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Original question:

UCC28780: ucc28780

UCC28780: ucc28780

robin gangopadhya18
Mastermind 6296 points
Part Number: UCC28780

Ben

I will test very carefully the dc case up to 380V & keep HV values displayed all along.

In all the 6 cases we have, each spreadsheet calculation gives Ropp_rec negative. There is no relationship in the equations other than how it figures in 1 place. How does the spreadsheet calculate this value? If we do not need max power shutdown, what value is best to use?

thnx

  • 0
    TI__Mastermind 27145 points

    Hi Robin,

    The UCC28780 EVMs are designed for universal AC input range so 380VDC input is not far away from the peak AC voltage of 264Vac input. I would also like to mention we have a reference design of UCC28780 coming from a PFC bus input:http://www.ti.com/tool/TIDA-010047

    This design might be a good reference for you.

    Can you send me your UCC28780 excel calculator? I can take a look at the Ropp calculation.

    Best Regards,

    Ben Lough

  • 0 in reply to Benjamin Lough
    Mastermind 6296 points

    Hi Ben

    Thanks a lot for the direction. I always find your cues of great value to me.

    Pl see attached xl of one case out of 6 we made. All have 380V input also out of a regulated PFC.

    Now that we are here: I will also like to know your observations about input  values I had to play with in order to get GaN derated properly, get positive value of Cout . In addition to Ropp,  Cout may come out negative.

     We used SLUC644b results extensively in the design calculations for all the 6 modules. And of course the magnetics.

    Hope you are keeping safe and cooped up in the home.

    robin

    6281.sluc664b_5V18xAMP_feb23_6.xlsx

  • 0 in reply to robin gangopadhya18
    TI__Mastermind 27145 points

    Hi Robin,

    I am holding up ok, I hope you are keeping safe as well.

    I did not notice any issues with the component values selected in the excel file. I asked a colleague with extensive experience with the ACF topology to review the file as well. I'll let you know if he has any concerns.

    I am still looking into the issue of Ropp or Cout becoming negative depending on certain inputs. The variables used to calculate Ropp and Cout in the excel should all be positive numbers so this shouldn't be happening. Would you be able to share a version of the excel calculator where you do see Ropp and Cout going negative? It will help me to troubleshoot.

    Best Regards,

    Ben Lough