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Title: Modelling and analysis of radial mode piezoelectric transformers and inductor-less resonant power converters
Author: Horsley, Edward Lewis
ISNI:       0000 0004 2717 3155
Awarding Body: University of Sheffield
Current Institution: University of Sheffield
Date of Award: 2011
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Within the electronics industry there is a continual demand for DC-DC power converters that achieve high power density at low cost. Since a piezoelectric transformer (PT) has an electrical equivalent circuit that is similar to several resonant converter topologies, a PT can be used to replace many of the reactive components in these topologies with a single ceramic component, thereby offering potential savings in cost, size, and mass. The first part of this thesis presents a new equivalent circuit model for one of the most promising types of PT, the radial mode Transoner. This model relates the electrical characteristics of the PT to the physical dimensions and material properties. Considerable insight is then gained about how to design these devices to meet a particular set of converter specifications whilst simultaneously maximising PT power density. The second part of this thesis concerns the effect of the rectifier topology on PT power density. Using concepts from material science, together with equivalent circuit models of both the PT and the rectifier topologies, it is shown that a given PT will always achieve a higher thermally limited maximum output power when used in an AC-output topology compared to a DC-output topology. The half-bridge inductor-less PT-based converter topology is particularly attractive because it requires no additional components between the half-bridge and the rectifier. However, it is difficult to achieve zero-voltage-switching (ZVS) without significantly compromising PT power density when using this topology. The third part of this thesis details the development and experimental verification of a new model for the ZVS condition. Using a normalisation scheme and numerical optimisation techniques, the requirements for achieving inductor-less ZVS are accurately quantified for the first time. The impact of these requirements on PT power density is assessed, and design guidelines for maximising PT power density are given.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available