How should common-mode/differential-mode filtering be combined in a smart controller PAC?

The common-mode and differential-mode filters of the intelligent controller PAC need to be designed in a coordinated manner to cover interference across the entire frequency band. The common-mode filter mainly targets ground loop and spatial coupling noise, using a CMZ3225A-510T common-mode inductor (51μH) and a Y capacitor, which attenuates common-mode noise above 1MHz by more than 20dB. The differential-mode filter targets power supply loop noise, using an X capacitor and a PWRA6045 power inductor to form an LC filter, effectively suppressing differential-mode interference from 150kHz to 10MHz.

When used together, the common-mode and differential-mode inductors can be integrated into a single composite filter. For example, the CMZ7060A-701T series; in the PCB layout, the common-mode filter should be placed close to the interface, and the differential-mode filter should be placed close to the noise source, with the two isolated by a ground plane; at the same time, ESD protection devices (such as ESDLC5V0D3B) and varistors (such as 7D820K) should be placed before and after the filter network to improve surge protection capability; tests show that this combination scheme can make the conducted emissions of PAC 10dB lower than the EN55032 limit in the entire frequency band of 150kHz-30MHz, and pass the IEC61000-4-5 combined wave test.