Research And Design Of Interleaved Parallel LLC Resonant Converter Based On GaN Devices

The rapid rise of 5G communication has put forward new requirements for communication power supply.Compared with 4G communication power,5G communication power requires DC-DC converter to have higher efficiency,smaller volume,higher output power,lower output current ripple and stronger stability.The interleave LLC resonant converter(SP-LLC converter)meets these requirements,so it can be used for 5G communication power.Gallium nitride(GaN)high electron mobility transistor(HEMT),as a representative switching device of the third generation wide band gap semiconductor,has the characteristics of fast on-off speed,high frequency response ability and good development prospect,so it has many excellent effects when applied to SP-LLC converter.The emphasis of this paper is to select good switching devices and reliable control mode to make the SP-LLC converter more efficient,more power density and more stable.First of all,monomer enhanced GaN HEMT is selected as the switching device of SP-LLC converter,and its static and dynamic characteristics are analyzed and compared with Si MOSFET and Cascode GaN HEMT.The results show that monomer enhanced GaN HEMT has better characteristics,lower loss and higher power density.Secondly,two control modes of single-channel full-bridge LLC resonant converter system,namely frequency conversion(PFM)and phase shift(PSM),are studied,including soft switch analysis and voltage gain characteristics.Complex and SP-LLC converter control method and passive effect bad flow to put forward a kind of PSM soft start + triple phase shift(TPS)control mode,this kind of control mode not only contains new PSM,PSM voltage stability and low ripple output current of strategy,can also be fixed system working frequency as resonant frequency as the highest efficiency,make the system have been working at the highest efficiency.On this basis,this paper introduces leakage inductance instead of magnetic integration technology into the system to further improve the power density of the system,so that it can meet the demand of 5G communication power.In addition,the steady-state equivalent model and current-sharing model of SP-LLC converter are established in this paper,and the simulation model of the system is established by Matlab,PLECS and Pspice simulation software to demonstrate the control effect of PSM soft start + triple phase shift(TPS).Thirdly,considering parasitic parameters inside GaN devices,a refined loss model of SP-LLC converter based on enhanced GaN HEMT is proposed.The transient loss and through-state loss of the system are calculated in detail,and compared with the transient loss of Cascode GaN HEMT,the advantages of enhanced GaN HEMT are highlighted,and the loss process of the system is analyzed in detail.The experimental results show that the loss value obtained by the loss model in this paper is only about0.6% from the actual value in the experiment.Finally,the experimental platform of SP-LLC converter with power of 0.8k W was designed and built,and the drive of GaN HEMT was designed,and PSM soft start was designed to reduce the initial peak of resonant current of the system.The experimental results show that the selected PSM soft start +TPS control can ensure the high efficiency and stability of the system.