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UCC28056: UCC28056 Supply voltage

Mason Noh
Expert 2490 points
Part Number: UCC28056
Other Parts Discussed in Thread: UCC28880

Hi TI,

My customer is using UCC28056 for 150W SMPS.

The supply voltage is provided from UCC28880 output voltage(15Vdc)

The issue is PFC output voltage dropped to 310V from 390V at 130W(full load:150W). This issue is occurred when UCC28880(High side buck)'s input is PFC output.

This issue is solved because I changed current sensing pattern as short as possible.

But when UCC28880 input is AC source, This issue is not occurred.

Could you explain about cause of this issue?

  • 0
    TI__Mastermind 27095 points
    Hi Mason,

    My thinking is the switching action and the resulting current loops of the high side buck might be getting coupled into the ZCD/CS pin of UCC28056 which is causing the switching pattern of the PFC to misbehave. When you changed the UCC28880 to being supplied by the AC input, you changed the current paths for the high side buck.

    Best Regards,
    Ben Lough