设计要求；设计一可调恒流源电路，输出电流范围2mA～20mA,最小刻度0.5mA,波动小于0.1 mA

可调恒流源设计

摘要

本系统以直流电流源为核心，MC34063为主控制器，通过电位器来设置直流电源的输出电流，并可由数码管显示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(AD0804)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。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， 通过数据形式的反馈环节，使电流更加稳定，这样构成稳定的压控电流源。

关键字:MC34063，恒流源，单片机，A/D

Adjustable constant current source design

Abstract

In this system the DC source is center and MC34063 is main controller, output current of DC power can be set by a potentiometer which step level reaches 1mA, while the real output current and the set value can be displayed by LED. In the system, the digitally programmable signal from SCM is converted to analog value by DAC (AD0804), 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. On the other hand, The constant current source can be monitored by the 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 so that output current is more stable, so a stable voltage-controlled constant current power is designed..

Key wards: MC34063, constant current source, single chip microcomputer, A/D

目 录

1 引言2

1.1研究目的和意义2

1.2国内外发展状况2

1.2.1国外发展现状3

1.2.2国内发展现状3

1.3 本文欲采取的研究方法4

2 设计方案5

2.1 总体方案5

2.2 MC34063恒流源系统6

2.3 电流显示系统7

2.3.1 单片机STC10F08XE8

2.3.2单片机晶振部分9

2.3.3 单片机复位部分10

2.3.4 数码管显示部分11

2.3.5 电流采样处理部分12

2.4 整体电路13

2.5 系统PCB图13

3 硬件介绍14

3.1 MC34063恒流源系统14

3.1.1 MC34063介绍14

3.2 电流显示系统16

3.2.1 单片机STC10F08XE16

3.2.2 模数转换介绍18

3.2.3 显示部分20

4 软件设计21

4.1 单片机选择21

4.2 编程软件介绍21

4.3 系统软件流程21

4.4 单片机程序22

5 实物说明及实验部分28

5.1 实物说明28

5.2 误差计算29

5.3 实验部分29

5.3.1 第一组实验29

5.3.2 第二组实验32

总 结35

参考文献36

致 谢38

1 引言

恒流源又叫电流源、稳流源，理想的恒流源具有以下特点：不因负载(输出电压)变化而改变；