Ferrite beads has high resistivity and magnetic conductivity, he equivalent resistance and inductance in series, but the resistance and inductance value is changing with frequency.
Inductance is better than ordinary high-frequency filtering properties, in the high frequency impedance, so can in a relatively wide frequency range of high impedance, so as to improve the effect of frequency filtering.
As a power supply filter, inductor may be used.
Magnetic beads is inductance circuit symbols but models can be seen on the use of magnetic beads on the circuit function, magnetic beads and principle of inductance is the same, only the frequency characteristics of different magnetic beads is composed of oxygen magnets, inductance consists of core and coil, a magnetic bead the ac signal is converted into heat energy, inductance store communication, slow release.
Magnetic beads can have larger block of the high frequency signal, specifications have 100 euro / 100 MMHZ commonly, it is much smaller than inductance resistance when in low frequency.
Is one of the current application development soon anti-interference components, cheap and easy to use, high frequency noise filtering effect is significant.
As long as the wire in the circuit through it (
I am using is like ordinary resistance appearance, wire has been through and agglutination, also have the form of SMT, but few see selling)
When the current through the wire, the little ferrite of low frequency current impedance, and will produce large attenuation of high frequency current.
In which high frequency current distribution in the form of heat, the equivalent circuit of an inductor and a resistor in series, the value of the two components are linked to the length of the magnetic beads in proportion.
Magnetic bead is a lot of more phyletic, the manufacturer shall provide technical indicators, especially the relationship between impedance and frequency magnetic beads curve.
Some have multiple holes, magnetic beads with wire through the impedance can increase the components (
The number of times square) through the magnetic beads
, but the increase in high frequency noise suppression ability could not as expected, with several magnetic beads series way will be better.
Ferrite magnetic materials, is caused by excessive current and magnetic saturation, permeability decline sharply.
Large current filter structure should be adopted on specially designed magnetic beads, also notice its cooling measures.
Ferrite beads not only can be used to filter out high frequency noise in the power circuit (
Can be used in the dc and ac output)
, and can be widely used in other circuits, the volume can be very small.
Especially in the digital circuit, the pulse signal with high order harmonic frequency is very high, is also a main circuit of high frequency radiation source, so can play the role of magnetic beads on this occasion.
Ferrite beads also filter the noise) is widely used in signal cable.
With HH - often used in power supply filter
500 as an example, the meaning of each field model: HH is a series, it is mainly used in the power supply filter, used in signal lines is HB series;
1 represents a component encapsulates a magnetic bead, if 4 is the encapsulation of the four side by side;
Material composition, H H, C, M for application of intermediate frequency (
50 - 200 mhz)
T low frequency applications (
High frequency applications, S (
3216 package size, long 3.
2 mm, width 1.
6 mm, namely 1206 size;
General for 100 MHZ)
Its product parameters mainly have three: impedance [
DC DC Resistance to hold (
Rated Current Rated Current (
Ferrite beads, the principle of the main raw material for ferrite magnetic beads.
Ferrite is a kind of ferrous cubic lattice structure of magnetic materials.
Ferrite materials for magnesium alloy iron or iron nickel alloy, its manufacturing process and mechanical properties similar to ceramic, color film.
Electromagnetic interference filter is often used in a class of magnetic core is ferrite materials, many manufacturers offer specialized for electromagnetic interference suppression of ferrite materials.
The characteristics of this material is a very big loss at high frequency, high permeability, he can is the inductance of the coil winding in the high frequency under the condition of high resistance between the minimum capacitance.
To suppress electromagnetic interference with ferrite, the most important performance parameter for magnetic permeability & mu;
Bs and saturation magnetic flux density.
Magnetic permeability & mu;
Can be expressed as the plural, real parts inductance, imaginary part on behalf of the loss, as the frequency increases.
As a result, its equivalent circuit series circuit of inductance L and R, L and R is a function of frequency.
When the wire through the ferrite core of inductance impedance is increased with the frequency and increase in form, but in different frequency when the mechanism is completely different.
Made up of inductive impedance at low frequencies, impedance, low frequency when R is very small, the core permeability is higher, so the large inductance, L plays a main role, electromagnetic interference is reflected and suppressed, and then the core loss is small, the whole device is a characteristic of low loss, high Q inductance, the inductance is easy to cause resonance in low frequency band, therefore, may sometimes appear interference phenomenon of enhanced after using ferrite beads.
At high frequencies, impedance by resistance to composition, with increasing frequency, magnetic core's permeability decreased, leading to the inductance of the inductance, inductance components decreases, however, at this time of the magnetic core loss increases, the resistance components increase, lead to the total impedance increases, when the high frequency signal through the ferrite, electromagnetic interference is absorbed into the form of heat energy wasted.
Ferrite components widely used in printed circuit board, power line and data line.
As in the power cord entry point plus ferrite inhibition of PCB components, can filter out high frequency interference.
Ferrite beads or magnetic bead is dedicated to inhibit signal lines, the high frequency interference in the power cord and rush disturbance, it also has the ability to absorb electrostatic discharge pulse interference.
Two element numerical size proportional to the length of the magnetic beads, and the length of the magnetic beads have obvious effects on inhibiting effect, the longer the length of magnetic beads inhibit the better the results.