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UCC28600: Device shutting off periodically

Jitendra Jain
Prodigy 175 points
Part Number: UCC28600

Hello expert,

We are using UCC28600aux_secondary.pdf for aux power supply 24V output. Input is from 200VDC to 1000VDC. We've modified REF_62W_FLY_1700V_SIC to have only single 24 V output. But the device shuts periodically with no or light load. Can you please look into the design (attached) and verify it?

Regards,

Jitendra

  • +1
    TI__Mastermind 19605 points

    Hi Jitendra,

    Thank you for the query on UCC28600.

    I think the overall schematic looks fine.

    I have attached the calculator also where you might need to slightly adjust the Rovp1 and Rovp2 resistors.

    3857.slvc104j.xls

    Ensure that the capacitor on CS and FB pin are as close as possible to the IC pins.

    The snubber circuit can be tuned further as I think it could be to OVP.  Consider adding a resistor in series D12 (around 30ohms) and also in series with D13 (10-20 ohms) as this can help with damping some energy at turn off time of the FET. 

    Also the snubber resistor could be increased to 100k with appropriately tuning the snubber cap to 1-4.7nF to damp out the high frequency ringing potentially truggering this shutdown.

    Regards,

    Harish

  • 0 in reply to Harish Ramakrishnan5
    Prodigy 175 points

    Hi Harish,

    Thanks for looking at it.

    Adjusting Rovp1 and Rovp2 resulted in continuous operation. We will review the snubber as well.

    Regards,

    Jitendra