Design Of Control Subsystem For Laser Power Supply

In recent years,the requirement of the power supply control system is increasing,which makes the traditional power control system no longer meet the people's demand for the reason of such drawbacks as low digital level,poor real-time performance,low accuracy and reliability.While with the development of power electronics,power devices and digital chips,increasing attention has been paid on the power control system of embedded devices since it has the advantage of high real-time performance,good reliability,real-time performance for communicating and diagnosing and processing of fault when compared with the traditional power systems.As a consequence,the control system to embedded power supply is more prospective in the field of research and industry.Based on this,this thesis designs a laser power control subsystem based on embedded devices.In this system,AVR microcontroller is the core control chip and circuits such as a multi-channel measurement signal conditioning circuit,isolation and driving circuit between analog signal and digital signal,communication unit and pulse forming unit are included.This system can be used to send control commands and configuration parameters,The data acquisition of voltage,current and temperature is mainly used in the system to achieve supervisory control of the operation state of laser power in real time and to ensure the normal operation of the power supply so that a laser emits light in a preset process by simply clicking a button.Moreover,fault diagnosis of power supply working state by data acquisition is used to timely detect faults and alarm to get many functions such as resistance of electrical surge breakdown,power-off protection and over-current protection,and then to avoid production accidents,thus saving a lot of manpower and accident expenditure.The hardware circuit of the laser power control system is designed based on ATMEL's MCU chip ATxmega128A1 as the core controller,including hardware part of CAN communication,current source circuit design,protection circuit and overcurrent protection circuit of temperature control system,driving current is controlled with the basis of the theory of inverse feedback while temperature is controlled on the foundation of the closed-loop control.With the base of the hardware circuit,the software is accomplished with AVR Studio platform of ATMEL with C language,realizing such function as data acquisition,fault diagnosis and the controlling of pulse signal generating.In this thesis,the whole structure is given and this system was debugged both in the lab and industrial field,and met the control demand of laser power.The result of test shows that system can achieve such functions as transferring and receiving of messages,diagnosing and processing of fault with good reliability and real-time performance for communicating.the stable output current(0.5-6 A)can be tunable above 20%duty cycle in the laser power,and the current deviation rate of driving circuit of laser can be controlled at 0.02%while the temperature offset proves to be controlled at ± 0.005°.In addition,the design of electrical isolation circuit further improves the anti-interference ability of the system;meanwhile,the software design part adopts the top-down modular design method strengthening the portability of the system.