Design Of TWT High-voltage Power Supply With Digital Control

Microwave power module(MPM)is composed of mini-traveling wave tube(TWT),solid state amplifier(SSA),and electronic power conditioner(EPC),which has the advantages of small volume,high efficiency,and high SNR.In order to meet the needs of military and civil applications,the modern microwave system puts forward more and more strict requirements for the power,efficiency,and volume of EPC.TWT high-voltage power supply is the key component of the EPC and to improve the overall performance of MPM,an efficiency and reliability design method of TWT high voltage power supply should be developed.In this paper,a TWT high-voltage power supply based on digital control technology is designed,which meets the working requirements and achieves high efficiency under full-load condition.The main contents are as follows:1.A FM-burst hybrid control strategy for LLC resonant voltage-multiplying converter is proposed,and the efficiency of the converter is improved under light-load condition.The working principles and characters of converter in two operating modes are analyzed.The FM control is employed to obtain high efficiency under full-load condition and the burst mode is adopted to decrease gain and loss under light-load condition or excessive voltage inputted.The method is improved to decrease the ripple of the voltage-multiplying circuit,and the safe switch is achieved in burst model by judging the resonant current.Compared with FM method,the converter is efficient under full-load condition using this method.2.The main circuit of the high voltage power supply is designed,which satisfies the demands of the TWT power supply.In order to realize multi-channel high voltage output,multilevel rectifier series output mode is adopted.The high voltage planar transformer is designed to realize the development of the super-thin power supply,which solves the technical problems of high power density.At last,the design steps of the main circuit are described,involving the parameter design of the resonant circuit,multi-stage voltage rectifier circuit and high voltage planar transformer.The development process of the high voltage planar transformer is introduced in detail as well.3.The implementation scheme of the digital control system is described,and the FM-burst hybrid control strategy is achieved.In order to solve the hardware circuit's high-voltage isolation problem,isolating driver circuit,negative voltage isolation linear sampling circuit,and resonant current detecting circuit are designed.According to the system requirements,DSP is chosen as the controller and the program flow chart of the digital control method is introduced.Finally,the digital control method is used safely in the TWT high-voltage power supply,and the high sampling precision and control performance of system is satisfied.4.An experimental prototype is made and based on the test results,the parameters and the design method is validated to be correct and rational.Tests also show that the hybrid control strategy has better efficiency curve than the original frequency conversion strategy under light-load condition.