Optimized Air-Gap Configuration for an Integrated Coupled Inductor With Lower Height and Reduced Core/Winding Losses

PCB-winding-based planar inductors have been widely adopted for the high frequency, high power density, and high efficiency power conversion. Due to the planarized structure of the magnetics, the position of the air gaps in a planar inductor not only dominates the flux distribution in the magnetic core, but also impacts the flux in the winding window. Therefore, both the core loss and winding loss are strongly related to the position of the air gaps. The flux in the magnetic core and the winding window of a four-poles structure coupled inductor for a critical-mode (CRM) Buck converter are analyzed in detail. An optimized four-poles structure with improved air gaps configuration is proposed to reduce the core loss and winding loss, as well as height of the inductor, and to improve the efficiency and power density. The influence mechanism of the air gap position on core loss and winding loss is revealed. Detailed optimal design of the proposed structure is presented. A prototype with height of 7 mm, power density of 800W/in
³
, and peak efficiency of 99% is developed to verify the effectiveness of the proposed coupled inductor.