A Novel Planar Nonlinear Coupled Inductor for Improving Light and Intermediate Load Efficiency of DC/DC Converters

With the development of data center, the two-stage voltage regulator module (VRM) is paid considerable attention. Since CPU goes into sleep mode frequently and spends a lot of time working at intermediate load in our daily use, it is important to have high light and intermediate load efficiency. This article proposes a novel planar nonlinear coupled inductor with a three-layer sandwiched structure, in which a middle layer made of high permeability material is sandwiched between two side layers made of low permeability material. Its nonlinearity can be controlled by configuring permeability, saturation flux density, and thickness of the high permeability middle layer. Benefitting from the structure, it can improve light and intermediate load efficiency, due to high self-inductance and low coupling coefficient. Besides, an analytic model is derived to calculate self-inductance and coupling coefficient for quick design, and design guidelines are summarized. A nonlinear coupled inductor and a conventional inductor with constant coupling coefficient are fabricated to compare the performance. Compared with the conventional constant coupling coefficient inductor, the proposed nonlinear coupled inductor could effectively improve the efficiency at light and intermediate load.