Application Of Trench-gate SiC MOSFET On LLC Resonant Converter

DC-DC converters are developing towards high frequency,high power density,and high efficiency.LLC resonant converter has become a popular topology for DCDC converters due to its soft-switching characteristics.It has many advantages such as high efficiency,high power density,high frequency,and low noise.LLC resonant converter can also achieve magnetic integration and reduce converter volume.With the development of converters,the shortcomings of LLC resonant converter switch tubes(Si MOSFET)based on silicon(Si)materials have become increasingly prominent,such as low switching frequency and large losses.In order to overcome the shortcomings of Si MOSFET,people began to develop a new type of silicon carbide(SiC)material MOSFET,which has many advantages such as high voltage resistance,high-frequency resistance,and high-temperature resistance compared with Si MOSFET.As the second-generation SiC MOSFET,the trench gate SiC MOSFET has lower onresistance and faster switching speed,enabling LLC resonant converters to achieve high frequency while ensuring high efficiency.This article firstly analyzes the topology and rectification structure of several converters and the working principle of the half-bridge LLC resonant converter.Secondly,the fundamental wave approximation analysis method(FHA)is used to model the steady state of the converter and calculate the DC gain of the converter.On this basis,the ZVS constraint conditions of the half-bridge LLC resonant converter are deduced and the parameter calculation steps are designed,and the components are selected according to the parameter calculation results.Simultaneously design the trench gate SiC MOSFET driver,complete the analysis of the static and dynamic characteristics of the trench gate SiC MOSFET,planar gate SiC MOSFET and Si MOSFET,and understand the body diode reverse recovery of the three types of switching tubes by building a double pulse test circuit characteristic.Finally,trench gate SiC MOSFET and Schottky diodes C4D10120 are used in LLC resonant converter.Use LTspice software to simulate the LLC resonant converter and analyze the influence of each parameter on the converter.By building an experimental prototype,the loss calculation of the experimental prototype is completed,and the resonant current waveforms under the three switching frequencies of LLC and the corresponding primary ZVS waveforms are tested at the same time,and the working efficiency is calculated.According to the previous analysis results,the dead time is optimized,and the efficiency of LLC resonant converters with different switches under different dead time is studied.