How to design the power supply filter circuit for an FTU?

The FTU power supply filter circuit needs to simultaneously suppress conducted emissions and provide immunity. The design employs a three-stage π-type filter structure. The first stage is the input terminal, using a CMZ7060A-701T common-mode inductor (700μH) paired with two safety capacitors (2×2.2μF/275V). The second stage is the DC-DC input terminal, using a PBZ2012E600Z0T ferrite bead (600Ω@100MHz) in series, with a 47μF/100V electrolytic capacitor and a 100nF/100V ceramic capacitor in parallel. The third stage is the IC power supply terminal, using a PWRA6045R6R8M0T power inductor (6.8μH) paired with a 10μF + 100nF decoupling capacitor. All filter capacitors use X7R or C0G material with an ESR of less than 0.1Ω. On the PCB layout, the filter circuit is located close to the power input, and the input and output lines are separated. This design enables conducted emissions to be 15 dB below the EN55032 Class B limit and passes the IEC 61000-4-5 2kV surge test.