The Design Of DC Constant-Current Source Controlled Based On SCM

At present, the technique of power supply is becoming a comprehensive technique imbued with multiplex techniques and playing a crucial role in providing the power supply with high quality and high efficiency to the following fields: telecommunication, technical instruments, computer, industrial automatic control, electric power engineering, national defence as well as some high-technology industry.In the paper we designed a DC constant-current power controlled based on SCM. The system adopt AT89S52 as hard core and the main circuit of constant-current source consist of darlington device TIP122 and operational amplifier OP07 which has high CMRR(Common Mode Rejection Ratio) and low temperature shift. Moreover, we adopt 12 bit D/A chip MAX532 and 16 bit A/D chip AD7715 to realize a real-time test and control to the current output controlled based on SCM. The display interface with 4×4 keyboard technique and LED enables operator to read the screen more intuitively.This paper adopt incremental PID control algorithm in software design,namely the output of digital controller is just the increment of controlled variable. Incremental control is a little improvement at algorithm. However, it has some advantage as follows: first, accumulating is not needed in equation, the decision of increment is just involved in last three sampling values and it can obtain good controlled effect with weighted processing. Next, the computer output only controlled increment every time, namely the variable value of position corresponding operator. So the range of influence is small and it will not affect the production process when the machine get out of order.In the end, the paper measured the primary parameter of the constant-current source. And it confirmed that the system has reached the anticipated objective. This system armed comprehensive functionalities in the following aspects: power suit, high credibility, simple circuit design. It can be used flexibly in the domain which in a demand of high-stable constant-current source with small power.