Q. What are the key parameters of power inductor?
Q. What is the difference between “for Choke” and “for DCDC”?
Q. What is the difference between "Non-Shielded" structure and "Magnetically Shielded" structure?
The key parameters of power inductor are as follows:
| Parameters | Definition |
|---|---|
| Inductance | Inductance is the property in an electrical circuit where a change in the electric current through that circuit induces an electromotive force (EMF) that opposes the change in current. The unit of inductance is the henry (H). 1 H = 1Wb/A |
| DC Resistance | Direct Current Resistance – DCR is the resistance of an inductor due to the resistance of the wire used in the winding, The lower the DCR the better. |
| Self Resonant Frequency (SRF) | The inductor’s self-resonant frequency is the frequency where the inductor and stray capacitor (among coil windings) resonates At higher frequency than this, the inductor looks electrically capacitive rather than inductive, and is expressed as a minimum value in megahertz (MHz). The higher the SRF, the higher the inductor’s effective frequency range. It is not recommended to use an inductor beyond its SRF limit. |
| Rated Current | Rated current is the maximum allowable current of the inductor. If the applied current exceeds the rated current, the self-temperature rise and the drop of Inductance value will exceed our specificiation, and hence reliability will be compromised. In case of Power Inductor, there are two different definitions to describe rated current - either based on self-temperature rise, or based on inductance change. |
Once current is applied to an inductor, the inductance value will change due to the effect of magnetic saturation. It is a parameter of inductance change vs. applied current.
Once current is applied to an inductor, temperature of inductor will increase due to self-heating. When self-heating exceeds a certain temperature, the inductor’s characteristics and reliability will be compromised; or in the worst case, will cause physical damage to the inductor.
In general, these terms can be used interchangeably as long as the parameters are in line with the application requirements. Since there is no clear rule to define these applications, each manufacturers use their own definition.
Application of a Inductor
Although Murata defines the application for each series as follows, they may be suitable for other different applications as well. If there are any questions, please contact us.
Once current is applied to an inductor, magnetic flux field is generated, which can couple to adjacent components or circuitry. With a magnetically shielded inductor, majority of magnetic flux field will be kept inside the inductor package, so coupling to other components or circuits is minimized. In a non-shielded inductor the magnetic flux field is radiated freely. There is performance trade-offs for both structures:
