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UCC256403: Support required for Primary Side Mosfet selection in LLC half bridge converter

Jilna Jayan
Prodigy 40 points
Part Number: UCC256403
Other Parts Discussed in Thread: UCC256404

Tool/software:

Hi Mike,

I have a query related to Primary side Mosfet selection for LLC half bridge circuit.

As per the calculation, drain current is coming 8.6A and Voltage 630V. So If I go with less RDSon & Coss Mosfets, the drain current rating will be too high.

Can you guide me how to approach this?

Regards,

Jilna Jayan

  • 0
    TI__Guru* 80356 points

    Hello,

    I am reviewing your inquiry and will get back to you shortly.

    Regards,

  • 0 in reply to Mike O'
    TI__Guru* 80356 points

    Hello,

    Please note the UCC256403 has peak current limit and over current protection to prevent the FET from seeing too much current.  The Rdson on of the FET is not what limits the currents.

    To keep the (I^2)*R losses to minimum it is recommend that you select the Rdson of the FET to limit power dissipation.

    You can protect your FETs from over current by properly setting up the ISNS pin of the UCC256404.  The following link will bring you to an excel tool that when followed will setup your ISNS pin to protect the FETs from an over current. 

    https://dr-download.ti.com/design-tools-simulation/calculation-tool/MD-4q9segeylW/01.00.00.0C/sluc675c.zip

    Thank you for interest in Texas Instruments (TI) products.  If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

    Regards,