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What is the working principle of a common mode inductor - Keller Electronics

Time:2023/8/25 Posted:Shenzhen Kaile Electronics Co., Ltd

Why can a common mode inductance modulator prevent electromagnetic interference? To understand these issues, we need to start with the common mode inductance structure. The common mode inductance filtering circuit, La and LB are common mode inductance coils. There are also common mode inductance filter inductors/EMI filter inductors, ferrite cores, dual wire parallel windings, good noise suppression strategies, high common mode noise suppression and low differential mode noise signal suppression, and low differential mode noise signal suppression interference sources.


The common mode inductance filtering circuit, La and LB are common mode inductance coils. Two coils are wound on the same iron core, with the same number of turns and phase (reverse winding). In this way, when the normal current in the circuit flows through the common mode inductance device, the current generates opposite magnetic fields in the coil of the same phase winding inductance device and deviates from each other. At this point, the normal signal current is mainly affected by the coil resistance (and a small amount of damping caused by leakage inductance); When the common mode current flows through the coil, due to the isotropy of the common mode current, a magnetic field in the same direction is generated in the coil, which increases the inductance of the coil and makes it appear high impedance, generating a strong damping effect to attenuate the common mode current and achieve the purpose of filtering.


In fact, if one end of the filtering circuit is connected to the interference source and the other end is connected to the interfered device, La, C1, LB, and C2 form two sets of low-pass filters, which can control the common mode EMI signal on the line at a very low level. This circuit can not only suppress the entry of external electromagnetic interference signals, but also attenuate the electromagnetic interference signals generated by the circuit itself, effectively reducing the intensity of electromagnetic interference.


At present, small common mode inductors produced in China adopt high-frequency noise suppression strategies and common mode choke structures. It has the advantages of no signal attenuation, small size, convenient use, good balance, convenient use, and high quality. Widely used in dual balanced tuning devices, multi frequency transformers, impedance transformers, balanced and unbalanced conversion transformers, etc.


There are also common mode inductance filter inductors/EMI filter inductors, ferrite cores, dual wire parallel windings, good noise suppression strategies, high common mode noise suppression and low differential mode noise signal suppression, and low differential mode noise signal suppression interference sources. In high-speed signals, it is not easy to deform, has a small size, is easy to use, has good balance, is easy to use, and has high quality characteristics. Widely used to suppress electromagnetic interference noise in electronic devices, personal computers, and peripheral devices such as USB cables, IEEE1394 cables for DVCs and set-top boxes, LCD panels, and low-voltage differential signals.

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