• State TI Thinks Resolved
  • Locked Locked
  • Replies 5 replies
  • Answers 1 answer
  • Subscribers 63 subscribers
  • Views 756 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

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.

UCC28700-Q1: Use of secondary winding for voltage regulation instead of the auxiliary winding?

Viktorija Cecil
Mastermind 18101 points
Part Number: UCC28700-Q1
Other Parts Discussed in Thread: UCC28600-Q1, UCC28C41-Q1, LM5021-Q1

Team, 

My customer is asking:

We have some technical questions on UCC28700-Q1 flyback controller. Since we do not need isolation for the output rail(12V shares input High voltage ground),Is it possible to use secondary winding for voltage regulation instead of the auxiliary winding? I know there is a cable compensation circuit that might need some tuning. In terms of grounding and other aspects, do you think it is feasible to eliminate the auxiliary winding?

This is 700+V to 12V conversion.

Thanks

Viktorija

  • 0
    TI__Intellectual 2910 points
    Viktorija,

    I have contacted the applications engineering team for this device. Since it is later in the workday in the US, most likely we will get a response by tomorrow on your inquiry.

    Regards,

    - Daniel
  • 0
    TI__Expert 7395 points
    Viktorija,

    Thanks for the interest here.

    This is an interesting question. I don't think we've tested this before but I don't see why it wouldn't work.

    Can you help me understand why this approach is of interest?

    Since it's not isolated I'm curious why you wouldn't just do a non-isolated flyback with direct voltage feedback from the output using something like ucc28600-q1, LM5021-q1, or ucc28c41-q1.

    What advantage do you gain trying to do PSR sensing when you don't need to?

    Regards
    John
  • 0 in reply to John Stevens
    TI__Mastermind 18101 points

    Thanks, John. Details from my customer:

    Thank you for the question and your suggestion. We are trying the think out of the box to make the product a bit more cost effective. The circuit might have two configurations based on our customer’s request. One configuration is with non-isolated power supply. The other is with isolated power supply. If we can eliminate the auxiliary winding in the transformer, that helps with cost. Also, if UCC28700-Q1 can handle both configurations, then we can have one BOM part with higher volume for this chip. At last, secondary  regulation requires opto-feedback which might increase cost and BOM count.

    If there are other better solution in your opinion, it is definitely welcomed. I will also look at the parts you mentioned.

    I hope this answers your concerns.

    Thanks

    Viktorija

  • 0 in reply to Viktorija Cecil
    TI__Expert 7395 points
    Viktorija,
    That all makes sense. This is perfect for the application. It sounds from your latest comment that for non-isolated version they only have primary and aux windings where the aux is the regulated output and bias for the chip. The aux winding and output winding can use the same winding. This potentially gets better performance because it eliminates the error caused by the coupling between the output winding and the aux winding. This is directly sensing the output voltage before the diode .
    The only thing they need to worry about is the output voltage. This works only if the output voltage is high enough to support the IC operation. Say, if they need 5V output, it is going to be a problem. But since they outlined 12Vout it shouldn't be a problem.
    This means they can use UCC28700-Q1 for both non-isolated and isolated applications. obviously for the isolated application they will still require primary, aux, and secondary windings like the standard flyback configuration shown in the datasheet.
    I hope this helps.

    Regards,
    John