Use of second-order switching surface in the boundary control of buck converter

A second-order switching surface in the boundary control of buck converters is studied in this paper. The formulated switching surface can make the overall converter exhibit better steady-state and transient behaviors than the one with first-order switching surface. Most importantly, it is applicable for converters operating in both continuous and discontinuous conduction modes. The switching surface is derived from estimating the state trajectory movement after a switching action, resulting in a high state trajectory velocity along the switching surface. This phenomenon accelerates the trajectory moving towards the target operating point. The proposed control scheme has been successfully applied to a 120W buck converter. Detailed large-signal characteristics and comparisons with the first-order switching surface will be discussed.