Use of DCR-optimized natural switching surfaces in the second-order sliding mode control of DC/DC buck and boost converters and current limiting methods

Abstract

Second-order sliding mode control utilizing natural switching surfaces has demon-strated robust dynamic performance in the control of switching buck and boost converters for start-up, load changes, and large signal disturbances. However, practical implementation often encounters challenges such as the chattering phenomenon and large inductor currents during start-up or loading transients. The primary focus of this research is proposing potential solutions for these practical issues. Assuming the parasitic resistances, such as the on-state resistances of switches and the equivalent series resistances of output capacitors, are relatively low, the direct current resistance (DCR) of the inductor becomes the primary parasitic resistance that causes chattering due to its damping effect. For this reason, the DCR of the inductor is taken into account in the system dynamics from which natural switching surfaces are derived. By incorporating these surfaces into the control laws, the chattering effect caused by losses is mitigated while maintaining effective control. Furthermore, current limiting techniques are proposed for converter protection and reliability. These techniques are integrated into the control laws to manage large inductor currents effectively during transients, thereby pre-venting potential damage and enhancing the overall performance of the converter. Through theoretical analysis, geometrical representations, and simulation studies, a comprehensive framework for minimizing chattering and managing large inductor currents in the second-order sliding mode control of buck and converters integrating natural switching surfaces is established.