Introduction of common mode choke

What is the relationship between common mode choke and inductors? Choke is a power magnetic component for electronic circuits. It is an inductor that blocks high frequency alternating current (AC) in the circuit while allowing lower frequencies or direct current (DC) to pass. The inductor is typically wound on the core by an insulated wire. The choke is capable of blocking high frequency alternating current while allowing lower frequencies to pass. In other words, if a device is used for blocking, it can be called a choke. However, if the device is used for a filter or LC circuit, it is simply referred to as an inductor. There are two different types of chokes: Audio Choke (AFC) and RF Choke (RFC). The Audio Choke (AFC) is designed to specifically block audio and power line frequencies while allowing direct current (DC) to pass. Radio frequency chokes (RFCs), on the other hand, are designed to block only radio frequencies while allowing direct current (DC) and audio to pass. The common mode choke is essentially a bidirectional filter: on the one hand, it is necessary to filter out common mode electromagnetic interference on the signal line, on the other hand, it is necessary to suppress itself from emitting electromagnetic interference to avoid affecting the normal operation of other electronic devices in the same electromagnetic environment. How to distinguish between common mode choke and single choke? Common mode choke and single choke are one of the effective components for anti-electromagnetic interference. They are widely used in various filters, switching power supplies, etc., but common mode choke is used to suppress common mode interference, while differential mode choke is used to suppress differential mode interference, both are important filter inductors. Although the common mode choke and differential mode choke (single choke) are filter inductors, the effect is different, which determines the appearance and the winding method. For the common mode choke, it is wound on the same core, and the coil diameter and coil of the two windings. The number of turns is the same, but the direction of the winding is opposite. One set of coils has two pins, so the common mode choke has 4 pins. The differential mode choke is wound around a core and has only one coil, so it only has Two pins, so the common mode choke and differential mode choke can be distinguished from the number of pins. common mode choke differential mode (single choke) How does the common mode choke work? In normal or differential mode (single choke), the current travels in one line, from one direction to the load, and propagates in the opposite direction after completing the circuit. In the common mode, the noise current propagates in the same direction on two lines. Thus, when the normal current in the circuit flows through the common mode inductor, the current generates a reverse magnetic field in the inductive coil wound in the same phase and cancels each other. At this time, the normal signal current is mainly affected by the coil resistance when there is a common mode current. When common mode through the coil, due to the same direction of the common mode current, the same magnetic field is generated in the coil to increase the inductive reactance of the coil, so that the coil exhibits high impedance and generates a strong damping effect, thereby attenuating the common mode. Current, for filtering purposes.

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