Controller design for resonant converters by automatable techniques

The application of the describing function method to model resonant power converters leads to nonlinear high-order models which can be linearized under small perturbation assumptions to yield small-signal linear models. These high-order models are processed by an invariant order reduction technique to obtain approximated transfer functions of lower order, expressed analytically without AC simulation. The automatable technique is demonstrated for the series-parallel resonant converter. After discussing various controllers as to parameter variation in the operation area, a robust controller is selected, assuring high dynamics in the whole operation region