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Do you still understand it (common mode inductance)
Sep 16, 2018



Do you still understand it (common mode inductance)


Common Mode Choke, also known as common mode choke, is a coil that is symmetrically wound in the opposite direction and has the same number of turns on a closed magnetic ring. The ideal common mode choke has an inhibitory effect on the common mode interference between L (or N) and E, and has no inductance suppression effect on the differential mode interference between L and N. However, the incomplete symmetry of the actual coil winding leads to the generation of differential mode leakage inductance. The signal current or supply current flows in opposite directions when flowing through the two windings, and the generated magnetic flux cancels each other out, and the choke exhibits a low impedance. The common mode noise current (including the disturbance current caused by the ground loop, also called the longitudinal current) flows in the same direction when flowing through the two windings, and the generated magnetic flux is added in the same direction, and the choke exhibits a high impedance, thereby suppressing the total The role of mode noise.


The common mode inductor is essentially a bidirectional filter: on the one hand, it is necessary to filter out common mode electromagnetic interference on the signal line, on the other hand, it is necessary to suppress itself from emitting electromagnetic interference and avoid affecting the normal operation of other electronic devices in the same electromagnetic environment. .


The common mode choke can transmit the differential mode signal, the differential mode signal with low DC and low frequency can pass, and the high frequency common mode noise presents a large impedance, which acts as a resistor, so it can be used. To suppress common mode current disturbance.



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