This paper presents a bidirectional dc-dc converter for use in low power applications. The proposed topology is based on a half-bridge on the primary and a current-fed push-pull on the secondary side of a high frequency isolation transformer. Achieving bidirectional flow of power using the same power components provides a simple, efficient and galvanically isolated topology that is specially attractive for use in battery charge/discharge circuits in dc UPS. The dc mains (provided by the ac mains), when presented, powers the down stream load converters and the bidirectional converter which essentially operates in the buck mode to charge the battery to a nominal value of 48 V. On failure of the dc mains (derived from the ac mains), the converter operation is comparable to that of a boost and the battery regulates the bus voltage and thereby provides power to the downstream converters. Small signal and steady state analyzes are presented for this specific application. The design of a laboratory prototype is included. Experimental results from the prototype, under different operating conditions, validate and evaluate the proposed topology. An efficiency of 86.6% is achieved in the battery charging mode and 90% when the battery provides load power. The converter exhibits good transient response under load variations and switchover from one mode of operation to another. Index Terms-Bidirectional power flow, currend fed push-pull, dc UPS.
Acquisitions and Acquisiiiacis et Bibliographie Services services biMiiraphiquesThe author has granted a nonexclusive licence diowing the National Library of Canada to reproduce, loan, distribute or seil copies of this thesis in microform, paper or electronic formats. Abstract A SINGLE STAGE POWER FACTOR CORRECTED AC/DC CONVERTER MATI'EO DANIELEApplications for A U D C converters that require high input power factor has been traditionally implemented by two power stages. In order to provide a cost effective and high density solution for low power applications, this thesis proposes a single stage isolated converter topology designed to achieve a regulated dc output voltage having no low frequency components and a hîgh input power factor. The topology is derïved from the basic two switch forward converter, but incorporates an additional transformer winding, an inductor, and a few diodes. The proposed circuit inherently forces the input current to be dkontinuous and ac modulated to achieve high input power factor. The
Acquisitions and Acquisiiiacis et Bibliographie Services services biMiiraphiquesThe author has granted a nonexclusive licence diowing the National Library of Canada to reproduce, loan, distribute or seil copies of this thesis in microform, paper or electronic formats. Abstract A SINGLE STAGE POWER FACTOR CORRECTED AC/DC CONVERTER MATI'EO DANIELEApplications for A U D C converters that require high input power factor has been traditionally implemented by two power stages. In order to provide a cost effective and high density solution for low power applications, this thesis proposes a single stage isolated converter topology designed to achieve a regulated dc output voltage having no low frequency components and a hîgh input power factor. The topology is derïved from the basic two switch forward converter, but incorporates an additional transformer winding, an inductor, and a few diodes. The proposed circuit inherently forces the input current to be dkontinuous and ac modulated to achieve high input power factor. The
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