Parabolic-Modulated Sliding Mode Voltage Control of Buck Converter

Abstract

Conventional hysteresis-modulated sliding mode (SM) controller exhibits a varying switching frequency. Existing SM controllers for achieving constant-switching-frequency operation often have complicated structures and/or are less straightforward to design to meet different steady-state, transient and loading requirements. In this paper, a new direct SM voltage controller based on parabolic modulation is proposed and applied to buck converter. The objective is to achieve constant-switching-frequency operation of a switching converter with simple control structure and good operating performance. Both theoretical study and experimental results of a buck converter show that the proposed parabolic-modulated SM control can achieve (i) constant switching frequency in the continuous conduction mode (CCM) and quasi constant switching frequency in the discontinuous conduction mode (DCM) of operation, (ii) inherent input-disturbances rejection and superior reference tracking performance, and (iii) seamless mode transition between CCM and DCM.