55011 Radiated emission
Hi,
I have designed a 37 W SMPS, with TOP257YN TO kılıf, I use 6mH and 100nF Common mode filter as usually PIEXPERT propose.. When we test the SMPS in 55011 Radiated tests, we see that the SMPS exceeds levels at 100 MHZ and so on, the graph is at the attachment called 1 .. Then we add 1oonF and increase the line filter inductance to 30mH in order to make pi filter... The new test results are in attachment 2.. But they are still to much.. what can be cause and the solution, I pay attention all the layout rules, short loops, paralel traces...
Comments
Dear Sarek,
I change the layout as possible as I can, there is not mak any difference,
I read AN 15 many times but there is not any information about the causes of the radiated signal 30MHz and 300 MHz.. since they aren't related to switching frequency it must be related with parasitic elements but ın AN 15 says these parasitics and ringing in the waveforms causes signals up to 30 Mhz.. But I haven't problem in that range..
Also at page 23 adding a capacitor between V+ pin of transformer and source pin, I tried but there is not any reasonable change in emission tests..
Is there any different application note
BEst regards
Hi,
Without reviewing the schematic of your power supply and board layout, I am afraid I cannot offer much more specific advise. You will need to send us those details to enable us to help you further.
Regards
PI-Sarek
Hi,
Without reviewing the schematic of your power supply and board layout, I am afraid I cannot offer much more specific advise. You will need to send us those details to enable us to help you further.
Regards
PI-Sarek
Hi,
Without reviewing your schematic, layout and transformer design, it is difficult to pinpoint the exact cause of radiated EMI failure.
I suggest that you review our application note AN-15 which explains how radiated EMI is generated and the possible solutions to fix the problems.
http://www.powerint.com/sites/default/files/product-docs/an15.pdf
As described in our application note, it is most effective to solve the EMI problems at source and any filter circuit adjustments should be used once it is confirmed that no further improvement can be achieved through layout modifications, transformer design changes or selection of parts.
Even small adjustments to the layout and orientation of components on a circuit board can make significant changes to the loop areas of high frequency loops and affect EMI performance.
Regards,
PI-Sarek