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UCC24612: 2.2KW DCDC high side Synchronous rectification

Part Number: UCC24612

We are using DC-DC input full-bridge LLC, the output specification is 14V 150A, using  high side  Synchronous rectification , currently using two UCC24612 driver chips for high side flyback, a single chip drives four MOS (single MOS tube Ciss is about 10nF), Please help to confirm whether it is satisfied, what other information do you need ?

  • Hello,

    The UCC24612 can be used in a high side SR driver for a flyback.  However, for LLC there is no benefit of driving the LLC from the high side and extra circuitry would be required to used for an SR on the high side.  If you are designing an LLC, I would recommend designing for low side.

    The FET driver is only capable of sourcing and sinking 4A.  So I am not sure if you can use the UCC24612 to drive for MOSFETs in  parallel.  I believe you could easily drive 1 per UCC24612.  It depends on the switching frequency (fsw) and ambient temperature (Tamb) and gate loss.

    With the following equations you can estimate gate loss based on switching frequency (fsw).  Please note that all of Pgate is dissipated by the UCC24612. 

    Ipeak=Qg/td(on) data sheet, from data sheet, Qg = Ipeak*td(on) = (10V/1.6ohm)*12ns=750 nC

    Pgate = Qg*Vg*fsw

    The following calculations can be used be used to calculate the maximum gate drive power (Pgate) the UCC24612 can handle.  Note RJA = 206.6 deg C/W.

    TJ = Tamb + Pgate*RJA = 125 deg C =  Tamb+Pgate*(206.6 deg. C/W)

    Tj-Tamb/RJA =  Pgate(max) = (125 deg C-Tamb)/206.2deg C)*W

    You also might find the following application note helpful in calculating FET losses.http://www.ti.com/lit/an/slyt664/slyt664.pdf

    Regards,