Boost converter with adaptive reference tracking control for dimmable white LED drivers

An LED driver consisting of dimmable current regulators and a boost converter with adaptive reference tracking control (ARTC) is proposed. The ARTC is realized with only one integrator and one subtractor to detect the voltage variation among the current regulators and then to generate an adaptive reference tracking voltage. Based on the reference tracking voltage, the driving voltage of the boost converter is dynamically adjusted, so as to not only maintain a minimum voltage on the current regulator but also keep the required LED-string current. A prototype control circuit including ARTC and PWM control fabricated with TSMC 0.35-μm 2P4M CMOS process validates the proposed technique. The measurement results show that the driving voltage of the boost converter is automatically regulated to compensate for the voltage alteration on the current regulators. Furthermore, the overall efficiency of the LED driver with ARTC is 6.1% better than that of the LED driver without ARTC.     

Effects of apparent image velocity and complexity on the dynamic visual field using a high-speed train driving simulator

Train driving is a highly visual task. The visual capabilities of the train driver affects driving safety and driving performance. Understanding the effects of train speed and background image complexity on the visual behavior of the high-speed train driver is essential for optimizing performance and safety. This study investigated the role of the apparent image velocity and complexity on the dynamic visual field of drivers. Participants in a repeated-measures experiment drove a train at nine different speeds in a state-of-the-art high-speed train simulator. Eye movement analysis indicated that the effect of image velocity on the dynamic visual field of high-speed train driver was significant while image complexity had no effect on it. The fixation range was increasingly concentrated on the middle of the track as the speed increased, meanwhile there was a logarithmic decline in fixation range for areas surrounding the track. The extent of the visual search field decreased gradually, both vertically and horizontally, as the speed of train increased, and the rate of decrease was more rapid in the vertical direction. A model is proposed that predicts the extent of this tunnel vision phenomenon as a function of the train speed.Relevance to industryThis finding can be used as a basis for the design of high-speed railway system and as a foundation for improving the operational procedures of high-speed train driver for safety.     

Value drivers of blockchain technology: A case study of blockchain-enabled online community

There is growing recognition that blockchain technology has significant potential to alter how organizations and people work and communicate. However, theoretical guidance concerning how organizations leverage blockchain technology to enhance value creation for users is still limited. Grounded in the socio-technical perspective and leveraging the rich data obtained from case analyses of blockchain-enabled online communities, this paper develops a theoretical model to identify the core value drivers that blockchain enables for online communities. The core value drivers include: a reputation-value system, data ownership mechanisms, and verification & tracking mechanisms. Our findings suggest that these three value drivers enhance value creation of online communities by motivating participation and protecting contributions.     

The driver,the road,the rules … and the rest? A systems-based approach to young driver road safety

The persistent overrepresentation of young drivers in road crashes is universally recognised. A multitude of factors influencing their behaviour and safety have been identified through methods including crash analyses, simulated and naturalistic driving studies, and self-report measures. Across the globe numerous, diverse, countermeasures have been implemented; the design of the vast majority of these has been informed by a driver-centric approach. An alternative approach gaining popularity in transport safety is the systems approach which considers not only the characteristics of the individual, but also the decisions and actions of other actors within the road transport system, along with the interactions amongst them. This paper argues that for substantial improvements to be made in young driver road safety, what has been learnt from driver-centric research needs to be integrated into a systems approach, thus providing a holistic appraisal of the young driver road safety problem. Only then will more effective opportunities and avenues for intervention be realised.     

桥式电路中不同封装SiC MOSFET串扰问题分析及低栅极关断阻抗的驱动电路

由于SiC MOSFET开关速度较快,使得桥式电路中串扰问题更加严重,这样不仅限制了SiC MOSFET开关速度的提升,也会降低电力电子装置的可靠性。针对SiC MOSFET的非开尔文结构封装和开尔文结构封装的串扰问题分别进行分析,栅漏极结电容的充放电电流和共源寄生电感电压均会引起处于关断状态开关管的栅源极电压变化。提出一种用于抑制串扰问题的驱动电路,该驱动电路具有栅极关断阻抗低、结构简单、易于控制的特点。分析该驱动电路的工作原理,提供主要参数的计算方法。最后通过实验测试了两种结构封装SiC MOSFET的串扰问题,并且对提出的驱动电路进行了实验,验证了其正确性以及对串扰问题的抑制效果。     

两相并联LCL-nT谐振型多路均流LED驱动器研究

针对大功率发光二极管(LED)应用场合下需要多路输出及各路电流均衡的问题,提出一种具有多路输出均流的两相并联LCL-n T谐振型电路拓扑结构,详细分析两相并联LCL-nT型谐振变换器的恒流特性、多路并联输出的均流特性以及移相调光控制策略;推导出恒流工作频率表达式和能够实现多路均流的负载范围,并对谐振网络的阻抗特性和电压增益特性进行了分析,在此基础上给出一种兼顾输出功率和开关管零电压开关(zero voltage switching,ZVS)的参数设计方法。最后设计1台200 W的实验样机,实验结果验证了所提出的电路拓扑具有良好的恒流特性和均流特性,并且能实现对LED的全范围调光。     

基于xPC Target的硬件在环平台的设计

基于xPC Target的硬件在环平台具有诸多优点而被广泛应用。阐述了实现此平台的3个主要步骤,包括双机系统的配置、启动盘的制作以及数采卡驱动的编写。由于以往的数采卡驱动编写方法非常繁琐,文中给出了一种快捷驱动设计方法。最后,搭建测试模型对平台进行测试。     

一种基于电压斩波和电流软启动CCR LED电源设计

恒流调节器(CCR)常用于中小功率家用LED照明驱动电源中,但是这类常见的电路在交流电压波动时可能出现电源效率和LED电流不稳定的现象。论述了这类驱动电路的工作原理,分析了问题产生的原因,提出一种基于电压斩波和电流软启动CCR LED电源的方案,理论分析和实验数据都表明这种改进方案非常有效地解决了前述问题。     

A power‐efficient 600‐mVpp voltage‐mode driver with independently matched pull‐up and pull‐down impedances

In this study, a large‐swing, low‐power voltage‐mode driver with independently matched pull‐up and pull‐down impedances is proposed. To achieve large swing and constant impedances during a transition, a P‐over‐N structure is implemented with regulators calibrating the impedances. Two regulators are dedicated to matching the pull‐up and pull‐down impedances by regulating the supply voltages of the driver and predriver, respectively. Because background impedance calibration loops are adopted to track the process, voltage, and temperature (PVT) variations, the proposed driver can operate properly without additional calibration time. To reduce the power consumption of the calibration loops, scaled replicas of the actual driver are used. Moreover, an analysis of design optimization for the proposed driver is presented. The proposed driver was fabricated in 65‐nm CMOS technology and verified at a 5‐Gb/s data rate. Measurement results show that the proposed driver has a voltage swing of 600 mV_pp and a horizontal eye opening of 0.5 UI. The prototype chip consumes 6 mW at a 1.0‐V supply. Copyright © 2014 John Wiley & Sons, Ltd.     

基于偏振调制型全光纤电流互感器的研究

随着电力系统输电电压等级和传输容量的不断提高,传统的电磁式电流互感器暴露出诸多问题已难以满足当今社会的需要。本系统通过对光纤电流互感器的理论基础进行了深入的研究,并在此基础上建立了光纤电流互感器数学模型;根据模型设计了光纤电流互感器光路系统,并根据光路特点选择了相关器件;根据光路系统输出信号的特点,设计了激光器驱动电路和光纤电流互感器信号检测电路,对检测电路的性能进行了单独测试;最后,设计了光纤电流互感器准确度测试系统,并对所设计的光纤电流互感器系统进行了整体测试。测试结果表明,在相同的测试环境下,该光纤电流互感器的输出具有极好的线性,测试结果符合 IEC 0.2S 级。