Research On Optimization Of Resonant Tank Parameters And Start-up Control Algorithm Based On State Trajectory Of LCC Resonant Converter For Medical X-Ray Generator

With the rapid development of medical imaging diagnostic technology,high-voltage DC power supplies in medical X-ray machines have received widespread attention.However,in addition to satisfying high reliability,high power density and high efficiency,DC power supplies for such high-voltage occasions also require fast dynamic response speed and lower output voltage ripple.The LCC resonant converter has the advantages of both series resonant converter(SRC)and parallel resonant converter(PRC).On the one hand,the leakage inductance and parasitic capacitance of the high-voltage transformer can be used as resonant components;on the other hand,the LCC converter can realize softness in the full load range.Zero Voltage Switch(ZVS),so this article uses LCC resonant converter as the main circuit topology for the high-voltage generator based on the medical X-ray machine.Aiming at the performance index requirements,the main research in this paper is as follows:First,this paper analyzes the working principle of the LCC resonant converter in detail and establishes the equivalent circuit model of the converter and the corresponding plane state trajectory by using the state plane analysis method.At the same time,a detailed analysis of the heavy load mode and light load mode under steady-state operation is carried out,and the state trajectory curves are drawn respectively.Secondly,for the plane state trajectory model,an optimized startup strategy based on trajectory control is proposed,which accurately controls the state of the LCC resonator and adjusts the switching frequency in real-time to increase the dynamic response speed to obtain a fast output voltage rise time.At the same time,in order to avoid the problem of voltage and current overshoot during the start-up process,the resonant current was optimized in the process of planning the trajectory.This ensures that the rise time is minimized under the condition that there is no overshoot during the startup process.In order to verify the effectiveness of the proposed modeling method and trajectory control strategy,a similar pipelined FPGA calculation scheme is proposed.By arranging calculation modules in FPGA,the state trajectory algorithm is split into various calculation tasks and sent to the calculation modules for completion,which saves resource utilization and improves calculation speed.Finally,in order to verify the feasibility of the proposed algorithm,it is applied to a140 k V/42 k W medical X-ray machine high-voltage power supply system,and the open-loop and closed-loop experiments under simulated load conditions and real X-tube operating conditions are completed.The experimental results show the superiority of the proposed control algorithm,which achieves a fast dynamic response and greatly improves the rise time.