A Series and Parallel Tuned DC-DC Resonant Converter with Hybrid Modulation

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Authors
Patel, Janki
Keyword
Power Electronics , Resonant Converter , LCLC , Series and Parallel tuned , DC-DC , Hybrid modulation
Abstract
Series and parallel tuned resonant converters have traditionally been operated at a constant frequency by employing Phase-Shift Modulation (PSM). It provides excellent efficiency from full - load to near no - load while maintaining zero-voltage switching (ZVS). However, the range of input voltage variations is limited. For the applications, where there is a wide variation in the input voltage as well as in the output load, the PSM technique is not able to maintain ZVS, resulting in switching losses. This thesis has studied the behavior and performance of the same converter under hybrid modulation in which both the frequency and the phase-shift are varied. It has been shown that the hybrid modulation technique allows the ZVS operation of the converter under widely varying input voltage and output load. Frequency-domain modelling is presented, and the performance of the converter is, first, studied under the variable-frequency modulation, and then under the hybrid modulation. It has been shown that the converter can provide better control against the input voltage variations than the fixed frequency modulation by ‘jumping’ the operating frequency from one region to another while maintaining ZVS. The range of the input voltage can be extended further by employing variable pulse-width modulation in addition to variable frequency. Unlike the constant-frequency operation, the converter exhibits some very interesting characteristics. The new characteristics help in minimizing the conduction losses and allow its operation under a wide range of input voltage and output load.
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