Improved linear sliding mode controller of buck converters through adding terminal sliding mode

In order to solve the problems of the traditional single closed-loop linear sliding mode (LSM) controller of Buck converter, such as slow response and bad steady accuracy, a new double-loop control structure and a terminal sliding mode (TSM) controller is introduced in this paper. Based on the differential equation model of Buck converter, a TSM controller and LSM controller are designed for the outer voltage loop and the inner current loop respectively, to guarantee the control of nonlinear dynamical behaviors of the capacitor and the inductor simultaneously, as well as to output the expected DC voltage in a finite time. The stability condition for the power switch `ON' and `OFF' is deduced. And the influences of the design parameters of TSM are also analyzed. Simulation comparisons validate the proposed improvement.