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UCC28070A: Need help selecting component values for different modes

Lauren Mayfield
Expert 7985 points
Other Parts Discussed in Thread: UCC28070

Editing to remove confidential information

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    TI__Mastermind 31580 points

    Hi Lauren,

    The UCC28070 is not designed to run from DC. The UCC28070 updates its QVFF table during the zero crossings of the AC line, VINAC pin goes to 0V. When operated from DC the QVFF table does not get updated and the controller will not operate correctly.

    Some customers have been successful in using the UCC28070 from DC but it requires an external circuit to pull the VINAC pin to ground periodically to trigger the update of the QVFF table.

    The input voltage and output voltage sense chains will have to be dynamically switched between the two modes. I suggest you run the excel design calculator to see how close the boost inductor values. The TI power stage designer tool may also be useful in comparing the two modes of operation from a power stage perspective.

    Regards

    Peter