How the common mode inductor acts as a bidirectional filter in the circuit？

There is a special application of mutual inductance, that is, common mode inductance.

Common mode inductors can also be called common mode chokes, which are commonly used in computer switching power supplies to filter common mode electromagnetic interference signals. In the board design, the common mode inductor acts as an EMI filter to suppress the electromagnetic radiation generated by the high-speed signal line from radiating outward.

The common mode inductor also acts as a bidirectional filter in the circuit. What kind of points do the common mode inductors need in order to be able to act as a bidirectional filter in the circuit? Let's briefly talk about it.

High initial permeability

The common mode inductor needs to have a high initial permeability. The initial permeability of the common mode inductor is 5-15 times that of the ferrite, so it has a large insertion loss. In the inhibition of conducted interference, it is better than ferrite.

High saturation magnetic induction

The common mode inductor needs to have a high saturation magnetic induction strength, which is 2-3 times higher than that of ferrite. In the case of strong current interference, it is not easy to magnetize saturation.

Excellent temperature stability

The common mode inductor needs to have excellent temperature stability. The higher the Curie temperature, the higher the temperature fluctuation is, the better the alloy property change rate is than the ferrite, and the stability is close to linear.

Flexible frequency characteristics

Common mode inductors require flexible frequency characteristics and are flexible enough to adjust the process to achieve the desired frequency characteristics. Different manufacturing processes and proper coil polymerization can obtain different impedance characteristics to meet the filtering requirements of different bands, and the impedance value is much higher than that of ferrite.

At present, the common mode inductor is widely used, it can be applied in RF and wired communication, information skill setting equipment, radar detector, automotive electronics, cellular phone, sucker, audio equipment, PDAs, wired remote control solution. System, short pressure electric module, electronic measuring equipment, computer room equipment, switching power supply and measurement and control system can see it!