The Design And Implementation Of High Precision Programmable Control DC Current Source

DC current source, as a branch of the DC power supply, has been widely used to many fields, such as scientific department, electricity power sector, measuring and testing sector. High-precision DC current source not only provide a stable output current for the device as a constant current source, but also be used to calibrate low-grade DC ammeter, resistance boxes and other measuring equipment as a standard source. Therefore, to develop a high-precision, low-ripple, wide-range and programmable DC current source become an important research direction of the power industry.This paper first describes the overall design and theoretical basis of the high-precision programmable DC current source, and then sub-chapter elaborates the design of hardware and software for the current source, and in detail analysis the applications of fuzzy control in terms of to adjust output current of DC current source with MATLAB simulation software. Finally, in accordance with the technical specifications of the DC current source were tested and analyzed and summarized outlook.The hardware system, based on STM32F103 micro-controller chip as the core of control, is composed of the auxiliary power supply module, digital control module,voltage to current converter module, range auto switch module, A/D sampling module,D/A converter module, the protection circuit, and so on. The software system consists of upper computer software and lower position machine software, the former to achieve the design of man-machine interface, the latter to achieve the adjustment of output current, automatic range switching and other functions, the PC transfer data to the current source via Ethernet communication.High Precision Programmable DC Current Source uses dual closed-loop construction, the inner loop improved the stability of the DC current source’s output current by the hardware PI regulator form a series of negative feedback, the outer loop improved the current accuracy by the fuzzy controller form a series of negative feedback to regulate the output current. The part of DC sampling used the anti-pulseinterference median filter algorithm to process the sampled data to reduce system errors and improve measurement accuracy. In terms of hardware and software design have been improved and optimized, integrated application hardware circuit anti-jamming technology, in the design of the PCB also optimize the layout of components and signal traces to reduce noise and output ripple; in the part of software designed fuzzy control algorithm to adjust the output current and accurate control power output, using a least squares method algorithm for the system calibration of DC current source.