| With the development of information technology and defense industry,the demand for AC-DC converters not only has grown exponentially,but also the higher efficiency and higher performance are desired.Compared with the customized development of AC-DC converter,the AC-DC power mudule has the advantages of saving time of development and strong versatility,which has been widely used in the construction of various AC-DC power supply systems.By integrating with PFC stage and isolated DC-DC stage,the high-power isolated AC-DC power module can not only solve the complex control problems caused by the operation sequence in the traditional scheme of PFC power module cascaded isolated DC-DC power module,but also less number of modules,lower cost and higher reliability can be achieved.On the other hand,it is found that the single-stage isolated AC-DC architecture has a small number of devices,but its power transmission capacity is limited,making it difficult to meet high-power applications.In contrast,the two-stage isolated AC-DC architecture has more advantages in high-power case.However,there are the following drawbacks:(1)the front-end boost PFC converter with diode bridge is widely used in the PFC stage,resulting in the lower efficiency,especially in the low input voltage;(2)the back-end isolated DC-DC converter mostly operates around 100k Hz,which limits the improvement of the power density of the power module;(3)Si MOSFETs are widely used in power modules.For silicon(Si)devices,the performance is difficult to improve significantly becaues the Si semiconductor technology has matured and approaches its theoretical limits,which hinders the further improvement of the conversion efficiency and power density of the power module.Therefore,in order to achieve high efficiency,high power factor and high-power density,this thesis fuocses on the two-stage isolated architecture,mainly study and discussion on converter topology,parameter optimization and digital control for the solution.Firstly,this thesis makes a comprehensive comparasion of various PFC topologies in terms of conversion efficiency,EMI characteristics,power density,and cost.Among them,the dual-boost bridgeless PFC topology is the most appropriate selection for front-end PFC converter.Based on the detailed analysis of the operation principle of dual-boost bridgeless PFC converter,the PFC inductance optimization,device selection and start-up inrush-current limiter circuit are discussed.Furthermore,how to obtain the high efficiency and high power density of back-end isolated DC-DC converter with high voltage input,low voltage and high current output is discussed.Through the comparative analysis of the various optional topologies,the primary side clamped ZVS Phase-Shift Full-Bridge(PSFB)converter is employed.In order to solve the problems of ZVS PSFB converter with Si MOSFETs,the ZVS PSFB converter based on GaN HEMTs is proposed.This thesis analyzes the operation principle and operation mode of GaN-based ZVS PSFB converter.The design consideration including the power stage parameters,high frequency GaN HEMT driver and digital control algorithm are introduced.Finally,a prototype of 1kW isolated AC-DC power module has been built in the laboratory.The experimental results show that:(1)for front-end PFC conver,the conversion efficiency of 97%and power factor of 0.993 can be obtained under the input voltage of 220V and full load condition,while the power density of 205.85W/in~3 can achieved.Furthermore,the efficiency and power factor maintain above 94%and 0.95 for the universal input voltage range and half load,repectively.(2)the GaN-based ZVS PSFB converter has the efficiency of 95.1%under the nominal input of 400V and full load condition,and maintains above 95%from half load to full load.(3)the total conversion efficiency is up to 92.1%under the input voltage of 220V and full load condition.As compared to the industrial product with part number of PFE1000FA-28,the efficiency is improved by 3%. |
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