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UCC28070A Vcc disconnect at standby mode

Hiroshi Doi35
Expert 2845 points
Other Parts Discussed in Thread: UCC28070A

Hi All,

My customer want to reduce standby power.
At standby mode, he want to disconnect the line of UCC28070A Vcc.
If Vcc terminal disconnected,
there remains some voltage on VINAC and VSENSE terminal.
Is this Ok for the reliability of UCC28070A?

  • 0
    TI__Mastermind 34465 points

    The situation you describe occurs every time the pfc circuit is powered up. The UCC28070A first receives signal voltages on VINAC and VSENSE pins.
    The VCC power is normally generated from a downstream converter and it takes time for this to start up and rise to the UVLO value of the UCC28070A.
    So the answer is yes this mode of operation will work.

    However in this situation the pfc circuit is off and the output voltage will slowly decay. You can actually disable the pfc by dragging VSENSE below 0.75V.
    This may be an easier option to implement and it should have the same effect.

    Regards,

    John Griffin