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The following shows the voltage (green) and current waveform (yellow) across an inductor in a buck converter designed to step down 30 V to 15 V with 0.2 A output current.

The inductor values according to the design are 2.3 mH (toroidal Fe dust core), and the capacitor used is 10 μF. The switching frequency is 100 kHz.

All the waveforms even across the diode and the gate pulse are fine, except the inductor current wave form. Can someone suggest what I should look for?

enter image description here

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    \$\begingroup\$ Looks like textbook core saturation. What's the saturation spec of your inductor? \$\endgroup\$
    – tobalt
    Commented Jan 27 at 17:49
  • \$\begingroup\$ Surely you mean microhenry? Why is the voltage reading in amperes? \$\endgroup\$
    – Tim Williams
    Commented Jan 27 at 19:10
  • \$\begingroup\$ Can you post a schematic? \$\endgroup\$
    – Voltage Spike ♦
    Commented Jan 27 at 20:54

1 Answer 1

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This looks like hard saturation. Past a certain current, your inductance crashes and therefore your dI/dt rises rapidly with a given voltage across it. You want to make sure you're always going to be operating your peak current well below your inductor saturation threshold.

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