ROBUST CONTROLLER-DESIGN FOR A SERIES RESONANT CONVERTER

Because of their reduced switching losses, allowing a higher operating frequency, dc-to-dc resonant converters have been used extensively in the design of smaller size and lighter weight power supplies. The ste ady state and dynamic behavior of both the conventional series and par allel resonant converters have been thoroughly analyzed and small-sign al models around given nominal operating points have been obtained. Th ese models have been used in the past to design controllers that attem pted to keep the output voltage constant in the presence of input pert urbations. However, these controllers did not take into account either load or components variations, and this could lead to instability in the face of component or load changes. Moreover, prediction of the fre quency range for stability was done a posteriori, either experimentall y or by a trial and error approach. In this paper we use mu-synthesis to design a robust controller for a series resonant converter (SRC). I n addition to robust stability the design objectives include rejection of disturbances at the converter input while keeping the control inpu t and the settling time within values compatible with a practical impl ementation.