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Investigation of a quasi-square parallel-resonant converter

A converter is proposed which is based on <i>parallel-resonant</i> technology, incorporating a capacitive filter. The convertor complies with a high-power, low voltage load specification, and is required to operate with a fixed switching frequency. The topology uses a combination of resonant tanks, and a clamped voltage technique, to maintain the advantages of more standard square-wave converters, whilst exploiting the desirable features of resonant conversion. The purpose of the proposed converter is threefold: 1. -to reduce the converter size by operating without an output filter choke; 2. -to reduce component stresses by clamping internal voltages, and so limiting voltage and current peaks; 3. -to reduce switching losses by limiting the volt-current product during the switching transient. The shape of the internal waveforms define the power transferred and are determined by values of resonant components positioned within a standard bridge circuit. As a result of these resonant components the converter efficiency at full load approaches 93%, and the characteristics of the EMI spectrum are favourable. Low power resonant techniques are well understood, however, operation at higher output powers requires careful construction techniques and consideration of various engineering compromises. An explanation of these is presented and justification for their choice is discussed. Three prototype converters are built and tested, and problems encountered during their development are highlighted. Results of two simulation techniques correlate well with the observed results, and a numerical modelling technique is developed as a design aid. As a result of the work at low output voltages it is shown that the converter is better suited to operation as the front-end of a <i>distributed power</i> power system, converting voltage from 270 V to 48 V.
Date January 1992
CreatorsPrice, Colin Franklin
PublisherUniversity of Edinburgh
Source SetsEthos UK
Detected LanguageEnglish
TypeElectronic Thesis or Dissertation

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