Design And Optimization Of GaN Multiple-output Active Clamp Forward Converters

With the rapid development of science and technology,human achieve a great success in exploring the universe.National aeronatics and space undertakings have made great progress.Spacecraft is playing an increasingly important role.At present,the variety and quantity of electronic products applied to satellites are becoming more and more complex.Operating voltage ranges of electronic equipment for scientific research are totally different.In order to meet the requirements of electronic equipment and provide sufficient power supply,multiple output converters that can solve these issues are becoming hot research topics.Currently the bus voltage of power supply in satellites is 28V.This voltage level is applied to the load supply power that less than 2KW.In the furture,the electronic equipment will be upgraded and the total supply power will be increased as well.The bus voltage of power supply will be raised to 100V.This paper focuses on the development trend of satelliate and solves the design of multiple-output converters with 100V input voltage.Adopting new generation of power device enhancement mode Gallium Nitride(eGaN)High Electron Mobility Transistors(HEMTs)will improve the performance of multiple-output converters.Compared to the silicon MOSFETs with the same voltage and current rating,the eGaN HEMTs have many advantages such as lower gate charge,faster switching speed and smaller package with much reduced parasitics.These advantages make the eGaN HEMTs more suitable to MHz dc-dc converters.Especially to the satellite power converters,the eGaN HEMTs can help to improve the reliability against the radiation in space application.The self-driven Synchronous Rectifier(SR)technique is usually adopted in low voltage and high current output channels.By comparing the differences of existing solutions,this paper adopts a self-driven circuit to solve the drive problem of SRs.At the same time,this article proposes a new optimization of multi-winding planar transformers.As for the multi-winding planar transformers,due to high complexity of multi-winding configuration,the leakage inductance of each winding is hard to calculate theoretically.Considering there are large numbers of winding layers,the possible winding arrangements are enormous.It is hard to reduce the amount of structures and screen out the precise optimal structure manually.More importantly,the output power difference in each winding involves different leakage inductance requirement of the windings accordingly.The winding configurations are far from manually interleaved structures,therefore finding the optimal multiple winding structure with different output power become a tremendous challenge.The proposed idea of this article is to build the mathematical model of leakage magnetic field energy and screen out all possible winding configurations to solve minimum value with Matlab programming.Then,only limited winding configurations need to be simulated in Maxwell,which saves a lot of design efforts.By analyzing the inductance matrix,the leakage inductance of multi-winding planar transformer can be obtained.Then,the optimal winding configuration is solved.A prototype with 1 MHz,100 V input,5 V/6 A and±12 V/0.83 A outputs was built.The number of layers in the planar transformer is 16.In order to further improve the performance of the multiple output converters.The total output power is 50 W.The measured leakage inductance matches the simulated results and is limited as low as 0.6%of the magnetic inductance.Compared with the first edition,the full load efficiency is over 87.2%(an improvement of 1.0%)within input voltage range.The power density is raised from 22.7 W/inch~3 to 28.5 W/inch~3.