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UCC3818: To clarify why there is no UCC3818 DRVOUT during AC input lost.

Eric Lai
Expert 4940 points
Part Number: UCC3818

Hi Expert,

Will need to clarify why there is no DRVOUT during AC input lost.

Conditions:

--PFC stage is running under AC input

--Turn off the AC input for serval AC cycle (60Hz) then turn on the AC input back 

--VCC is in the biased and keep in the regulation still during AC lost

Results and support need:

No DRVOUT during AC input lost is observed.

Once AC input is back, the DRVOUT will resume the switching after 2mS waiting.  

May we know why there is no DRVOUT during AC input lost. Is it expected behavior for UCC3818?

And pls advice the behavior of the UCC3818 internal to disable the DRVOUT during AC lost and why need 2ms waiting.

Best regards,

Eric Lai

 

Field Application Engineer

Texas Instruments Taiwan Limited

O: +886-2-2175-2582

M: +886-909-262-582

E-Mail:Eric.Lai @ti.com

  • +1
    TI__Mastermind 43580 points

    Hi Eric,

    It is difficult to be sure without seeing the schematic, but the control logic for the UCC3818 requires the IAC current from the AC voltage to properly regulate. Without this the device is not able to regulate properly:

    Does this answer your question?