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    Non isolated 30W offline LED driver and common mode noise filtering

    Hi
    We are doing a non-isolated, offline, 30W PFC Boost-Buck LED driver.
    In order to get better filtering of common mode emissions, would you say it is preferable for us to take an earth wire to the PCB? (then we can also use Y capacitors to earth, as well as a common mode choke)

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    Re: Non isolated 30W offline LED driver and common mode noise filtering

    This is a hard topic, I suggest you test with care!
    If you liked the post, please press "Give points" and "Helped me".


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    Re: Non isolated 30W offline LED driver and common mode noise filtering

    in 20 years at two power converter manufacturer, i never saw a connection to earth as you describe.
    not a good plan


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    Re: Non isolated 30W offline LED driver and common mode noise filtering

    Thanks, but LC filtering common mode noise is surely more attenuative of it than common mode inductance alone?



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    Re: Non isolated 30W offline LED driver and common mode noise filtering

    Quote Originally Posted by wwfeldman View Post
    in 20 years at two power converter manufacturer, i never saw a connection to earth as you describe.
    not a good plan
    Huh? You've never seen a common mode choke combined with C to earth?


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    Re: Non isolated 30W offline LED driver and common mode noise filtering

    common mode chokes, C line to line and line to neutral, but not neutral to earth

    copper cables chassis to earth but not pcb to earth


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    Re: Non isolated 30W offline LED driver and common mode noise filtering

    Quote Originally Posted by wwfeldman View Post
    C line to line and line to neutra
    For US mains (single phase 120Vac), "line to line," "line to neutral," and "line to hot" are all equivalent. Are you thinking of a split phase system?


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    Re: Non isolated 30W offline LED driver and common mode noise filtering

    three phase
    delta gets line to line
    wye gets line to neutral



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    Re: Non isolated 30W offline LED driver and common mode noise filtering

    CM chokes with no earth will work - but often a test spec calls for metal foil pressed against device ( which is connected to Earth ) thus introducing C to earth - then the measurements are taken at the LISN - thus a very good wide band CM choke is needed to pass this test ...



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