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Original question:

UCC28910: Modify EVM for 12V output

UCC28910: Modify EVM for 7.2V/7.5W output

Molly Huang
Prodigy 310 points
Part Number: UCC28910
Other Parts Discussed in Thread: UCC28911,

Hello Team, 

We are working with the UCC28910 & UCC28911 EVM.

Can you give some guidance on how to modify these two EVMs to support 7.2V/7.5W output?

Thanks,

Molly Huang

  • 0
    TI__Expert 6080 points
    Hello Molly,

    Thank you for your interest in UCC28910/1, I will guide you to the excel calculator tool avaliable on the web page of both the products. This tool will help you to modify the board components to suit your new spec. I have attached the links to both the calculators.
    Note: the calculations for the EVM board components are done using these calculators.

    www.ti.com/.../sluc503
    www.ti.com/.../sluc624

    I hope this helps.

    Regards,
    Sonal
  • 0 in reply to Sonal Singh
    TI__Prodigy 310 points
    Hello Sonal,

    Thanks for your reply.
    We modified resister of EVM to change output from 5V to 7V.

    UCC28910 works fine, but UCC28911 appears audible noise in 7Vout, do you have any suggestion to solve this issue? Thanks.

    Regards,
    Molly
  • 0 in reply to Molly Huang
    TI__Expert 6080 points

    Hello Molly,

    Generally, audible noise is due to the transformer vibrating if it's not properly glued or varnished, Or it could be due to loop stability or noise-induced jitter. Can you be a bit more specific about the noise in your system, eg: what load/line condition do you hear the noise at? what is the freq of the controller? how does the output switch node look like at this occurrence?

    for a quick check, I will recommend decreasing the Cout capacitor, this will increase the Fsw and hopefully push you out of the audible freq zone.

    Regards,

    Sonal

  • 0 in reply to Sonal Singh
    TI__Intellectual 2110 points

    Hi Sonal,

    Thanks for your suggestion. Please let me address more details about this issue.

    They changed our UCC28911EVM output from 5V to 7V and tested it. Below is their test result.

    • Has audible noise from transformer:

    1. Vin: 110V, Output: 7V/60~70mA. (It did not help if they increase output capacitor from 1200uF to 2200uF)

    • No audible noise:

    1. Vin: 110V, Ouput current is smaller than 40mA or larger than 90mA.

    2. Vin: 220V, no audible noise for all current.

    Here is the measurement waveform that they connect 100ohms at load which means output current = 70mA. (Has audible noise).

    Figure 1. Drain to GND

    Zoom in

    Could you please let us know how to solve the audible noise at Vin:110V, Output: 7V/70mA? Thank you.

    Best Regards,

    Polly Chung

  • 0 in reply to Polly Chung1
    TI__Intellectual 2110 points
    Hi team,

    Could you please help the questions on previous post? Thank you.

    Regards,
    Polly
  • 0 in reply to Polly Chung1
    TI__Expert 6080 points
    Hello Polly,

    Apologies for the late reply.
    The controller seems to be misbehaving because of it is switching in packets, I will recommend to check the VDD if in case it is not high enough during this period.

    Regards,
    Sonal