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UCC28070: Power Factor improvement on ucc28070

Wei Cheng Liu
Prodigy 250 points
Part Number: UCC28070

Hi Host

I need to improve the PF of power board(900W), but I tried several times to change the compensation of Current feedback or voltage feedback on UCC28070.

But the result is still not good enough. 

Can you help to make a list or advice some ideas for me?

there are my waveform as below. cH1 is input current at 110Vac full load. ch4 CAOB pin

  • 0
    TI__Mastermind 34465 points

    Hello Wei Cheng Liu,

    It is possible that you have used the wrong value of RSYNTH resistor or that the current sense signal is not be accurately sensed.

    First of all I would check CSA and CSA.

    You should see a signal like the attached

    Then I  would use the Excel calculator tool for the UCC28070 and check that the recommended parameter values are close to what you are using.

    Regards

    John

  • 0 in reply to John Griffin1
    Prodigy 250 points
    Hi John
    Thanks your advise, after re-calculating Rsyn, I'd found some disturbance on PFC switching, I added a PNP to turn off mosfet, the turn off spike voltage on Vgs was turn on mosfet again, that made extra noise and implicated CSA and CSB. The PF is better now, current waveform of input also better looking.

    Best Regards
    Liu