A fixed frequency duty-ratio based digital sliding-mode controller for DC-DC buck converter

Abstract

The hysteresis modulation (HM) based sliding mode control (SMC) implementation results in variable frequency, where the converter's operating frequency cannot be measured accurately. This will have a negative impact on circuit component and filter design. Furthermore, it is sensitive to the disturbances and the parameter uncertainties. To maintain constant switching frequency during line and load regulation, a duty-ratio (DR) based sliding-mode (SM) control approach is proposed in this paper and applied to a DC-DC buck converter. The translation of the SM control law for HM and DR scheme implementation by using field programmable gate array (FPGA) for DC-DC buck converter is illustrated. A simple and self-explanatory design and implementation procedure are also addressed. The performance and robustness of the proposed DR-based SM controllers are validated by both simulation results using MATLAB/Simulink and experimental results. The robustness of the SM controller is tested at various operating conditions and compared the results with HM-based SM and conventional linear controller. © 2018 American Scientific Publishers All rights reserved.