Functional block diagram of the fourth-order PWM converters with DCM

An algorithm for computation of the elements of the functional block diagram for the fourth-order PWM converters with discontinuous conduction mode (DCM) is presented in this paper. The model with averaged characteristic coefficients is used as canonical dynamic (ac small signal) model of the converter, because it can be directly transposed into a functional block diagram. The elements of this model of the converter are deduced through the state-space averaging method. The algorithm can be applied for modeling and analysis of four configurations: non-isolated Sepic, Zeta, Cuk and ripple-free input-current boost PWM converters. The application of the algorithm and its implementation with the MATLAB environment are exemplified on a non-isolated PWM Sepic converter with DCM. Studies regarding the influence of the parasitic elements and coupling coefficient over the dynamic properties of the converter are given too.