If want to improving the toroidal ferrite core indcutor, you must select a reasonable shield diameter,
Shielding is a double-edged sword, which can reduce EMC and other interference, but also increase the loss of the coil and reduce the Q value. Therefore, the size of the shield should not be too small. However, the size of the shield is too large, will increase the volume, so to choose a reasonable size of the shield diameter.
When the ratio of shield diameter Ds to coil diameter D meets the following value, that is, Ds/D = 1.6-2.5, the Q value will be reduced by no more than 10%.
Guangzhou feineng is the toroidal power inductor manufacturers , free express your opinion to probe into the issue.