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UCC38050: Can UCC38050 PFC Controller be used out of the universal input range?

Aaron_Rangel
Intellectual 440 points
Part Number: UCC38050
Other Parts Discussed in Thread: UCC28050

Hello,

I have a doubt about the UCC38050 PFC controller input range of usage.

I mean, I do not really know if it is possible to use that kind of device in a range that it is not the universal input range (85Vac-265VAc).

The design example UCC38050 100-W Critical Conduction Power Factor Corrected (PFC) Preregulator, SLUU138A.pdf is designed according to the universal input range and the UCC38050 datasheet does not indicate any about more narrowed input range.

To stick to the point, in my case, I have to perform 2 designs providing PFC solutions (PFC>=0.95) as follows:

  • Buck-boost.
    • Input range 42Vac (-20%,+10%).
  • Boost.
    • Input range 12Vac (-20%,+10%).

Is there any possibility of doing that with this kind of driver? If not, Has Texas any available driver for designing that?

Looking forward to hearing any comment or help about this issue.

Regards.

  • 0
    TI__Guru* 81346 points

    Hello Aaron,

    PFC is generally used in off line power.  Japan is 100V AC, The US is 120V and Europe 230V and Europe.  Generally 85V to 265V covers the full range.  These converters will generally work down to 65V RMS which is a 4 to 1 input range.  With a PFC boost at these voltage a PF of greater than 0.95 can be achieved.  If the design was to use a flyback, which is similar to a buck boost because of the discontinuous flyback input current a PF of greater than 0.9 can be achieve but 0.95 is most likely not possible.

    Your applications seem to have an extremely low AC source voltage.  You should be able to design for these voltages if you wish.  You should also be able to use the application note you reference.  I would suggest making the minim input voltage 20 % less than your nominal input and the maximum 20% more than your nominal.  Set the boost to voltage to greater than 4% your maximum AC input.

    At these low input voltages you may not be able to achieve a PF of greater than 0.95.  This is because at these low voltages your rectifier diodes drop in your bridge rectifiers will have an effect on the multiplier input of the UCC28050 (MULTIN) and will create crossover distortion.  I am not exactly sure how high of PF can be achieved at these low voltages. I would believe a PF of 0.9 might be achievable but you will have to experiment to see what is achievable in this unique low voltage application.

    Regards,

    Mike

  • 0 in reply to Mike O'
    Intellectual 440 points
    Hello Mike O',

    Thanks for your fast and accurate reply.

    In fact, I have never designed a PFC Boost in such a "narrowed" and low AC sourge voltage, I always used universal input range.

    I assume that I could only achieve a PF of 0.9 at the most, as you state, but this is more or less the same value that I would reach with a passive (and heavier) solution. So, it is very likely that the design of a PFC Boost under these requirements would not be worth it, although you suggest me to test and experiment in any case (Ok, of course!)

    Quite clear, I think.
    Thank you.

    Regards,
    Aarón.
  • 0 in reply to Aaron_Rangel
    TI__Guru* 81346 points

    Hello Aaron,

    I was glad that I could help and good luck with your design.

    Regards,

    Mike

  • 0 in reply to Aaron_Rangel
    Prodigy 210 points
    Hi Mike, I was wondering if the rectifier bridge could be Mosfets switched to lower voltage drop and improve PF in this application. Regards, Peter
  • 0 in reply to Peter Repka
    TI__Guru* 81346 points

    Hello Peter,

    You could possibly do this you would have to comeup with circuitry to drive the FETs.

    Regards,

    Mike