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UCC24612: UCC24612 datasheet

user5781628
Intellectual 970 points
Part Number: UCC24612
Other Parts Discussed in Thread: UCC28780,

Hi,

In the page 15 of datasheet, it say "b) Shorter turn-off delay since the SR MOSFET gate voltage is already reduced close to the threshold level and the SR can be turned off with virtually no further delay."

What is the benifits of "Shorter turn-off delay"?

Why UCC28780 wants to shorter turn-off delay time to sacrifice the conduction loss due to lower gate driver voltage?

Thanks!

BR

  • 0
    TI__Expert 8210 points
    Eleven

    UCC24612 is a VDS sensing SR controller, which means that it turns the SR FET on and off based on the voltage sensed across the SR FET. While this allows the controller to work with multiple topologies and operating modes, non-ideal elements of integrated circuits like delays can cause it to not work properly which need to be accommodated for.

    This description on page 14 of the datasheet refers to the proportional gate drive, where the gate to source drive voltage is reduced to just above the SR FET turn on threshold. The reason this is done is to help accelerate turn off, since there is less charge in the gate that needs to be removed before the FET turns off. This faster turn off helps eliminate shoot thru (current conducing in first quadrant from drain to source of SR FET), which is an undesired effect that reduces the converter efficiency.

    The following Power Supply Design Seminar paper has more details if you have further questions
    Paper: www.ti.com/.../slup378.pdf
    Presentation Slides: www.ti.com/.../slup379.pdf
    Video: training.ti.com/power-supply-design-seminar-2018-training-series


    Best Regards,
    Eric