Simple design of selected 3-element converters by scaling the solution of the LC parallel resonant converter

An efficient and practical method for steady-state design of selected 3-element parallel resonant DC/DC power converters is presented. To a good approximation, the output voltage and current of an LLC converter can be obtained by multiplying the output voltage or current of the parallel LC converter by a ratio of the parallel and series inductances. The LLC converters with and without an output filter inductor are examined for various conduction modes. The peak voltage and current stresses on the resonant elements also depend on the same ratio. An experimental LLC-type parallel resonant power converter is built to further ensure the validity of derived equations and the feasibility of removing the filtering inductor.