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UCC28600 for Offline to 24V DC

Mike H Meyer
Expert 1560 points
Other Parts Discussed in Thread: UCC28600

I'm trying to identify an offline to 24V @5A solution.  I've searched through the reference designs and the PMP5141 would work but PFC plus half-bridge seems like overkill.  I'd like to see if a flyback configuration could work.  I located the PMP2723 based on the UCC28600 and noted that the eval board is set up for 19.4V and is rated at 6.2A which is very close.  Would it be a simple feedback adjustment to go to 24V or would it require an adjustment to the magnetics to make this work?

  • 0
    Expert 1920 points

    Given your input voltage and power is the same, the primary side of your coupled inductor could be the same as the one in the PMP2723. Try to calculate the difference in duty cycle of the two conditions (24V versus 19,4V).

    Try to adjust the feedback. Perhaps it works - my guess it does since your output power is the same and the output current is less than in the PMP2723.

  • 0 in reply to CWilson
    TI__Genius 15910 points

    Given that the UCC28600 is a quasi-resonant controller that modulates both the switching frequency and the peak current (on-time) over the operating range, calculating the duty cycle isn't as easy as one might think.  The UCC28600 design calculator is recommended for determining the magnetics, the sense resistor, the power limit resistor, and the ovp resistors.  These components all work together to modulate the frequency and primary current for resonant switching, while setting the protection features of the design at the same time.  I have enclosed a design calculator which shows the component values that I would recommend to start you off on your 24V/5A design although you NEED to fill in the specific parameters of your prefered switching MOSFET on the QR Design Tool page before this tool could be considered completely valid for your specific design.  The QR Simulator page shows the performace profile of the theoretical converter over the operating range.  Other than making sure the MOSFET parameters are filled in, also be sure that the input capacitor that you select is sized appropriately to provide not more than the Vbulk(ripple) that is input in column C row 16 on the QR Design Tool page as the power stage design is based upon the minimum valley voltage of the bulk input rail.

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