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Inductor Current Waveform-Buck Converter

Hari T O0
Genius 3820 points

Hi

May I know why inductor current is not starting from zero for a buck converter.

Please find the attached wave from.In the inductor current waveform equation there is a term for time .Whet T=0 it shoud start from zero ,but the waveform is different.

May I know why.

Regards

Hari

ΔI+L=(Vin−Vout/L)*ton=(Vin−Vout/L)*DT

  • 0
    TI__Guru 71526 points

    Hello Hari,

      Thank you for using E2E; to further assist with your inquiry, please provide the device/part number for the circuit in question. 

    Regards,

    ~Leonard 

     

  • 0
    TI__Genius 11085 points
    The time zero in this waveform is the beginning of a switching cycle. It is not the first cycle when the buck converter is starting up. The waveform is a steady state waveform in continuous conduction mode, when inductor current waveform is the same triangal shape every switching cycle. The DC (average) of the waveform is the same as the load current. The peak to peak ripple is dependant on Vin, Vout, L and switching frequency. The equation should be ton*(Vin-Vout)/L
  • 0 in reply to YangZhang
    TI__Guru**** 191445 points
    The peak to peak inductor ripple current equation is ILp-p = (Vout/Vin) * (Vin - Vout) / (Fsw * Lout). And yes the waveform you reference is the steady state operating condition, not a start up waveform.