Switching regulator based on switched-inductor SEPIC DC-DC converter with a continuous input current for lithium-ion batteries

Abstract

"This study discusses a control strategy applied to the switched-inductor single-ended primary-inductance converter (SEPIC) converter suitable for applications where the voltage delivered by a DC source varies from above or below the nominal value. The SEPIC converter can provide a non-isolated positive output voltage for the above applications; moreover, it exhibits better characteristics when combined with a switched-inductor cell. A design-oriented procedure is given that appropriately selects the elements of the converter for a given output voltage and power delivery requirements. A control scheme with two loops is chosen. A high-gain compensator is used in the inner loop such that the average inductor current follows a current reference. A proportional integral (PI) controller is used in the outer loop for output voltage regulation. The controller was designed using loop-shaping techniques and applied to regulate an output voltage of 21 V. The design was verified with experimental results in a switching regulator where step changes were applied to the load. The performance of the switching regulator was also tested for variations of the input voltage."