If a pair of coils in the same direction are wound around a magnetic ring made out of a certain magnetic material, when alternating current passes through, magnetic flux is generated in the coil due to electromagnetic induction. For differential mode signals, the magnetic flux generated is the same in magnitude and opposite in direction, and the two cancel out each other, resulting in a very small differential mode impedance generated by the magnetic ring. For common mode signals, the magnitude and direction of the magnetic flux generated are the same, and the superposition of the two results in a larger common mode impedance of the magnetic ring. This characteristic reduces the impact of common mode inductance on differential mode signals and has good filtering performance against common mode noise.
The common mode inductor is essentially a bidirectional 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 also needs to suppress the electromagnetic interference itself from emitting outward to avoid affecting the normal operation of other electronic devices in the same electromagnetic environment.
The detailed advantages are shown in below:
(1) The annular magnetic core has good electromagnetic coupling, simple structure and high production efficiency;
(2) High working frequency, high power density, frequency between about 50kHz~300kHz.
(3) Excellent heat dissipation characteristics, with a high surface area to volume ratio, a very short heat channel, convenient for heat dissipation.
(4) Ultra-low insertion loss;
(5) High impedance characteristic of high-frequency inductance;
(6) Good quality with reasonable cost;
(7) Stable structure.
(1) Using high frequency ferrite core, vertical winding of flat wire;
(2) Uniform distribution parameters and good consistency of parameters;
(3) Automatic production with large current and high inductance can be achieved;
(4) With high current and excellent anti-EMI performance;
(5) Conformance of distributed parameters;
(6) High current density, high frequency, high impedance;
(7) High Curie temperature;
(8) Low temperature rise, low loss, etc.
Commonly used in computer switching power supplies to filter common mode electromagnetic interference signals. In board design, common mode inductors also serve as EMI filters to suppress the radiation and emission of electromagnetic waves generated by high-speed signal lines.
Widely used in air conditioner power supply, TV power supply, UPS power supply, etc.