Single-input multi-output configurations of interconnected power converters and applications

Abstract

This thesis aims to analyze two-stage single-input multi-output configurations constructed from interconnected DC-DC converters, which can feed multiple loads at various power levels. A complete family of 16 possible configurations that include conventional voltage-source-mode (VSM) converters and the less known current-source-mode (CSM) converters, covering all possible termination types (voltage type and current type) and connection styles (parallel connection and series connection), is derived. These configurations are compared in terms of power sharing capability, mutual effects among interconnected modules, basic control requirements and load characteristics. Specifically, four of the configurations are identified to have advantages over the others and are studied in depth. Various choices of constituent converters and their connection configurations are presented and compared. To illustrate the detailed design considerations and the choice of suitable configurations and the corresponding control schemes, a two-stage configuration consisting of a VSM buck converter as the pre-stage and two series-connected CSM boost converters as the post-stage is proposed to drive light-emitting-diodes (LEDs) under high input voltage conditions. The derivation of the corresponding small-signal model, control design and parameter design is given. Experimental results are presented to verify the basic properties of this configuration and the applicability of the design process. Finally, the specific features of the two-stage configuration consisting of the VSM buck converter and series-connected CSM boost converters are further explored. The first stage of this configuration can operate both in continuous current mode and discontinuous current mode with the same closed-loop control scheme. Besides, a minimal current control scheme can be used to reduce the second-stage voltage stress and improve the load capacity of the converter. This thesis presents the essential circuit theoretic basis for development of multi-output converters for all applications covering voltage and current types of input and output terminations. The family of single-input multi-output configurations presented is complete and exhaustive for all possible voltage and current interfaces and using either series or parallel connection styles.