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UCC28911: UCC28911D - Usage for wide range input flyback

ANURAG LOKHANDE
Intellectual 260 points

Part Number: UCC28911
Other Parts Discussed in Thread: UCC28881, UCC28910, UCC28701

Tool/software:

Hi,

We have use case of 

Input voltage range 19V to 60V DC and 20V to 265V AC.

Output of 12V, 80mA.

Flyback.

I came across UCC28911D and UCC28881DR

https://www.ti.com/lit/ug/sluuba1/sluuba1.pdf?ts=1752826665497&ref_url=https%253A%252F%252Fwww.ti.com%252Ftool%252FUCC28911EVM-718

UCC28881DR

https://www.ti.com/lit/df/tidrs78a/tidrs78a.pdf?ts=1752826638278

I have EVM of UCC28911D.

If I change the transformer, is it possible to configure UCC28911D for required specifications.

I have transformer for wide input voltage range. 

https://www.we-online.com/components/products/datasheet/750370271.pdf

I am trying to configure UCC28911D as given in UCC28881DR EVM. Not able to work.

Am I missing some information?

Thanks and regards,

Anurag

  • 0
    TI__Guru* 86286 points

    Hello,

     

    Based on your power level the UCC28881 would be a better choice for your design.

     

    The UCC28910 was designed for higher power levels and uses primary side regulation.   It may have problems regulating the primary peak current of an 80-mA output design.  The primary current in this design will be much lower than the output current.  The controller most likely is struggling or cannot control this low primary current.

     

    Below is the schematic of the UCC28881 reference design you mentioned.  It is primary side regulated.  I think this is a better choice for your power level and I would recommend using this controller for your design instead.

     

    Regards,

  • 0 in reply to Mike O'
    Intellectual 260 points

    Hi,

    Thanks for your reply.

    UCC28910  --> switching frequency --> 115 kHz

    UCC28881DR --> switching frequency --> 62 kHz

    Due to size constrains, we would like to try on smaller size transformer.

    UCC28910  Design, when I remove D4, and directly give 20V to VDD with 10 Ohm resistor(R7) in series, UCC28910 does not start switching. 

    R9 and R10 changed to R9 = 23.46k and R10 = 8.02k for low input voltage startup 10V RMS. 

    Transformer changed to https://www.we-online.com/components/products/datasheet/750370271.pdf

    Can you please suggest if I can try something with UCC28910 before moving to UCC28881DR.

    Regards,

    Anurag

  • 0 in reply to ANURAG LOKHANDE
    TI__Guru* 86286 points

    Hello,

     

    As previously mentioned I would not recommend using the UCC28910 for this low power application due to the low currents. There is an internal current mirror that will not work with those low peak currents in the UCC28910/1 devices.  So you can’t use these devices for your application.  

     

    The UCC28701 is a primary side regulate flyback controller that uses an external FET and can control down to lower peak currents with an external shunt resistor that can be adjusted.  This device does not have the internal current mirror limitation.  This controller will work up to 130 kHz and will help you reduce the size of your transformer.  You can find the data sheet at the following link.

    https://www.ti.com/lit/ds/symlink/ucc28701.pdf

     

    Regards,