| With the development of more electric aircraft, electrical system has partially replaced the hydraulic and pneumatic systems, increasing the capacity of the aircraft power system. To meet the demand for large capacity and high efficiency, the 270V high voltage DC power supply system and variable frequency AC power system will become the developing trend of modern aircraft power system. The two types of aircraft power system both have the 270V dc bus voltage, which cannot power the most on-board equipments directly. Therefore, the bus voltage must be converted to the type of power required by the DC/DC converter.The purpose of this thesis is to develop a high efficiency DC/DC converter with the 270V input and 8V/430A output for the Airborne Radar Transmitter. The difficulties of this project are discussed and the corresponding solutions are proposed. Then, PWM-controlled full-bridge LLC resonant converter is selected as the main topology for the purpose of ZVS realization, simple control and easy current limiting. The frequency-domain and time-domain characteristics analysis of the converter are performed, which disclosing that there are two kinds of ZVS mode. Considering the steady operation, starting and current limiting state, soft switching conditions and methods of selecting switching frequency are discussed. To ensure a high efficiency at low voltage and large output current condition, several synchronous rectifier technologies of LLC converter are compared and summarized, in which current-driven synchronous rectifier is analyzed and detail circuit design is conducted. Finally, a PWM controlled full-bridge LLC resonant converter is built. Experimental results show the validity of theoretical analysis and parameters design.
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