Design of linear quadratic regulators for quasi-resonant DC-DC converters

Small-signal models of quasi-resonant (QR) power converters with current-mode control, obtained by state-space averaging, suggest that a linear feedback law can be used to improve the dynamic response of the converter. This can be done by seeking a gain vector that places the closed-loop poles at the locations desired. Instead, the authors use optimal control techniques, together with those small-signal models, to design a robust voltage controller for QR converters that overcomes some uncertainties that may corrupt the results obtained by classical design methods. As an example, they present the design procedure and experimental results for a 1 MHz QR-ZVS buck converter with a linear quadratic regulator (LQR).