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UCC21732: Desat protection when current flowing from source to drain

Anoop kumar N
Intellectual 798 points
Part Number: UCC21732

Hello Experts

I am using Synchronous rectification at the PSFB secondary side where the load current flow is from source to drain. So my doubt is whether this ucc21732 can be used for getting of desat protection ? 

Thanks and regards

Anoop kumar N

  • 0
    TI__Genius 13470 points

    Hi Anoop,

    The short circuit protection of the gate driver is essentially a comparator which is referenced to the SOURCE of the MOSFET.

    The customer could use the UCC21732 OC-pin comparator input to measure the voltage drop across a shunt resistor that would need to be placed in the main power loop. Since this shunt resistor would be in the gate loop path the voltage will also affect the gate voltage. The shunt resistor would add additional power dissipation, which could be okay depending on the load current level.

    • Would this work in your application?

    Best regards,

    Andy Robles

  • 0 in reply to Andy Robles
    Intellectual 798 points

    hi andy, thank you for the reply.

    schematic was ready where i connected the drain point to the oc pin. later i realized that normal load current flow is from source to drain. adding this this resistr in power loop not at all a feasible solution. because load current is around 100amps

    Thanks and regards

    Anoop kumar N

  • 0 in reply to Anoop kumar N
    TI__Genius 13470 points

    Hi Anoop,

    For the OC-pin in UCC21732 to be used in DESAT it needs to have the configuration shown in Figure 54 of the UCC21732 datasheet:

    Having the current flow from Source to Drain would apply a negative voltage on the Drain net with respect to the Source.This means that the traditional circuit implementation would not work in your application.

    I believe this circuit could potentially work if you were to design an inverting buffer circuit between the Drain and the Cathode of the high voltage DESAT diode, but I have never seen this type of circuit implemented myself before.

    Best regards,

    Andy Robles