A unified derivation of second-order switching surface for boundary control of DC-DC converters

A unified derivation of second-order switching surface for boundary control is proposed. It is applicable for a range of basic DC/DC converters and their derivatives. The switching surface dictates the switching instants of the main switch in the converter. The distinct feature of this control method is that the entire converter can ideally reach the steady state in two switching actions after it is subject to a large-signal disturbance. The control method addresses a complete operation of the converter and does not differentiate startup, transient, and steady-state periods. Moreover, the same control law is applicable for converters operating in continuous or discontinuous conduction modes, and with minimum or nonminimum phase characteristics. The proposed derivation method is general-oriented and can identify the circuit variables needed in the switching function. The design procedures and performance of the proposed control method have been evaluated on a 200 W 48/48 V buck-boost converter prototype.