Magnetic Integration of Coupled-Inductor with Optimized Air-Gaps for A CRM Buck Converter

PCB-winding-based planar have been widely adopted for 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 dominates the flux distribution in the magnetic core, thus the core loss is closely related to the position of the air gaps. This paper thoroughly analyzes the flux in the magnetic core of a four-pole structure coupled inductor for a critical-mode (CRM) Buck converter and studies an optimized four-pole structure with improved air gap configuration to reduce the core loss, as well as the height of the inductor, and to improve its efficiency and power density. The influence mechanism of the air gap position on core loss is revealed, and a detailed optimal design of the studied structure is presented. To verify the effectiveness of the studied coupled inductor, a prototype with a height of 7mm, a power density of 800W/in3, and a peak efficiency of 99% is developed.