• State TI Thinks Resolved
  • Locked Locked
  • Replies 8 replies
  • Answers 1 answer
  • Subscribers 66 subscribers
  • Views 1347 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.

WEBENCH® Tools/UCC28700: Off-line Isolated AC-DC PS Design (Dual output)

Eymard Cruz
Prodigy 40 points
Part Number: UCC28700
Other Parts Discussed in Thread: UCC28600, UCC28910, PMP8590

Tool/software: WEBENCH® Design Tools

Hello Sirs,

I am looking to design an isolated offline AC-DC PS with the following requirements,

Vin:  85-265 VAC

Vout1: 24VDC @ 250mA

Vout2: 24VDC @ 250mA

Using Webench, I received recommended designs and is leaning towards a design using the UCC28700.

Q1:  Is the UCC28700 a good part to move forward with my design based on my requirements?

Q2:  I used webench to generate solutions for a dual output PS based on my requirements.  Webench recommended design shows single output on the schematic.  It generated specs for a transformer that has a single output.  Is webench only able to make the calculations for a single output?  Is the recommended circuit that I got from webench a calculation for only a single output?  Is there guidance for calculations when dual output is required or is it the same calcs from the data sheets?

I am new in PS design.  This is my first attempt at doing this and from what I gather it is entirely it's own descipline (SMPS Design).  Your guidance here would be sincerely appreciated.

Best Regards,

Eymard Cruz

  • 0
    TI__Mastermind 32910 points
    Hello Eymard,

    The UCC28700 is a good device for your application, based on the requirements that you listed. There are a number of other parts that can also do the job.

    I tried the Webench design for 2 outputs and got the same single-output result as you did. I think this is a problem in the Webench simulation tool, and I will notify the appropriate group about it. You should get a design for 2 output windings (not counting the auxiliary). I don't think you can automatically apply the calculation result for one output to the other, despite them being identical in this case.

    I will ask another engineer to support you further on this design, because I will not be available for several days.

    Regards,
    Ulrich
  • 0 in reply to Ulrich Goerke
    TI__Expert 7395 points
    Eymard,
    Thanks for your interest in TI here. As Uli said he's out for a couple days so i'll offer my comments here as well.

    Webench does not currently have the ability to do multiple output designs for AC/DC. That is something that we're planning on adding but it's not fully available yet.

    I'm going to take a look through our reference designs and see if we have anything close to what you need. I have just a few questions to help me in this search.

    1) what is the lowest load that each output will have?
    2) what voltage regulation accuracy do you need across load line on each output? if 1 rails becomes unloaded with the other heavily loaded you may see the unloaded rail voltage increase beyond 5% for example.
    3) do you have a standby power requirement for this supply? (is this with outputs completely unloaded or with specific light loads?)
    4) what isolation voltage do you need between primary and secondary? what about between each of the 24V outputs? basic, functional, or reinforced isolation?

    Regards,
    John
  • 0 in reply to John Stevens
    Prodigy 40 points
    Hello John,

    Thank you for the respond.


    I made an error on my initial post. I posted two 24 VDC outputs at 250mA. I am actually looking for 2 outputs (24VDC @ 250mA and 5 VDC @250mA). The current requirements are approximations. I will make measurements to have a more accurate value.

    In response to the list of questions you provided.

    1) I will make this measurement.
    2) I am looking to replace an Arch Electronic module (AHCN-24S) that provides +/- 2% accuracy. The line regulation is at +/-.3% and load regulation is at +/-.5%. I currently have LDO's that gradually drops the 24VDC to lower voltages (17VDC, 10VDC, 5VDC, and 3.3VDC.
    3) I don't have standby power requirements. This will power specific light load.
    4) The AHCN-24S provides I/O Isolation up to 3000VAC. I would like to meet that same requirement. The goal on having two isolated output is to eliminate/reduce noise.

    I hope this gives you a better picture.
  • 0 in reply to Eymard Cruz
    TI__Expert 7395 points

    Eymard,

    Thanks for that information. I think the best design to use to start is PMP8642 that I've attached using UCC28600. You would have to check on the isolation of the transformer/opto to make sure it meets your requirement but this was fully built and tested and seems to meet your needs. I think the output cap is pretty oversized for a special transient requirement when it was made but you could lower that for your project.

    Additionally, I've also added PMP8590 using UCC28910 that is much simpler, but may not meet your regulation requirements. This was also built and tested. you may have to clamp or preload the outputs to limit the regulation. And if you need better than 5% on one of the outputs you may need a Linear regulator as well.

    Regards,
    John PMP8642 Rev_A BOM.pdfPMP8642 Rev_A BOM.xlsPMP8642 Rev_A_TestResults.pdfPMP8642_Rev_A_pads.pdf

  • 0 in reply to John Stevens
    Prodigy 40 points

    Hello John,

    Thank you for the information.

    I am moving forward with the UCC28910 with my design.  I am staying away fro the UCC28600 family due to limited board space.  I am now working with Wurth Electronics in identifying a suitable transformer for my application.  I also plan to bring in a development board for the UCC28910.  Is the PMP8590 board available to be purchased for evaluation?  I will reach out should I encounter any issues.  Thank you for the help.

    Best Regards,

    Eymard Cruz

  • 0 in reply to Eymard Cruz
    TI__Expert 7395 points
    Eymard,

    Great to hear. I've contacted the board designer and local FAE named Ahmed to get you a board of PMP8590. I'll let you know how that progresses if they don't contact you here in e2e.

    Regards,
    John
  • 0 in reply to John Stevens
    Prodigy 40 points

    Hello John,

    Sounds good Sir.  Thank you.  I have met Ahmed in a workshop last week.  I'll look forward to getting the development board.  Again thank you.

    Best Regards,

    Eymard Cruz

  • 0 in reply to Eymard Cruz
    TI__Intellectual 2685 points

    Hi Eymard,

    I sent you an email following up. Did you get it?