Terminal sliding mode control for Buck converter with structure of voltage and current double closed loop

In order to solve the problems of the traditional single closed-loop linear sliding mode (LSM) controller for Buck converter such as slower response speed and worse steady accuracy, a terminal sliding mode (TSM) control method with structure of voltage and current double closed loop is proposed. A load observer was designed to estimate the unknown resistance load as well as to realize the over-current protection. The unified differential equation model of Buck converter for the case of switching ON/OFF was established based on kirchhoff's law and a TSM controller and LSM controller was designed for the outer capacitor voltage subsystem and inner inductor current subsystem respectively to guarantee the transient performance and expected DC voltage output in the finite time. Meanwhile, the unified stability condition of Buck converter for the case of switching ON/OFF was deduced by the existence condition of sliding mode control. Simulation comparisons with the traditional method validate the the efficiency of the design.