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Thread: SMPS with PFC

  1. #41
    diysmps Senior Member res_smps's Avatar
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    I think I have to correct this statement
    Quote Originally Posted by res_smps View Post
    Sorry Silvio,
    With the presence of PFC, capacitor requirements can be smaller, I attach an excel file for PFC calculations (I downloaded from onsemi website) in post # 5
    I thought the PFC frequency determined the size of the capacitor, I was wrong
    from the worksheet, capacitor requirements are not determined by the PFC frequency, please check this formula (pic) below
    cbulk.jpg

    *for the same power, the higher the output voltage the smaller the capacitor needs
    Last edited by res_smps; 10-11-2019 at 02:13 PM.

  2. #42
    *for the same power, the higher the output voltage the smaller the capacitor needs

    In the pfc circuit to my believe the value of the capacitor determines the hold time at load.

    Check this ( I sent you mail)

    NCP1653 Spread sheet Res.pdf
    Last edited by Silvio; 10-11-2019 at 09:56 PM.

  3. #43
    diysmps Senior Member res_smps's Avatar
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    Quote Originally Posted by Silvio View Post
    *for the same power, the higher the output voltage the smaller the capacitor needs

    In the pfc circuit to my believe the value of the capacitor determines the hold time at load.

    Check this ( I sent you mail)

    NCP1653 Spread sheet Res.pdf
    Dear Silvio,

    yes, that also true. Thank you for the file, I also previously shared it here (zip files) in post #2

    please ignore the picture in post #41, there was an error
    cbulk.jpg
    cbulk value is determined from the highest results from the following 2 formulas :
    1) 10000*Pout/(0.01*Vripple*2*pi*Fac*Vout^2
    or
    2) 2000*Pout*Thold/(Vout^2-Voutmin^2)
    from the formula this parameter determines the cbulk
    1. Line frequency (Fac) 50/60Hz
    2. Pout
    3. Tholdup
    4. Vout
    5. Vripple
    Pout and Vout appear in both formula
    Last edited by res_smps; 10-11-2019 at 10:39 PM.

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