Why are there two ratings for the rated current of power inductors?

2023-08-14 18:28

The rated current of power inductors is determined by two methods: the “rated current based on self‑heating, Irms,” and the “rated current based on the rate of change of inductance, Isat,” each of which carries significant importance. The “rated current based on self‑heating, Irms,” specifies the maximum allowable current according to the component’s heat generation; exceeding this limit may result in component damage or system failure.

In recent years, amid the global trend toward energy efficiency, demands for lower power consumption in electronic devices have continued to rise, making power‑supply design technology increasingly critical.

In practical power‑supply design, inductor selection is particularly critical. In DC‑DC converters, the inductor is the second most important component after the IC. By choosing an appropriately rated inductor, higher conversion efficiency can be achieved.

The primary parameters used when selecting an inductor include inductance, rated current, AC resistance, and DC resistance; among these, there are also concepts specific to power inductors.

For example, power inductors have two types of rated current—what exactly is the difference between them? To address this question, we will explain the rated current of power inductors here.

The rated current of power inductors is determined by two methods: the “rated current based on self‑heating” (Irms) and the “rated current based on the rate of change of inductance” (Isat), each of which carries significant implications.

“Rated current Irms based on self‑heating” is a current rating that uses the component’s heat generation as its criterion; operating beyond this range may result in component damage and system failure.

Meanwhile, the rated current Isat, which is based on the rate of change of inductance, is defined as the current at which the inductance drops by a specified amount. Operating beyond this range may result in increased ripple current, potentially degrading the IC’s performance.

Furthermore, depending on the magnetic circuit configuration of the inductor, the tendency toward magnetic saturation—and consequently, the tendency for the inductance to decrease—varies.

For open magnetic circuit types, the inductance remains relatively flat as the DC current increases, up to a specified current value; however, beyond this threshold, the inductance drops sharply. In contrast, for closed magnetic circuit types, the permeability decreases gradually with increasing DC current, resulting in a more gradual decline in inductance.

Tongyou Group’s integrated‑mold inductor manufacturing equipment and its full product lineup wowed visitors at the Shenzhen High‑Tech Fair, drawing an exceptionally enthusiastic crowd.

Wang Yi, Director of the Sichuan Provincial Employment Service Administration, paid a visit to Tongyou Microelectronics to conduct an inspection and provide guidance.

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In the current trend toward product miniaturization, inductor sizes continue to shrink to meet the demands of consumer electronics, automotive applications, fast‑charging systems, and AI devices for slimmer form factors and higher integration. Meanwhile, advances in high‑permeability, low‑loss magnetic powders and high‑performance coil materials enable small‑size components to satisfy requirements for high current handling and low losses.

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