Pulse train controlled buck converter with coupled inductors

Abstract

Pulse train (PT) controlled switching DC/DC converters possess advantages of simple structure, fast dynamic response, good robustness etc. but also accompanied by undesirable low-frequency oscillation phenomenon when the converters are operated in continuous conduction mode (CCM). To mitigate the low-frequency oscillations of PT controlled buck converters, a novel buck converter with coupled inductor is proposed in this paper. Firstly, the mechanism of the low-frequency oscillation is analysed, the corresponding oscillation suppression method is discussed and the discrete-time model of the proposed converter is constructed. Furthermore, the bifurcation and time-domain diagrams of the output voltage and the switching peak current in terms of coupling coefficient and load variation are reported, and the influence from the coupling coefficient and load on low-frequency oscillation behaviours is revealed. The experimental results verify that the output voltage of the PT controlled proposed buck converter can be timely adjusted based on proper configuration of the coupling coefficient, and hence the low-frequency oscillation can be eliminated and the maximum switching peak current can be decreased.