How to select power inductance?

- Sep 20, 2018-

Power inductors are used in dc-dc circuits to accumulate and release energy to maintain a continuous current. It is said that integral molding inductors, NR magnetics inductors, SMT power inductors belong to the power inductors, then how to choose the power inductors? Power inductance should be selected according to the selected dc-dc chip. Generally, the specification book of dc-dc chip has recommended inductance value, as well as the calculation of relevant parameters. It is not necessary to explain how to select the type from the perspective of inductance itself.

Inductance value

Inductance values recommended in the dc-dc chip specification should be used in general. The larger the inductance, the smaller the ripple, but the larger the size. Generally, small inductance can be used to improve the switching frequency, but the higher switching frequency will increase the system loss and reduce the efficiency.

Rated current
Power inductance generally has two rated current, namely temperature rise current and saturation current. When the inductance current passes through, the temperature rise will be generated due to the existence of loss. The higher the current, the higher the temperature rise will be. Within the rated temperature range, the maximum permissible current is the temperature rise current.
The inductance value can be increased by increasing the magnetic permeability of the magnetic core, which is usually made of ferromagnetic materials. The phenomenon of magnetic saturation exists in ferromagnetic materials, that is, when the magnetic field strength exceeds a certain value, the magnetic induction strength does not increase, that is, the magnetic permeability decreases, that is, the inductance decreases. The maximum permissible current in the range of the rated inductance is the saturation current.