用7109A／D实现智能仪表的自动量程转换

由7109A/D芯片构成单片机A/D接口电路,该电路通过改变A/D转换器的基准电压与积分电阻的取值实现自动量程转换功能。     

用锁相环提高A／D变换器的串模抑制比

本文阐述了用锁相环提高双积分型A/D转换器串模抑制比的工作原理,设计了锁相时钟电路。实验证明,采用这种方法可将双积分型A/D转换器测量结果的稳定度提高至少一个数量级,测量的准确度也显著提高。这种方法适用于积分型A/D转换器,且电路简单,成本低,因此具有普遍的实用价值。为目前广泛使用的双积分型数字多用表或高精度双积分型A/D转换模板配置锁相时钟电路,可显著提高仪表自身的串模抑制比,特别适用于在工频干扰强的环境中进行准确测量。     

高压直流数字微安表

本数字微安表由双积分A／D转换集成芯片ICL7135与高压保护电路组成，用于测量高压电力设备（试品）中的泄漏电流，3位半液晶显示，测量范围0－1999uA，文章较详细地介绍了测量原理，给出了电路，并对高压多级保护电路作了详细说明。     

用双积分A/D转换器进行非线性校正的实践

本文论述了在A/D转换过程中消除传感器非线性误差的方法,给出了双积分非线性A/D转换进行非线性校正的应用电路,该方法和电路已用于工程设计中,线性度达1×10~(-3),取得了良好的效果。     

称重测控系统的A/D转换电路设计

针对AD7706芯片组成的A/D转换电路硬件、软件的设计方法进行阐述与论证。实践表明,基于AD7706高精度A/D转换电路组成的称重单片机测控系统,具有测量精度高、测量速度较快、性能稳定等特点。     

一种便携式智能仪表电源系统

在便携式智能仪表中,一般都包含信号采样与放大电路、A／D与D／A转换电路、单片机等电路或器件,因此要求仪表的电源系统能够提供多种形式且稳定度高的直流电压。例如,提供高低直流电压和正负极性直流电压等。另外,这些仪表通常用干电池供电,希望电源系统本身功耗应极低,以延长电池寿命。使用三端稳压器件、变频技术或分立元件组成的变换电路,很难同时满足上述要求,     

用AVR单片机实现高性能、低成本温度A/D转换

电饭煲、热水器、空调、消毒柜等家电越来越多地采用单片机控制,提高产品智能化。温度是这些家电重要的参量,但必须通过A／D（模／数）转换才能送到单片机处理。实现温度A／D转换可用专用A／D转换芯片,或用带A／D转换的单片机,但价格较贵,8位以上的A／D转换芯片价格更是成倍增加。在竞争激烈的家电行业中,为了节省成本、提高产品竞争力,希望A／D转换价廉、分辨率高。 对于有内部比较器和端口有高阻态的单片机,可利用单片机的软、硬件资源,外接少量的电阻、电容和测温元件,就可实现高分辨率、低成本温度A／D转换。1 用AVR单…     

LIM331与PIC16F73单片机的连接与驱动

介绍了一种应用WF转换器LM331芯片组成的A／D转换电路，它具有接线简单，价格低廉，转换精度高等特点，而且LM331芯片在转换过程中不需要软件程序驱动，与AD574等需要软件程序控制的A／D转换电路相比，使用方便。     

3（1／2）位双积分A／D转换器的微机数据采集接口

本文介绍的双积分A/D 转换器组成的数字式仪表,可广泛用于工业自动化控制、环境监测等方面。文中重点介绍了MC14433,3 1/2位双积分A/D 转换芯片与微机的接口线路。     

基于Hal1传感器转速控制电路设计与实现

本文采用SS495A型号霍尔传感器设计与实现转速控制电路。即通过减法电路减去传感器自身电压,得到磁信号引起的微弱电压变化量,然后用OP07CP搭建的放大电路将电压信号改变量放大50倍,又通过抬高电路将电压信号转换为A／D转换器能识别的范围为0～5．6V正电压值后送入A／D转换器,将模拟信号转换为数字信号,由STC89C52RC单片机程序控制LCD液晶进行显示,后通过D／A转换器将数字信号转换成模拟信号控制电机转速。     

A memristive dual-slope A/D converter

As an emerging device, memristor has several excellent properties like changeable memristance, nonvolatility, and nanoscale. Based on complementary metal-oxide-semiconductor (CMOS) dual-slope analog-to-digital (A/D) converter, this paper proposes a memristive dual-slope A/D converter. Owing to the usage of memristor, the proposed memristive A/D converter not only has more compact circuit structure and simpler control timing than the CMOS one but also has advantages over the existing memristive conversion circuits in circuit design and application. For the memristive A/D converter, a conversion process consists of two count procedures. By means of controlling the memristance change in the two count procedures, the A/D converter converts an analog signal to the corresponding digital count value. Meanwhile, the conversion result is inferred according to the circuit structure of the A/D converter. Then, combining the conversion process and PSPICE simulation, this paper analyzes the anti-interference performance of the A/D converter. Further, the robustness of the A/D converter is presented, applying the similar analysis methods. The analysis results demonstrate that the proposed A/D converter has good anti-interference and robustness performances.     

一种新型双管正-反激直流变换器

该文提出一种对称式RCD箝位的倍流整流双管正-反激型直流变换器.它采用两个RCD电路交错筘位的结构,克服了传统双管正激型变换器占空比D＜0.5的缺点.在继承单管有源筘位正-反激型变换器的宽范围输入、高效率优点的同时,将主开关管电压应力降低为原来的一半.改进的RCD箝位结构是一种轻微耗散型箝位电路,大幅提高传统RCD型电路磁复位效率.该文详细分析了变换器稳态工作特性以及关键参数的设计,通过一个200V～400V输入、10V/15A输出的样机验证了该拓扑工作原理和特点.     

一种软件实现A／D转换的方法

本文以单片软件方法实现Ａ／Ｄ转换的一个应用为例，阐述这种极低成本，较高精度高的软件Ａ／Ｄ转换的原理及实现。在采集速度要求较低的场合下，可替代专用Ａ／Ｄ电路，降低系统成本，其性能价格比也高于由软件ＰＷＭ方法，比较器及ＲＣ电路组成的Ａ／Ｄ转换电路。     

一种电源-电容串联型直流变换器

提出了一种电源-电容串联型直流变换器,这种拓扑结构可以同时为两路直流电源升压,并且有效降低了半导体器件的电压与电流应力。与双路Boost型直流变换器相比,该电源-电容串联型直流变换器在不增加功率器件数量的前提下,显著降低了半导体器件的电压与电流应力,适用于分布式光伏并网逆变器的直流变换级。主要涉及该直流变换器的运行方式、电压与电流应力分析、效率对比,并通过实验验证了该直流变换器的可行性。     

A unipolar converter for a switched reluctance motor

A switched reluctance motor requires a power converter circuit to control the unipolar phase current in its phase windings. A converter circuit for a four-phase reluctance motor that uses only four switches is described. Unlike previous circuits with one switch per phase, the switches are created at the motor voltage. Each switch is connected to two of the four phase windings. The switching signals must be carefully derived so that independent control of the phase currents is maintained despite the common connections. Analysis is given to predict the ideal switching algorithm for the converter circuit. This produces the optimum torque at all speeds and currents. Experimental results are given for the performance of the proposed converter circuit as compared with that of other circuits with one switch per phase. It can be seen that for a given supply voltage and peak phase current, the novel converter circuit produces superior torque output from the motor. The low number of switches in the coinverter together with the performance of the four-phase reluctance motor will result in an ideal low-cost variable-speed drive     

An accurate reference-generating circuit for successive approximation current mode A/D converters

As pressures increase on VLSI designers to use a lower supply voltage of 3.3 V rather than the present 5 V, current mode signal-processing techniques will surely become increasingly important and attractive. This paper presents the design of a reference-generating (RG) circuit which employs a current mode divide-by-two circuit. Current dividers are usually implemented by using resistor networks or weighted transistors. the division accuracy of such solutions is limited by resistor or transistor mismatch. In this study the proposed divide-by-two circuit does not rely on well-matched components and high-gain op amps to achieve high accuracy. This paper also addresses the relationship among the operation and accuracy of the division process, the transistor mismatch and the resolution of a converter which employs the RG circuit. the proposed RG circuit can be implemented not only for medium-speed successive approximation current mode A/D converters but also for A/D converter arrays achieving a high conversion rate.     

Design and analysis of an electronic ballast with a secondary DC output

An electronic ballast circuit for a high‐frequency operated fluorescent lamp, which uses switched‐capacitor techniques, is presented in this paper. A part of energy in the electronic ballast is derived to a secondary DC output as a power supply. All the switching devices are zero‐current switching in the proposed circuit. The circuit is integrated with the function of a DC/DC converter. Therefore, the circuit has a dual functionality with simple control method. Simulation results and experimental results of the ballast with an FL‐15D lamp are used to verify the performance of the proposed circuit. Copyright © 2007 John Wiley & Sons, Ltd.     

高速DSP与串行A/D转换器TLC2558接口的设计

根据高速定点DSP芯片TMS320F206的特点，提出了使用串行A/D转换器TLC2558作为DSP系统的模拟量输入部分，解决了以往基于并行数据传输的A/D转换器不能与高速DSP进行很好配合的问题，在此基础上设计了DSP与串行A/D转换器连接的硬件电路，并就A/D转换的软件设计时应注意的问题进行了探讨。     

一种新型程控信号放大器设计及其应用

给出一种用二级D／A转换器实现程控增益变化的方法，分析了电路工作原理并给出应用实例，此种放大器增益由单片机输出的数字量控制，适用于计算机测控和智能仪表系统。     

一种新颖的并联谐振倍压变换器

提出了一种适合于高压小电流的功率变换器——并联谐振倍压变换器PRDVC)。文中对PRDVCs的工作原理进行了详细分析,给出了该电路的一个应用实例,即5kV/50m A 高压电源。此外还给出了实验波形。