1、 I 摘 要 恒流源在实际工 程中是一种 用途广泛的 供电设备。 本系统 以 AT89S52 单片机为主控制器， 通过键盘可以设置直流电源的输出电流， 设置步进等级可达 1mA，并可由数码管显示实际输出电流值和电流设 定值。系统由单片机程控输出数字信号，经过 D/A 转换器输出模拟量， 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。设计出了
2、能精 确输出 20mA2000mA 数控可调直流恒流源。实际测试结果表明，本 系统实际应用于需要高稳定度小功率恒流源的领域。 关键词关键词：恒流源；AT89S52 ；D/A II Abstract Const current source is a widely used power supply equipment in engineering .In this system the DC source is center and 89S52 version single chip microcomputer (SCM) is main controller, output current
3、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 LED. In the system, the digitally programmable signal from SCM is converted to analog value by DAC , then the analog value which is isolated and amplified by operati
4、onal 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
