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UCC39002: Current Sharing LLC Power Modules

Mark Scott1
Prodigy 30 points
Part Number: UCC39002
Other Parts Discussed in Thread: TPS2412, UCC29002

I'm a designer of a 1KW AC to DC Converter (single output) and trying to design a current sharing and active ORing circuit using TI's UCC39002 and TPS2412 respectively and am having extreme difficulty in getting it to perform. I would like to mention the AC side is an LLC topology fed from a PFC topology. A schematic will follow shortly.current share.pdf

  • 0
    TI__Mastermind 31360 points

    Hello Mark,

    Thank you for your interest in TI sharing and ORing controllers.

    When I compare your schematic diagram with the TPS2412 application diagram, I see that you have a MOSFET Q13 in series with the C input, whereas the datasheet shows the C pin connected directly to the common output bus.  It is possible that Q13 is not behaving as you intend for it.
    I suggest to bypass Q13 with a source-to-drain short-circuit to see if operation improves. 

    Furthermore, the GND pin of the TPS2412 is tied to the common GND through a PNP Q11, which may not be driven on hard enough. 
    I suggest to short it out, too.

    Regards,
    Ulrich 

  • 0 in reply to Ulrich Goerke
    Prodigy 30 points

    Yes you are correct. However this is a 48V system and I am following TI's High-Voltage ORing with Low-Voltage Controllers (SLUA486-October 2008). Please check this paper to verify it's purpose is correct for my application.

    Thank You

  • 0 in reply to Mark Scott1
    TI__Mastermind 31360 points

    Hello Mark,

    I apologized for my delayed response.

    I looked at SLUA486 and indeed your implementation of the PNP on the GND pin is correct, per the App-Note.
    However, I noticed that in your schematic, the VDD pin of the TPS2412 is connected to a 12Vdc source through a diode and resistor, whereas the App-Note shows TPS2412 VDD "hanging" from the 48V rail.  That difference may account for the trouble you are having.  

    I think the 12Vdc source maybe should provide bias power only to the UCC39002 sharing controller, and not also to the TPS.
    Please try removing R84 and connecting TPS2412 VDD directly to the 48V input rail, as shown in Figure 1-4 on page 3 of SLUA486.

    Regards,

    Ulrich

  • 0 in reply to Ulrich Goerke
    Prodigy 30 points

    Hello,

    Thank you for your response. You are correct, the schematic was in error but not the working prototype. The prototype is wired exactly as you had suggested. It was purely a schematic error. I have made some positive advancements since this response. I have made some component changes in the feedback of the UCC39002 and others noise issues that show some great progress.

    I found a topic on a Mathcad file that is more specific than the user guide and addresses much more detail in using the UCC39002. I found this in one of the may responses from other users on this UCC39002 forum. However, I had to enter the equations manually and it was quite tedious (15 pages). Is there a Mathcad file that can be provided? I'd love to have it. Can you help with this? I will close this account after your positive response to this request.

    Thank You

  • 0 in reply to Mark Scott1
    TI__Mastermind 31360 points

    Hello Mark,

    I found both a Mathcad calculator tool and an Excel calculator tool in the product folder for UCC29002:

    Mathcad 2000:
    https://www.ti.com/lit/zip/sluc045

    Excel:
    https://www.ti.com/lit/zip/sluc684

    I hope this Mathcad is the one you are looking for.

    Regards,
    Ulrich