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UCC28781-Q1: Webench or Excel how to use?

mister Q
Prodigy 10 points
Part Number: UCC28781-Q1
Other Parts Discussed in Thread: UCC28782,

Input 350VDC out from a active PFC.

Output 65V

now my Problem:

in Webench i can't customize the ratio of the Trafo, i can search and there are only fixed ratios to select? in addition  i  only can calculate 150W and there is only ucc28782 to select.

I have a fixed trafo with additional AUX-Winding  (6:1) and a sec-Winding (6:1)

i tried the Excel tool SLURAZ0C? 

The Excel file dosen't work?

No matter what I enter, the sheet doesn't calculate anything: Error in formulas: #NAME? 

Office 2016 Pro

Do u have a Excel which works? THX

  • 0
    TI__Mastermind 35640 points

    Hello Mister Q, 

    Thank you for your interest in the UCC28782 and UCC28781-Q1 flyback controllers. 

    The Excel tool SLURAZ0C belongs to the UCC28782 device and it does work.  There are no #NAME errors in it.
    I suggest that you download a new copy from the TI website ( https://www.ti.com/lit/zip/sluraz0 ) to replace the one you have now.  May it became corrupted somehow. 

    At this time, TI does not have an Excel tool dedicated to the UCC28781-Q1 controller, unfortunately. Development of this tool is currently resource-limited.  

    The Webench design tool is programmed to provide a number of design options for a given set of inputs.  However it is not a true simulation program and cannot provide unlimited flexibility in customizing all parameters, including transformer turns ratio.  
    I suggest to take the transformer design provided by Webench and mathematically evaluate the performance changes based on your desired changes in turns ratio. 

    If you entered Webench using 350Vdc for the input voltage, then possibly Webench may be limiting your options based on power level. 
    I suggest to enter the AC input range of your PFC "front-end" and see what designs Webench provides.  Then you can ignore the PFC part of the calculated design.   

    Regards,
    Ulrich

  • 0 in reply to Ulrich Goerke
    Prodigy 10 points

    Thanks for your

    quick reply.

    i tested the excel, same error. no change in values.

    When unlocked, the problem can be seen, no names are defined?

    Is this only a problem of my PC/ excel? i tested it on 4 PCs (all have excel 2016)

    I have already used some Excel sheets from other chips of Ti  for example LM51xx and it work well.

    So thats why I think the declaration of the names is corrupt. see pictures

    best regards

  • 0 in reply to mister Q
    TI__Mastermind 35640 points

    Hello Mister Q, 

    Thank you for showing the screenshots of the #NAME issue that you are experiencing.

    Firstly, I'd like to remind you that this Excel Tool has been in successful world-wide use for several years, and although the current revision is at "C", I have never encountered an issue with #NAME errors and complete lack of variable name definitions.   

    In an attempt to recreate your problem, I downloaded a fresh copy of SLURAZ0C for the TI website into a test folder and changed the decimal point separator to the European comma (in the Files > Options > Advanced window).

     

    That successfully changed all the decimal points to commas, to match your view. 

    Then I changed "Vin_type" to DC and started filling in 1's in every entry down to row 37, to match your view. 
    I found three interesting differences: 

    1.  Changing to DC should cause the units in column E to change from "Vrms" to "V".  My did; yours did not.
     
    2.  When I double-click on cell D21, the formula alignment is to the left, as highlighted below.  

    Your alignment above is shifted right, with space at the variable name and the "_Brownin" aligning more under the "Vrms".
    I found this would happen only if I insert spaces ahead of the formula in the formula box. 
     >>> 

    3.  I don't get any #NAME errors, and I do get a built-in warning in F34; your example does not get the warning.

    4.  Finally, my Name Manager shows all of the defined variables, even though yours does not: 


    Given the above test results, I must conclude that this Tool works as expected for most of the world, but there is something about your PC settings that corrupt the file at your location.  
    Unfortunately, I'm not a PC expert, so I don't know the proper system-level settings or how to solve this problem for you.
    I suggest to download a fresh copy and try running the program without unlocking it. 

    Regards,
    Ulrich