Inductor Peak Current Check

Ipeak = Idc + V × Δt / (2 × L)

Calculator

Result
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Formula

ΔI = V × Δt / L, Ipeak = Idc + ΔI/2

Description

In a switching converter, the inductor current ramps up during the on-time and ramps down during the off-time. The current ripple ΔI depends on the applied voltage, on-time, and inductance. The peak current is the DC component plus half the ripple: Ipeak = Idc + ΔI/2. If Ipeak exceeds the inductor saturation current, the inductance drops dramatically, causing current to spike and potentially damaging the converter. This is the most critical check in power inductor selection.

Variables

  • ΔI — Peak-to-peak current ripple (A)
  • V — Voltage across inductor during on-time (V)
  • Δt — Switch on-time (s)
  • L — Inductance (H)

Practical Notes

The forward result returns ΔI (the full ripple). To get Ipeak, add Idc + ΔI/2. Choose an inductor with saturation current rating at least 20% above Ipeak at maximum operating temperature. Ferrite inductors lose saturation current with temperature, while powdered iron types are more stable but have lower initial permeability.

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