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Original question:

UCC28951-Q1: Erratic C,D drive outputs even with both voltage and current well below setpoint

UCC28951-Q1: UCC28951 PSFB DC-DC

Dr.J.Aran Glenn
Prodigy 80 points
Part Number: UCC28951-Q1
Other Parts Discussed in Thread: UCC28951

Tool/software:

Dear Sir,

We are using UCC28951 for designing PSFB Board for 4kW Charger. The dead time(DT) is Non-Uniform and there is a difference in Dead Time(DT1) and dead time (DT2) in all the high side switches A and C and low side switches B and D. The following results are the dead time between the switches

A and C VGS output DT1 500ns

A and C VGS output at DT2 1.7us

B and D  VGS output at DT1 680ns,

B and D VGS output  DT2  1.42us

Can you please advise how to change it as a Uniform Dead Time between all switches?. Thanks

  • 0
    TI__Guru* 85616 points

    Hello,

    Your inquiry is under review and I will get back to you shortly.

    Regards,

  • 0 in reply to Mike O'
    TI__Guru* 85616 points

    Hello,

    It looks like you have ADEL and ADELEF setup to use adaptive delay, that is why your adaptive dead time is not fixed.  I would recommend using a fixed delay approach, which 98% of our customers find much easier than doing an adaptive delay approach.  This requires connecting ADEL and ADELEF to a DC voltage or ground.

    The following link will bring you to an application note that reviews the step by step design process of a phase shifted full bridge using the UCC28951 that uses a fixed delay approach.  Inside the application note there is also an excel design tool that goes along with the application note.  You can use both of these tools to design your phase shifted full bridge and check your design.

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

    The application note will not only help you to design based on your efficiency goals but gives guidance on fine tuning the design to achieve ZVS down to 50 % load.  Over the years customer have found this application note to be quite useful.  I hope it helps you as well.

    Thank you for interest in Texas Instruments (TI) products.  If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

    Regards,