Research On Ultra-Wide Range Input Voltage DC/DC Converter

Aero Engine Controller is the core control unit of an aircraft.As a critical equipment,its power supply is regulated by a power electronic converter from wide input voltage and wide frequency AC source provided by a special permanent magnet generator.Based on a single-stage flyback converter,a DC/DC converter with ultra-wide voltage range of 35V~440V input,28 V output is developed in this thesis.This thesis carried out the following several aspects of research work.(1)The traditional start-up circuit has large start-up loss,which is not suitable for ultra-wide input voltage.Therefore,the active start-up circuit is studied.After starting up,the start-up circuit is cut off and the loss of start-up circuit is reduced.(2)Under the working condition of low voltage and full load,according to the influence of turn ratio on the voltage and current stress of the primary and secondary switches,the turn ratio range is narrowed.Then the primary and secondary switches are determined.Finally,the transformer turn ratio is optimized based on the loss of the primary and secondary switches,selecting the lowest loss and determining the turn ratio.(3)In order to reduce the secondary rectification loss,this paper adopts synchronous rectification.For the synchronous rectification technology,this paper analyzes and compares the advantages and disadvantages of various synchronous rectification driven methods,finally selecting the synchronous rectification chip driven method.At the same time,two kinds of voltage detection and judgment methods are further introduced: the linear prediction method based on volt-second balance principle and the method of detecting the drain voltage.The traditional detection method is limited by the chip pin voltage and can not exceed 200 V,which is not suitable for the wide range of input conditions in this paper.Therefore,a voltage-driven synchronous rectification detection expansion circuit is proposed,clamping the detection point voltage effectively,which is suitable for ultra-wide range input voltage occasions.Finally,an 80 W prototype with 35 V ~ 440 V input,28 V output is fabricated.The simulation and experiments verify the theoretical analysis and the effectiveness of the proposed active start-up circuit and the voltage-driven synchronous rectification detection expansion circuit.