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UCC256303: FET Dead when start up that peak current is over 50A.

Dexter Choi
Expert 2795 points
Part Number: UCC256303

Dear Sir,

I have a problem. It is FET Dead of H/S & L/S when start up that peak current is over 50A.

It is possible below spec to use UCC256303?

can you please advise me any comment for below spec.

1. Topology : LLC

2. Input/output : 70~90VDC / 24V/10.0A

3. Specification

   1) Trans and resonant Tank => Lp&Lr Trans

       - Pri : 20T , Sec : 10T

       - Lp : 220uH

       - Lr : 40uH

       - Cr : 40nF

   2) IC : UCC256303

       - Vcc : external Bias

       - Blk : external Bias

       - Vcr(up) : 47pF/1KV

       - Vcr(low) : 2.2nF

       - Isns(up) : 47pF/1KV

       - Isns(low) : 330R

   3) Primary FET

       - Vds : 200V

       - Id : 27A

       - Id_pulse : 100A

  • 0
    TI__Mastermind 27105 points

    Hi Dexter,

    Sorry to hear about the issue. Let me review the material you shared and get back to you early next week.

    Best Regards,

    Ben Lough

  • 0 in reply to Benjamin Lough
    TI__Mastermind 27105 points

    Hi Dexter,

    I calculated the gain curve with the power stage parameters you provided. The power stage does not have enough gain to support 24V at 240W.

    The power stage needs to be redesigned to achieve higher gain if your customer would like to stay with LLC topology. 

    I also want to mention the design spec (70V-90V input, 24V, 240W output) fits very well with active clamp forward topology. Here is an active clamp forward reference design that is close in input range and output power to your customer's design spec:http://www.ti.com/tool/PMP7376

    Best Regards,

    Ben Lough