Analytic solutions for LLCC parallel resonant converter unify the design and analysis of two- and three-element converters

A practical method for the steady-state design of parallel resonant DC/DC power converters is presented. The method uses a set of pre-derived equations from an LLCC-type series-parallel resonant converter (LLCC-SPRC). Although four tank elements are used in an LLCC-SPRC, only two ratios of these tank elements are needed during design. The values of the four tank elements can be found from the design results. In addition to designing an LLCC-SPRC, the prederived equations can also be used to design and analyze conventional LCC-type series-parallel (LCC-SPRC), LLC-type parallel (LLC-PRC), and LC-type parallel (LC-PRC) resonant power converters. In other words, four power converters can be designed by the same equations. A design procedure along with design examples is given. Experimental circuits are implemented and measured based on the design results to verify the validity of the derived equations and the design procedure.