湖 南 科 技 大 学 毕业设计（论文）答辩记录
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摘 要
电子负载与传统的模拟电阻性负载相比具有节能、体积小、效率高等优点，在电源、通讯、汽车、蓄电池等领域得到了较好的应用，并已成为当前研究的热点。电子负载由数字控制器、检测与驱动电路、通讯电路等组成，数字控制器控制MOSFET或晶体管的导通量（占空比大小），实现对电源参数的稳定控制。
本设计主要包括两部分：数据采集及相关动作的下位机和实现远程监控的上位机。 下位机从直流电子负载系统方案分析入手，讨论了整个系统的硬件电路和软件实现，并给出较为合理的解决方案。为便于控制的实现和功能的扩展，采用了ATMEL公司的AVR单片机ATmega88作为核心控制器，设计了控制电路、检测电路、通讯电路和驱动电路，通过软硬件的协调配合，实现了整个设计。单片机输出不同占空比的PWM波形，控制MOS管的导通和关断时间，调节流过场效应的电流。
上位机使用Visual C++开发平台，实现了对电子负载老化电压、老化电流等数据的实时显示，上位机设置负载电流大小，电压超限报警等功能。
基于AVR单片机的电子负载监控系统实时监测输入电子负载的老化电压、老化电流，实现单个上位机监控大量下位机的功能，极大的减少了人员冗余，改善了工作人员的劳动条件，对实际生产具有指导意义。
关键词：电子负载；ATmega88；PWM；监控系统
ABSTRACT
Electronic load can save less energy and is smaller in size and more efficient than resistance load. Therefore, electronic load is generally used to power, communication, automobile, accumulator and so on. Electronic load is becoming increasingly the hotspot. The electronic load includes of digital controller, detection and driver circuit and communication circuit. Digital controls the on and off time of the MOS transistors witch expend energy of the power supply. It is realized that the parameter of the power be controlled steadily.
The system mainly was composed by two parts. One is the data acquisition and related actions for the next bit plane. The other is remote monitoring of the host computer.
The next bit plane scheme of direct current electronic load is analyzed, especially the hardware and software realization is discussed particularly in the paper, and a reasonable solution scheme is presented. For the sake of the control and functional expansion, ATmega88, AVR microcontroller produced by ATMEL Corporation, is used as the core controller of whole control circuit. Control circuit includes of detection circuit, communication circuit and driver circuit. Through the coordination of the software and hardware, the design can be realized. The microcontroller output will be PWM waveforms with different duty cycle. According to control the on and off time of the MOS transistors, the current of FET can be regulated.
The electronic load monitoring system base on AVR microcontroller monitor the input voltage and current by the electronic load in real time. Realized single host computer monitor a mass of next bit plane, greatly reducing the redundancies and tend to improve the working conditions. So it can get some guiding significance for the actual production.
Key Words: Electronic load; ATmega88; PWM; Monitoring system
目 录
第一章 绪论 ......................................................................................................................... 1
1.1 研究背景 ...................................................................................................................... 1 1.2 研究意义 ...................................................................................................................... 2 1.3 电子负载研究现状 ...................................................................................................... 2 1.4 本课题研究的内容 ...................................................................................................... 3
第二章 电子负载系统分析 ............................................................................................. 5
2.1 电子负载系统方案 ...................................................................................................... 5 2.2 硬件和软件功能的分配与协调 .................................................................................. 5
2.2.1 软件设计 ............................................................................................................ 5 2.2.2 系统软件和硬件联机调试 ................................................................................ 5 2.3 工业控制及集中控制系统 .......................................................................................... 6
第三章 系统硬件设计 ...................................................................................................... 7
3.1 核心处理器 .................................................................................................................. 7 3.2 直流稳压电源设计 .................................................................................................... 11
3.2.1 直流稳压电源的基本原理 .............................................................................. 11 3.2.2 三端固定式稳压器 .......................................................................................... 12 3.2.3 系统供电设计 .................................................................................................. 12 3.3 电压及电流数据采集 ................................................................................................ 14 3.4 I/O扩展 ....................................................................................................................... 16 3.5 PWM控制电路 .......................................................................................................... 18 3.6 通信电路设计 ............................................................................................................ 19
第四章 下位机软件设计 ................................................................................................ 22
4.1 下位机软件总体设计 ................................................................................................ 22 4.2 数据采集及计算 ........................................................................................................ 22 4.3 PWM程序设计 .......................................................................................................... 24 4.4 I2C程序设计 .............................................................................................................. 25 4.5 通信程序设计 ............................................................................................................ 31
4.5.1 单片机USART0口 ......................................................................................... 31 4.5.2 通信协议 .......................................................................................................... 34 4.2.3 电压电流数据采集 .......................................................................................... 35
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