ROBUST CONTROLLER-DESIGN FOR A PARALLEL RESONANT CONVERTER USING MU-SYNTHESIS

DC-to-dc resonant converters have been the object of much attention la tely, These converters have the potential to provide high-performance conversion without some of the problems associated with classical puls e-width modulation (PWM)-based converters, thus allowing for smaller, lighter power supplies, However, in order to achieve this, a suitable control circuit, capable of maintaining the desired output voltage und er different operating conditions, is required, In the past, small sig nal models obtained around the nominal operating points were used to d esign controllers that attempted to keep the output voltage constant i n the presence of input perturbations. However, these controllers did not take into account either load or components variations, and thus c ould lead to instability in the face of component or load changes, Mor eover, the prediction of the frequency range for stability was done a posteriori, either experimentally or by a trial-and-error approach. In this paper we use mu-synthesis to design a robust controller for a co nventional parallel resonant converter, In addition to guaranteeing st ability for a wide range of load conditions, the proposed controller r ejects disturbances at the converter input while keeping the control i nput and the settling time within values compatible with a practical i mplementation, These results are validated by means of detailed nonlin ear circuit simulations obtained using P-spice.