Tool/software:
We are currently using the EVK circuit and have found that the high-speed signals on the board are being interfered with by the transformer. Are there any methods or countermeasures to resolve this issue?
Hi Jacky,
May I know the frequency of the noise? Is it conducted or radiated EMI?
The high-speed noise could be the high order harmonics of the switching frequency (high magnitude at n x 250kHz). If so, reducing the dV/dt at turn on and turn off to make the Vds not such “rectangular” could reduce the higher order harmonics. Normally turn off dV/dt is higher than turn on dV/dt, you can adjust the gate resistor to 20 -40 Ohm and disable the fast turn-off circuit
The transformer is usually a big components to amplify the noise. A shielded transformer could be better.
Also adding chokes or beads can help to reduce the EMI output of the PoE board. But if the contributor is the transformer leakage inductance in the air, the filters effect could be limited.
Check details in
Practical Guidelines to Designing an EMI Compliant PoE Powered Device with Isolated Flyback
Best regards,
Diang
