Research On High Input Voltage LLC Resonant Converter

With the development of power electronic technology and appearance of new high performance power electronic devices, high voltage, large conversion ratio and high frequency power supply have been widely used in high-speed rail, aerospace, medical treatment and energy Internet,etc.In this paper a new four transformer primary series secondary paralleled LLC resonant converter is designed for the application of high voltage input and low voltage output aircraft power supply system. SiC MOSFET has the advantages of high voltage, high temperature and good switching characteristics, and the transformer primary series secondary paralleled topology suitable for high conversion ratio. SiC MOSFET is used as the switching device in the design to realize high power density and high switching frequency.The converter sharing a resonant network can reduce the switch number with its transformer primary side connected in series and its secondary side connected in parallel. Moreover, this circuit have a good current sharing characteristic to avoid the power imbalance caused by different parameters. The working principle and special working conditions of the circuit are discussed in this paper. The working condition of LLC resonant converter in overload and light load is studied and the solutions are given.Finally, simulation verification is conducted by software of PSIM and Maxwell 3D, and experiment verification is carried out based on a 4000W prototype with digital control. Simulation and experimental results show the correctness of theoretical research and the circuit parameter design.