This report presents a project that has been made to present the design of a planar transformer as a part of a series loaded resonant DC/DC converter in a power unit. The design is based on an existing transformer that is not planar and so the characteristics of the transformer is translated into a planar version. A multilayer printed circuit board (PCB) design was made to fit a chosen magnetic ferrite core that was chosen based on the magnetic characteristics of the old core. Calculations were made for the loss of both core and windings and the final results show that it is possible to design a planar transformer from a traditional transformer.