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Original question:

UCC39002: Paralleling 2 or 3 Forward Isolated Converters for increased power

UCC39002EVM: Paralleling 2 or 3 Forward Isolated Converters for increased power with secondary syncrhronous mosfet

seenivasan ovureddy
Prodigy 20 points
Part Number: UCC39002EVM
Other Parts Discussed in Thread: UCC39002, UCC29002

Tool/software:

Dear sir,

We bought one UCC39002EVM board to test the load sharing concept. But we get some problem to parallel the module. Without OR-ing diode or mosfet, we could not connect two forward isolated converter. In this forward converter, we are using self driven synchronous mosfet for secondary side control instead of diode.

We have some doubts about this IC(ucc39002).

1. Does this IC work with synchronous control modules? or do we need some extra protection circuit like OR-ing diode or mosfet.

Thanks,

Seenivasan O.

  • 0
    TI__Mastermind 40580 points

    Hello Seenivasan, 

    The UCC29002 load-share controller does not care if the power modules have synchronous rectifiers or not, however, the modules themselves probably do need some protection such as ORing diodes or MOSFETs to prevent reverse-current between the N modules.  This is because the SR FETs are not synchronized between modules. 

    Regards,
    Ulrich

  • 0 in reply to Ulrich Goerke
    Prodigy 20 points

    Thanks Ulrich.

    May I request you to please share any suggested schematic or design?

    I assume I will need one ORing MoSFET for each module input. Am I correct in this assumption?

    How do you recommend driving the ORing MoSFET? Can I avoid an expensive gate drive? May be an O-Ring Controller like TPS24xx series?

    Assuming a load of about 12V/8A per module, what would you recommend as the current rating of the MoSFET assuming a 70 Deg C ambient operating temperature? i.e. how much derating should I plan for? I am assuming about

  • 0 in reply to seenivasan ovureddy
    TI__Mastermind 40580 points

    Hello Seenivasan, 

    You are correct that you will need one OR-ing MOSFET for each module output (not input). 
    A controller like the TPS24xx series can work, and there may be more recent OR-ing controllers available now on TI.com. 

    I do not support the OR-ing controllers, so I can't answer questions on their use and how to select the MOSFET. 
    Please post these questions on E2E as a separate dedicated thread for the TPS part number.  That will be answered by the appropriate expert. 

    This app-note can help you configure the TPS... with the UCC29002: https://www.ti.com/lit/pdf/slua550 

    Regards,
    Ulrich