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UCC28019: Input Current distorted

Holly Gu
Intellectual 2750 points
Part Number: UCC28019

Hi Team,

   My customer is using UCC28019 for PFC, input 230VAC, output is 390V, full load is 1KW. When output power is ~300W, the input current waveform is distorted.

   SCH is like PMP2552. What parameters can be changed to improve input current waveform? Full load seems much better.

  • 0
    TI__Mastermind 34465 points

    Hello Holly,

    The PM2552 was optimised for a full load of 1kW and if you operated at a lower power the voltage on the DC side of the bridge will never fully drop to zero around the zero crossings of the AC input voltage. At 300W the cap C3 has a residual voltage and this voltage prevents the rectifier diodes from providing current at the zero crossings. That is what you are seeing in the scope waveforms.
    You can decrease the value of C3 and increase the value of the EMI filter cap C1,C2 and this should improve the current shape.

    Even with the waveform above, the power factor is probably very good and you really need to measure power factor and harmonic distortion in order to know whether you meet your design requirements. Do you have a specification for these parameters ?

    Regards

    John