Comparison of resonant power converters with two, three, and four energy storage elements

In general, analysis of Resonant Power Converters (RPCs) is more complex than conventional converters. Consequently, it is common to adopt methods that facilitate the analysis. One of them is the First Harmonic Approximation (FHA). It assumes that only the fundamental harmonic of the current/voltage quantities affects the RPC operation, thanks to the filtering action of the resonant tank network (RTN) embedded in RPCs. The RPC stages can then be represented by simple equivalent circuits with sinusoidal solicitations and the operation can be studied by the standard linear ac analysis. In this paper the characteristics of RPCs with RTN made of two, three, and four elements are investigated using the FHA method. Input impedance, voltage gain and efficiency are derived and discussed for the various topologies. Merits and limitations of the topologies are also addressed.