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About Input current ripple in the DCDC regulator

GARAM AN
Intellectual 1990 points

Hello,

I could find that there is a input current ripple on the buck converter, it should be removed by input cap.

I thought that input voltage and current come from external, so i do not understand the buck converter can make the input current ripple.

Why the input current ripple comes out because of buck converter?

Thank you

  • 0
    TI__Genius 12735 points

    Hello,

    As the buck converter is switching it is only pulling current from the input supply while the high side FET is on. While the low side FET is on, the output is powered by the output inductor discharging its energy, resulting in the input supply current rapidly decreasing. When the high side FET turns back on there is a large in-rush of current to charge the inductor before being turned off again. This results in an input ripple current. 

    The input capacitors can help decrease the input ripple current by decreasing the input ripple voltage. By reducing the dips in input voltage, the amount of current drawn while the high side FET is on is slightly decreased, thus decreasing the input ripple current.

    Best regards,

    Layne J