Design And Realization Of High Frequency And High Efficiency GaN-based LLC Resonant Converter

With the continuous development of switching mode power supply technology,in small and medium power applications,people have higher and higher requirements for the power factor,efficiency and power density of the switching mode power supply.Compared with Si devices,GaN devices has lower Figure of Merit(FOM),which brings smaller gate charge capacity and smaller on-resistance.The GaN devices are applied in LLC resonant converter,it can effectively improve the efficiency and power density of switching mode power supply while improving the working frequency.In this paper,the internal structure,characteristic parameters,and related losses of GaN power devices are analyzed firstly,combining with the analysis results,in order to better reflect the performance advantages of GaN devices in high-frequency application scenarios,a monolithic integrated gate drive GaN power device is adopted as a switching device,combined with the soft switching characteristics of LLC.A GaN half-bridge LLC resonant converter with a resonant frequency of 1MHz is designed to reduce the volume of resonant elements in the LLC resonant loop and improve the power density while ensuring the efficiency.The active power factor correction circuit is designed as the front-stage AC-DC conversion circuit to provide a stable DC input for the latter stage,which solves the efficiency problem of LLC in a wide range of voltage input,while improving the power factor of the prototype,reduce the line loss and harmonic pollution,improve the quality of power supply.Finally,an experimental prototype of GaN half-bridge LLC resonant converter with power factor correction circuit,100-250VAC input,100W output,and 1MHz resonant frequency was built.Compared with the 300KHz-GaN-100W prototype,the volume of resonant inductance was reduced by 50%.The resonant capacitance volume is reduced by about 95%.Under the full load(50V/2A)output condition,the power factor of the prototype can reach above 0.98 in the full voltage input range,the LLC part switching frequency is 0.9MHz,the whole machine efficiency is 91%,and the power density is 21.85W/in~3.