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UCC28950: Can UCC28950 work without SR?

Brian Wang0
Expert 5240 points
Part Number: UCC28950

Hi team,

My customer is developing a PSFB power supply, and they intend not to use SR to save more cost. And the product does not have high efficiency request.

UCC28950 seems a good option, and I would like to confirm whether this device support diode rectifier? Or do we have any other device that do not have SR?

Regards.

Brian

  • 0
    TI__Guru* 83306 points

    Hello,

    The UCC28950 can work without SRs.

    The following link will bring you to the 600 W UCC28950 evaluation module user's guide.  There is an efficiency graph of what can be expected when designing with the UCC28950.  https://www.ti.com/lit/pdf/sluub02

    You can possible design it for high efficiency choosing less lossy components.  The following link will bring you to an application note that goes through the step by step design of a phase shifted full bridge using the UCC28950.  You can use this to select components based on your efficiency requirements.  

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

    Regards,

     

  • 0 in reply to Mike O'
    TI__Expert 5240 points

    Hi Mike,

    Appreciate your confirmation.

    If customer wants to eliminate SR, what is the specific modifications needed? I noticed we have the 2 following ways to do that:

    1. Directly keep OUTE/F NC. And replace SR fets with diode.

    2. Setting a high SR light load turn-off threshold to turn off OUTE/F output and keep OUTE/F pin NC.

     Regards,

    Brian

  • 0 in reply to Brian Wang0
    TI__Guru* 83306 points

    Hello,

    1. When not using the SRs I generally put a 10 k ohm resistors from out E and F to IC ground.  This just helps with noise.  However, some designers have used this with open pins.

    2.  Where you set the DCM threshold does not matter if you are not using SRs.  You could tie this pin to ground if you wanted.

    Regards,