双闭环控制精密直流信号源的研究与设计

发布时间：2018-09-01 13:34

【摘要】：在科学研究或电子产品测试中,需要用到各种信号源,提供电压或电流信号给被测系统以确定被测系统各项性能参数。本文有针对性地提出了一种输出范围在0-10V内任意可调,精度为0.01%的直流信号源设计方法,该方法以4个12位DAC叠加来实现高精度D/A转换,通过单片机进行输出控制,并利用片外24位A/D构建了反馈校正模块,建立了一个闭环控制系统,从而有效提高了系统的整体精度。该信号源在硬件上分为以下几个模块:电源模块、按键与显示模块、RS232通讯模块、基准源模块、D/A转换模块、运算放大模块、A/D转换模块及MCU主芯片模块。文中详细介绍了各模块的工作原理及电路设计过程,为保证精度,各模块采用线性电源供电,A/D及D/A转换器的参考电压均由外部具有极低温漂的基准源提供,闭环电路由24bit ADC构建,校准数据储存在外部32KB*8bit的EEPROM中,电路中所有运放均具有极低的失调电压,确保输出稳定。软件设计采用模块化思路设计,使用C语言编写,包括按键与显示、A/D和D/A控制、电压校正算法及输出调整等。主程序设计成状态机,分别为校验模式,输出模式,停止模式。校验模式通过采样80组数据完成校正表的建立;输出模式主要完成用户设定值的输出,通过调用校正表中的数据采用增量式PID控制完成输出调整并进行OLED显示;停止模式下通过控制ADC通道关闭,输出停止。经调试样机及输出测试,所设计的直流信号源精度达到了0.01%,性能稳定可靠,不仅满足了设计要求,还节约了成本,适用于一般的电路测试,也适用于其他需要高精度直流信号的场合。
[Abstract]:In scientific research or electronic product testing, it is necessary to use various signal sources to provide voltage or current signals to the system under test to determine the performance parameters of the system under test. In this paper, a design method of DC signal source with adjustable output range of 0-10V and accuracy of 0.01% is proposed. The method uses four 12-bit DAC superposition to realize high-precision D- A conversion, and the output is controlled by single chip microcomputer. The feedback correction module is constructed by using 24 bit A / D, and a closed loop control system is established, which effectively improves the overall accuracy of the system. The signal source is divided into the following modules: power supply module, key and display module RS232 communication module, reference source module D / A conversion module, operation amplifier module A / D conversion module and MCU main chip module. In this paper, the working principle and circuit design process of each module are introduced in detail. In order to ensure accuracy, the reference voltages of each module are supplied by external reference sources with extremely low temperature drift, which are supplied by the reference voltage of the A / D and D / A converters supplied by linear power supply. The closed-loop circuit is constructed by 24bit ADC and the calibration data is stored in the EEPROM of the external 32KB*8bit. All the operational amplifiers in the circuit have extremely low offset voltage to ensure the output stability. The software design is based on modularization and C language, including the control of key and display, voltage correction algorithm and output adjustment, etc. The main program is designed as a state machine, check mode, output mode, stop mode. The calibration mode completes the establishment of the calibration table by sampling 80 sets of data, the output mode mainly completes the output of the user set value, and the data in the correction table is controlled by incremental PID to complete the output adjustment and OLED display. In stop mode, the output stops by controlling the ADC channel. After debugging the prototype and testing the output, the precision of the designed DC signal source is up to 0.01, and the performance is stable and reliable, which not only meets the design requirements, but also saves the cost, and is suitable for the general circuit test. It is also suitable for other occasions where high precision DC signals are required.
【学位授予单位】：苏州大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN792

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