Research On 270V High-voltage DC/DC Converter

In modern aviation aircraft, in order to reduce the power loss of power supply system, improve the efficiency and reduce weight, the high voltage 270 VDC power supply system is applied. But some of the airbone equipments need the 28 VDC voltage power supply. So the research on the high step-down ratio converter is useful and challenging.In order to adapt the wide input voltage range, and be able to output short-circuit current. This paper adopts the LLC-DCT(LLC resonant converter working at resonant frequency) as the first stage, the synchoronous rectification Buck converter as the second stage. To improve the whole efficiency of the converter, this paper does a lot of jobs as followed.Firstly, to reduce the power loss of LLC-DCT, this paper does a lot of research:(1) to reduce the transformer winding loss, the matrix transformer technology is adopted.(2) Ansoft PExprt simulation is modeled to study the winding impedance and leakage inductance of the transformer under different matrix transformer structures.(3) Ansoft Maxwell 2D simulation is modeled to design the matrix transformer. Secondly, to improve the efficiency of Buck converter, this paper does a lot of research:(1) to improve the efficiency, the loss of the switches is studied, the opitimal swithes are chosen. The relationship between output voltage ripple and parasitic parameter is studied to reduce the output voltage ripple.(2) to output short-circuit current, the reduction of the inductance peak current is studied. Finally, to improve the overall unit stability, the soft start-up method of every stage and the overall converter is given.At last, a high step-down 270VDC-28 VDC, rated power 2.8k W converter prototype is designed. The efficiency at full load is 94.1%, the power density is 5kW/kg.