In DC/DC converter systems, power electronic circuits are reaching switching efficiencies close to 100 percent nowadays. Thus, most of the energy loss appears inside the passive magnetic circuit of the converter, which at the same time is the component that requires most space in the system. In order to battle this issue, research during the last century has been focused on planarization, hybridization and integration techniques with the goal to achieve higher efficiencies and decrease the profile and volume of the devices. In addition, higher frequencies have been applied to achieve a higher power density of the magnetic systems, but with the negative consequence of stronger parasitic effects such as proximity and skin effects inside the magnetic circuit. This thesis deals with the development of an integrated magnetic system in a L-C-T (Inductor-Capacitor-Transformer) configuration, with the assistance of Finite Element Method (FEM) computer modeling, which is supportively used to accelerate the development process. Computational simulation method is used to indicate and address the physical issues, which cannot be identified with conventional measurement methods.