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UCC2813-5-Q1: adjust current sense limit

Kay Bollerhof
Prodigy 10 points
Part Number: UCC2813-5-Q1

Hi, I try to develop an isolated DC/DC with 9 - 32 V input and 12 V output with 3 A. If I decrease the input voltage under about 20 V, the output voltage is decreasing too. I think the problem is the current sensing of the controller. How can I adjust the current limit of the primary coil? I can find only information about how the sensing works but not how to adjust.

Best regards
Kay

  • 0
    TI__Genius 13660 points

    Hi Kay,

    It may be caused by duty cycle limitation or over current limitation.  

    The maximum duty cycle of UCC2813 is less than 50%. Please check your design and to see if the duty cycle is limited.

    May I know what is the condition when it happened? light load or full load or it doesn't matter? And you can capture the waveform at CS pin, and check if goes above 1V which will terminal PWM output.

    You can decrease the value of current sense resister value to increase the threshold of primary current over-current protection.

    Regards,

    Teng