Three-phase LLC Resonant Converter Based On Planar Magnetic And GaN Device

With the increasing concerned on the continuous development of sustainable and green development concepts,the low-carbon development trend aimed at “carbon peak” and“carbon neutrality” has brought enormous challenges to various fields such as 5G communication andaerospace systems.The design of high-efficiency and high-powerdensity power electronic converters has become a hot and difficult issue.Compared with traditional wire-wound technology,flat magnetic technology is increasingly being applied in high-frequency converters due to its excellent characteristics such as high current density,good heat dissipation,and high power density.The third-generation semiconductor Ga N devices are more suitable for high-frequency,high-efficiency,and high-power-density converters because of their advantages such as fast switching speed,low on-resistance,and small size.Therefore,a Ga N three-phase high-frequency LLC resonant converter based on flat magnetic components is studied in this thesis.Firstly,the development status of three-phase LLC resonant converters,highfrequency magnetic components,and wide-bandgap semiconductor Ga N is analyzed in this thesis.The three-phase LLC resonant converter has the advantage of naturally reducing output current ripple,so it can effectively reduce the volume and height of the output filter capacitor,and the original star connection structure of the primary side has a certain selfequilibrium current capacity,without additional current-sharing control.In the context of high frequency,the application of flat magnetic compoments and Ga N devices is conducive to achieving miniaturization and high efficiency of converters,effectively improving the performance of converters.Based on this,a Ga N three-phase LLC resonant converter with flat magnetic components is proposed.Secondly,the working principle of the three-phase LLC resonant converter is described in detail,and the voltage gain expression is derived through fundamental analysis method to analyze the gain characteristics of the converter.Meanwhile,the principle and characteristics of the new semiconductor device Ga N are also introduced,and an enhanced Ga N drive circuit is designed.The resonant parameters are designed according to the performance indicators of the converter,and the circuit structure and parameters of the three-phase LLC resonant converter are verified using PSIM software.The parasitic parameters of high-frequency flat magnetic components and their impact on the LLC resonant converter are analyzed.Based on this,a flat magnetic component with decoupled resonant inductance and transformer is designed.Various PCB winding structure are proposed and their layout methods are optimized.The Maxwell finite element simulation tool is used to simulate the flat magnetic component,and the AC resistance,and inductance and magnetic core loss parameters of the magnetic component are extracted.The magnetic flux density of the magnetic core and the current density distribution of the winding are observed to verify the rationality of the flat magnetic component design.Finally,the software and hardware design of the converter are completed,and an experimental prototype with a power of 500 W and a resonant frequency of 710 k Hz is built for experimental verification.The experimental results show that the converter achieves constant output voltage and balanced three-phase current within a certain frequency range.Moreover,the Ga N switch realizes zero-voltage turn-on within the full load range,and the efficiency is high in the entire operating range,which the peak efficiency attains 95.9%.