基于阻容降压的稳压电路设计

为了解决给智能家用电器所用到的ASIC芯片提供稳定电源电压的问题,设计出阻容降压的稳压电路,该电路对市电进行阻容降压、半波整流、滤波,在稳压电路引入深度电压负反馈使输出电压稳定,该电路具有抗电网干扰和防浪涌功能;经过瞬态分析后,输出电压最终稳定在5.085 9 V,与实际电路测试结果5.04 V仅相差0.045 9 V,该稳压电路已成功应用于电子产品中。     

提高电子电路抗干扰能力经验谈

作为一个电子设计制作者与爱好者在设计带微处理器的电子产品时,如何提高系统的抗干扰能力和电磁兼容性是设计者必需考滤的一个问题。本人就自己在电子设计制作过程中积累的一点经验供大家参考。一、减小来自电源的噪声电源在向系统提供能源的同时,也将其噪声加到所供电的电源上。电路中微控制器的复位线,中断线,以及其它一些控制线最容易受外界噪声的干扰。电网上的强干扰通过电源进入电路,即使电池供电的系统、电池本身也有高频噪声。模拟电路中的模拟信号更经受不     

基于机体温度的简易内嵌控制电路的设计

本设计针对电气设备机体内部或内嵌电气设备的机体环境温度控制需要,提出了一种基于机体温度的简易内嵌控制电路的设计,用来实现对电气设备机体内部或内嵌电气设备的高温保护,预防减少故障.该设计根据阻容降压原理,并改进设计电源为电路供电,以热敏温度电阻为核心,利用电压比较器实现温度状态判断,并实现电路控制和报警.该电路简易实用,成本低,可靠性高。     

如何在环形变压器上增加新绕组

众所周知,环形变压器具有漏磁小、效率高、干扰小等优点。所以,目前在各种功率放大器中得到了广泛的应用。在一些功放中,“环牛”的功率具有一定的储备余量,但在一些房间面积不大的家庭功率放大器经常处于轻载状态,变压器的容量并没有充分发挥出来,效率较低。此外,大多数功率放大器的前置级与功放后级又同时共用一套电源(特别是在只有一个变压器的功放中),有些前级的电源只仅仅通过简单的阻容退耦降压从后级电源中获得,这样前级的工作就要受到后     

1999年12期考考你解答

问题一:“功放级输出端阻容件”解答 [解答一]山东日照市五中97级3班付强此阻容件的作用是与扬声器一起组成纯电阻负载,使负载不再呈电感性,保护功放管,同时也有消振作用。电阻可取与扬声器阻抗同值的,电容可由扬声器音圈电感值/(扬声器阻抗)~2求出。在功放的电源电压较低或功放管反向耐压较高的情况下可以不加该阻容件。 [解答二]湖北丹江口市郧阳师专97化工班丁宗庆功放级输出端并接电阻和电容的作用是构成“茹     

IBM PC/XT电源维修小经验

IBM PC/XT采用对电网适应范围宽、损耗小的开关电源,主要功能是向微机系统提供所需的+5V、-5V、+12V、-12V的四档电源。该电源的一个特点是无负载或负载达不到要求时,电源就不工作,无输出电压。因此,要加电检修电源,一定要接上15欧姆的电阻或直接接上主机板(笔者就曾空载测试电源无输出。而连上主机板后正常工作的情况)。该电源的另一个特点是系统电源直接从交流 220V(110V)经整流滤波得到300V变换电压。省去了电源变压器,设计合理,使用安全。但对维修人员十分危险,在触电时,电能全部加到触电者身上(而不是     

风洞测控系统干扰及抑制

风洞中交流电机调速器、直流电机调速器及继电器等动力设备运行时将产生强干扰。它们从电网、信号线、地线进入测试系统。抑制干扰也从电源系统、地线、信号线等方面采取措施,通过隔离、屏蔽、滤波、接地等方法,在软件上采取数字滤波。     

脉宽调制型开关稳压电源

本文介绍我们对脉宽调制型晶体管开关稳压电源研制情况。文章着重讨论电源的脉宽控制电路、有负偏压的驱动电路、电源的可靠性、保护和射频干扰等问题。由于水平有限,不妥之处请予指正。一、概述一般电子设备中用的直流稳压电源是采用传统的串联调整式的直流稳压电源。这类电源调整管上消耗功率较大,影响了效率。当使用电网作为输入电源时,为了降压、隔离、需要一个笨重的变压器,整个设备增加     

一种实用的抗电源干扰电路

在工业过程控制和实时控制中，经常出现电网瞬时断电或电压突然下降等干扰情况，使得微机系统陷入混乱，数据丢失。为此，人们采用加强电源滤波、光电或变压器隔离、加强屏蔽、专用电源等方法，但都不能从根本上有效地解决干扰问题。本文采用电源电压监视器芯片TL7705A设计了一种适用于单片机系统的抗电源干扰电路，成功地解决了这一问题。TL7705A是美国德克萨斯仪器公司推出的产品，它能在短时间内（500us）对所监测电源上的瞬态欠压，瞬间脉冲干扰，电源断电作出反应，产生可设定宽度（10～10）PS的复位脉冲。抗电源干扰电路的设计思…     

高可靠性PLC控制系统设计点滴

0引言工业控制系统的设计必须把可靠性放在第一位,设计一个可靠的PLC控制系统应从硬件和软件两方面着手。1硬件设计1.1合理的电路设计大功率感性负载的通断会引起火花,火花的频带包含低频到高频,容易对PLC造成干扰。消火花电路可有效减少火花带来的干扰,直流电路可在负载并联继流二极管,交流电路可在负载并联阻容或压敏电阻。大功率电动机起动时会对电网造成干扰,多个电机同时起动时尤甚。干扰信号通过电网进入PLC,不利于系统可靠稳定运行。除了加强电源滤波外,如果允许,在程序设计时应该错开几个电机的起动时间。当PLC发生异常或者故…     

Only connect: teaching, technology and telesis

Abstract This paper describes an approach to the design of interactive multimedia materials being developed in a European Community project. The developmental process is seen as a dialogue between technologists and teachers. This dialogue is often problematic because of the differences in training, experience and culture between them. Conditions needed for fruitful dialogue are described and the generic model for learning design used in the project is explained.     

European Community policy and the market

Abstract This paper starts with some reflections on the policy considerations and priorities which are shaping European Commission (EC) research programmes. Then it attempts to position the current projects which seek to capitalise on information and communications technologies for learning in relation to these priorities and the apparent realities of the marketplace. It concludes that while there are grounds to be optimistic about the contribution EC programmes can make to the efficiency and standard of education and training, they are still too technology driven.     

一种自适应子融合集成多分类器方法

融合集成方法已经广泛应用在模式识别领域,然而一些基分类器实时性能稳定性较差,导致多分类器融合性能差,针对上述问题本文提出了一种新的基于多分类器的子融合集成分类器系统。该方法考虑在度量层融合层次之上通过对各类基多分类器进行动态选择,票数最多的类别作为融合系统中对特征向量识别的类别,构成一种新的自适应子融合集成分类器方法。实验表明,该方法比传统的分类器以及分类融合方法识别准确率明显更高,具有更好的鲁棒性。     

Avoiding semantic and temporal gaps in developing software intensive systems

Development of software intensive systems (systems) in practice involves a series of self-contained phases for the lifecycle of a system. Semantic and temporal gaps, which occur among phases and among developer disciplines within and across phases, hinder the ongoing development of a system because of the interdependencies among phases and among disciplines. Such gaps are magnified among systems that are developed at different times by different development teams, which may limit reuse of artifacts of systems development and interoperability among the systems. This article discusses such gaps and a systems development process for avoiding them.     

Designing economic np control charts: A programmed simulation approach

This paper presents control charts models and the necessary simulation software for the location of economic values of the control parameters. The simulation program is written in FORTRAN, requires only 10K of main storage, and can run on most mini and micro computers. Two models are presented - one describes the process when it is operating at full capacity and the other when the process is operating under capacity. The models allow the product quality to deteriorate to a further level before an existing out-of-control state is detected, and they can also be used in situations where no prior knowledge exists of the out-of-control causes and the resulting proportion defectives.     

The development of robot art

Going through a few examples of robot artists who are recognized worldwide, we try to analyze the deepest meaning of what is called “robot art” and the related art field definition. We also try to highlight its well-marked borders, such as kinetic sculptures, kinetic art, cyber art, and cyberpunk. A brief excursion into the importance of the context, the message, and its semiotics is also provided, case by case, together with a few hints on the history of this discipline in the light of an artistic perspective. Therefore, the aim of this article is to try to summarize the main characteristics that might classify robot art as a unique and innovative discipline, and to track down some of the principles by which a robotic artifact can or cannot be considered an art piece in terms of social, cultural, and strictly artistic interest. This work was presented in part at the 13th International Symposium on Artificial Life and Robotics, Oita, Japan, January 31–February 2, 2008     

Explanation and prediction: an architecture for default and abductive reasoning

Although there are many arguments that logic is an appropriate tool for artificial intelligence, there has been a perceived problem with the monotonicity of classical logic. This paper elaborates on the idea that reasoning should be viewed as theory formation where logic tells us the consequences of our assumptions. The two activities of predicting what is expected to be true and explaining observations are considered in a simple theory formation framework. Properties of each activity are discussed, along with a number of proposals as to what should be predicted or accepted as reasonable explanations. An architecture is proposed to combine explanation and prediction into one coherent framework. Algorithms used to implement the system as well as examples from a running implementation are given.     

Three Process Perspectives: Organizations, Teams, and People

This paper provides the author's personal views and perspectives on software process improvement. Starting with his first work on technology assessment in IBM over 20 years ago, Watts Humphrey describes the process improvement work he has been directly involved in. This includes the development of the early process assessment methods, the original design of the CMM, and the introduction of the Personal Software Process (PSP)^SM and Team Software Process (TSP){^SM}. In addition to describing the original motivation for this work, the author also reviews many of the problems he and his associates encountered and why they solved them the way they did. He also comments on the outstanding issues and likely directions for future work. Finally, this work has built on the experiences and contributions of many people. Mr. Humphrey only describes work that he was personally involved in and he names many of the key contributors. However, so many people have been involved in this work that a full list of the important participants would be impractical.     

基于复小波噪声方差显著修正的SAR图像去噪

提出了一种基于复小波域统计建模与噪声方差估计显著性修正相结合的合成孔径雷达(Synthetic Aperture Radar,SAR)图像斑点噪声滤波方法。该方法首先通过对数变换将乘性噪声模型转化为加性噪声模型,然后对变换后的图像进行双树复小波变换(Dualtree Complex Wavelet Transform,DCWT),并对复数小波系数的统计分布进行建模。在此先验分布的基础上,通过运用贝叶斯估计方法从含噪系数中恢复原始系数,达到滤除噪声的目的。实验结果表明该方法在去除噪声的同时保留了图像的细节信息,取得了很好的降噪效果。     

How do children do mathematics with LOGO?

Abstract  This paper considers some results of a study designed to investigate the kinds of mathematical activity undertaken by children (aged between 8 and 11) as they learned to program in LOGO. A model of learning modes is proposed, which attempts to describe the ways in which children used and acquired understanding of the programming/mathematical concepts involved. The remainder of the paper is concerned with discussing the validity and limitations of the model, and its implications for further research and curriculum development.