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Original question:

SMPS input capacitor and pi filter selection values

UCC28064A: PFC inductor selection

balasubramani r
Expert 1170 points
Part Number: UCC28064A

Hi There,

Im in design phase with UCC28064A PFC ic . My question is what is the criteria to select the inductor value whether it should be based on Vmin or Vmax?

In datasheet it is suggested to go with Vmax but in Design notes is based on Vmin w.r.t. inductor selection Formula. 

Kindly have the technical people thought. 

My requirement is 390V, 600W design . 

My min Switching Frequency is 40KHz. 

  • 0
    TI__Mastermind 27145 points
    Hi Balasubramani,

    I would suggest calculaing the inductance at both Vmax and Vmin and pick the lower of the two calculated values as your inductance. This will ensure the converter always operates above the desired Fmin.

    Best Regards,
    Ben Lough
  • 0 in reply to Benjamin Lough
    Expert 1170 points
    Hi Ben,

    I could see some reference design they have used inductor w.r.t Vmin not Vmax. Is there any specific reason since we dont want to exercise at our bring up time.

    Any Help here?
  • 0 in reply to balasubramani r
    TI__Mastermind 27145 points
    Hi Balasubramani,

    I would suggest using the equations in the UCC28064A datasheet. It is not a given that the switching frequency will be at its minimum at low line, it can happen at high line as well depending on the design parameters. Calculating the inductance at both low line and high line using equations 19 and 20 in the datasheet will ensure that the PFC will always stay above Fmin.

    Best Regards,
    Ben Lough