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TPS23754 opreation swtiching frequency adjust

Jacky Chen29
Genius 4735 points
Other Parts Discussed in Thread: TPS23754

Hola,

I have a question about switching frequency adjust of TPS23754;

I'm using TPS23754 as new design and we changed Rfrs resistor value from 69.8k to 34.8k for 484kHz switching frequency purpose.

But  it seems cannot support 25W output (Vout=12V) after we changed Rfrs！

  • 0
    TI__Mastermind 40560 points
    Hi Jacky,

    Your efficiency might have been compromised by changing the frequency such that there is more current flowing through the primary such that is reaching peak current sooner. This might be worth looking into and decreasing R243. Be sure not to saturate the transformer. Since this is a flyback design, I recommend looking into SLVA305C that gives a step by step procedure for designing a flyback. Why was the frequency increased? Efficiency will be compromised and it will not reduce your total solution by much.
  • 0 in reply to Darwin Fernandez
    Genius 4735 points

    Hola Darwin,

    Thank you so much for reply soon, one more question, can you provide me a reference circuit for using TPS23754 with 480kHz operation switching frequency？thank you again.

  • 0 in reply to Jacky Chen29
    TI__Mastermind 40560 points
    Hi Jacky,
    Unfortunately we currently do not have a 25W PoE solution with this high of frequency for the reasons stated above. Overall, what is the goal of having an increased switching frequency? I recommend talking to your local FAE if a specific custom design is needed.