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UCC2818: UCC2818 PFC converter issue

Moha ABA
Prodigy 90 points
Part Number: UCC2818

Hello,

I designed a PFC converter which has the following features :

Vinac = 85V~130V (Typical input voltage is 115Vac)

Frequency = 400Hz ~ 800Hz. ( go from 400Hz to 800Hzn, avionic power supply)

Vout = 260V/ Poutmax = 150W.

I m using the controller UCC2818.

My issue is about the current harmonic distortion. I want to know if there is trick that exists to improve the distortion during the current crossing of zero.

I used your mathcad file and your note application to choose peripheral component (voltage and current loops).

bellow the current waveform @Pout=400W, Vin=85V, Vout=260V.

The waveform is correct except when the current is crossing zero.

I tried to change current loop component, it allows to improve the current waveform and harmonic distortion but it is not enough to meet the specifications.

Thank you for your help.

  • 0
    TI__Mastermind 34465 points
    Hello Laurent,
    The UCC2818 has been designed for applications with 50/60 Hz line frequency inputs. If you use this part at higher frequencies such as 400Hz you will begin to see line current distortion around the zero crosssings. This happens because of the phase lead introduced by the input filter of the pfc.
    The phase lead means that the input current is attempting to change direction prior to the end of each half line cycle of the input voltage.
    The rectifier diodes will be reverse biased by the hold up on the DC side of the bridge when the voltage reverses and so the line current is prevented from flowing .
    This phenomenon is discussed in the paper : " Demystifying zero-crossing distortion in single-phase PFC converters" and you can request a copy at this web site:
    www.researchgate.net/.../3960285_Demystifying_zero-crossing_distortion_in_single-phase_PFC_converters

    Regards
    John
  • 0 in reply to John Griffin1
    Prodigy 90 points

    Hello John,

    Firstly I would like to thank you for your answer.

    I create my account and the full-text requested is not available on the site web. Do you have any idea about this or if you already have It can you share it please ?

    What I understood is that we must modify the input capacitor of the PFC. Is that true ?

    For the my design I used 100nF capacitor and for diodes I used Ultrafast Plastic Rectifier. To avoid the zero crossing oscillation should we use a specific diode technology ? or specific capacitor technology ?

    Thank you so muck for you reply.

    Best Regards,

    Laurent

  • 0 in reply to Moha ABA
    TI__Mastermind 34465 points
    Hi Laurent,
    This is an IEEE document and unfortunately I cannot give you a free copy.
    However I was able to find the attached technical paper and it is available to view on the internet:
    pdfs.semanticscholar.org/.../c442ba58abb024583519c782495db2f2604e.pdf
    I hope this is of some help.
    May I ask what is your product application ?
    Your power level is only 150W and this should be within the capability of the DC source and so avoid the use of a pfc circuit.
    Regards
    John
  • 0 in reply to John Griffin1
    TI__Mastermind 34465 points
    Hi Laurent,
    I am going to close this post since I thing the question was answered as much as it could be and there has been no new information in almost 3 weeks.
    Please open a new post if you need further information.
    Regards
    John