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UCC28782: UCC28782- calculations similar to 28780?

robin gangopadhya18
Mastermind 6296 points
Part Number: UCC28782
Other Parts Discussed in Thread: UCC28780

Hello Ulrich:/Jaden

We are transitioning out to UCC28782 .

Since this part is in all respects similar to UCC28780 excepting perhaps behavior as a charging converter, we used SLUC644C version of the spreadsheet to estimate various design values.

I attached a copy of our selection of input, output etc.

There are some lines that come up with #VALUE" calculation. Why is that?

Any help in the matter of fixing these lines will be highly appreciated.

Is it because of output power &/or current?

robinSLUC664C20V200W_UCC28780CALCun2.xlsx

  • +1
    TI__Expert 7080 points

    Hi Robin,

    If you change the transformer turns ratio below 8 , The line of #VALUE will be correctly shown . I believe that large turns ratios in here results in a large duty cycle that maybe caused this problem. for 20V output voltage , I recommend you chose a 5 turns ratio , while primary turns is 25T and secondary is 5T , The 10 turns ratio will get a 200V reflected voltage , that is not suitable for choosing primary side FET . 5 turns ratio is a good start point for the design.

    Thanks.

  • 0 in reply to Jaden Ning
    Mastermind 6296 points

    Jaden:

    thnx for the tip.

    That said, we are planning to use all GaN devices. Because of the very competitive characteristics of our implementation, it is possible to use 1200V GaN!

    So we can have more flexibility in Nps, turns etc.

    Can we get access to the SLUC644C spreadsheet to run such "what if " scenarios by entering values in the blocked cells? Of course, our entries will still follow the rules given the UCC2782 d/s.

    BTW: our first modules using UCC2871X based dc-dc converter show 93% MAX efficiency for a 10W solution....dual output, with tight coupling, both outputs show very decent regulation...so there is something interesting going on here. ...traditionally, one anticipates 73% or so.

  • 0 in reply to robin gangopadhya18
    TI__Expert 7080 points

    Hi Robin,

    Understand, but 650V GaN maybe has better performance than 1200V GaN FET.

    TI don't release the unlocked calculator , so I am sorry to say we also don't has this version.

    It's amazing that 10W solution can achieve 93% efficiency , good job !

    Thanks.