Fully-Integrated Solid Shunt Planar Transformer for LLC Resonant Converters

A new topology for achieving high leakage inductance in inserted-shunt integrated magnetic planar transformers is proposed. In the proposed topology, two one-segment shunts are placed across the planar E-core air gap and between the primary and secondary windings. The proposed topology benefits using solid inexpensive ferrite shunts, making manufacturing easier. A detailed mathematical model is derived from which a design methodology is developed, providing accurate estimation for the leakage and magnetising inductances. The theoretical analysis has been verified using finite-element analysis and experimental implementation. AC resistance analysis and efficiency comparison are also presented for the proposed topology and a recent topology with inserted-segmental-shunt, which shows the proposed topology provides higher efficiency because of lower AC resistance. In addition, an isolated LLC resonant converter is designed and built to investigate the performance of the proposed topology in practice. The three magnetic components needed for the designed LLC resonant converter is integrated in a single planar transformer using the proposed topology and the converter operates properly.