Control Strategy for Core-Loss Reduction in High-Frequency Transformers

High-frequency transformers (HFTx) are typically one of the lossiest, bulkiest and heaviest components in a power electronics system with galvanic isolation; for this reason, many literatures are saturated with research in HFTx size and loss optimization. These approaches are limited to the transformer design and manufacturing, and typically rely on complex algorithms. In this study, a circuit-based approach to reduce the transformer overall losses through specifically addressing the core loss, is proposed. This approach allows the implementation of a simple control strategy to reduce the HFTx core loss by transferring a desired RMS voltage (thus supplying a desired power to the load) from its primary to secondary side with low peak AC flux density. It is also independent of the HFTx design and manufacturing, thus can be implemented in a system that is already built. However, the control strategy can still be taken into consideration as part of the design stage of the system so as to build a transformer as small as possible without much sacrifice in its losses. A Z-source-inverter-based isolated power converter is used in this research to validate the control strategy, but the same concept can be implemented with any kind of converter that has control over the voltage shape across the transformer. Theoretical analysis shows that the converter's overall efficiency can be high using the proposed control strategy, especially at light load conditions. Tradeoffs of implementing such kind of control strategy are also addressed in this paper.