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  • TI Thinks Resolved

LM5017: LM5017 Airgap Flybuck Calc Xlsx

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Replies: 5

Views: 104

Part Number: LM5017

Hello TI,

A. Kindly reply to the related thread https://e2e.ti.com/support/power-management/f/196/t/783364

B. LM5017 flybuck transformer xlsx, Air gap calculation Cells I29 & I33, use complex equation comprising of Centre leg length (a), width (b) and le/μe ratio.

Rectangular center leg equation "I31*I32/2*(1/I26-(I31+I32)/I31/I32-SQRT(((I31+I32)/I31/I32-1/I26)^2-4/I31/I32))" translates into

 

and round center leg equation uses diameter in place of length and width I28^2/2*(1/I26-2/I28-SQRT(1/I26^2-4/I26/I28))

Please share document link for above complex equation

  • Hello ,

    A- I have replied to the thread .
    B - I have sent your request to designer of this calculator

    --Ambreesh
  • In reply to Ambreesh Tripathi:

    when to expect reply or may be share email contact details
  • In reply to luck luck:

    Refer to page 4 of this doc for more details on cross-section dimensions a and b relation to effective core gap
    www.ti.com/.../slup127.pdf

    For more details contact the Magnetic vendor .

    ---Ambreesh
  • In reply to Ambreesh Tripathi:

    Ambreesh Tripathi
    Refer to page 4 of this doc for more details on cross-section dimensions a and b relation to effective core gap
    www.ti.com/.../slup127.pdf

    [Luck] Had already referred this document.
    Since it does not help visualize/derive the equation used in xlsx, that we preferred contacting e2e for insights.


    For more details contact the Magnetic vendor .

    [Luck] Magnetic vendor won't be of any use here. Kindly request author of the xlsx to interact directly in the forum or over email.



    ---Ambreesh

  • In reply to luck luck:

    The document i shared earlier , precisely goes into details of Air gap estimation you are looking for . You will need to go over the complete documentation to derive the equation . 

    Refer to page 8 of this document :

    Effective permeability of composite material to reach to obtain desired inductance  :

    You can put this equation ie le/ue in 6a  and that will result in quadratic equation . Remember that Ae is cross sectional area which is equal to a*b

    Ag=(a+lg)(b+lg)

    If you solve the quadratic equation , you will arrive to the equation mentioned in the Excel calculator . 

    ----Ambreesh 

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