatively low bulk capacitor voltage in the universal line voltage and also complies with the Standard IEC 61000-3-2 Class D limits. Moreover, since it uses the voltage-driven SR, it achieves a high efficiency. The operational principle and theoretical analysis are presented. Experimental results for a 100?W (19?V/5.3?A) adapter at the VF were obtained to show the performance of the proposed converter.     

A single-stage power-factor-corrected AC/DC converter

This paper presents a single-stage isolated converter topology designed to achieve a regulated DC output voltage having no low-frequency components and a high-input power factor. The topology is derived from the basic two-switch forward converter, but incorporates an additional transformer winding, inductor and a few diodes. The proposed circuit inherently forces the input current to be discontinuous and AC modulated to achieve high-input power factor. The converter output is operated in discontinuous mode to minimize the bulk capacitor voltage variations when the output load is varied. Analysis of the converter is presented, and performance characteristics are given. Design guidelines to select critical components of the circuit are presented. Experimental results on a 150 W 50 kHz universal input (90-265 V) 54.75 V output AC/DC converter are given which confirm the predicted performance of the proposed topology     

等离子及拼接液晶大屏在电视演播背景系统中的应用

详细介绍了青岛电视台新闻演播室背景大屏系统的构成,各主要设备的特点,以及在维护使用中的一些体会。对于电视技术工作者来说,不但要熟悉背景大屏系统的结构和工作原理,还要熟悉控制软件和播出软件的使用方法,才能不断提高设备维护水平。     

A novel single-stage half-bridge AC-DC converter with high powerfactor

A new single-stage AC-DC power converter based on a half-bridge converter suitable for low-power applications is proposed. The proposed converter offers high power factor and direct conversion from the line voltage to an isolated DC output voltage. High power factor is achieved by adding a resonant circuit between the rectifying diodes and half-bridge leg. For soft switching, a half-bridge series-loaded resonant converter is adopted as a DC-DC converter part. A prototype is built and tested to show the validity of the proposed converter     

用于触摸屏控制电路的低功耗模数转换器设计

为了降低触摸屏控制电路的功耗,本文提出了一种低功耗逐次逼近型模数转换器(SAR ADC)。对该SAR ADC所采用的电容阵列数模转换器(DAC)、比较器和逐次逼近寄存器等进行了研究与设计。首先,基于两级并串耦合电容设计电容阵列DAC结构,并设计配套的参考电平转换方案。接着,设计两级全动态比较器,并分析比较器的工作原理。然后,基于动态逻辑设计低功耗低误码逐次逼近寄存器。最后,基于180nm CMOS工艺,在1V电源电压,200kHz采样频率和96.243kHz输入频率条件下对SAR ADC进行了仿真。仿真结果表明:积分非线性误差(INL)和微分非线性误差(DNL)分别为0.222/-0.203LSB和0.231/-0.184LSB,无杂散动态范围(SFDR)为76.56dB,信噪失真比(SNDR)为61.50dB,有效位(ENOB)为9.92位,功耗为0.464μW,品质因素(FOM)值为2.4fJ/Conv.-step。本文设计的低功耗SAR ADC满足触摸屏控制电路应用要求。     

ZVZCS single-stage PFC AC-to-DC half-bridge converter

A zero-voltage- and zero-current-switched single-stage AC-to-DC half-bridge converter with high power factor is presented to reduce the switching losses and to achieve sinusoidal, unity power factor input currents. The single-stage approach, which combines a boost converter used as power-factor correction with a half-bridge converter used as DC-to-DC conversion into one power stage, has a simple structure and low cost. At the same time, the switching losses could be considerably reduced, because the switches of the proposed converter are designed to be turned on at zero voltage and off at zero current. Detailed analysis and experimental results are presented on the proposed converter, which is operated at constant switching frequency and in discontinuous conduction mode     

大屏幕彩电用有源功率因数补偿电路

分析大屏幕彩电开关电源的功率因数,讨论其补偿基本原理,并针对传统的大屏幕彩电开关电源,重点介绍大屏幕彩电用有源功率因数补偿电路的设计方法,并给出试验结果。     

A novel three-phase single-stage distributed power inverter

In this paper, a novel three-phase, DC/AC converter suitable for distributed power applications is proposed. The system consists of three DC/DC boost converters with a common point and operating as a three-phase inverter with intrinsic step-up capability. The converter obtained can invert, amplify and, where possible, regenerate bidirectional power sources such as fuel-cells, small gas turbines, and photovoltaic arrays. There are two main advantages to the system: the use of only six insulated gate bipolar transistors and small passive elements, and the fact that it does not need reverse voltage blocking capability. Simulation and experimental results show the effectiveness of the proposed system during both steady-state and dynamic operations.