The role of common mode inductance is far more important than you think

The role of common mode inductance is far more important than you think

In addition to the large impedance and insertion loss under the earth's magnetic field, which has an excellent inhibitory effect on Ruoduo interference, the common mode inductance exhibits a resonance-free insertion loss characteristic in a wide frequency range. It is precisely because of this characteristic that We summarize it as an inductance commonly used in switching power supplies for computers to filter common-mode electromagnetic interference signals.
Here I have to mention EMI, the old enemy of common mode inductors. EMI refers to electromagnetic interference. And our common mode inductors are specialized in electromagnetic interference. It can be said to be handy for preventing EMI. Why can common mode inductors prevent EMI? Combined with common mode inductors The structure will be analyzed for you:
The filter circuit containing the common mode inductor, La and Lb are the 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 inductance, the currents generate opposite magnetic fields in the inductive 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; When the current flows 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 to increase the inductive reactance of the coil, so that the coil exhibits high impedance and produces a strong damping effect, thereby attenuating the common mode. mode current to achieve the purpose of filtering.

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