Question: EMC Common Mode Noise Suppresion

lexington

lexington

@lexington-Q2yKoM • Oct 27, 2024
Dear to all experts,

I thank you first in advance for all the help and advices given. The question that I would like to ask is regarding the combination of usage in ferrite core and Y-capacitors as noise suppression. The design comparison which I would like to ask is as attached. There are two different method of placing the Y-capacitors to filter out the common mode noise. When I took this design and scan the conducted emission, I found that there are times design A is better than design B but there are times where design B is better than design A.

May I know what is the difference in noise between both design? I know that both are made to cancel out common mode noise so why is there a difference between the two design? Thanks for all the reply and help.

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  • Harshad Italiya

    Harshad Italiya

    @harshad-ukH5ww • Jun 30, 2013

    Hi #-Link-Snipped-# first of all welcome to CE.

    I am not sure about main difference between these two designs but I remember during one seminar by Wurth Electronics they have mentioned something about frequency effect on Common Mode rejection circuit. I think these two design may have some relation with it.

    I also come to know about one good guide on Common mode rejection circuit. #-Link-Snipped-#
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  • lexington

    lexington

    @lexington-Q2yKoM • Jun 30, 2013

    Thank you Harshad for the warm welcome and first to reply.

    Very interesting article that you have gave me and yes I agree that Common mode noise does has relationship with the frequency range. I have read the link you have showed me and it does provide me understanding in the common mode noise.

    Unfortunately, it did not provide any differences between the design as stated earlier or which is a better design. I thank you again for more help and advices. Thanks.
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