High Frequency And Wide Range LCC Resonant Converter Based On Resonant Tank Switching Technology

Medical X-ray machine plays a very important role in the diagnosis and treatment of modern medical system.The performance of high-voltage power supply of X-ray machine directly determines the quality of X-ray.The goal of medical high voltage power supply is smaller volume,smaller weight,higher power,smaller output ripple,faster dynamic response speed and higher efficiency.This paper first introduces the research status of X-ray machine high-voltage power supply,silicon carbide devices and LCC resonant topology wide range output technology,and investigates and analyzes the existing solutions to the problem of wide working frequency range caused by wide range output.The main circuit structure and working mode of the LCC resonant are analyzed,as well as the soft-switching working conditions in each working mode.Analyze the gain characteristics of the LCC resonance topology according to the fundamental equivalent model.Aiming at the problem of LCC resonant tank parameter design,the voltage and current stress of the resonant components and its change rule are discussed.Based on the determination of the maximum operating frequency of the LCC converter,a resonant tank parameter design method based on electrical stress is proposed.The effectiveness of resonance parameters and design method is verified through Simulink open-loop simulation.The parameter design method of the resonant tank based on electrical stress is based on the known maximum operating frequency of the LCC converter,and the maximum operating frequency of the LCC converter is restricted by the switching loss of the power device.The switching loss of power devices is proportional to the switching frequency,and accurate prediction of the switching loss can provide guidance for determining the maximum operating frequency of the LCC converter.This paper studies the composition and modeling of parasitic capacitance of Si C MOSFET,and predicts the switching characteristics of Si C MOSFET on this basis.The accuracy of the prediction results of switching characteristics of Si C MOSFET is verified by a double-pulse experimental platform.According to the predicted switching loss,determine the maximum operating frequency of the LCC converter.Aiming at the problem that the gain range,frequency range and electrical stress cannot be considered at the same time when the LCC converter has a wide range of output,the switching method of the LCC resonant tank under the condition of constant load and variable gain is studied.Add an additional LCC resonant tank to achieve a constant load wide range output within a given frequency range.Based on the specific design steps of the resonant tank switching method,the voltage stress,current stress and gain range of each method are compared.The feasibility of the resonant tank switching method is verified through experiments.Analyze the frequency characteristics of the LCC resonant topology when the load and gain are co-variations.On this basis,the method of dividing the working area of the LCC converter is studied.The equal gain lines dividing method and equal frequency lines dividing method are proposed.Divide the target working area into several sub-areas,and each sub-area corresponds to a different resonant tank,and the variable load wide range output is implemented within a given frequency range.Experiments have verified the feasibility of the work area division method.