Averaged modelling of switched-inductor cells considering conduction losses in discontinuous mode

Many PWM DC-DC converters contain a switched-inductor cell for which an average-value model is required. However, the presence of parasitics associated with the cell's components complicates the development of accurate averaged models, especially for the discontinuous conduction mode. Here is described an improved full-order, large-signal averaged switching cell. The proposed averaged cell takes into account conduction losses as required by the energy conservation principle and provides a more accurate duty-ratio constraint. The final model shows improvement over several previously established averaged cells in predicting large-signal, time-domain transients as well as small-signal, frequency-domain characteristics.