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UCC28950: Unexpected Waveform Observed at Startup with UCC28950

Conor
Guru 12235 points
Part Number: UCC28950

Tool/software:

Hi,

We have observed unexpected waveforms during the startup of a switching power supply using the UCC28950.
The details of the issue are summarized in the attached Excel sheet for your review.
UCC28950_20250729.xlsx

Could you please help us investigate the root cause?

Thanks,

Conor

  • 0
    TI__Guru* 86286 points

    Hello,

     

    The way the comp is jumping up and down it looks like you have a loop instability.

    The following link will bring you to an application note that goes through the step by step design process of phase shifted full bridge using the UCC28950.  There is a section on compensating the voltage loop.  I believe if you fix the voltage loop compensation it will fix your issue.  There is also a link to the excel design tool in the application note that uses the same equations.

     https://www.ti.com/lit/pdf/slua560

    Regards,