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Original question:

UCC28780: Hard Limitation of minimum Vin

UCC28780: Small Signal Model, KE value

Domingo De Maio
Prodigy 50 points
Part Number: UCC28780

Hi,

I wonder if TI can provide the "KF" value mentioned in the Data Sheet (Figure 37. Small-Signal Model of ACF in AAM Loop).

Thank you,

Domingo

  • 0
    TI__Guru* 85926 points

    Hello Domingo,

    I reviewed the data sheet and cannot find this information.  I have forwarded this question to the applications team to investigate it further.

    I just wanted to let you know we are working on it.

    Regards,

  • 0 in reply to Mike O'
    TI__Guru* 85926 points

    Hello Damingo,

    Please note and application engineer has been assigned to this issue and is looking into it for you.

    Regards,

  • 0
    TI__Mastermind 40350 points

    Hello Domingo,

    Sorry for the delay in this reply. It took some time to find the correct information.

    The bulk voltage to secondary current transfer function represented by Kf in the simplified model of Figure 37 in the UCC28780 datasheet is this:

    The terms in this equation are defined in the datasheet in various places. The derivation of this equation (and others) is discussed in a paper presented at APEC-2019 by Pei-Hsin Liu:

    P. Liu, "Small Signal Analysis of Active Clamp Flyback Converters in Transition Mode and Burst Mode," 2019 IEEE Applied Power Electronics Conference and Exposition (APEC), Anaheim, CA, USA, 2019, pp. 241-248.

    Unfortunately, I cannot provide the paper directly since it is copyrighted, but you may obtain it through IEEE.

    Regards,
    Ulrich