FEA modeling of the low profile coupled inductor with non-uniform flux distribution

The high frequency 3-dimension (3D) integrated Point-of-Load (POL) module has been demonstrated with more than 800W/in³ power density, in which the low profile inductor serves as the substrate carrying the active components. The performance of the magnetic substrate can be further improved by inversed coupling two single-phase inductors. However, the non-uniform distributed flux and permeability in the low profile coupled inductor, raises some new challenges for its inductance and core loss modeling. The accuracy of the conventional reluctance and core loss model, which usually assume uniform flux and core loss density in the core, are questionable. Therefore, the Finite Element Analysis (FEA) simulation tool is used to develop the inductance and core loss models. With these FEA models, the coupled inductor substrates are designed and evaluated for Multi-MHz two-phase 3D integrated POL modules. The impact of the inversed coupling on the magnetic performance of the inductor substrate is also discussed. The comparison between coupled and non-coupled inductors reveals that the inversed coupling can reduce both the core volume and core loss by 40%. The analytical results are verified by the experimental data.