电子机电论文编号:JD131  字数:14905,页数:49

目录
1  电子负载的原理及概述 .....................................................1
1.1  电子负载的定义 .........................................................1
1.2  电子负载的工作方式..................................................... 1
1.2.1恒定电流方式 ...........................................................2
1.2.2恒定电阻方式........................................................... 2
1.2.3恒定电压方式 ...........................................................3
1.3  电子负载设计模块方框图..................................................3
2  电流、电压的测量技术 .....................................................4
2.1  电流的测量..................................................... ........4
2.1.1电流的检测方法......................................................... 4
2.1.2几种常用电流传感器的性能比较........................................... 5
2.1.3 ACS750型集成电流传感器的原理与应用.....................................5
2.2  电压的测量............................................................. 6
3  模数、数模与单片机接口技术............................................... 8
3.1  D/A转换器接口..................................................... .....8
3.1.1典型D/A转换芯片DAC0832................................................. 8
3.1.2运算放大器的考虑 ......................................................10
3.2  A/D转换器接口 .........................................................10
4  系统硬件设计............................................................ 13
4.1  系统显示模块.......................................................... 13
4.2  MOSFET场效管的应用.....................................................14
4.2.1 MOS型场效应管的特点...................................................14
4.2.2 MOS型场效应管的输出特性曲线 ..........................................14
4.2.3 MOS型场效应管的选型...................................................15
4.3  基准电源的产生..................................................... ...15
4.3.1 TL431介绍..................................................... .......15
4.3.2 TL431的应用..................................................... .....16
4.4  集成运放的应用 ........................................................18
4.4.1 集成运放基本反相放大电路应用..........................................18
4.4.2 集成运放基本同相放大电路应用 .........................................19
4.4.3 集成运放基本差动放大电路应用..........................................19
4.5  AT89S51单片机的应用....................................................20
4.5.1 AT89S51单片机性能特点 ................................................20
4.5.2 AT89S51各引脚图及各管脚功能...........................................21
4.6  系统保护电路的设计.................................................... 23
4.6.1过流保护.............................................................. 23
4.6.2 过压、短路保护 .......................................................24
5  系统软件设计 ............................................................25
5.1  汇编程序设计概述...................................................... 25
5.2  模块式子程序设计...................................................... 26
5.2.1  ADC0809模数转换子程序设计 ...........................................26
5.2.2  DAC0832数模转换子程序设计............................................27
5.3  电子负载程序设计流程图 ................................................27
6.1 硬件系统的可靠性设计 ...................................................30
6.1.1硬件系统的可靠性设计...................................................30
6.1.2 硬件系统可靠性设计所注意事项 .........................................30
6.2 软件系统的可靠性设计 ...................................................31
6.2.1指令冗余.............................................................. 32
6.2.2拦截技术.............................................................. 32
6.2.3软件“看门狗”技术.....................................................33
7  结论.....................................................................35
致谢 .......................................................................36
参考文献................................................................... 37
附录：电子负载设计程序..................................................... 38

摘要
本设计介绍了基于51系列单片机为控制单元，以模数转换器ADC0809测量电压电流参数，以数模转换器DAC0832输出控制电压，通过运算放大器对电流电压信号的比较放大，直接控制大功率场效管的通过电流值，吸收电源提供的大电流,从而模拟复杂的负载形式、测试电能输出装置或转换装置的输出性能。在对比传统测试所用的静态负载的基础上, 提出新型电子负载的概念, 并作了原理和电路分析及电路调试, 同时进行了功能完善及性能改善的探讨。实验证明, 该装置解决了传统测试中用电阻、电阻箱、滑线变阻器等模拟不了复杂负载的问题，能对测试电源进行恒电阻负载测试，恒电压负载测试和恒电流负载测试。
在对大功率直流电源的带负载能力测试试验中，本设计更显其自身的优越性。若对场效管进行扩展，此设计测试的最大电流可达±75A，测试最大负载功率可达500瓦。完全满足日常生活中大部分电源的带负载能力测试工作。
关键词：电子负载；单片机（MCU）；数模（D/A）；模数（A/D）。

Abstract
In this design, we introduce an equipment ,which is controlled by 51 series singlechip.By this equipment, voltage value and current value are measured using the chip of Analog to Digital Convertor ADC0809. The controlled-voltage value is formed by using the chip of Digital to Analog Convertor DAC0832. We call this equipment E-LOAD.By using this equipment, we can test the output
Level of some power supply systems. It can replace some kinds of rheostats in some areas.Different from the usual rheostats,this E-LOAD equipment can simulate most  kinds of the load.
 This article introduces a method to measure the voltage and currtnt of power system with a microprocessor.The equipment,using software, processes the data in real-time and all along the line.
It can also calculate and compensate the error of every algorithm,
And increase the precision in measurement.
 In our test,if this E-LOAD can be effectively  extended,
It can measure the current level highly at ±75A. It also can measure the power level highly at 500 Watts.

Key Words: E-LOAD, SingleChip(MCU), Analog to Digital Convertor,
           Digital to Analog Convertor.