Fully-Integrated Planar Transformer With a Segmental Shunt for LLC Resonant Converters

This article presents two topologies, which provide high leakage inductance in shunt-inserted integrated magnetic transformers. These differ from conventional designs by replacing the low-permeability magnetic shunt of a planar transformer with high-permeability magnetic shunt segments, separated by many small air gaps. This approach results in a shunt with the same bulk permeability as the conventional design, while using lower cost and readily available magnetic materials such as ferrite. A modeling and design approach, which can estimate the leakage and magnetizing inductances precisely is provided for each topology. Theoretical analysis is presented and verified using finite-element analysis and experimental implementation. Ac resistance analysis for both transformer topologies is also presented. In addition, an LLC resonant converter is built to verify the performance of the proposed fully-integrated magnetic transformers in practice. It is shown that the proposed topologies can integrate all three magnetic components of an isolated LLC resonant converter in a single planar transformer, which reduces the converter's volume and cost.

Automated summary

This article presents two topologies for high leakage inductance in shunt-inserted integrated magnetic transformers. The topologies use high-permeability magnetic shunt segments and small air gaps to replace the conventional low-permeability shunt, achieving the same bulk permeability while using lower cost magnetic materials. The article provides modeling and design methods to accurately estimate leakage and magnetizing inductances, and verifies them through theoretical analysis, finite-element analysis, and experimental implementation. The performance of the proposed topologies is confirmed through the construction of an LLC resonant converter, showing reduced volume and cost.