Verification of LLC resonant converter applied a current-balancing high-frequency transformer with multi-output windings

DC-DC converters of hybrid vehicles and electric vehicles are required to become smaller and lighter for building roomy and light weight EV. High-frequency switching can be used to miniaturize DC-DC converter. However, the influence of the skin effect and the eddy current become large. Parallel operation of converter is often for current applications using multiple winding transformers in order to reduce of skin effect. However, it is difficult to equalize the each current of converter due to unbalance of winding resistance, drop voltage of diodes and so on. In this paper, the parallel LLC converter applied a current-balancing high-frequency transformer is proposed. The proposed converter can realize nearly equal current even if the stray impedance of secondary circuit of LLC are unbalanced.