Analysis of low profile ferrite material based planar shell core inductor

The inductance of a coil can be increased by passing the magnetic flux through a high permeability magnetic core. Due to flux leakage in most of the inductor designs, not all of the magnetic flux flows in the core. In this paper, we propose a low profile planar shell core inductor and investigate the effect of leakage flux on inductor's electrical performance in terms of inductance, resistance and quality factor. We compare our proposed planar shell core inductor to a traditional toroid inductor with a rectangular core. We demonstrate that enclosed inductor's windings in the core reduce the leakage flux and hence increase the inductance of the planar shell core. We present the simulation results of the magnetic field distribution in the core and in the surrounding air. The proposed design of a planar shell core inductor achieves up to 2-5 % increase in the inductance compared to a traditional toroid inductor using the same area for the flux flow in both designs. Moreover, we present experimental results of the electric performance of such low profile planar shell core inductor.