• State
  • Locked Locked
  • Replies 4 replies
  • Subscribers 63 subscribers
  • Views 299 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

UCC28950: ucc28950 output ossiclation

mehmet özdemir
Prodigy 120 points
Part Number: UCC28950

Hello 

I am designing a PSFB with 250V input 82v output power, I have made similar designs before but I am encountering a new problem, the output voltage of the power circuit oscillates around 1v when there is no load Tue.

but even when there is a 5w load, this situation disappears, so what is the reason for this situation?.

  • 0
    TI__Guru* 86286 points

    Hello,

    Your inquiry is under review.

    Regards,

  • 0 in reply to Mike O'
    TI__Guru* 86286 points

    Hello,

    There are many things that can cause your loop to oscillate.

    1. Feedback loop does not have enough phase margin

    2. Current sensing is not setup correctly

    3. Transformer turns ratio is incorrect

    4. To much slope compensation

    The following link will bring you to an application note that goes through the step by step design process of a phase shifted full bridge using the UCC28950.

    There is also a link inside the tool to an excel design file.  You can use both of these tools to review and check your design.

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

    Regards,

  • 0 in reply to Mike O'
    Prodigy 120 points

    Hello, first of all, thank you for your answer.

    When the circuit reaches a certain temperature, the output oscillation that occurs during idle operation disappears and works correctly until it cools down again

    In this case, it first makes me think that there is a problem with the current transformer, but I changed it 3 times, the same situation continued, my question is how can the transformer I disconnected from another working circuit cause this situation ?

    Best regards

  • 0 in reply to mehmet özdemir
    TI__Guru* 86286 points

    Hello,

    The current sense transformer may not be bad.  It is the placement of it and that it may not be resetting.  Try moving it to the input of the HBridge and setting it up per the app tool and note to see if you get better behaivor.

    Regards,