Efficient Switched-Capacitor Converters
Switched-capacitor (SC) power converters are a class of converters comprised entirely of capacitors and switches. These converters contain no bulky magnetic components and are well suited for miniaturization and silicon integration. In this thesis, a comprehensive framework for the design and analysis of efficient, high-performance switched-capacitor DC-DC converters is presented. A precise, curvature-based averaged modelling technique is first proposed. The generalized technique provides a complete characterization of the converter at all steady-state operating conditions. From this model, a simple and accurate expression for the output impedance is derived. The technique is applied on a number of SC converter topologies and compared with existing steady-state models. An approach to model the dynamic behaviour of SC converters based on the generalized state-space averaging method is also described and demonstrated on a conventional SC converter. Furthermore, a procedure to determine the attainable ideal conversion ratios of any SC converter structure is presented. This procedure is applied on a generalized SC structure and the performance limits of multiphase switched-capacitor DC-DC converters are examined. Based on these results, a novel multiphase SC converter structure with variable-gain is proposed. The converter utilizes an optimized switching configuration with an increased number of attainable ideal conversion ratios, for the given number of capacitors and phases. This property allows the converter to maintain high efficiency across a wide range of operating conditions while reducing size, cost and switching losses. Finally, an integrated implementation of the proposed SC converter is designed, analyzed, and tested. The converter generates a regulated 3.3 V output from a 2.6–5.5 V input at up to 165 mA of output current and is fabricated using 0.35 µm CMOS technology. Details on the implementation are provided, including methods to drive and control the integrated converter. The simulated and experimentally measured performance of the circuit is presented and compared with existing converters.
URI for this recordhttp://hdl.handle.net/1974/25650
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