Using powder materials to replace air-gaps for fringing flux reduction

Amorphous or nanocrystalline cores are the preferred choice for designers when building smaller power inductors, as the materials offer a much higher possible saturation flux density compared with ferrites.

However, to store a high amount of energy, power inductors made from these materials require a relatively large air gap. This isn’t a complete solution as fringing flux entering the space around the air-gap, due to forced eddy current losses, causes further design issues. Using multiple small air-gaps can resolve this, but it can be costly, as additional manufacturing efforts are required.

This paper explores an alternative solution to large or multiple air gaps in power-inductors – lower permeability powder materials.