Switching frequency regulation in sliding mode control for synchronous buck converter

Abstract

This study aims to control the switching frequency of synchronous buck (SR-buck) converters using the second-order sliding mode controller by prescribed control law. The relation between position of the switching line and the switching frequency is discussed at stable state. On-resistance of MOSFET and ESR of inductor and capacitor are taken into account. A hysteresis method is proposed to change the position of switching line to control the switching frequency, and the equation of calculating hysteresis width is deduced. The differentiator with the discrete super-twisting is designed. Numerical simulation results under rated working condition, load disturbance, voltage perturbation, and switching frequency variation have been presented. Switching frequency variation is discussed and can be controlled accurately when the working condition is fixed. It validates the effectiveness and feasibility of the method proposed in this study.

Keywords

• power convertors
• variable structure systems
• frequency control
• frequency regulation
• mode control
• synchronous buck converter
• switching frequency
• mode controller
• prescribed control law
• switching line
• frequency variation