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About the reference design : TIDA-00701 for 120W outputs using UCC28740

alpha
Expert 2530 points
Other Parts Discussed in Thread: TIDA-00701, UCC28740, LM5023, UCC28630

to whom it may concern

Our customer want to design 120W AC/DC Converter which specification is as following.

- input : 90Vac - 240Vac
- output : DC24V / 5A

They refered TIDA-00701 that is used UCC28740 as controller and tried to simulate using WeBench.

But unfortunatelly , it was not able to genarate the WeBench report.

Could you please tell whether UCC28740 is able to drive up to 120W or not?

Your reply would be appreciated.

Thanks and best regards.

  • 0
    TI__Mastermind 31580 points
    Hi,

    The UCC28740 is designed for power levels in the range of 5W to 40W approximately. For higher power flyback designs we recommend the LM5023 or the UCC28630 devices.

    There is 65W nominal 130W maximum 24V design for the UCC28630, http://www.ti.com/tool/PMP9643. The design would have to be redesigned to run continuously at the 120W level but the reference design gives an idea of the performance available.

    Regards

    Peter
  • 0
    TI__Genius 9130 points
    The UCC28740 was initially intended for lower power applications, so the Webench model for the device is also likely to have built-in assumptions or limitations on the power level. I will check with the Webench team and report back when I get an answer.


    Meanwhile, since the TIDA-00701 design has successfully used the UCC28740 up to 84 W (24 V @ 3.5 A, allowing margin for CC limit @ 3.8 A on that design), it should be possible to use the UCC28740 at 120 W output. The main limitation would be the drive capability of the DRV pin. TIDA-00701 does provide for an external totem-pole drive (Q6/Q7 on the sch), but they were not used.

    The need for an external totem-pole on the DRV would depend on the choice of Flyback FET used, and the size of the total gate charge of the chosen FET. But it should be possible to use the UCC28740 at 120 W with the totem pole driver.

    Since Webench does not seem to support this power level for UCC28740, you could use the TIDA-00791 Design Guide, and make your own 120-W design calculations using that as a guide.

    Alternatively, you could use the UCC28740 Excel design calculator tool, available from the UCC28740product folder here:
    www.ti.com/.../sluc487


    I hope this helps answer your question.

    Thanks,
    Bernard