Design oriented analysis of fourth-order LCLC converters with capacitive output filter

An analytical methodology for the rapid steady-state analysis of fourth-order resonant power converters, with capacitive output filter, is proposed. The technique extends previously published work on LCC converters to the more common, but more complex, LCLC counterpart. The output filter/rectifier and load circuit are represented by multiple ‘equivalent’ passive components that permit the subsequent calculation of the steady-state voltage conversion ratio and the estimation of the voltage and current stresses on the resonant-tank components. The resulting methodology facilitates the derivation of four design synthesis procedures for LCLC converters based on various user-definable constraints. Simulation results and measurements from a prototype fourth-order converter are used to demonstrate the accuracy of the proposed methodology, whose computational requirement is comparable to that for classical fundamental-mode approximation.