Precision Digital Switching Power Supply System

As the developing of electronics industry,the power supply in electronic devices developed from linear power supply to SMPS(Switching Mode Power Supply).The SMPS takes more and more important role in electronic industry,and is applied in many field,such as communication, computer,automation,military,industry,agriculture,etc. High resolution digital SMPS becomes the hotspot in the power supply field.More and more attention has beed payed to how to realize high resolution digital SMPS,and it has already taken a long step develop.Improving the resolution of digital SMPS by new techniques becomes a forever topic.Under the learning of the status and develping trend of SMPS ,considering the practical requirement of task,a control system of SMPS implemented by microcontroller with high resolution,high speed,high integration is carried out.By combining the embedded system and power electronics,it is discussed that a high resolution SMPS's output voltage with 0.01% resolution PWM wave output, in the basis of microcontroller,and the PWM wave Double modulation arithmetic.The technique of PWM wave Double Modulation is reasonable in theory.Beacuase of the great amount of system task and the high requirement of realtime performance, there are few systems were realized by now,applying this arithmetic. The task of realtime display on LCD and the complicated control arithmetic are implemented in this SMPS system,and a microcontroller with high resolution,high speed,high integration, large memory is necessary.In this paper,the design theory of S/H ware module which forms the SMPS control module and the design scheme is discussed in detail.In this system,the digital compute-control module is implemented with Samsung's high resolution,high integration,ARM core microcontroller S3C44B0 and AD converter with 16bit resolution produced by AD Company,AD7705.The AD7705 implements the data acquisition of the voltage and current feedback signal,and transfer the data to microcontroller through SPI bus,which is implemented with S3C44B0's GPIO,for computation and display.This SMPS is applied in execrable circumstances,so when designing the hardware circuit,EMC problem is also discussed,which insures the SMPS system working stability.System software design includes microcontroller application program,data acquisition program,AD7705 driver program,PID arithmetic, embedded realtime OS UCOS transplant,and other application program.The SMPS with high resolution discussed in this pager has the features of digital control,high resolution,high integration,easy operating,good anti-EMI performance.And it can be referenced for digital SMPS developing,system output resolution improving.