What are the selection criteria for common-mode inductors and differential-mode capacitors for edge boxes?

The selection of common-mode inductors and differential-mode capacitors for EMC filtering in edge computing boxes depends on the specific requirements. Common-mode inductors need to provide high common-mode impedance in the interference frequency band, for example, to suppress conducted emissions from 150kHz to 30MHz. The CML4532A-101T is selected; its name is CML common-mode inductor 4532, its size is 4.5×3.2mm, 101T, and its inductance is 100μH. Its impedance curve reaches 2kΩ at 10MHz, meeting the requirements. The selection criteria for differential-mode capacitors (X capacitors) are: they must be able to withstand the rated voltage and ripple current, and their self-resonant frequency must be higher than the interference frequency. For a 24V power supply, a 0.47μF 100V X7R capacitor is recommended. If suppressing lower-frequency differential-mode noise is required, the capacitor can be increased to 1μF, but it should be noted that an excessively large capacitor will affect startup. In addition, the common-mode inductor must also consider the rated current not being saturated. For edge computing box currents under 3A, the CML4532A's rated current of 5A is sufficient. A small 0.01μF capacitor in parallel with the differential-mode capacitor provides better high-frequency characteristics. Spectrum analyzer verification shows that this combination attenuates by 20dB at 0.15MHz.