Research On The Filament Power Supply For High-Voltage Accelerator Application

With the development of the irradiation processing technology,the traditional cobalt source has been gradually replaced by the high voltage electron accelerator which is widely used in sewage treatment,medical and health,food preservation for its clean,environmental protection and high efficiency.High voltage electron accelerator has two power supply,that is,high voltage power supply(HV-PS)and filament power supply(F-PS).F-PS provides the current through the filament in electron gun to emit electron beam,the electron beam is accelerated by the strong electric field in the electron tube via HV-PS,and finally reaches the target.In order to ensure the safety and reliability of the high voltage electron accelerator,the design of F-PS has meet many requirements,such as strong stability,good thermal performance,wide output regulation.Compared with the traditional transformer modulation,the power electronic converter is easier to meet the requirements.This paper proposes an optimized separate series resonant converter for such an F-PS.The high-frequency transformer is placed very near to the low voltage and high current filament to reduce the conduction loss on the secondary-side wires,and the parasitic inductance of the wires,transformer and filament can be fully utilized as resonant components.The H-bridge with zero voltage switching is used in the required load range by setting the appropriate switching frequency,so that the thermal problem can be alleviated in the vacuum environment.In the case of large output current regulation,the series resonant converter needs to work in a wider frequency band,which is not conducive to the design of the transformer and the magnetic components.In order to solve the problem,the H-bridge is proposed to be operated in either half-bridge or full-bridge structure to narrow the switching frequency range.A special switching strategy is also proposed to eliminate the oscillation of voltage and current during structure switching,ensuring the safety operation of converter and the stable vacuum environment around the filament.Finally,a prototype of the converter has been built.The experimental results match well with the theoretical analysis,and the feasibility of the proposed control strategy is verified.