Definition and function of common mode inductance

Common mode chokes, also known as common mode chokes, are often used in computer switching power supplies to filter common mode electromagnetic interference signals. 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 needs to suppress the electromagnetic interference emitted by itself, so as not to affect the normal working electromagnetic environment of other electronic devices in the same area. In short, the production of common mode inductors should meet the following requirements: The wires wound on the coil core should be insulated from each other to ensure that no breakdown or short circuit occurs between the coil turns under the action of instantaneous overvoltage.

Common mode chokes, also known as common mode chokes, are often used in computer switching power supplies to filter common mode electromagnetic interference signals. In the design of the circuit board, the common mode inductance also plays the role of EMI filtering to suppress the electromagnetic waves radiated by the high-speed signal line.

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 needs to suppress the electromagnetic interference emitted by itself, so as not to affect the normal working electromagnetic environment of other electronic devices in the same area.

In short, the production of common mode inductors should meet the following requirements:

(1) The wires wound on the coil core should be insulated from each other to ensure that no breakdown or short circuit occurs between the coil turns under the action of instantaneous overvoltage;

(2) When a large instantaneous current flows through the coil, the magnetic core should not be saturated;

(3) The magnetic core in the coil should be insulated from the coil to prevent breakdown between the two under the action of transient overvoltage;

(4) The coil should be wound in a single layer as much as possible to reduce the parasitic capacitance of the coil and improve the ability of the coil to withstand instantaneous overvoltage.

What are the requirements for common mode inductors? Generally speaking, pay attention to selecting the required frequency band. The larger the common mode impedance, the better. Therefore, when choosing a common-mode inductor, you need to check the device information, mainly based on the impedance frequency curve. In addition, you should also pay attention to the effect of differential mode impedance on the signal, especially for high-speed ports.