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Common mode inductor core working principle

2019-04-03 10:01:44

The common mode inductor core filter circuit, La and Lb are common mode inductors. The two coils are wound on the same core with the same number of turns and phase (wound reverse). Thus, when a normal current in the circuit flows through the common mode inductor, the current generates a reverse magnetic field in the inductive coil wound in the same phase and cancels each other. At this time, the normal signal current is mainly affected by the coil resistance (and a small amount of leakage). The damping caused by the sense); when there is a common mode inductor core current flowing through the coil, due to the same direction of the common mode current, a magnetic field in the same direction is generated in the coil to increase the inductance of the coil, so that the coil is high. The impedance produces a strong damping effect, thereby attenuating the common mode current for filtering purposes.


In fact, when one end of the filter circuit is connected to the interference source and the other end is connected to the interfered device, 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 to be low. On the level. The circuit can suppress the external EMI signal incoming, and can attenuate the EMI signal generated when the line itself works, and can effectively reduce the EMI interference intensity.
A small common mode inductor produced in China adopts high frequency noise suppression countermeasures, common mode choke coil structure, no signal attenuation, small size, convenient use, good balance, convenient use and high quality. Widely used in double-balanced tuning devices, multi-frequency transformers, impedance transformers, balanced and unbalanced conversion transformers, etc.

There is also a common mode filter inductor/EMI filter inductor with ferrite core, double wire winding, good noise suppression countermeasures, high common mode noise suppression and low differential mode noise signal suppression, low differential mode noise signal suppression interference The source is difficult to be deformed in a high-speed signal, has a small volume, has a good balance, is easy to use, and has high quality. The common mode inductor core is widely used in suppressing EMI noise of electronic equipment, USB lines of personal computers and peripheral devices, IEEE 1394 lines of DVC, STB, liquid crystal display panels, low voltage differential signals, and the like.