Abstract：In response to the "double carbon" strategy，the state has made great efforts to develop new energy.

As an important carrier of distributed new energy，the DC building microgrid system has attracted extensive

attention. In the DC building microgrid system，as the core link of voltage and power conversion，DC converter still

faces the problem of wide load range and high efficiency caused by the lack of light load soft switch. Therefore，

based on resonant LCLC converter，an optimization method of synchronous rectifier energy feedback control

efficiency was proposed. By controlling the advance conduction time of the synchronous rectifier，the energy

feedback path was constructed，and a new operation mode was added to the resonant mode to realize the output side current feedback. In this way，the turn-off current of the lagging leg switch could be increased to provide sufficient energy for the charging and discharging process of the switch output capacitor within the dead time，ensuring the realization of ZVS soft switching. Based on the LCLC synchronous rectifier multi resonant DC-DC converter，the principle and mode operation process of synchronous rectifier advance conduction control were introduced in detail. The dead time charging and discharging process of the lagging bridge arm switch was analyzed，and the constraint boundary of zero voltage switching （ZVS） implementation was refined. Combined with the mathematical model constructed by time-domain analysis method，the advance conduction time of synchronous rectification required by ZVS of lag leg under full load condition can be obtained. Finally，a 500 W experimental prototype was built. The experimental results show that the proposed method can effectively improve the light load operation efficiency by 92.44%，which proves the correctness of the theory.

      Key words：phase shift modulation（PSM）；resonant converter；soft switching；synchronous rectification；light load efficiency