Negative Valley Soft Switching Design of Three-phase Interleaved Parallel DC/DC Converter

Conventional three-phase interleaved parallel DC/DC converter systems operating at high frequency conditions increase switching losses, resulting in lower system efficiency. For this reason, this paper proposes a negative-valley inductor current soft-switching technique for DC/DC converters, which replaces the conduction loss with a smaller turn-off loss, thus improving the system efficiency. In the paper, the working principle of Buck circuit is analysed in detail, the relationship between the output current ripple and duty cycle of the interleaved Buck converter is deduced, and the general boundary conditions of inductor current for soft-switching operation are obtained by solving the KCL and KVL equations in columns, so as to derive the feasible region for soft-switching. Meanwhile, a capacitor is connected in parallel on the drain-source pole of the MOSFET to further reduce the turn-off loss. Finally, a three-phase interleaved parallel Buck converter circuit simulation model and an experimental prototype are constructed to verify the effectiveness of the technical approach, and the efficiency is as high as 97% at 4kW, which is 2.2% higher than that of the conventional three-phase interleaved parallel Buck converter.