Common Mode Choke Core | What is a common mode choke?

Common Mode Choke Core | What is a common mode choke?

Common mode choke, also called common mode choke coil, is a coil with opposite directions and the same number of turns symmetrically wound on a closed magnetic ring. The ideal common mode choke coil has a suppression effect on the common mode interference between L (or N) and E, but has no inductive suppression effect on the differential mode interference existing between L and N. However, the actual coil winding is not completely symmetrical, which will lead to the generation of differential mode leakage inductance. When the signal current or power current flows in the opposite direction in the two windings, the generated magnetic flux cancels each other, and the choke coil presents low impedance. The common mode noise current (including the disturbance current caused by the ground loop, also known as the continuous current ) flows in the same direction when passing through the two windings, and the generated magnetic flux is added in the same direction, and the choke coil presents h high impedance, thereby suppressing the common The effect of mode noise.

The common-mode inductor is essentially a two-way filter: on the one hand, it needs to filter out the common-mode electromagnetic interference on the signal line, and on the other hand, it must restrain itself from emitting electromagnetic interference to avoid Affecting the normal operation of other electronic devices in the same electromagnetic environment.

The common mode choke coil can transmit differential mode signals, both DC and low frequency differential mode signals can pass through, but it presents a large impedance to high frequency common mode noise, so it can be used to suppress turke ho bur curr are generally used at the power line input.

Common mode inductive choke coil is an important part of switching power supply, frequency converter, UPS power supply and other equipment. Its working principle: when the working current flows through two opposite coils, two magnetic fields H1 and H2 that cancel are each generated . At this time, the working current is mainly damped by the ohmic resistance of the coil and the small leakage inductance at negligible working frequency. If there is an interference signal flowing through the coil, the coil presents a high impedance, which produces a strong damping effect to attenuate the interference signal.

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