• State Resolved
  • Locked Locked
  • Replies 2 replies
  • Subscribers 63 subscribers
  • Views 409 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

UCC25600EVM: Power management forum

marco ciambottini
Prodigy 90 points
Part Number: UCC25600EVM
Other Parts Discussed in Thread: UCC25600, UCC256403

Hello,

I'd like to design my first resonant converter and I started from the study of the UCC25600EVM.

I also read the slup263 and made the calculations with the UCC2564X design tool because it is more accurate of the UCC25600 one.

The big issue is about the transformer design:

I see that the eval-board uses Vitec P/N 75P8105, the turn ratio is 17:1 and no construction info is reported. I suppose it is a PQ32/30.

If the material was N87, I calculated a magnetizing inductance of 1.5mH while the calc. sheet (and slup263) says 210uH.

The question is: shall the magnetizing inductance be exactly 210uH or is that the minimum required?

How could I obtain 210uH? With air gap?

Further info about the 75P8105 construction specifications (wire awg, strands, etc..) woud be appreciated.

Thanks and best regards,

Marco
  • 0
    TI__Expert 8210 points

    Marco

    First off, for a new resonant LLC design we recommend that you use UCC256403, which is our most recent LLC controller.  It has many performance improvements over UCC25600, such as integrated half bridge gate driver, HV startup and improved transient response from Hybrid Hysteretic Control http://www.ti.com/lit/an/slua834a/slua834a.pdf.

    75P8105, which is the transformer used in UCC25600EVM, was designed by Vitec.  If you have questions about the specifics of this transformer design, such as core material or wire used, we recommend you reach out to them.

    If you have questions on transformer construction (such as how to design to a specific inductance), I recommend that you review the Magnetics Design Handbook https://www.ti.com/seclit/ml/slup132/slup132.pdf.

    In resonant LLC the magnetizing inductance is used to determine what the resonant tank frequency is.  Changes in the inductance will move the ideal operating point, and corresponding operating frequency.  If the inductance moves too far from the desired value, it has the potential to prevent the converter from being able to support the full operating range.  You can use the excel design calculator to determine what changes in the magnitizing inductance has in your design, and help determine what the abs min and abs max inductance needs to be.

    Best Regards,

    Eric

  • 0 in reply to Eric Faraci
    Prodigy 90 points

    Hello Eric,

    thank you for the fast support.

    I already wanted to use the UCC25604X family because of the improvements, my only doubt is about the possible obsolescence of that "complex" controllers and the impossibility in the future to find a second source.

    Anyway, I made some attempts with different Lm values and understood the boundaries.

    Now the issue is only about the transformer, I will contact Vitec.

    Best regards,

    Marco