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TIDA-00701: 100 W 24V Power Supply using UCC28051 PFC controller and UCC28740 Flyback controller

ahsan tipu
Prodigy 250 points
Part Number: TIDA-00701
Other Parts Discussed in Thread: UCC28051

Hi, 

I am designing a 100W 24V power supply as detailed in design note tida-00701 and I have a few queries regarding the design:-

1) Page number 45 section 7.4 of the design note says that the altium project files may be downloaded from the tida-00701 webpage but I couldn't find the files there. I emailed the TI support and they told me to post on the forum and try asking the design engineers at TI's e2e forums if such files are available.

2) My second question is regarding the PFC design using the UCC28051. On page 11 section 4.2.9 "Multiplier Setup", there is an equation (equation 17) given which gives the ratio of Rac1 to Rac2. But when I plug in the values given in the schematic (page 42 figure 41), equation 17 doesn't hold true. I have assumed the following values:-

Rac1=680k+680k+680k

Rac2=8.25k

Vac(max)=265 Vac

I went through the design details given in the UCC28051 datasheet. When I plug in the values used in the schematic given in the datasheet, the equation holds true.

Please help me identify if I am making some mistake in my calculations or is there an error in the design note. I have attached the tida-00701 design note for reference. 

  • 0
    TI__Mastermind 31580 points
    Hi Ahsan,

    I need to find the original designer for this TIDA, please give me a day or so.

    Regards

    Peter
  • 0 in reply to Peter Meaney
    Prodigy 250 points
    Hi Peter,
    Thank you for replying. Yeah I'll wait for you to get to the source of this design.
  • 0 in reply to Peter Meaney
    Prodigy 250 points

    The authors, as mentioned in the document tida-00701, are Latif Ameer Babu and Krishna Dora. Kindly get me in touch with them as I have a few other queries regarding the design as well. 

  • 0 in reply to Peter Meaney
    Prodigy 250 points
    Hi Peter,

    Any updates?
  • 0 in reply to ahsan tipu
    Prodigy 10 points

    Hi I am Krishna Dora, 

    Please use a value of  Rac2 = 13k for better results. (lower values than these still work but we need to be careful that we do not increase the value further)

    The system still works with Rac2 = 8.5k  because the feedback compensation signal (which will be multiplied to MULT pin signal)  automatically adjusts itself to generate the required current reference.

    Please post your remaining questions here or mail them to "dvmmkrishna@gmail.com" i will be glad to support you.

    Kind regards

    Krishna Dora

  • 0 in reply to krishna dvmm
    TI__Prodigy 670 points

    Thanks Krishna,

    The Resistor Rac2 on board tested is 13.67k and in schematic shows 8.25k. Thanks Tipu for identifying the error. We will update the schematics accordingly.

    Please use Rac2 = 13.7k

    Thank You,

    Regards,

    Latif Ameer

  • 0 in reply to Latif Ameer
    Prodigy 250 points

    Thanks a lot Mr. Lateef Ameer for the correction. There seems to be a similar issue in section 4.2.10 "Output Voltage Setpoint". The value calculated for RFB2 is 6.41k while it shows 10.5k in the BOM. Can you please clarify this also as to which value should be used?

    We really appreciate the work that you guys put in while designing these application notes and they prove to be of immense help for us designers. That being said, I would request you to kindly review and update this design note (tida-00701) and BOM so that discrepancies are resolved and they may be followed for accurate results. Especially since certain sections such as 4.2.11 "Control Loop Compensation" and 4.4.9 "Feedback Elements" don't the show calculations involved and there is no way to be sure about the values of the components.  

    P.S. I have sent you a TI e2e friend request. Please accept it. 

  • 0 in reply to ahsan tipu
    Prodigy 250 points
    Any update regarding my query?