Evaluation of High-Current Toroid Power Inductor With NdFeB Magnet for DC–DC Power Converters

This paper presents an experimental evaluation of a high-current toroid power inductor (TPI) with a NdFeB permanent magnet (PMTPI). By adding a small piece of a fabricated NdFeB-N35EH magnet (the magnet volume is ~0.36% of the PMTPI ferrite core volume) in the air gap of the TPI, the saturation current of the PMTPI is doubled with the same size and inductance value. The desired dimensions of the NdFeB-N35EH permanent magnet (PM) are calculated before fabrication, and then, the fabricated PM is characterized. The ~6.8-μH PMTPI is tested in a 5-2-V buck power converter. Results show that, compared with a TPI with the same size and inductance (~6.8 μH) without the PM, the saturation current of the PMTPI is doubled (from 7 to 14 A). Compared with another TPI with a larger size needed to double the saturation current, the ferrite core weight of the PMTPI is reduced to 53.6%, and the core volume is reduced to 59.2%. Experimental results also show that the addition of the NdFeB-N35EH PM does not introduce additional power losses and increase of temperature for the PMTPI and does not affect the power converter efficiency.