Reducing Parasitic Capacitances of Ring-Core Inductors

In this work, we analyze the impact of the permittivity of the material of the core and of the configuration of the winding on the parasitic capacitance that typically undermines the performance of ring-core inductors at high frequencies. Inductors with NiZn and MnZn ferrite cores and with both loose and tight windings have been constructed, measured and compared. Also, a high-frequency circuit model of the inductors has been employed along with a simple characterization technique to obtain equivalent circuits of the ring-core inductors. This has allowed us to quantify the impact of the different core choices and winding strategies on the performance of the inductors up to frequencies of at least 30 MHz. Our results demonstrate that the parasitic capacitance of single-layer ring core inductors can be reduced by using winding strategies that are different for NiZn and MnZn cores. We conclude that the different responses of inductors made with different core materials is due to the differences in the permittivity of the ferrite materials of the core.