The Research Of Critical Techniques Of Super Fast Scanning Power Supply

The lastest data in 2020 shows that the number of new cases of malignant tumors in China has reached 3.929 million annually,and the number of deaths has reached2.338 million.Comparing to traditional radiotherapy,chemotherapy,surgery and other treatment methods,Proton Therapy is one of the treatemt which rarely effect healthty cells on human body.Based on its unique Bragg Peak effect of proton beams,Proton Therapy attarcts lots of attation among today’s internationl reasearch.The design and manufacture of scannning power supply is a critical techniques for the manfacture of beam deliver system of Proton Therapy equipment.There are a limited number of reference articles about scanning power due to the confidientiality of commerical scanning power supply.To meet meet the requirement for a futher improvement of scanning speed,this article introdues the circuit topology,simulation and digital control strategy of this power supply.Two scanning power supplies have been built and tested due to the demand of proton treatment system.The maximum output current of SCAN-V-PS is±700,the current rising slope is bigger than 906)/,the ripple ratio of load current is less than1008).The maximum output current of SCAN-U-PS is±450,the current rising slope is bigger than 1606)/,the ripple ratio of load current is less than1008).The steep varation of induced voltage from 0V on steady state and 1183 V duing current rising process will seriously damaginig the stability of this power supply.In the fullfillment of these two paradoxical demands.A power supply based on IGBT H-bridge and MOSFET H-bridge has been designed.This circuit topology series these two types of H-bridge circuits together,acquirnig a high current rising slope of IGBT H-bridge,high precision current and low ripple current of MOSFET H-bridge simultaneously.Matlab,Math CAD,CCS were used during the research and design process of this power supply.This article educed the small signal model of phase shifted full bridge circuit.The parameters of PI compensation loop was identified by the transfer function of this model.Modular design and phase-shifted full bridge control were adopted by this power supply thus increase the ripple frequency of load current.To achieve passive current sharing and high stability,several phase-shifted full bridge circuit output in parallel,each of them has an L filter in series,thus decrease the demand of PWM output ports number.Based on deep negative feedback principle,big signal analysis were used to analyze the critical parameters when current fast jumps.The matlab simulation results manifested these analysis.The actual experiments’ result proves the overall caculation and resonable structure of this power supply are theoritical correct.The super fast scanning power reaches all technique requirements.