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Wire position of trans in UCC28600

HIRATA MITSUO
Intellectual 490 points
Other Parts Discussed in Thread: UCC28600

Hi

We designed UCC28600's fly back circuit with trans by using [UCC28600 Design Spreadsheet](SLVC104).

We investigated the way to be up efficiency.
We found that its way was to change how to wind wire of trans.

Page 5 of [Design Considerations for the UCC28600](SLUA399B) has Figure4 "Example of a Recommended Transformer Design".
Figure4 has that Bias is between Secondary triple insulated wire and 1/2 Primary.-A
However,its way to be up efficiency has that Bias is between Inslation tape and 1/2 Primary.-B

If Bias position changes from A to B, we are worry about [UCC28600 Design Spreadsheet] value.
Because [UCC28600 Design Spreadsheet] value may have the value calicurated with trans based on Figure 4.

Please teach us the action we should do,if we change Bias position.
And teach us the changing points that its action is infuluence with parameters of [UCC28600 Design Spreadsheet](SLVC104).

We will change the circuit value based on its changing points
Best regards,
Mitsuo Hirata

slua399b.pdf

0027.SLVC104I.xls

  • 0
    TI__Mastermind 31580 points
    Hi Hirata-san,

    I have asked one of our engineers to reply to you with some guidance on the transformer design.

    Regards

    Peter
  • 0 in reply to Peter Meaney
    Intellectual 490 points

    aHi, Peter-san

    Thank you for your reply.

    I will hope the answer from the engineers.

    Best regards,

    Mitsuo Hirata

  • 0 in reply to HIRATA MITSUO
    TI__Expert 4015 points

    Hi Hirata, I do not see with a problem with your proposed structure and I don't think it will affect the parameter values in your circut.

    Keeping the bias winding close to the secondry winding is generally desirable in PSR flybacks as the controller senses the output voltage via the bias winding so it is important to keep the bias and output windings closely coupled. For the UCC28600 however, the output voltage is sensed through the opto coupler and the bias winding is only used to sense the OVP and and valley points.

    For these parameters, such close coupling is not required and moving the bias to outside the 2nd half primary will improve the efficiency as you observe. You may see a slight increase in the OVP point, which you can compensate for by adjusting Rovp1 and Rovp2. I think it is unlikely though.

    Hope this helps.

    Thanks

    Billy