Closed-loop digital control of resonant converters

A sampled-data model to describe the dynamics of small perturbations away from a cyclic steady state of resonant converters, and associated transfer functions were obtained in earlier work. A discrete microprocessor-based controller, designed using the above dynamic model, has been built and tested on a simulation of a series resonant dc-dc converter, set up on the Massachusetts Institute of Technology Parity Simulator. The control methods implemented are state feedback and periodic output feedback, each designed to achieve a specified set of closed-loop poles. The controller has been implemented using the Parity Simulator Generalized Controller. Results of the closed loop response showed an improvement over the open loop response. Also, the effect of the delay caused by calculations in the computer on the closed-loop dynamics of the converter is investigated. Results have shown that this delay can be important and should be modeled in the dynamics.