Magnetic Beads and inductor

There are some applications for magnetic beads and inductors. Now let's make a brief summary of them.

In our circuit design, magnetic beads are mainly used to suppress high-frequency conducting interference signals, while inductance is mainly used to suppress low-frequency interference signals. When EMI suppression is performed on interference signals with a wide frequency band, multiple inductance or magnetic beads of different properties must be used at the same time.

The high-frequency equivalent circuit of the inductor is as follows:

It can be seen that when the frequency is high, the Inductance Coil has a distributed capacitor.

The inductance impedance curve is as follows:

Theoretically, the conductive interference signal is restrained. The larger the inductance, the better the capacitance. At the same time, the larger the inductance distribution capacitance, the two will offset each other, as shown in, when the inductor is large, its impedance to high-frequency interference signals may be smaller than that of the inductor.

So, if we want to further increase the suppression frequency, the Inductance Coil has to use its minimum limit value, only 1 circle or less than 1 circle.

Magnetic Beads, that is, the penetrating inductance, are the inductance coils with less than 1 turns, and their inductance volume is relatively small, only a few uh-dozens of uh. Of course, magnetic beads do not suppress high-frequency signals, and they also have their ownCutoff frequency(This is related to the materials of the magnetic beads. Generally, Ferrite Magnetic Beads are used.) generally, they are from dozens of MHz to several hundred MHz. Therefore, we usually call the effective magnetic conductivity of magnetic beads, it also refersWithin a certain frequency rangeThe relative permeability.

For the effect of magnetic beads, it not only can effectively suppress some high-frequency conduction interference, but also an important role is to conduct electromagnetic shielding, its shielding effect is even better than that of the shielding line, in addition, it can avoid the trouble of grounding the shield line, and has a strong suppression effect on common-mode interference signals. The electromagnetic shielding method is also very simple, so that a pair of wires can pass through the middle of the magnetic beads.

In short, when using magnetic beads and inductance, we must fully understand their basic characteristics and differences, and select different devices based on different occasions so that they can be used properly.