论文编号:CK046论文字数:10179,页数:34
摘 要
光谱仪在检测过程中，只有光源保持较高稳定性的前提下，才能保证测量得到的吸光度值准确可靠。要使溴钨灯其光辐通量稳定在0.1%内,相应的供电电压波动要在0.1%以下，所以必须配套专用的光源供电电源。鉴于设计要求故要求恒流源有稳定的输出电流，而且精度要求较高。
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4mA，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（AD7543）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。
关键词：压控恒流源；智能化电源；闭环控制
Abstract
Spectroscope in examination process, only then the photo source maintains under the high stable premise, can guarantee the survey obtains extinction value accurate reliable. Must make the bromine-tungsten lamp its light spoke flux to stabilize in 0.1%, the corresponding power line voltage fluctuation must below 0.1%, must therefore form a complete set the special-purpose photo source electric power supply. Therefore in view of the fact that the design requirements the request constant current has the stable output current, moreover the accuracy requirement is high.
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 4mA, 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 (AD7543), 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 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.
Keywords: voltage-controlled constant current source；intelligent power；closed loop control
目 录
1 前 言2
2 系统原理及理论分析3
2.1单片机小系统组成3
2.2系统性能3
2.3恒流原理3
3总体方案及模块电路设计6
3.1总体方案论证及比较6
3.2 恒流源方案选择7
3.3反馈闭环方案选择8
3.4控制单元方案选择8
3.5电源方案选择10
4 软件设计11
4.1 AT89S52简介11
4.1.1引脚结构及功能12
4.2主程序模块MAIN14
4.3闭环比较子程序模块BIHUAN14
4.4电流设置子程序模块SETUP16
4.5键盘中断子程序模块KEYSCAN16
4.6显示中断子程序模块LED18
5 系统的调试21
5.1 数字电路部分的调试21
5.2 数据测试及分析21
5.2.1输出电流测试21
5.2.2步进电流测试22
5.2.3工作时间测试22
5.2.4误差分析23
5.2.5纹波电流测试23
6 总 结24
7 致 谢25
高稳定性卤钨灯光源的研制......