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UCC28063A: Questions about the operation of the UCC28063A PWMCNTL pin.

Bob Lee62837
Mastermind 7230 points
Part Number: UCC28063A

Dear support member,

My customer used UCC28063A.

I have a question.

(Question)
When AC interruption occurs from the state of normal operation and the PFC voltage falls below the PWMCNTL threshold,
I would like to switch the PWMCNTL terminal from GND potential to open.

Is there any problem in usage?


(Because)
When AC interruption occurs, VINAC is fixed to GND.
I am concerned if the operation switching from the PFC control state will not affect the operation of the PWMCNTL pin.


(According to datasheet)
PWMCNTL is
GND potential at or above the PWMCNTL threshold of the HVSENSE pin that is dividing voltage.
Open at or below the PWMCNTL threshold of the HVSENSE pin that is dividing voltage.

If you look at the block diagram, it seems that operation is switched from PFC control state.


Best regard.
Bob Lee.

  • 0
    TI__Mastermind 31060 points

    Hello Bob san,

    Thank you for your interest in the UCC28063A PFC controller.

    The state of the PWMCNTL output is determined only by the voltage at HVSEN input, the COMP and PHB voltage levels, and by the Phase-Fail detector output. This can be seen in the block diagram.  The voltage at VINAC is irrelevant to this output.

    HVSEN is a scaled sensing of the PFC output voltage, and the PWMCNTL output will be low (GND) as long as 2.5V < HVSEN < 4.87V.  If AC power is lost, PFC output voltage will begin to fall, but PWMCNTL will stay low for as long as HVSEN > 2.5V depending on how much load there is.  If only one phase loses power, then the Phase-Fail Detector will shut off PWMCNTL after 12ms of sustained phase loss.  But if both phases are lost (no ZCA and no ZCB) then this is not considered as a phase-failure.  So PWMCNTL will stay low, as long as HVSEN > 2.5V.

    I hope this answers your questions and concerns.

    Regards,
    Ulrich

  • 0 in reply to Ulrich Goerke
    Mastermind 7230 points

    Dear Ulrich Goerke,


    Thank you very much for your answer.

    I reply my customer your answer.
    I will feedback it.


    Best regard.
    Bob Lee.

  • 0 in reply to Bob Lee62837
    TI__Mastermind 31060 points

    Thank you, Bob san.

    Unless there are further questions on this topic, I will close this E2E thread.

    You may re-open it if your customer needs more information, or you may start a new one on a different topic.

    Best Regards,
    Ulrich

  • 0 in reply to Ulrich Goerke
    Mastermind 7230 points

    Dear Ulrich Goerke,

    Thank you very much for reply.

    My customer solved.

    Best regard.
    Bob Lee.