Research And Equipment Development Of High Voltage And High Power Magnetron Microwave Power Supply

The microwave power supply provides stable and reliable high-voltage DC power for the anode of the magnetron,and is widely used in industrial fields.The traditional microwave power supply uses low-frequency transformer and voltage multiplier circuit to increase voltage level,which has the disadvantages of large volume,large ripple,low efficiency,and unadjustable output power,resulting in severe restriction on the development of microwave technology.With the development of power electronics technology,the DC-DC converters is developing in the direction of high frequency,miniaturization,high efficiency,high power density,and high stability.Applying the high frequency DC-DC converter to the microwave power supply can improve the efficiency of the microwave power supply,reduce its volume,and realize continuous wide-range adjustment of output power.Therefore,it is of practical significance to study a high voltage,high frequency,high power microwave power supply with high efficiency,high stability,high power density and adjustable output power.This paper takes the high voltage and high power magnetron microwave power supply device as the object,and studies its topological structure,operation mode and principle,control strategy in Burst mode,operation mode switch control strategy and other key technologies.The main research contents are the following aspects:(1)Aiming at the design requirements of high voltage output and high efficiency operation of high-voltage and high-power magnetron microwave power supply,the LCC resonant series parallel combination structure is studied.The single module of the structure is composed of a LCC full bridge inverter circuit and a voltage multiplier circuit.Based on the above topology,the basic stage of resonant tank controlled by Pulse Frequency Modulation(PFM)and Pulse Width Modulation(PWM)are analyzed in detail by time domain analysis method,and the expressions of voltage and current state variables of each basic stage are derived.Based on the basic stage of the resonant tank,under the constraints of continuity,symmetry and zero crossing of the resonance current,the operation modes of the microwave power supply under PFM control and PWM control are derived separately,and the characteristics of the different operation modes are analyzed.In high voltage and high power applications,the gain distribution and power distribution of the microwave power supply in different operation modes under PFM and PWM control.(2)Aiming at the problem of wide-range voltage regulation and high-efficiency operation of high-voltage and high-power magnetron microwave power supply,the three-degree-of-freedom coordinated voltage regulation method of switching frequency,duty cycle and Burst control period is studied.When the load is heavy,the output voltage is adjusted through the switching frequency;when the load is light,it’s adjusted through the duty cycle;when the load is extremely light,it’s adjusted through the Burst control cycle.In order to solve the problem that the existing dual pulse Burst control based on state trajectory needs to solve the polar coordinates of each inflection point,which results in large amount of calculation,complex solution process and output voltage jitter easily,this paper proposes a fixed on time Burst control method of three pulse based on the time domain analysis of the operation mode of microwave power supply,which simplifies the solution process of pulse length and eliminates the output voltage jitter.The efficiency of the microwave power is improved by the three pulse Burst control method when the load is extremely light.Aiming at the problem of voltage and current overshoot in the switching between the PWM control and the Burst control of the microwave power supply,a switching strategy based on operation mode analysis is proposed to realize the fast and smooth switching of the control method.Finally,the effectiveness of Burst control based on operation mode analysis and the feasibility of the control strategy for switching between PWM control and Burst control are verified by simulations and experiments.(3)The design of the 22 k V/120 k W high-voltage high-power magnetron microwave power supply is carried out.The parameter design of the main circuit is introduced in detail,and the control circuit of the power system and the flowchart are designed.The main circuit parameter design includes the design of high frequency inverter,the design of high frequency high voltage transformer,resonant parameter design and the design of high frequency rectifier.Among them,from the perspective of device selection,the parameters such as the voltage and current peak values of different voltage multiplier topologies are compared in detail.A22 k V/15 k W single-module high voltage magnetron microwave power supply experimental platform was built according to the resonance parameters.The rated operating points were verified by experiments,and the topology,control strategy and device development used were verified for feasibility.