Design guideline for magnetic integration in LLC resonant converters

The aim of this paper is to present a comprehensive design methodology for the magnetic integration of the series and shunt inductances of the resonant tank in an LLC resonant converter within the transformer. The design procedure applies to symmetrical core-bobbin structures with two separate slots for the primary and secondary windings. A specific leakage inductance A_sigma. (per square turn) that depends on geometrical parameters only is derived. This is used, together with the cross section and winding area of the core, to define two other core parameters that allow the designer to identify the minimum ferrite core size suitable for the application.