Please find the attached CE-Conducted Emission graphs,
After adding filters we are able to get very low conducted emission at switching frequency but emission level of harmonics are more than expected. also we did some modification in filter circuit that’s bringing the emission level still down(at 500 kHz only) but harmonics looks unaffected by this we don’t understand the reason why this harmonics causing the issue.
We designed the board earlier also there conducted emission was failing at 500kHz,then we modified ckt to change the choke emi filter.
Now emission @ 500kHz reduced but harmonics are more but the same if i remove the snubber resistor R7 harmonics dissappearing . But removing the snubber ckt could be problem for RE test. unit already passid RE test with snubber resistor.
Please tell us the solution. How come harmonics emission level could be more than the switching frequency if i add snubber resistor.
