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UCC28051: Can you get rid of coupled inductor for UCC28051

Nick52556
Intellectual 280 points
Part Number: UCC28051
Other Parts Discussed in Thread: UCC28056,

Hello,

I have a cost sensitive application I need to have a PFC frontend for in the 250W range. A DC output of something around 400VDC +/-10% is good enough. There is a post regulated stage with isolation.

My current issue is looking at the coupled inductor on the reference design. This thing is super expensive. No way I can use that. Looking at the datasheet though, I think I can get rid of it right? The coupled inductor does two things from my 1000-ft view. First it makes a VCC voltage that is low and somewhat more efficient instead of taking it off the high voltage rectified AC. Then the second thing it does is make the ZCD pin low enough voltage.

For the VCC, I already have a high voltage linear regulator that is making a nice 12VDC from the rectified AC. I also have an auxilliary winding on the next stage that makes a nicer 40V that could make VCC more efficient if I need. So assuming I don't care about efficiency and just use the linear regulator, I don't need the coupled inductor for that.

For the ZCD, can I not just use a resistor divider off the D1/Q1/L1 node to get the same effect?

Since I am making a custom board for this as it is obviously a non-standard use case, I'd like to make sure this is possible. Especially since I can't simulate it in LTSPICE :(

Thanks

  • 0
    TI__Guru* 86266 points

    Hello,

    The UCC28056 was design for CrM PFC and does not require the aux winding/couple inductor.

    The following link will bring you to the product page.  Where you will find the data sheet, application notes, reference designs, as well as, the Webench design tool.

    Regards,

  • 0 in reply to Mike O'
    Intellectual 280 points

    This doesn't really answer my question.

    It's an alternate part, I could use but the power limits in the datasheet make it seem like it is low power only. As I said I need 250W to my load, so I need a PFC capable of 300W. However I don't see where the limits on the UCC28056 come from. The Webbench tool only allows 270VAC maximum input. Why? It doesn't look like there is a limit that can't be overcome with external component selection correct? I need to be able to survive 300VAC input (277VAC nominal).

    I am also still wanting to know if the 28051 can be used without an aux winding. As it is now, I get no switching on the gate drive signal at all. It is my understanding it should at least switch every so often due to the timeout period. The VCC is being supplied externally with a 15VDC lab supply. The input is driven by a AC Power Supply.

    No SPICE simulation means this part is difficult to prototype with for anything other than the reference design.

  • 0 in reply to Nick52556
    TI__Guru* 86266 points

    Hello,

    The UCC28051 needs an aux winding to detect zero current.  It will not work without it. 

    The UCC28056 will work without and aux winding for ZCD. I did not know that Webench limited the input to 270V.

    I do have another option for you.  You could design continues conduction PFC that does not require an aux winding to detect ZCD.

    There is excel design tool and I double checked it will allow you do design for a 300 V ac input.  You can find it at the following link.

    Regards,