How Common-mode inductors work

Release time:

Feb 24,2022

Why Common-mode inductor can prevent EMI? To figure this out, we need to start with the structure of the Common-mode inductor.

Common-mode inductor company
Common-mode inductor filter circuit, La and Lb are Common-mode inductor coils. The two coils are wound on the same core with the same number of turns and phases (winding reversed). In this way, when the normal current in the circuit flows through the Common-mode inductor, the currents generate opposite magnetic fields in the inductor coils wound in the same phase and cancel each other out. At this time, the normal signal current is mainly affected by the coil resistance (and a small amount of due to Damping caused by leakage inductance); when there is a common mode current flowing through the coil, due to the same direction of the common mode current, a magnetic field in the same direction will be generated in the coil and the inductive reactance of the coil will be increased, making the coil appear as high impedance, A strong damping effect is produced to attenuate the common mode current and achieve the purpose of filtering.
In fact, if one end of the filter circuit is connected to the interference source and the other end is connected to the interfered device, then La and C1, Lb and C2 form two sets of low-pass filters, which can make the common mode EMI signal on the line be controlled at a very low level. on the level. Common-mode inductor manufacturers tell you that this circuit can not only suppress the incoming of external EMI signals, but also attenuate the EMI signals generated by the line itself, which can effectively reduce the intensity of EMI interference.
A small common-mode inductor produced in China, adopts high-frequency noise suppression countermeasures, common mode choke coil structure, no signal attenuation, small size, easy to use, good balance, easy to use, high quality and so on. Common-mode inductor manufacturers tell you that they are widely used in double-balanced tuning devices, multi-frequency transformers, impedance transformers, balanced and unbalanced conversion transformers, etc.
Common-mode inductor manufacturers tell you that there is also a common-mode filter inductor/EMI filter inductor using ferrite core, double-wire winding, good noise suppression countermeasures, high common-mode noise suppression and low differential-mode noise signal suppression, The low differential mode noise signal suppresses the interference source, is difficult to deform in high-speed signals, has the advantages of small size, good balance, convenient use and high quality. Common-mode inductor manufacturers tell you that it is widely used in suppressing EMI noise of electronic equipment, USB lines of personal computers and peripheral equipment, DVC, STB's IEEE1394 lines, liquid crystal display panels, low-voltage differential signals, etc.