Application of extremum co-energy principle for homogenizing current distribution in parallel-connected windings in transformers: Design optimization of winding turn allocation among winding layers

Shirakawa, Tomohide; Umetani, Kazuhiro; Hiraki, Eiji

doi:10.23919/epe17ecceeurope.2017.8099115

Cited by 4 publications

(1 citation statement)

References 21 publications

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“…It also lacks physical meanings or intuition. [36] proposed application of the extremum co-energy principle for calculation and prediction of the current distribution and resulting AC resistance. It was verified by the experiments.…”

Section: Introductionmentioning

confidence: 99%

Optimal Design of Megahertz $LLC$ Converter for 48-V Bus Converter Application

Cai

Ahmed

et al. 2020

IEEE J. Emerg. Sel. Topics Power Electron.

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The intermediate bus architecture employing the 48V bus converter is one of the most popular power architecture. 48V to 12V bus converter has wide applications in telecommunications, networks, aerospace, and military, etc. However, today's state of the art products has low power rating or power density and becomes difficult to satisfy the demand of increasing power of the loads. To improve the current design, a GaN (Gallium Nitride) based two-stage solution is proposed for the bus converter. The first stage Buck converter regulates the 40V to 60V variable input to a fixed 36V bus voltage. The second stage LLC converter convert the 36V to 12V by a 3:1 transformer. The whole solution achieves the fixed frequency control. The thesis focus on the detail design and optimization of LLC converter, especially its transformer. To have high density and high efficiency, the transformer design becomes critical at MHz frequency. The matrix transformer concept is applied and a merged winding structure is used for flux cancellation, which effectively reduces the AC winding losses. A new fully interleaved termination and via design is proposed. It achieves significant reduction in loss and leakage flux. In addition, to study the current sharing of parallel winding layers, a 1-D analytic model is proposed and a symmetrical winding layer scheme is used to balance the current distribution. The hardware is built and tested. The proposed two-stage converter achieves the best performance compared to the current market. Intermediate bus architecture (IBA) has wide applications in telecommunication, server and computing, and military power supplies. The intermediate bus converter (IBC) is the key stage in the IBA, where the DC bus voltage from the front-end power supply is converted to a lower intermediate bus voltage. Traditional IBC suffers from bulky magnetic components including inductors and transformers.This work illustrates the design and implementation of a two-stage IBC, where the firststage Buck converter will provide regulation and the second stage LLC converter will provide isolation. Thanks to the soft-switching capability of LLC, the magnetic volume can be significantly reduced by raising the switching frequency of the converter. Therefore, planar magnetics can be used and placed directly inside of the printing circuit board (PCB), which allows for higher power densities and easy manufacturing of the magnetics and overall converter. However, as the frequency goes higher, the AC losses of the transformer caused by the eddy current, skin effect, and proximity effect become dominant. As a result, high-frequency transformer design becomes the key for the converter design. First, matrix transformer concept is applied to distribute the high current and reduce the conduction loss. Second, a novel merged winding structure is proposed for better transformer winding interleaving. Third, a new terminal structure of the transformer is proposed. Finally, the current sharing between parallel windings are modeled and studied. All the eff...

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Section: Introductionmentioning

confidence: 99%