The Design Of An AC-DC Converter Based-on Gallium Nitride Transistor

The performance of power switch transistor plays an important role in the performance of power electronic system.As one of the wide-band gap semiconductors,gallium nitride transistors have smaller parasitic parameters and on-resistance.It is potential to substitute traditional Si-based MOSFETs and promote the continuous development of power conversion systems in the direction of high operation frequency,high efficiency,high power density,and low cost.This paper focuses on the design of a kind of high-performance AC-DC converter which contains GaN transistor.During the process,the problems of utilizing GaN devices are found and solved.Considering the design specification of the conversion system,the AC-DC prototype has been realized by the way of pre-stage Buck power factor correction and post-stage Buck DC-DC cascade connection.The research contents are as follows.(1)According to the electromagnetic compatibility requirements for harmonic frequency restrictions and system power factor requirements,the appropriate range of operation frequency and output voltage were determined.A proper power factor correction chip was selected to build a control loop to sample the input voltage,filtered inductance current and output voltage of the module,so as to reduce the harmonic content of input current and enhance power factor.Considering the role of each component in the system,the selection of the components was carried out from the perspective of voltage and current stress.Also,the power loss generated by each component was analyzed.(2)A Buck DC-DC based on constant conduction valley current control was built.Then the components in the power loop were selected and the power consumption generated by the power switch was calculated.Considering the characteristics of low threshold voltage and small safety margin of gate source voltage of GaN device,a halfbridge bootstrap drive circuit with clamping function was built.The influence of parasitic parameters on the driving characteristics of GaN device and the performance of the system was analyzed,and the PCB layout was optimized.In order to ensure the working reliability of the system,the dead-zone link was set up.The dead-zone loss was reduced by using the synchronous transistor inverse parallel Schottky diode.After the design work was completed,the PCB circuit design was carried out and the performance test of the experimental prototype was finished.Eventually,a highperformance AC-DC converter with input voltage range of 100Vac-240 Vac,output power of 100 W,efficiency of more than 90% and power factor of more than 0.9 is realized.