• State TI Thinks Resolved
  • Locked Locked
  • Replies 5 replies
  • Answers 3 answers
  • Subscribers 62 subscribers
  • Views 469 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.

UCC28740: Solution survey of UCC28740 when voltage of HV pin requires at least 1.5 kV

Jui Huan Lee
Prodigy 40 points
Part Number: UCC28740
Other Parts Discussed in Thread: TIDA-00173, UCC28711, UCC28742, UCC28600

Hello

I am interesting in low power consumption function of UCC28740, but I need at least 1.5 kV for HV pin which is annotated with 700V in datasheet,

Do you have any recommendation or solution for this case? thanks so much   

  • 0
    TI__Mastermind 26225 points
    Hi Jui Huan Lee,

    Thanks for your interest in UCC28740. As you noted, the HV pin of UCC28740 is only rated to 700V. The simplest method would be to use a resistor string and zener to feed the HV pin. This method is used in TIDA-00173 to feed the UCC28711 HV pin from a 1.2kV rail. This approach would diminish the power savings however.

    Another method would be to add a depletion mode MOSFET in series with the resistor string and turn off the depletion FET using an external circuit once startup is complete. This approach would allow for more power savings but requires more components to ensure proper on/off operation of the FET.

    Best Regards,
    Ben Lough
  • 0 in reply to Benjamin Lough
    TI__Prodigy 40 points
    Hi Benjamin

    Thanks for your kindly reply, but I am curious about 2 question.

    1. You have mentioned about 1.2 kV in your solution, but what I need is to support 1.5 kV, is there any conflict in side this application?

    2. What about use UCC28742 to replace UCC28740, do you have reference command also containing power saving function?

    thanks so much again
  • 0 in reply to Jui Huan Lee
    TI__Mastermind 26225 points
    Hi Jui Huan Lee,

    1. This is just an example of using resistor string + zener to feed a HV pin from a high voltage rail. This concept would still be applicable at 1.5kV.

    2. UCC28742 does not have a high voltage startup function but you can still use a resistor string to trickle charge VDD. The benefit of UCC28742 is it requires very little startup current so you can make the resistance larger and reduce the static power loss in the string.

    Best Regards,
    Ben Lough
  • 0 in reply to Benjamin Lough
    TI__Prodigy 40 points
    Hi Benjamin

    Could you kindly recommend the depletion FET SPEC and reference cost for 1.5 KV power ? Cause we have no related exp before. Our demand is to find power saving and high efficiency solution and it seems that your solution 1 with string + zener can't decrease power consumption.

    What's more I am also curious about the difference between UCC28600 with UCC28742, could you briefly introduce the beneficial of both device ? thanks so much for your kindly reply
  • 0 in reply to Jui Huan Lee
    TI__Mastermind 26225 points
    Hi jui Huan Lee,

    IXTT2N170D2 might be an option to consider for the depletion FET:IXTT2N170D2

    The primary difference is UCC28742 is a DCM flyback and is generally used for ~30W or so. UCC28600 is a quasi-resonant flyback which can be used up to 150W or so. This blog on choosing the right flyback controller might also be helpful for you:e2e.ti.com/.../choosing-the-right-flyback-controller-for-your-design

    Best Regards,
    Ben Lough