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UCC28950: UCC28950 Minimum duty requirement

user6004348
Intellectual 390 points
Part Number: UCC28950
Other Parts Discussed in Thread: UCC28951,

HI Sir

i design a 800W series model ,the output V is 12V,24V,36V,48V,54V

Because I want to fix the number of NP turns,so i must adjust Duty to achieve it

Is there any suggestion that Duty should not be less than the minimum?

TKS

  • 0
    TI__Mastermind 25570 points

    Hello

    THe best place to start would be to use the Excel calculator tool for this product - you can find it on the product web page.

    In a buck derived topology like the PSFB (UCC28950 / UCC28951)  the input to output relationship is Vo = D Vin (Ns/Np). The converter will be most efficient when operating at a large duty cycle byt typically a designer will set the nominal duty cycle to be about 70%. This allows the input voltage to increase or decrease while still allowing adjustment range

    Unless you have a special reason for using a single transformer for the output range from 12V to 54V then it would be much, much better to design an optimum transformer for each output voltage and to keep the nominal duty cycle around the 70% range.

    Regards
    Colin