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UCC25600: How to design aux supply for fast startup

Brian Antheunisse
Expert 5305 points
Part Number: UCC25600

Hi guys,

My customer wants to use UCC25600, and is confused about how exactly to design the aux bias supply. (they need fast startup)

Do we have any documentation that elaborates on how to design that circuit? I see them all over the place in EVMs and such, but no explanation on design considerations. 

Thanks,

Brian  

  • 0
    TI__Guru 73785 points
    What do you mean by "they need fast startup"? Do you mean they want to know to make a converter startup faster than what, and / or specs? Or they want to learn how to design the aux faster? Please clarify your questions.
  • 0 in reply to Hong Huang
    TI__Expert 5305 points

    Hong,

    Exact words from customer:

    "I really need to have a fast startup due to this supply being used to control a isolated IGBT driver for parallel high voltage and high current IGBT modules. Do you have any documentation that may help on setting up an auxiliary winding and circuit to power the UC25600 controller?"

    Their spec is 750Vdc - 1073Vdc to 15Vdc out at only 15W. They chose LLC instead of flyback because they believe this will get them smaller magnetics, they have a tiny space they are working with. 

    Thanks,

    Brian 

  • 0 in reply to Brian Antheunisse
    TI__Guru 73785 points

    I do not think we have a document for this as usually this power level bias is done by a flyback. But I think the idea is similar, i.e., need to add a high voltage startup circuit like the below (dashed block) so the startup time can be designed with these components.