How to filter out differential mode interference in intelligent low-voltage monitoring units?

Differential-mode interference filtering employs a π-type filter structure and a differential-mode inductor. A PWRA6045R6R8M0T power inductor (6.8μH) is connected in series at the DC power input, along with two 22μF/100V electrolytic capacitors and a 100nF/100V X7R ceramic capacitor in parallel. For the AC monitoring circuit, a PBZ3216E120Z0T ferrite bead (120Ω@100MHz) is connected in series, along with two 4.7nF/630V X2 safety capacitors for differential-mode filtering. PCB design: Power traces are widened to 1.5mm, and the filter capacitors are placed close to the IC, less than 3mm away. ESD3V3D3B protection is also used for the sampling input. This solution can reduce differential-mode noise by more than 30dB and power ripple by less than 30mV, meeting the IEC 61000-4-17 voltage fluctuation test requirements.