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UCC28056: Max Power using this PFC controller

Part Number: UCC28056

Hi,

I am into designing universal input, 480W power supply with CVCC characteristics for battery charging application.

I would be using front end PFC followed by half bridge LLC as power conversion scheme.

While selecting PFC controller, I am looking at UCC28056x. I noticed that ref design of 165W is given in the datasheet.

Can this controller be used to design the PFC stage for a 480W power supply with the DC-DC stage being a LLC ? Will an external Mos driver be required ?

How do we handle start up of the IC ? I don't see it has a high voltage start up pin.

PS - Please recommend a suitable, low cost, LLC controller with adaptive dead time control to go in this project.

Regards

Sanjay

  • Hi, 480W will be a challenge but is theoretically possible. 

    The DRV pin has -0.7A/+1A drive capability, so if you use a large FET, you will likely need to add a buffer.

    Another thing to keep in mind that the UCC28056x uses a resistor on the DRV pin to set a delay time to get optimal valley switching in the normal range for this part.  The larger FET required for a 480W design may need a longer delay time than is available and likely have a higher turn-on losses in the FET.

    The startup is controlled by VCC which is supplied externally; either with a separate supply or from one of our LLC controllers from their RVCC pin (see next comment regarding LLC controller).

    As far as an LLC controller with adaptive dead time control (which also has an RVCC output), we recommend our UCC25640x family.  See that attached selection guide.

    .1106.UCC25640x Selection Guide.pdf

    If you have further questions regarding the LLC controller, please open a separate E2E thread.

  • Hi Ray,

    Thanks for your reply. So, you are saying that if a buffer (or driver) is used, I can design a 480W using ucc28056x, right ?

    In the Boost stage, I intend to use 2 Mosfets in parallel as a switch.

    Regards,

    Sanjay

  • Hi Sanjay,

    I'm not aware of a reason why the buffer/driver can't be used with one or more large MOSFETs to extend the power capability of the UCC28056.

    However, don't forget about the DRV-programmed turn-on delay issue I mentioned in my initial response.  Again, there is the possibility of insufficient turn-on delay capability, TZCDR7.  If the FETs are large enough, the longest selectable delay may not be long enough to allow the drain voltage to fully reach the resonant valley for valley switching.  Thus the FETs will turn on at higher voltage resulting in higher turn-on loss than expected.

  • Hi Ray,

    Thank you for detailed explanation.

    That helps.

    Regards,

    Sanjay