Planar transformers have emerged as crucial elements in high power density designs due to their low profile and ease of manufacturing. In this paper, a new infinite-shape winding is proposed which employs the side legs of E cores to obtain double effective turns. A planar transformer is proposed using the infinite-shape winding and a ELP64/10/50 core for a 48V-400V Dual Acitve Bridge (DAB) converter opertaing at 120kHz. By employing a single infinite- shape winding on the 48V side, equivalent to two effective turns, the high-voltage side PCBs can fit into a lower-profile core while maintaining minimal inter-winding capacitance. To meet the demands of this high-power application, parallel infinite- shape PCBs are utilized to increase current capability. A novel interleaving method is proposed to achieve balanced magnetic field exposure and equal current distribution for the parallel windings effectively reducing ac resistance. A 5kW converter utilizing the proposed planar transformer achieves 98.5% peak efficiency and 3.7 kW/L power density, while the transformer itself reaches 43 kW/L power density with 99.75% efficiency at full load operation
