Most emi filters must use a common mode inductor. Since the common mode inductors have high impedance in a wide frequency range, the high-frequency noise generated by the high-frequency switching power supply can be suppressed. And the common mode inductor why the magnetic core is a ring was also introduced before, here is the main point of the design to consider what factors?

The basic parameters required for designing a common mode inductor are input current, impedance and frequency. The input current determines the size of the winding conductor. When calculating the diameter of the wire, the calculation value of 400 amps per square centimeter is generally used, but other calculation values may also be used according to the temperature rise acceptable to the inductor. In almost all cases, a single wire is used because it is not only the cheapest, but the copper damage from high-frequency skin effects can help reduce noise.

The basic parameters required for designing a common mode inductor are input current, impedance and frequency. The input current determines the size of the winding conductor. When calculating the diameter of the wire, the calculation value of 400 amps per square centimeter is generally used, but other calculation values may also be used according to the temperature rise acceptable to the inductor. In almost all cases, a single wire is used because it is not only the cheapest, but the copper damage from high-frequency skin effects can help reduce noise.