Sliding mode control strategy with maximized existence region for DC-DC buck converters

Abstract

In this article, a sliding mode control (SMC) strategy with maximized existence region (ER) is presented for DC-DC buck converters. The ERs of the sliding mode are determined from the existence condition of the SMC. It is shown that the ER can be enlarged to its maximum size by an optimum sliding coefficient whose equation is determined analytically. Also, it is pointed out that the enlargement of the ER results in a considerable improvement in the dynamic response of the output voltage. In addition, it is shown that the optimum sliding coefficient is not sensitive to the variations in the DC input voltage and load resistance. Moreover, the capacitor current that is employed in the sliding surface function to avoid the derivative operation does not lead to any steady-state error in the output voltage in case of an uncertainty in the capacitance value. The correctness of the proposed control approach is validated by computer simulations and experimental results. These results demonstrate that the proposed SMC strategy results in an excellent dynamic response without overshoot and undershoot in the output voltage and inductor current and guarantees a maximized ER for the sake of stronger closed-loop stability.