Research On Low Voltage Single Switch High Frequency Power Converter

In the field of power electronics technology,increasing the switching frequency of the power converter dramatically to reduce its size and weight has become the pursuit of industrial electronics and consumer electronics.When the switching frequency is increased to high frequency（3MHz³0MHz）or even very high frequency（30MHz³00MHz）,the volume and values of passive components are greatly reduced,which will effectively promotes the miniaturization and weight reduction of the system,and can also increase the power density.High frequency switched mode power supply has significant technical benefits,great development potential and bright market prospects,and has inspired the research interests of plenty of scholars.Thus,this paper starts to study 20MHz high frequency power converters.In this paper,the theoretical derivation and numerical analysis method is proposed to optimize the design of Class E inverter and ClassΦ₂ inverter,which ensures that the switch accurately realizes ZVS characteristics at any duty cycle,thus the design speed and accuracy of the inverters are improved.Meanwhile,the modeling and analysis of Class E resonant rectifier is completed,the voltage stress of the diode and the equivalent impedance of the rectifier are obtained,which provides the guidance for the design of the rectifier.Based on Class E inverter and ClassΦ₂ inverter respectively,this paper builds two non-isolated HF prototype,the test results prove the rationality and high accuracy of the above design method.In order to further reduce the voltage stress of the switch,improve the input voltage level and operational safety of the system,this paper proposes a novel isolated low voltage stress HF topology.Firstly,the phase angle of the switch impedance is constrained to make it slightly inductive,thus ensuring the ZVS characteristic of the switch.Then,the amplitude of the switching impedance is constrained,and the voltage harmonic characteristics in the circuit are adjusted,so that the voltage stress of the switch is reduced from the conventional 4 times of the input voltage to 2.5 times.This topology can effectively reduce the system volume and improve the system efficiency.Compared with commercial discrete magnetic components,planar PCB structures have higher quality factor,therefore,cause less power loss when used in HF systems.In this paper,a PCB magnetic structure with variable winding width is proposed and adopted in HF system,which can further reduce the parasitic resistance of the component.The theoretical analysis and finite element analysis are combined to study the electrical characteristics of the component.And the accurate and fast calculation of its electrical parameters is realized,which effectively improve the performance of the system.This paper adopts an improved resonant driving circuit to reduce its input current through the resonance of the parallel branch,thus the driving loss can be effectively reduced.The ON-OFF control strategy is adopted to realize the closed-loop control of the system,which promises the high operating efficiency of the system within a wide range of load variation.A 20MHz isolated low voltage stress HF DC/DC experimental prototype with12V input,5V/5W rated output is designed and built in this paper.The test results are in good agreement with the expected targets.The efficiency is always higher than 77%when the system is at a load rate of 50%to 100%,and the full load efficiency is 79.4%.