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Common mode choke
Common mode choke is usually used to filter common mode EMI signals in switching power supplies of computers. In the design of the board, the common mode choke also plays the role of EMI filtering, which is used to suppress the electromagnetic wave radiated by the high-speed signal line.
Description
Common mode choke is a common mode interference suppression device with a ferrite core. It is composed of two coils with the same size and the same number of turns symmetrically wound on the same ferrite ring core. The winding direction of the coil is the opposite, forming a four-terminal device. When the differential mode current flows through the two coils, two mutually counteracting magnetic fields H1 and H2 are generated. At this time, the working current is mainly damped by the coil ohmic resistance and the small leakage inductance under the negligible operating frequency, so the differential mode signal can pass through without attenuation. When the current flows through the common-mode current, the magnetic flux in the magnetic ring overlaps with each other, thus having a considerable amount of inductance The coil shows high impedance and a strong damping effect, which can restrain the common-mode current. Therefore, the common-mode choke can effectively suppress the common-mode interference signal in the balanced line but has no effect on the differential mode signal transmitted normally.
Features:
High reliability, small size, low cost, easy to insert circuit board, lead-free products, in line with ROHS directive.
Application:
It is widely used in AC tuner, fax, small size fluorescent lamp, video recorder, and color TV to suppress noise conducted by AC line common mode choke.
Drawing:
Features:
High reliability, portable, closed magnetic design, small size, low cost, easy to insert circuit board, lead-free products, in line with ROHS directive.
Application:
It is widely used in AC tuner, fax, small size fluorescent lamp, video recorder, and color TV to effectively suppress the noise conducted by AC line common mode choke.
Drawing:
Characteristics
Impedance characteristics of common mode choke
The common-mode choke has high initial permeability, high impedance, and insertion loss in the geomagnetic field. It has an excellent suppression effect on interference and shows no resonance insertion loss in a wide frequency range.
High initia magnetoconductivity
The initial magnetoconductivity of the common-mode inductor is 5-20 times higher than that of ferrite. So it has higher insertion loss, and its suppression effect on conducted interference is much greater than that of ferrite.
High saturation magnetic induction
2-3 times higher than ferrite. In the case of strong current interference, it is not easy to magnetize to saturation.
Excellent temperature stability
At higher Curie temperature, the change rate of properties of the alloy is obviously lower than that of ferrite, and the change of properties is close to linear.
Flexible frequency characteristics
More flexible by adjusting the process to obtain the required frequency characteristics. Different impedance characteristics can be obtained by different manufacturing processes and proper coil explosion, which can meet the filtering requirements of different wavebands and make the impedance value much higher than that of ferrite.
Application
Common mode choke is mainly used for common-mode interference filtering of the power grid and anti-shock interference of electronic equipment and electronic instruments.
