Modeling and Design of Integrated Inductor and Transformer Considering Superposed Flux Density in On-Board-Charger

In the DC-DC stage of On-Board-Charger (OBC), the volume of transformer and AC side inductor can occupy more than 1/4 of the total volume, which becomes a key restriction to the improvement of power density. Magnetics with split-windings structure can construct enough leakage inductance to achieve integration and thus reduce the total magnetics volume dramatically. However, when referred to the core size design, only the transformer’s flux density is taken into account to determine the cross-section area in the existing papers. On condition that the flux density of the parasitic inductor is large enough, the flux density of integrated magnetics will far outweigh the approximation mentioned above so as to cause the risk of core saturation. This paper gives an analysis and design for integrated magnetics considering the superposed flux density of inductor and transformer based on split-windings structure. A 6.6kW prototype based on LC series resonant DC-DC converter with about 37% reduction of magnetics volume is built to verify the feasibility of the proposed design procedure.