What Is a Power Inductor?
A power inductor is an inductor designed to carry high current and store energy in DC-DC converters. It's the heart of switch-mode power circuits.
What Does It Do?
In a buck or boost converter, while the transistor switches on and off rapidly, the power inductor temporarily stores energy and delivers it to the output as smooth current. So it must keep the current ripple low.
Saturation Current (Isat)
It's the most critical rating: when the current through the inductor exceeds a certain limit, the core enters saturation, the inductance drops abruptly and the current rises uncontrollably. The circuit's peak current must stay below the inductor's Isat.
| Parameter | Meaning |
|---|---|
| Inductance (µH) | Energy storage / ripple |
| Isat | Saturation current limit |
| Irms | Continuous current (heating limit) |
| DCR | Winding resistance (loss) |
What to Look at When Choosing?
The required inductance, the circuit's peak and continuous current, the allowed DCR and the physical size are determined. Low DCR means high efficiency, and enough Isat means safe operation.
Where Is It Used?
Power supplies, processor supply stages (VRM), LED drivers, automotive power modules and charging circuits.
Common Mistakes
- Looking only at inductance: if Isat and Irms are ignored, the inductor saturates or burns.
- Size/heat trade-off: a small inductor saves space but heats up more.
- Wrong shielding: an unshielded inductor radiates magnetic noise to its surroundings.
Frequently Asked Questions
What's the difference between Isat and Irms?+
When is a shielded inductor needed?+
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