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UCC28951: Isolated DC-DC converter

Francesco Rizzotto
Prodigy 85 points
Part Number: UCC28951

Tool/software:

Hi,

I'm currently in the process of designing an isolated DC-DC converter with the following specifications:

  • Input Voltage: 22-36V
  • Output Voltage: 20-200V
  • Output Power: 600W
  • Isolated 
  • Power over full range

Do you think the UCC28951 would be a suitable choice for this design?

Thank you for your valuable insights!

Best regards,

Francesco

  • 0
    TI__Guru* 85896 points

    Hello,

    In practice we recommend that you keep the input and output ranges less than 3 to 1.  However, 5 to 1 is possible.  The issue is with changes in duty cycle.

    If you design for 90% maximum duty cycle at low output full load.  When the design is at high output voltage will require 9% duty cycle at full load.  Controlling over this range will not be the problem.  It is when you decrease the duty cycle.  If you go down to 10% load you will not be able to achieve 0.9% duty cycle.  Please note this is based on peak current mode control design.

    You might be able to do this with a voltage mode control design using the UCC28951.  You will need a DC blocking capacitor in series with the transformer but the rest of the power stage design will be similar to peak current mode control.

    The following link will bring you to an application note that describes how to design a PSFB in peak current mode control.  It should help you design the power stage.  Remember you will need add a DC blocking capacitor in series with the transformer.

    https://www.ti.com/lit/pdf/slua560

     

    You will have to setup the RT and RSUM resistors based on data  sheet recommendations for voltage mode control. 

    Also, the application note does not cover to how to compensate the voltage loop.  I would recommend using a type 3 compensator and a network analyzer to compensate the voltage loop.

    Regards,