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UCC29910A: BUCK FPC for 3phase ACDC Supply 240W

Lutz Naumann
Expert 6450 points
Part Number: UCC29910A
Other Parts Discussed in Thread: UCC29910, UCC28180, UC3825

Dear team,

we started investigating a buck PFC for a 3 Phase power supply without neutral line. The input voltage is 400-480VAC. The power supply is planned for 240W. For cost reasons we want to use a single PFC stage after the B6 rectifier. I found only one BUCK PFC controller UCC29910. Further I found a document for a single phase Ref Design using UCC28180 as an inverted BUCK PFC. This controller might be an option for the final design as well.

To familiarize with the BUCK PFC I'm looking at the UCC29910EVM right now. A spreadsheet exists to do the calculations. Will the spreadsheet also be valid for voltages going that high or should it be used fro single Phase designs only? What intermediate voltage would be a good choice knowing lots of discussions about an appropriate conduction angle?

Many thanks

Lutz

  • 0
    TI__Mastermind 27105 points

    Hi Lutz,

    This is much higher voltage and much higher power than we typically see this controller used in. I would be concerned about scaling the LINESNS pin to an appropriate value at max AC input limiting how low you can set the output bus voltage and giving poor power factor correction. If you do decide a buck PFC is needed, I would suggest UCC28180 which does not need to sense the rectified AC line directly. 

    If you could also help me understand a little more about your application, my understanding with 3 phase AC input EN61000-3-2 class A is used in which only maximum values are specified for the harmonics. Normally this means power factor correction is only needed if the total input power is >few kW. Is power factor correction a must have for this application?

    Best Regards,

    Ben Lough

  • 0 in reply to Benjamin Lough
    TI__Expert 6450 points

    Hi Ben,

    the PFC is not needed per definition. 

    We think of reusing a existing LLC stage which already exists. Perhaps some minor modifications. This LLC runs of a 395V intermediate voltage. Without a PFC the 400-480VAC just rectified and filtered would result in a non constant intermediate voltage and this will not be optimal for the following LLC. The idea is if we had a BUCK stage lowering the intermediate voltage to a defined level. This way we could optimize the LLC and potentially reused most parts of the existing design.

    thanks

    Lutz  

  • 0 in reply to Lutz Naumann
    TI__Mastermind 27105 points

    Hi Lutz,

    Thanks for the background information. I think your best bet is likely with a voltage mode, fixed frequency, PWM controller like UC3825 + external driver. You will have more flexibility for tailoring the buck converter behavior to suit your application of an intermediary bus.

    Best Regards,

    Ben Lough