A GENERAL MODEL FOR SWITCHED DC-DC CONVERTERS INCLUDING FILTERS

A continuous, low frequency, small signal model, valid for all types of converters -both in heavy and light modes, is developed in this paper. The method, which easily allows to take into account, both input and output filters, leads to a new general canonical block diagram enhancing the respective contributions of the cell and of the filters. From it, all the desired transmittances (between the output, the duty cycle and/or the voltage source) can be derived in a straightforward general form, enlightening in particular the influence of the filters on the dynamics and the stability of the system. The method is considered as an averaging method since it considers, at the initial point, the mean value, on one cycle, of the current injected in the filters. A judicious use of state space methods and averaging methods allows an easy implementation of these models, whatever the complexity of the input-output filters.