基于单片机的数控恒流源设计

摘要

本系统以直流电流源为核心，AT89S52单片机为主控制器，通过键盘来设置直流电源的输出电流，设置步进等级可达1mA，并由液晶显示（LCD）显示出实际输出电流值和电流设定值。本系统由单片机程控输出数字信号，经过D/A转换器（TLV5638）输出模拟量，再经过运算放大器隔离放大，控制输出功率管的基极，随着功率管基极电压的变化而输出不同的电流。在通过键盘设定好需要输出电流值后，单片机对设定值按照一定的算法进行处理。经D/A输出电压控制恒流源电路输出相应的电流值。单片机系统还兼顾对恒流源进行实时监控，输出电流经过电流/电压转变后，通过A/D转换芯片，实时把模拟量转化为数据量，再经单片机分析处理，通过数据形式的回馈环节，使电流更加稳定，这样构成稳定的压控电流源。实际测试结果表明，本系统与传统稳压电流源相比，具有操作方便、输出电流稳定度高的特点。

关键词：直流电流源；单片机；压控电流源

ABSTRACT

In this system the DC source is center and 89S52 version single chip microcomputer (SCM) is main controller, output current of DC power can be set by a keyboard which step level reaches 1mA, while the real output current and the set value can be displayed by LCD. In the system, the digitally programmable signal from SCM is converted to analog value by DAC (TLV5638), then the analog value which is isolated and amplified by operational amplifiers, is sent to the base electrode of power transistor, so an adjustable output current can be available with the base electrode voltage of power transistor. Using the keyboard to set the needed output current value, The SCM based on some specific algorithm to deal the certain settings for processing. Corresponding voltage output by the ADC output voltage-controlled current source circuit.On the other hand, The constant current source can be monitored by the SCM system real-timely, its work process is that output current is converted voltage, then its analog value is converted to digital value by ADC, finally the digital value as a feedback loop is processed by SCM so that output current is more stable, so a stable voltage-controlled constant current power is designed. The test results have showed that this system, compared with the traditional regulated current source, has easy to operate and features high output current stability.

KEY WORDS:DC Current Source；single chip microcomputer(SCM)；V oltage-controlled -current source

目录

第一章绪论 ........................................................................................... 错误!未定义书签。

1.1恒流源的发展历程 ......................................................................... 错误!未定义书签。

1.1.1 电真空器件恒流源的诞生...................................................... 错误!未定义书签。

1.1.2 晶体管横流源的产生和分类.................................................. 错误!未定义书签。

1.1.3 集成电路恒流源的出现和种类................................................ 错误!未定义书签。

1.2恒流源意义....................................................................................... 错误!未定义书签。

1.3课题的主要内容............................................................................... 错误!未定义书签。

1.4论文的总体结构............................................................................... 错误!未定义书签。第二章方案论证.................................................................................. 错误!未定义书签。

2.1系统简介........................................................................................... 错误!未定义书签。

2.2系统总体设计................................................................................... 错误!未定义书签。

2.3方案论证 ........................................................................................... 错误!未定义书签。

2.3.1 主控器................................................................................................................... - 5 -

2.3.2 供电电源.................................................................................... 错误!未定义书签。

2.3.3 恒流源........................................................................................ 错误!未定义书签。

2.3.4 D/A和A/D转换器的选取 ........................................................ 错误!未定义书签。

2.3.5 输出电流检测............................................................................ 错误!未定义书签。

2.3.6 键盘............................................................................................ 错误!未定义书签。

2.3.7 显示............................................................................................ 错误!未定义书签。第三章系统硬件设计 ............................................................................................... - 11 -3.1主控电路设计 ................................................................................... 错误!未定义书签。

3.2供电电源设计 ................................................................................. 错误!未定义书签。

3.2.1 主电源........................................................................................ 错误!未定义书签。

3.2.2 单片机电源................................................................................ 错误!未定义书签。

3.3恒流源电路设计............................................................................... 错误!未定义书签。

3.4D/A转换电路设计 ......................................................................... 错误!未定义书签。

3.5电流检测电路设计........................................................................... 错误!未定义书签。

3.5.1电流检测原理介绍..................................................................... 错误!未定义书签。

3.5.2 采样电阻的计算...................................................................... 错误!未定义书签。

3.6键盘电路设计................................................................................... 错误!未定义书签。

3.7显示电路设计................................................................................... 错误!未定义书签。第四章系统软件设计 ........................................................................ 错误!未定义书签。

4.1控制算法 ........................................................................................... 错误!未定义书签。

4.2系统软件的结构 ............................................................................... 错误!未定义书签。

4.2.1 总体流程.................................................................................... 错误!未定义书签。

4.2.2 按键部分流程图........................................................................ 错误!未定义书签。

4.2.3 LED显示中断子程序流程图 .................................................... 错误!未定义书签。