On the efficacy of sampled-data modelling of switched networks

The limitations of sampled-data modelling in determining the frequency response of switched networks such as switching power converters are highlighted. A general scheme for constructing small-signal difference equations used in sampled-data models is given. This scheme overcomes the limitations of current approaches used in obtaining input-to-output responses. However, in common with all other sampled-data modelling approaches, problems of accuracy and appropriate choice of formulation of difference equations still remain. Consequently, the use of sampled-data models to determine frequency response is not recommended. However, the difference equation formulation scheme developed here may be used in a small-signal describing function modelling approach which is demonstrated by the authors to be accurate, have no ambiguity of use and no frequency limitations-in contrast to sampled-data modelling.