Half-Turn LLC-DCX Based Two-Stage DC-DC Converter for Wide Input Voltage Range Applications

Compared with the traditional single-stage converter architecture, the two-stage architecture has the advantage of being able to maintain high efficiency over the full input voltage range. However, in low voltage and high output current applications, the Buck+LLC-DCX based two-stage solution could not maintain high efficiency with the increasing of power level due to the low middle bus voltage. Thus, a Boost+LLC-DCX based two-stage converter is employed to reduce the conduction loss and improve efficiency. In addition, to further reduce the conduction losses at the secondary side of LLC-DCX converter, a half-turn transformer is adopted. Furthermore, the implementation and optimization of the half-turn transformer have been carried out. A 200-400V input, 28V/1.8kW output prototype has been fabricated in the lab. The experimental results show that the full load efficiency of the prototype is higher than 94%.