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UCC28631: Over Power Mode

Hirotsugu Kobayashi
Mastermind 9540 points
Part Number: UCC28631
Other Parts Discussed in Thread: UCC28630

Hi, team.

Does UCC28631 have a Over-Power Mode?

Is the Maximum Output Power of UCC28631 100% of Pnom?

  • 0
    TI__Genius 9130 points
    Kobayashi-san,

    The UCC28631 does not have an internal overload timer (like the timer in UCC28630), but it does still include the CC-mode output current limit.

    The max power depends on how you define Pnom.

    From the datasheet page 46 Fig. 41, Pnom is the nominal rated power, and the design guide on pages 51-61 show the way to calculate the inductance and Rcs values to set the Pnom operating point to occur at the boundary of DCM/CCM at minimum bulk cap voltage, and at 60-kHz switching frequency. With this design, the maximum peak power is 2*Pnom.

    With UCC28630, the 2*Pnom cannot be taken continuously, because it will trip the internal overload timer. For the same power stage design using UCC28631, 2*Pnom can be delivered continuously. Above this level, the CC-mode current limit will take effect and reduce the output voltage to keep the output current constant – until the VDD rail drops below UV, then the controller will go into hiccup mode.


    If this answers your question, please click the "verify answer" button.

    Thanks,
    Bernard
  • 0 in reply to Bernard Keogh
    Mastermind 9540 points
    Hello Bernard
    Thank you for your support .

    I don't want to use by CCM Mode.
    Is it possible by DCM mode limitation to use?
  • 0 in reply to Hirotsugu Kobayashi
    TI__Genius 9130 points
    Kobayashi-san,

    You can use the design guide to target the boundary of CCM/DCM at Vmin and at a certain max power - that way it should run DCM at all input voltages > Vmin and all loads < Pmax.

    However, the power stage can and will be able to into CCM transiently during startup, output overload (i.e. whenever Vout is low and power is high) and maybe during load transients.

    It's not possible to guarantee DCM-only under every possible operating condition, since the IC is not QR (deliberately, so that it can support CCM mode).

    Bernard
  • 0 in reply to Bernard Keogh
    Mastermind 9540 points

    Hi, Bernard.

    Is it possible to design UCC28631 as P5=Pnom, P4=50% Pnom?

    I'd like to design that it won't be over the target electric power.

    Best Regards,

  • 0 in reply to Hirotsugu Kobayashi
    TI__Genius 9130 points
    Kobayashi-san,

    Yes you can do this.

    If for example, Pnom = 100 W, then you can design for P5 = 100 W & P4 = 50 W.

    You would then use a nominal power level of 50 W in the Excel design calculator, and it will automatically use Ppeak = 2 times the nominal level, i.e. 100 W.

    Thanks,
    Bernard