Switching power supply generally introduces common mode noise in the frequency range from 10 kHz ~ 50 MHz or even higher. Therefore, to effectively reduce these noises, the common mode inductor shall have a high enough impedance. To achieve this specification, the high permeability Manganese-zinc ferrite and the amorphes material are the most appropriate choices. The Common Inductor's impedance Zs consist of the inductance Xs and the resistance Rs.
Soft-Switching Resonant Inductor
With the increasing demands of the soft-switching power supply circuit, many producers are confronting the low homogeneity in mass production, which refers to the source of controlling signal which is generated by the leakage inductance of the transformer and stray capacitance of power MOSFET. To get rid of this problem, the common solution is to add the resonant inductance. Therefore the designer shall consider the choice of an inductor with properties of: