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THD of UCC28070

Sam Guo
Intellectual 380 points
Other Parts Discussed in Thread: UCC28070

UCC28070 is a two-phase PFC controller.  It has internal current synthesizer.  One can use a current transformer to measure the up-slope or FET current and the chip can add the down slope to form a triangle inductor current for average current mode control.

 

I heard that the line input current harmonics is not small with this chip due to the current synthesizer.  What is your experience?  What is the best THD you got at Vin = 120VAC and full power?

 

I appreciate your help.

 

Sam Guo

  • 0
    TI__Guru* 86266 points

     The THD of this device runs about 8% at full load.  A resistor based solution would be sub 5%.  The device does meet EN61000-3-2 harmonic content and has a PF of greater than 0.95.

    Regards,

  • 0 in reply to Mike O'
    Intellectual 380 points

    Hi, Mike:

    Thank you very much for your answer.   

    I have two more questions:

    1. With the resistor based solution, where is the shunt resistor inserted to measure the current for each phase?
    2. Is the resistor current waveform of the triangle shape (whole cycle current) or of a slope shape (part of the cycle current)?

    Sam Guo