Common mode inductors

Common mode inductors (common mode chokes) need to meet the requirements

Common mode Choke, also known as common mode choke, is commonly used in computer switching power supplies to filter common mode electromagnetic interference signals. In the board design, the common mode inductor also acts as an EMI filter to suppress the electromagnetic radiation generated by the high-speed signal line from radiating outward.

(1) The wires wound on the core of the coil should be insulated from each other to ensure that the breakdown of the coil does not occur under the action of instantaneous overvoltage;
(2) When the coil flows through a large instantaneous current, 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 transient overvoltage;
(4) The coil should be wound as much as possible, which can reduce the parasitic capacitance of the coil and enhance the coil's ability to withstand transient overvoltage.

Under normal circumstances, at the same time pay attention to select the frequency band required for filtering, the larger the common mode impedance, the better. Therefore, we need to look at the device data when selecting the common mode inductor, mainly based on the impedance frequency curve. In addition, pay attention to the influence of differential mode impedance on the signal, mainly focusing on differential mode impedance, paying special attention to high-speed ports.

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