Duality approach to the study of switched-inductor power converters and its higher-order variations

Abstract

Switched-inductor technique is a duality counterpart of the conventional switched-capacitor technique. On the other hand, the duality principle is also a useful technique for power converter topology study that is now illustrated by a duality between conventional switched-capacitor and the switched-inductor. The basic switched-inductor converters with current conversions 2, 1/2 and -1 are derived using the duality principle to basic switched-capacitor converters. The operation principle and conversion method have been illustrated in detail. High order of current conversion is also illustrated using the switched-inductor concept. For high step-down version, only two transistors are needed. For high step-up version, the number of transistors is equal to the step-up conversion ratio. Simulation and experimental tests have confirmed the proposed new concept of power conversion. This study presents a useful study guideline to the switching techniques, current sharing and the duality principle for the converters. The converters find applications to power up current-based loads such as light-emitting diode in a digitised manner. The circuits can also be used to provide conversion for current source such as photovoltaic to give multiple or fractional current output. Current mode controlled electrical machine can also be realised easily by the proposed circuit.