Reduction of the Mutual Couplings between Inductor and Capacitor with Rotated Inductor Winding
The mutual inductance between inductors and capacitors in EMI filters makes capacitor and EMI filter performance worse at high frequencies. The traditional inductor windings are located on the two sides of the inductor. This winding structure makes the leakage flux asymmetrical to the center line of the capacitors. As a result, the net flux linking capacitors, which contribute to the mutual inductance between the inductor and the capacitor, is not small. In order to improve EMI filter's performance, two inductor windings are proposed to be rotated by 90 degree. After the windings are rotated, the magnetic flux is symmetrical to the center line of the capacitors. The net flux linking to the capacitors is therefore greatly reduced. There is more than 90% mutual inductance reduction measured in experiments. As a result, EMI filter's performance is also improved at high frequencies.