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UCC2894: Design Files for PMP7391

Hardik Shah
Prodigy 10 points
Part Number: UCC2894
Other Parts Discussed in Thread: PMP7391, , UCC2897A

Hello,

Looking for Active clamp Forward (High Side) design for 300VDC to 400 VDC input with 24V / 300W output. Came across PMP7391 reference design. 

Need any excel or MathCad based design calculator to update the reference design as per specs from 24V/7A to 24V/12.5A.

Thanks!!

  • 0
    TI__Mastermind 48055 points

    Hi,

    The attached is an excel design sheet to programming the IC.

    SLUC662_UCC2894.xlsx

  • 0 in reply to Hong Huang
    Prodigy 10 points

    Hello Hong,

    Thanks for quick reply. I have checked the excel and it does help to select control components. I was looking for little more help where I can add some specs for primary and secondary mosfets with output inductor to calculate losses. Is it possible to get any design calculation files for it? Also, for such design, what is the max efficiency under 390VDC we can expect based on your experience. Please let me know.

    Regards,

  • 0 in reply to Hardik Shah
    TI__Mastermind 48055 points

    Hi,

    At 390Vdc input, the efficiency should be over 90% (94% is possible but not easy), at 24Vout, and Pout = 300W, from my design experience, if using SR at the secondary side.

    I will search to see if any reference can be found for the power stage.

  • 0 in reply to Hong Huang
    Prodigy 10 points

    Hello Hong,

    We are using SR for secondary. Efficiency is very important for us. So upfront we are doing loss calculation and verifying with simulation. A good design file (excel/MathCad) from Ti will help a lot to avoid surprises later in design. Please see if possible to provide. 

    Regards,

  • 0 in reply to Hardik Shah
    TI__Mastermind 48055 points

    Hi,

    We do not have a design file for power stage of UCC2894. But this below application note can be referenced on its power losses calculations. It is based on UCC2897A but the power losses estimation ok to use. UCC2894 is on the same core design as UCC2897A.

    www.ti.com/.../slua535a.pdf

  • 0 in reply to Hong Huang
    Prodigy 10 points

    Hello,

    I will refer the suggested PDF. Do you suggest to use TI Power Supply Designer tool for such calculation? And secondly, what is the main cause not achieving efficiency higher than 94% for ACF? ANy possibility if we use very low Rds(on) Mosfets on primary and secondary?

  • 0 in reply to Hardik Shah
    TI__Mastermind 48055 points

    Hi,

    The main reason actually is switching losses instead of conduction losses. You would have to balance Rdson, gate charge and Coss and actually low Rdson MOSFET may have higher gate charge and Coss. Other major power losses are transformer core and copper, and output inductor, also the SR MOSFET cross conduction when you use self-driven to save money.