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UCC28700: Modify PMP10468 to get 12V/2A

Majdi Thouabtia
Prodigy 20 points
Part Number: UCC28700
Other Parts Discussed in Thread: PMP10468, , PMP10276

Hi,

I would like to change the Transformer from 750811647 (OUT 24V/1A) to 750314727 (12V/2A) in order to get an output of 12V/2A. According to the datasheet I need to change some resistor and capacitor values. I tried to get the same values like in the reference design but some values did not make any sense. 

Would it be enough to change the transformer or should I change something else? Please let me know, what values need to be changed in order to get the wanted output.

Thanks in Advance!

Best Regards,

Majdi 

  • 0
    TI__Prodigy 590 points

    Hello,

    Your thread  has been assigned. You should receive a reply shortly.

  • 0 in reply to Pye Naing
    TI__Guru 67795 points

    Hello,

    24V seems like a popular output voltage.  Did you check the TI reference design library to see if there was design with a 24 V output that you could use instead?

    When it comes to the reference design and transformer you are working with  you could possibly get 12 V out the transformer; however, you would run deep into discontinues mode and may not get the full 1 A output.  To get 12V work properly would require more turns.

    Please note that if you wanted Wurth would be more than happy to design a transformer for this application as well.   If you decide that is what you would like to do you there are tools that can help with your design.  You can use Webench or Excel it will give what is required for the design.

    Besides changing the transformer turns ratio you will have to change the VS divider resistors and the current sense resistor.  Besides those changes the 24V reference design should work for 12V.

    Regards,

  • 0 in reply to Mike O'
    Prodigy 20 points

    Hi,

    thank you for the quick response! 

    We are using the same design as in PMP10468 to get the 24V/1A. I'm trying to get the values of the VS divider resistors and the current sense resistor using the calculations in the datasheet and also the excel tool for the calculation. I still do not understand where the used values on the PMP10468 are coming from. I just need the calculations made for this design. Would you be nice and upload the calculation with the used values in PMP10468? 

    I used the calculation tool to calculate the values of resistors using the new transformer to get 12V/2A but I got negative values in P_BUDGET even if I tried to adjust the values. Can you please also upload the calculation for the 12V/2A? 

    Regards,

  • 0 in reply to Majdi Thouabtia
    TI__Guru 67795 points

    Hello,

    The excel design tool and application note were used to design the UCC28700 evaluation module which you can find at the following link.

    I will forwarded your request to the power supply designer of this reference design so he can share his design equations with you.

    Regards,

  • 0 in reply to Mike O'
    TI__Expert 3720 points

    Hi,

    PMP10276 is a design with 12V/2A output.

    For both PMP10276 and PMP10468 design, I use mathcad calculation file I created by myself. 

    PMP10468RevA.mcdMathcad - PMP10276RevA.pdf

    Hope the files are useful.

    Regards,

    Sheng-Yang Yu