What should be noted when selecting inductors?

In our engineer's new product proposal, it is necessary to select various inductors to meet the performance requirements of the product. What should be noted when selecting inductors?

1. Inductance and allowable error

Inductance refers to the nominal value of inductance measured at the frequency required by the product technical specifications. Inductance is measured in units of Henry, milliHeng, microHeng, and nanoHeng, with errors subdivided into F levels (± 1%); G-level (± 2%); H-level (± 3%); J-grade (± 5%); K-level (± 10%); L-level (± 15%); M-level (± 20%); P-level (± 25%); N-level (± 30%); The most commonly used ones are J K. M-level.

2. Rated working current

Take 1.25 to 1.5 times the rated current of the inductor as the maximum operating current. Generally, it is safer to reduce the rating by 50%. In practical engineering applications, only the saturation current of the inductor is measured, and then 80% of it is taken as the rated current.

3. DC resistance

Except for power inductors that do not measure DC resistance (only check wire specifications), other inductors must specify the maximum DC resistance according to requirements, generally the smaller the better.

4. Testing frequency

Correctly measure the inductor L Q. The DCR value must first apply alternating current to the tested inductor according to regulations, and the closer the frequency of the current is to the actual operating frequency of the inductor, the better.

5. Stability of inductance

The ratio of the change in inductance △ L/△ t generated by an inductor due to a change in ambient temperature of 1 ℃ to the original inductance L value is the temperature system a1 of the inductor, A1=△ L/L * △ t. In addition to determining the stability of the inductance temperature coefficient, attention should also be paid to the changes in inductance caused by mechanical vibration and aging.

6. Inductive packaging dimensions

Inductive packaging generally includes SMT packaging and plug-in packaging. If the packaging description is clear in the bill of materials, it can reduce the probability of using the wrong materials. The packaging form of an inductor refers to a description of the shape and volume size of the inductor.

Most of the selection specifications for inductors are similar, so it is generally necessary to pay attention to these matters. The specific requirements need to be based on the circuit design to meet the parameter performance.