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UCC28056: Can the UCC28056 be biased from an aux winding on the primary inductor for Vcc?

Shawn Workman
Genius 13900 points
Part Number: UCC28056

Is it possible to create an auxiliary winding off of the PFC inductor to bias the UCC28056 after startup?

Is there an issue doing this with this part and/or any transition mode controller like this?

What are the advantages and disadvantages of doing this?

  • +1
    TI__Genius 9140 points

    hi Shawn,

    it should be able to use aux-winding on PFC inductor to supply UCC28056. 

    one important thing is that UCC28056 do not have high voltage start up, so you still need to add bias voltage on UCC28056 before it start up, the same as most of Flyback that do not have high voltage start up. And the circuit will influence the standby power.

    one another concern when using aux-winding for PFC VCC supply is that the votlage on  aux-winding is not stable among the input votlage range. So you need to add a buck or LDO between aux-winding and VCC of UCC28056, the circuit will also have power loss.

    Most of real application supplies UCC28056 VCC through downstream stage.