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UCC28950: Design issue

Florian Wallaert
Prodigy 50 points
Part Number: UCC28950

Tool/software:

Hello,

I'm trying to design a dc/dc power converter using the UCC28950 controler. The features of the converter are the following : 18V to 50V input (28V nominal), 28V and 10A isolated output.

I based my design on the one we find in the datasheet and the values available on the WeBench suggestion. 

The issue I'm encountering is that at 18V input, I cannot have the 28Vout needed (at 10A). If I lower the ouput current then the converter is able to provide the 28Vout. 

I tried to simulate the circuit with ideal component (mosfet and diodes), and to adjust the current sense resistors but it doesn't work...

Do you have any idea on how I can resolve my problem ? 

Thanks in advance,

Florian Wallaert

  • 0
    TI__Guru* 85716 points

    Hello,

    Your inquiry is under review.

    Regards,

  • 0 in reply to Mike O'
    TI__Guru* 85716 points

    Hello,

    More than likely your transformer turns ratio is off or your current sense resistor and/or current sense transformer sensing circuitry is not setup correctly.

    The following link will bring you to an application note that goes through the step by step design process of a phase shifted full bridge using the UCC28950.

    There is a section on how to calculate the transformer turns ratio and how to setup the current sensing for the UCC28950.  

    https://www.ti.com/lit/pdf/slua560

    You can also use the reference design schematic in the application note to compare to your schematic and verify that it is setup correctly.   You can also use the application note and the excel design referenced within the excel tool to check your design as well.

    Thank you for interest in Texas Instruments (TI) products.  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.

    Regards,