Research on Digital Synchronous Rectification for a High-Efficiency DC-DC Converter in an Auxiliary Power Supply System of Magnetic Levitation

In this paper, a new auxiliary power supply system of magnetic levitation based on the LLC DC-DC converter is proposed. The switches of the DC-DC converter are SiC MOSFET, which enables high frequency, high temperature, and high power density. For further improving the efficiency of the system and realizing the stability of the output voltage under different load conditions, the digital synchronous rectification (DSR) based on the phase shift control strategy is proposed. The prototype of the LLC DC-DC converter based on SiC MOSFET is implemented, which can realize zero voltage switching (ZVS) and zero current switching (ZCS). Then, the thermal image of DSR is presented, which proves that the power loss of SiC MOSFET with DSR is relatively low. Additionally, the system efficiency among the Si IGBT, SiC MOSFET, and SiC MOSFET with DSR is analyzed and the prototype demonstrates 98% peak efficiency. Finally, simulations, experiments, and data analysis prove the superiority of the proposed DSR strategy for the new auxiliary power supply system of magnetic levitation.