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UCC28880: wide vin high vout lo load no audible noise

Hiroshi Doi35
Expert 2845 points
Part Number: UCC28880
Other Parts Discussed in Thread: UCC28810, UCC28910

Hi all,

I want to give me cct.

Because WEBENCH cannot meat this design.

Vin     DC38V to DC156V
Vout   20V
Iout    30mA
Freq.   Over 20kHz (all Vin range)

No isolation
No stop at Input voltage increasing.
No big losses by Preload
Not must, but want to use 2.2mH or 2.7mH use.

Actual cct problem is,

Inductor value reduce -> Stop osc. High Vin
Inductor value increase -> Freq. under 20kHz

Please give me cct. using UCC28880.

  • 0
    TI__Mastermind 26700 points
    Hello Doi-san,

    Thank you for considering the UCC28880 controller for your project. I have been working with the UCC28880 Design Calculator ( www.ti.com/.../getliterature.tsp ) to find component values.

    For the low power level (0.6W out) and wide input range, the calculator recommends about 1mH inductance to operate above 20kHz. Using 2.2mH or higher drives the typical switching frequency down to ~14 kHz or lower. But 1mH may cause the frequency to reach the 62kHz limit.

    I've been studying your concerns for a while, but I need more time to think about it some more.
    I'll get back to you.

    Regards,
    Ulrich
  • 0 in reply to Ulrich Goerke
    Expert 2845 points

    Ulrich-san,

    Thank you for your support.

    But the customer's real input range was more wide.  DC33V to DC156V.

    UCC28880 cannot meet this.  It's over the max. duty limit.

    We have to cancel UCC28810 order.

    Any way, how about UCC28910 buck ?

    Vin DC33V to DC156V
    Vout 20V
    Iout 30mA
    Freq. Over 20kHz (all Vin range)

    No isolation
    No stop at Input voltage increasing.
    No big losses by Preload

    If you can find good parts value, please teach me.

    Thank you!