Inductor energy, peak current, and clamp paths
Inductor energy rises with current squared. When current is interrupted, the circuit must provide somewhere for that energy to go.
Why does interrupted inductor current need a defined energy path?
Inductor current cannot change instantly. If the normal current path opens, voltage rises until current can continue through a diode, clamp, snubber, avalanche path, or energy-transfer path.
Model summary
- Stored energy: E = 1/2 * L * I^2.
- Peak current usually sets stored energy and saturation risk.
- The receiving clamp or snubber must absorb or transfer the stored energy without overstress.
Worked example
A 100 uH inductor at 2 A stores E = 0.5 * 100 uH * 2^2 = 200 uJ.
At 3 A, the same inductor stores 450 uJ, more than double, because current is squared.
That energy must be considered in the switch, diode, clamp, TVS, snubber, or capacitor path.
Practical sequence
Calculate stored energy at peak current, compare with saturation margin, then identify the exact component path that receives the energy during turn-off or a fault.
Common mistakes
- Using average current instead of peak current for energy or saturation checks.
- Assuming nominal inductance remains constant near saturation.
- Letting a switch avalanche accidentally instead of designing the clamp path intentionally.
When the approximation breaks down
- The ideal energy equation does not model core loss, copper loss, temperature rise, saturation curve, or transient clamp dynamics.
- High-energy switching and fault cases may need device-specific avalanche, SOA, thermal, and waveform review.