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UCC24624: 400V SR Application

Francis Jiang
Expert 3190 points
Part Number: UCC24624

Tool/software:

Hi Team,

Customer uses UCC24624 as SR controller, but currently they improve their system output from 200V to 400V, and the VD voltage stress of UCC24624 is not enough for this application.

I think maybe we can use resistor to divide the high voltage of VD, and maintain the linearity of the VD input, would like to double check with you of this solution risk. Could you please help check? Thanks a lot.

BRs,

Francis

  • 0
    TI__Intellectual 1040 points

    Hi, 

    The solution may not work, as UCC24624 SR controller determines the conduction time of the SR-MOSFET by comparing the drain-to-source voltage of the MOSFET against a turn-on threshold and a turn-off threshold. The gate driver output is driven high when the VDS of the MOSFET becomes more negative than VTHVGON and is driven low when VDS becomes more positive than VTHVGOFF.

    If you are using the above solution, while comparing the scaled value of VDS with VTHVGON and VTHVGOFF, will yield wrong conduction time of SR. 

    Regards,

    Sougata

  • 0 in reply to Sougata Nayak
    TI__Expert 3190 points

    Hi Sougata,

    I think Vthvg-on and Vthvg-off are fixed values, right? So the turn-on point and turn-off point can also be designed, right? Why it will lead to a wrong conduction time? Could you please help me further understand it? Thanks in advance.

    BRs,

    Francis

  • 0 in reply to Francis Jiang
    TI__Intellectual 1040 points

    Hi Francis,

    although Vthvg-on and Vthvg-off are fixed values, but as you are sensing scaled down version of Vds by the resistor divider method, the moment when actual Vds touches  Vthvg-on and Vthvg-off values and the moment scaled down version of Vds touches  Vthvg-on and Vthvg-off will be completely different. Thus, the conduction time will change.

    Regards,

    Sougata