Research On LLC Resonant Converter Based On GaN Device

The switching frequency of traditional isolated DC/DC converters can not be increased with the development trend of power electronics technology,which leads to large volume and low efficiency of traditional isolated DC/DC,due to the limitation of the device and the circuit topology.And the traditional resonant DC/DC converter has many disadvantages,such as high cycle energy,large circuit loss and poor voltage regulation performance.However,the LLC resonant converter can achieve zero voltage switch(ZVS)of the primary side switch and zero current switch(ZCS)of secondary side.low switching loss,can work in high frequency switch,and it has good voltage regulation performance and high efficiency;the voltage stress of the device is small,so it is easy to select and realize integrated magnetics technology.The new GaN power device has the advantages of small gate charge,fast switching speed,low conduction loss and no reverse recovery.The application of the soft switching technology in the LLC resonant converter can greatly reduce the switching loss caused by the high frequency,so as to improve the efficiency and power density of the converter.The research work of this paper is mainly carried out from the following:First of all,the structure analysis and characteristic parameter comparison of GaN power devices and Si MOSFET,according to the requirements of GaN device's switching characteristics on GaN device driver circuit,several feasible GaN drive circuits are studied and analyzed,the driving circuit of the GaN half bridge evaluation board is used to test and the driving signal waveform is analyzed.Secondly,the comparative analysis of the LLC resonant converter and other DC/DC converter topology shows that the LLC resonant converter has a great advantage in the voltage regulation performance,efficiency and power density,the working principle and mode of LLC resonant converter based on GaN are analyzed,using the fundamental analysis method to analyze the characteristics of LLC resonant converter,the circuit design method is given,and the control method of half bridge evaluation is introduced.Finally,the parameters of the LLC resonant converter is designed and simulated according to the parameters,then use the half bridge evaluation board to build a rated input voltage 400 V,output voltage 48 V,the resonance frequency is 1MHz LLC resonant converter experiment platform based on GaN devices,the experimental waveforms are tested to verify the correctness of the theoretical analysis and design method.