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UCC28061: Peak current around 0Vac

ol
Intellectual 480 points
Part Number: UCC28061

Hi,

I used UCC28061 @ 1.5kW. It works well but I saw on grid current some peaks around 0vac. If I increase the power, the current increase too and the peak is less visible but in transient it is a trouble.

How can I smooth the current and obtain a perfect sinus ?

Regards

Ol

peak current around 0Vac.pdf

  • 0
    TI__Mastermind 26735 points

    Hi OL,

    There will always be some distortion near the AC voltage zero crossing but what can help is to reduce the bandwidth of the PFC. The goal is to make COMP very flat across the AC line cycle and we do not want COMP to react to the instantaneous line voltage. You could also try reducing the capacitance to the right of the bridge.

    Best Regards,

    Ben Lough

  • 0 in reply to Benjamin Lough
    Intellectual 480 points

    Hi Ben,

    I will perform some tests this evening.

    Reducing input capacitor is possible I will try to place 1uF instead of 2 uF actually.

    For COMP, what do you propose ? increase C ?

    I suppose C.

    Best regards,

    OL

  • 0 in reply to ol
    Intellectual 480 points

    Hi Ben

    I reduced Vin capacitor from 2.2uF to 0.5 uF and the 0 crossing is little better. However I saw that current is very noisy at the max of the sinus. Do you have any idea about that ? To more gain in loop comp ?

    Best regards,

    Ol

  • 0 in reply to ol
    TI__Mastermind 26735 points

    Hi Ol,

    I think what is happening is that after decreasing the capacitance to the right of the bridge, this is not enough filtering to attenuate the inductor current ripple and that is causing a "hairy head" in the input current profile. If you increase your X capacitance, it should help attenuate the noise in the input current at the peak of AC line.

    Best Regards,

    Ben Lough

  • 0 in reply to Benjamin Lough
    Intellectual 480 points 
    hi Ben

Exactly, by removing the capacitor, I introduce noise. So, I added capacitors around 6.6 uF and the signal is now better up to 210 Vac, but beyond that I still have problems with the photo recorded below.

I have not yet determined if it came from the network or if it was generated by the card itself.
Tell me if you've already identified something like this

    Best regards, 

    OL
  • 0 in reply to ol
    TI__Mastermind 26735 points

    Hi Ol,

    I would suggest checking the COMP voltage and see if it is still flat and stable.

    Best Regards,

    Ben Lough