Remaining Inductor Current Phenomena of Complex DC–DC Converters in Discontinuous Conduction Mode: General Concepts and Case Study

Remaining inductor current phenomena occur in several dc–dc converters operating in discontinuous conduction mode, but they do not agree with the classical definition of the discontinuous conduction mode. Since these special phenomena often cause misunderstanding during theoretical analysis and engineering applications, a reexamination is performed in this paper. Based on the investigation of energy characteristics, a new explanation of the discontinuous conduction mode is proposed so that all discontinuous cases, including the remaining inductor current phenomena, can be unified by the proposed concepts. The paper presents the canonical explanation, existence conditions and main solving principles, which simplify the derivation process of steady-state performance of a complex dc–dc converter. Case study on a fifth order self-lift Luo converter and a seventh order re-lift SEPIC converter are performed, respectively, and the corresponding simulation results are shown to validate the theoretical analysis.