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UCC28951-Q1: UCC28951-Q1

Rajashekar Koutla
Intellectual 590 points
Part Number: UCC28951-Q1

hello

I have designed DC DC converter of 1.32KW of 13.2V output using UCC28951-Q1. I calculated power losses for primary mosfets ( that is coming 17W ) and secondary side 2 synchronous rectifiers power losses that is 95W . Now i need to calculate thermal resistance of heatsink required for totall power loss of (17W +95W) those mosfets. how to calculate effective thermal resistance of heatsink required along with the size of the heatsink ?help me in this regard.

thanks and regards 

rajashekar

  • 0
    TI__Mastermind 25570 points
    Hello Rajashekar

    Thermal design is difficult to describe but ...
    You will probably have some mechanical constraints.
    If you have 95W of power to shed and want to keep the surface temperature at 100C in a 25C ambient then the thermal resistance needs to be at (100C-25C)/95W or about 0.78CperW. Airflow will improve this. the size of the heatsink needed will depend on a lot of factors, its orientation (vertical or horizontal), its aspect ratio (length/Width), how the MOSFETs are positioned on the part - etc, etc.

    Given a choice I would use separate heatsinks for the primary side and secondary side MOSFETs to help reduce the amount of common mode noise which could flow from sec to pri. I would also ground the heatsinks to a local ground referenct (pri or sec as relevant).

    The best thing to do is to contact a heatsink manufacturer and ask for their advice.

    Regards
    Colin
  • 0 in reply to Colin Gillmor
    TI__Mastermind 25570 points
    Hello Rajashekar

    I'm closing this thread. Please feel free to open a new one at any time if you have a question.

    Regards
    Colin