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UCC28950: Transformer calculations doubts for reference design

Eze Bayer
Prodigy 150 points
Part Number: UCC28950

Hello, I saw in the calculations of the transformer in the reference design that the total RMS current of the secondary is 36A, but the output current of the source is 50A. Is this relationship because the voltage across the transformer is higher than the output voltage, so the power relationship is maintained when passing through the LC circuit?

Thanks

Ezequiel

  • 0
    TI__Guru 65965 points

    Hello,

    To review this I wanted to see if you were correct.

    This is an RMS equation for a trapezoidal symmetrical waveform.  I know this is not the same as the output of the RMS current of PSFB transformer with SRs.  However we can use it to estimate the RMS current.

    The Total RMS estimation on this design I estimate is 50.083A and not 36 A.  Sorry for the error.  

     Regards,

  • 0 in reply to Mike O'
    Prodigy 150 points

    Hello Mike, thanks for answer, from UCC28950 datasheet, page 41 eq 37, it shows

    I understand that it is the current of each secondary, 36A. Is correct? Could be possible that both secondaries sum to output 50A? 

  • 0 in reply to Eze Bayer
    TI__Guru 65965 points

    Hello,

    I believe you are correct.  The secondary RMS current in each winding is 36 A.  So in this case the average current in each winding would need to be 25 A average to provide a total of 50 A of average output current.

    Regards,

    Mije