• State
  • Locked Locked
  • Replies 3 replies
  • Subscribers 65 subscribers
  • Views 584 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.

UCC28251: Pulse width difference is seen between OUTA and OUTB

Kenji Ninagawa
Expert 4190 points
Part Number: UCC28251

Team,

 

Our customer is working on Full-Bridge configuration with UCC28251, then pulse width unbalance is seen between OUTA and OUTB.

 

Here are the phenomena;

- No issue is seen at IC individual working,.

- When the output current is low, the both pulse width are balanced.

- When the output current is larger, unbalance pulse width can be seen. (waveform I sent)

- Finally overload protection makes the system stop due to transformer saturation.

 

I understand OUTA and B of UCC28251 generally must work like "Mirror".

And I think any external factor of IC should make the unbalance issue because IC individual work has no problem.

 

So could you please give any advice about what could cause such a pulse width unbalance ?

 

 

よろしくお願いします。

Thanks and Regards,

Metropolitan (Tokyo) Area FAE  Kenji Ninagawa

  • 0
    TI__Mastermind 40350 points
    Hello Ninagawa-san,

    I have notified the appropriate team of your question, and someone knowledgeable of the UCC28251 should reply to you soon.

    Regards,
    Ulrich
  • 0
    TI__Intellectual 1550 points

    Hi Kenji,

    somehow I have trouble viewing the content of the pdf file. I was asked to download a font package to view the file. Can you send it to my email w-huang3@ti.com.

    Did you measure the controller PWM outputs (i.e. the input of the gate driver) and the output of the gate driver when the issue occurred?

    Regards,

    Wangxin

  • 0
    TI__Intellectual 1550 points
    Hi Ninagawa-san,

    Based on the schematic you sent out, the full bridge uses voltage mode control which means the OUTA and OUTB pulses are supposed to be matched. The waveforms included in the pdf file shows very noisy and unstable falling edge of the pulse. It doesn't necessarily indicate unmatched pulses. I would first recommend to try different trigger options to get more stable and less noisy waveforms. If it still shows unmatched pulses, please provide the difference of the widths of the two pulses and the input voltage and load current. In addition to the pulses, please include also the RAMP signal and COMP signals on the scope in order to confirm the stability of the PWM generation.

    Regards,
    Wangxin