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UCC28065: OCP Recovery Behavior in UCC28065 – Simultaneous ON of Both MOSFETs

Conor
Guru 12400 points
Part Number: UCC28065
Other Parts Discussed in Thread: UCC28060, UCC28070

Tool/software:

Hi,

We are currently evaluating the UCC28065 for a dual-phase interleaved PFC application. In the datasheet section 8.3.14.2, it is described that after an overcurrent protection (OCP) event, both MOSFETs are turned ON simultaneously once the inductor current drops near zero.

We would like to inquire about the following:

  1. What is the technical reason or design philosophy behind this behavior in the UCC28065?
    Other vendors’ interleaved PFC controllers (e.g., NCP1632, L4981, etc.) typically resume normal interleaved switching after OCP without applying simultaneous ON to both MOSFETs.

  2. This behavior results in a temporary current peak approximately twice as high as normal, requiring larger sensing resistors and tighter design margins.
    Are there any TI interleaved PFC controllers that do not use this simultaneous ON recovery method, and instead resume switching in a staggered (interleaved) manner after OCP?

We would appreciate any insights into the design rationale as well as recommendations for alternative devices if applicable.

Thanks,

Conor

  • +1
    TI__Mastermind 40580 points

    Hello Conor, 

    For your questions:
    (1)  I don't know what the technical reason is for this design choice.  The family of interleaved transition-mode (TM) PFC controllers (UCC28060, -61, -63, -64, -65) began almost 20 years ago and the original designers are no longer with TI.  Their reason for that choice is lost.
    I can speculate that it may have had something to do with the way the Phase-Locked-Loop works which controls the interleaving phase shift.

    (2)  The UCC28070 CCM interleaved PFC controller does not restart both channels simultaneously after OCP.  This one restarts in a staggered manner.  But it is CCM, not TM.
    Actually, the OCP of each channel (set by PKLMT pin) is independent of the other.

    Regards,
    Ulrich 

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