介绍了一种闭环智能数控直流电流源的设计原理和实施方案，该方案采用自行设计制作的高精度电压源，利用单片机、PWM和运算放大器构成A/DD/A转换器来控制场效应管导通状态的原理，达到了输出恒流的目的。整个系统采用89C58单片机作为主控部件，将预置电流值数据送入D/A转换器，经硬件电路变换为恒定的直流输出，同时使用采样电阻将实际输出电流转换成电压送入A/D转换器，并将其反馈到单片机中构成闭环系统，进而实现预设值和实际值的比较，再通过调整D /A转换器输出的电压来改变场效应管的导通状态，减小了实际值与预设值之间的误差，实现了电流可预置、可步进调整、输出的电流信号可直接数字显示的功能。采用硬件闭环、软件闭环、软件实时积分、实时滤波的方法，锁定输出电流，从而实现了高精度恒流源的目的。此次所设计的电流源具有精度高、结构简单、工作稳定、操作方便、成本低廉、带负载能力强等优点-The scheme adapts high precision voltage source designed by ourselves Micro Control Unit (MCU) D/A converter and amplifier to control the transmitting state of field effect transistor which attains constant current. The system adapts MCU 89c52 as main control part the output current is transformed into the voltage by sample resistant and the voltage is sent to D/A converter and then sent to the MCU compared with the setting current. If there exist errors we should adapt D/A converter output and change the transmitting state of field effect transistor. The actual value is directed to the setting value. The direct current reaches the constant value. The closed loop control and PID arithmetic is used to realize high precision and wide range in the software design part. The intelligent current source realizes that the output current can be preset adjusted step by step and displayed in digit directly. Above functions are operated by keyboard within the current source. The stability of this