摘要：恒流源又叫稳流源、电流源。 目前，在传感器技术、现代通信以及超导等高科技领域，恒流源被广泛应用，它在一些高新技术中起着关键作用，提供高效率、高质量、和高可靠性的电源，具有良好的应用发展。79849

本文设计的列车车载恒流源是一种基于51单片机控制的直流恒流源，选择单片机STC89C51作为主控芯片，核心是稳流源和直流稳压电源，与单片机的最小系统结合控制输出电流。本次设计通过独立式按键电路与单片机相连接，读入控制数据，通过LED数码管可以显示数控电源的输出电流设定值，再利用软件进行判断，从而起到控制电源输出的作用。单片机依照键盘的设定之后计算出恒流的数值，接着送到PCF8591的数模转换器，因为数模转换器的输出电压和恒流电路是有一定比例的，所以就可以通过计算得到恒流值的大小。

这款设计实现了较为简单的人机对话，拥有设计简单、控制方便、调节清晰、容易携带、低成本等优势，拥有比较强的实用性。

关键词： 恒流源；单片机；D/A转换

Design of train mounted constant current source

Abstract: The constant current source and the current source, a current source。 At present, the sensor technology, modern communications and other high-tech fields of superconducting, constant current source has been widely used in some high-tech, it plays a key role in providing efficient, high quality, high reliability and power supply, has good prospects for development。

    Train the design of the constant current source is a DC constant current source based on 51 single chip control, select the MCU STC89C51 as the main control chip is the core of the current source and DC power supply, combined with the smallest single-chip system to control output current。 The design is connected by independent type key circuit and single-chip microcomputer control data read can display the set value, the output current of the control power through the LED digital tube, then using the software to judge, and thus play a role in controlling the output power。 After setting the keyboard microcontroller according to calculate the constant current value, and then sent to the DAC PCF8591, because There is a certain ratio between the output voltage of the digital to analog converter and the constant current circuit, so the magnitude of the constant current can be calculated。

This design has achieved a relatively simple man-machine dialogue, with simple design, convenient control, clear adjustment, easy to carry, low cost and other advantages, with relatively strong practicability。

Key words: constant current source; single chip microcomputer;D/A conversion

目录

1 绪论 1

 1。1 课题的目的和意义 1

 1。2 恒流源的发展历程和趋势 1

 1。3 恒流源的应用 2

  1。3。1 在半导体器件参数的测量上的应用 2

  1。3。2 在计量领域中的应用 3

  1。3。3 在物理试验中的应用 3

  1。3。4 在其它领域中的应用 4

 1。4 引起稳定电源输出不稳定的主要原因 4

 1。5 本文的主要工作与内容安排 5

2 硬件电路的设计 6

 2。1 恒流源设计方案选取 6

  2。1。1 恒流源的三种设计方案