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UCC28070: Use of Common Mode Choke in Interleaved PFC

Conor
Guru 15230 points

Part Number: UCC28070

Tool/software:

Hi,

I am currently designing an interleaved PFC circuit using the UCC28070 and would like to inquire about the feasibility of using a common mode choke as the boost inductor.

Since common mode chokes are typically designed for EMI filtering rather than energy storage, I believe they may not be suitable for this application. However, I would like to confirm with you:

  1. Is it possible to use a common mode choke as the boost inductor in a UCC28070-based interleaved PFC circuit?
  2. If feasible, are there any specific considerations regarding coil polarity or other design aspects?

I appreciate your guidance on this matter.

Thanks,

Conor

  • 0
    TI__Mastermind 40580 points

    Hello Conor, 

    It is NOT feasible to use a common-mode choke (CMC) design for the UCC28070-based interleaved PFC circuit.  

    As you mentioned, CMCs are not designed for energy storage and the boost-PFC requires energy storing inductors. 

    For a CMC, the current in one winding is matched by and equal and opposite current in the other winding to cancel the flux in the core.
    Only leakage flux and flux from common-mode noise currents (usually very low amplitude) can exist in the core without saturating it. 

    The interleaved PFC currents are not equal (except two points in time each cycle where their amplitudes cross), so the CMC is almost always in a saturated state, and there for useless for energy storage and PFC.

    Regards,
    Ulrich