Common mode filter

The common mode filter usually uses a ferrite core and is wound in two wires. Low differential mode noise signals suppress interference sources and are difficult to deform in high speed signals. Good noise suppression countermeasures, high common mode noise suppression and low differential mode noise signal suppression.

Shape and structure

The shape and electrical schematic of the common mode filter in the domestic color TV set are shown in the figure.

Effect

It is to eliminate the "switching interference" unique to the switching power supply to ensure that the TV itself and other devices in the power grid are free of interference. Common mode filter circuit as shown

Characteristic

A ferrite core is used, and the two wires are wound together. Low differential mode noise signals suppress interference sources and are difficult to deform in high speed signals. Good noise suppression countermeasures, high common mode noise suppression and low differential mode noise signal suppression.

Common mode filter designs are relatively simple, including common mode capacitors, baluns or common mode inductors. The common mode capacitor bypasses the common mode current of the two input lines to ground, and the common mode inductor exhibits a balanced impedance, that is, the impedance of the power line and the ground line are equal, and this impedance exhibits an impedance characteristic to the common mode noise.

Application

Suppress electronic equipment EMI noise. DVC, STB's IEEE 1394 line. LCD panel, low voltage differential signal. USB cable for personal computers and peripherals.

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