Difference and connection between magnetic beads and inductor

 

Magnetic Beads have high resistivity and magnetic permeability, which is equivalent to a series of resistance and inductance, but the resistance value and Inductance Value Change with frequency. It has better high-frequency filtering characteristics than ordinary inductor, and presents resistance at high frequencies, so it can maintain a high impedance within a very wide frequency range, thus improving the FM filtering effect.

Inductance can be used as a power filter. The circuit symbol of the magnetic beads is inductance, but the model can be seen that the magnetic beads are used in the circuit function. The magnetic beads and the inductance are the same in principle, but the frequency characteristics are different.
Magnetic Beads are composed of oxygen magnets, and the inductance is composed of a magnetic core and a coil. The magnetic beads convert the AC signal into heat energy, and the inductance stores the AC and slowly releases it out.
Magnetic Beads have a major obstacle to high-frequency signals. Generally, the specification is 100 euro/100 mmhz, which has a much lower resistance than inductance at low frequencies.
Ferrite Bead is a fast-growing anti-interference component. It is cheap and easy to use, and has a significant effect on filtering out high-frequency noise.
In a circuit, as long as the wire passes through it (I use the ordinary resistance, the wire has passed through and glued, there is also a form of surface mount, but rarely seen sold ). When the current in the wire passes through, ferrite has almost no impedance on the low-frequency current, but it will have a great attenuation effect on the high-frequency current. High-frequency current is emitted in the form of heat. Its Equivalent circuit is a series of inductance and a resistor. The values of the two components are proportional to the length of the magnetic beads. There are many types of magnetic beads. Manufacturers should provide technical indicators, especially the curve of the relationship between impedance and frequency of magnetic beads.

Some magnetic beads have multiple holes, and the component impedance (the square of the number of beads passed) can be increased when the wires pass through. However, the noise suppression capability increased at high frequencies cannot be as expected, however, it would be better to concatenate several magnetic beads.
Ferrite is a magnetic material that produces magnetic saturation due to excessive current, resulting in a sharp reduction in the magnetic conductivity. Large Current filtering should adopt specially designed magnetic beads, and pay attention to the heat dissipation measures.
Ferrite Magnetic Beads can be used not only in power supply circuit to filter out high-frequency noise (can be used for DC and AC output), but also widely used in other circuits, and their volume can be very small. Especially in digital circuits, pulse signals contain high-frequency harmonic waves, which are also the main source of high-frequency radiation. Therefore, magnetic beads can be used in such cases.

Ferrite Magnetic Beads are also widely used in Noise Filtering of signal cables.
Take the HH-1H3216-500 commonly used in power filter as an example, the meaning of each field of the model is:
HH is a series of it, mainly used for power filter, used for signal line is HB series;
1 indicates that a component encapsulates a magnetic bead. If it is 4, it encapsulates four beads side by side;
H indicates the composition of the substance. h, C, and m are used for intermediate frequency applications (50-200 MHz ),
T low frequency applications (50 MHz), s high frequency applications (200 MHz );
3216 encapsulation size, length 3.2mm, width 1.6mm, that is, 1206 encapsulation;
500 impedance (generally MHz), 50 ohm.
There are three main product parameters:
Impedance [Z] @ 100 MHz (OHM): Typical 50, minimum 37;
DC resistance (m ohm): maximum 20;
Rated current rated current (MA): 2500.
What magnetic beads have you answered?
Principles of magnetic beads
The main raw materials of magnetic beads are ferrite. Ferrite is a magnetic ferrous material with cubic lattice structure. Ferrite material is iron magnesium alloy or iron nickel alloy, its manufacturing process and mechanical properties are similar to ceramics, the color is gray black. Ferrite material is a kind of core often used in electromagnetic interference filters. Many manufacturers provide Ferrite Materials specially used for electromagnetic interference suppression. This material is characterized by high-frequency loss, with a high magnetic conductivity, which can be the smallest capacitance generated between the coil winding of the inductor at a high frequency and high impedance. The most important performance parameters for ferrite used to suppress electromagnetic interference are magnetic permeability μ and saturated magnetic flux density BS. The magnetic permeability μ can be expressed as a complex number, and the real part constitutes an inductance. The imaginary part represents loss and increases with the increase of frequency. Therefore, the equivalent circuit is a series circuit consisting of inductance L and resistance R. Both L and R are frequency functions. When a wire passes through this ferrite core, the inductance impedance increases with the increase of frequency, but its mechanism is completely different at different frequencies.

In the low-frequency section, the impedance is composed of Inductance inductance. Low-Frequency R is very small, and the magnetic permeability of the core is high. Therefore, the inductance is large, and the electromagnetic interference is restrained by reflection, at this time, the loss of the core is small, and the entire device is a low-loss, high Q-characterized inductor, this inductance is easy to cause resonance, so in the low frequency segment, sometimes the interference is enhanced after ferrite beads are used.

In the high-frequency band, the impedance is composed of resistance components. As the frequency increases, the magnetic permeability of the core decreases, resulting in reduced inductance and inductance. However, when the loss of the core increases, the resistance component increases, as a result, the total impedance increases. When high-frequency signals pass through ferrite, electromagnetic interference is absorbed and converted into heat energy for dissipation.

Ferrite suppression elements are widely used in printed circuit boards, power cords, and data cables. For example, if a ferrite suppression element is added to the power cord inlet of the printed board, high-frequency interference can be filtered out. Ferrite Magnetic rings or magnetic beads are used to suppress high-frequency interference and Spike interference on signal lines and power cables. They also have the ability to absorb electrostatic discharge pulse interference.

The size of the two elements is proportional to the length of the magnetic beads, and the length of the magnetic beads has a significant impact on the inhibition effect. The longer the length of the magnetic beads, the better the inhibition effect.
Difference between magnetic beads and inductor
Inductance is an energy storage component, while magnetic beads are an energy conversion (consumption) device. Inductance is mostly used in the power supply filter loop, focusing on the suppression of conductive interference; magnetic beads are mostly used in signal loop, mainly used in EMI. Magnetic Beads are used to absorb ultra-high frequency signals, such as RF circuits, PLL, oscillating circuits, and ultra-high frequency memory circuits (DDR, Rambus, etc.). They must be added to the input part of the power supply, inductance is an energy storage component used in LC oscillator circuit, medium and low frequency filter circuit, and its application frequency is rarely more than 50 MHz.

1. Chip Inductor: a large number of Inductive Components and EMI filter elements are used in the Board circuit of electronic devices. These components include Chip Inductor and chip magnetic beads. The following describes the characteristics of these two devices and analyzes their common application scenarios and special application scenarios. The advantage of surface mount components is the small package size and the ability to meet the actual space requirements. In addition to the impedance value, current loading capacity, and other similar physical properties, the through-hole connector and other surface mount devices have similar performance characteristics. When chip inductor is needed, the inductor must implement the following two basic functions: circuit resonance and throttling. A resonant circuit includes a resonant circuit, an oscillating circuit, a clock circuit, a pulse circuit, and a waveform circuit. The resonant circuit also includes a high-Q band-pass filter circuit. To make the circuit produce resonance, the capacitance and inductance must exist in the circuit at the same time. Parasitic Capacitance exists at both ends of the inductor, because the ferrite body between the two electrodes of the device is equivalent to the capacitance medium. In a resonant circuit, the inductor must have high Q, narrow inductance deviation, and stable temperature coefficient to meet the requirements of the resonant circuit for narrow band and low frequency temperature drift. The high Q circuit has sharp resonance peaks. Narrow inductance offset ensures minimum deviation of resonant frequency. Stable Temperature Coefficient ensures stable temperature variation at the resonant frequency. The difference between the standard radial Inductor and the axial Inductor and the chip inductor is that the package is different. Inductance structure includes medium material (usually alumina ceramic) winding, or hollow coil and magnetic material winding. In power applications, when used as a throttling ring, the main parameters of Inductance are DC resistance (DCR), rated current, and low Q. When used as a filter, the Wide Bandwidth feature is desired. Therefore, the high Q feature of inductance is not required. Low DCR can minimize the voltage drop. DCR is defined as the DC resistance of a component without an AC signal.

2. chip magnetic beads: the function of chip magnetic beads is mainly to eliminate RF noise in the transmission line structure (), RF energy is the AC Sine Wave Composition superimposed on the DC transmission level, DC components are useful signals, while RF energy is useless electromagnetic interference transmitted along the line and radiation (EMI ). To eliminate unnecessary signal energy, use a chip magnetic bead to act as a high-frequency resistor (the attenuation). The device allows the DC signal to pass through and filter out the AC signal. Generally, the high-frequency signal is above 30 MHz. However, the low-frequency signal is also affected by the chip magnetic beads.

The chip magnetic beads are composed of Soft Ferrite Materials and constitute a rock-shaped structure with high volume resistivity. Eddy Current Loss is inversely proportional to the resistivity of Ferrite Materials. Eddy Current Loss is proportional to the square of the signal frequency. Benefits of using a chip magnetic bead:
Small and lightweight. High impedance is available in the noise frequency range to eliminate electromagnetic interference in transmission lines. Close the magnetic circuit structure to better eliminate the string winding of signals. Excellent magnetic shielding structure. Reduce the DC resistance to avoid excessive attenuation of useful signals.

Significant high-frequency and impedance characteristics (better energy elimination ). Eliminate parasitic vibrations in high-frequency amplification circuits. It works effectively within the frequency range of several MHz to several hundred MHz. To correctly select the magnetic beads, you must pay attention to the following points: the frequency range of the unwanted signals. Who is the noise source. How much noise is needed. What are the environmental conditions (temperature, DC voltage, structural strength ). What is the circuit and load impedance. Whether there is space to place magnetic beads on the PCB. The first three pieces can be determined by observing the impedance frequency curve provided by the manufacturer. The three curves in the impedance curve are very important, namely resistance, inductive resistance and total impedance. The total impedance is described by zr22 π Fl () 2 +: = FL. For a typical impedance curve, see Datasheet of the magnetic beads.

Through this curve, choose the magnetic beads with the highest impedance within the desired frequency range and the signal attenuation below low frequency and DC as small as possible. The impedance of the chip magnetic beads is affected when the DC voltage is too high. In addition, if the operating temperature is too high or the external magnetic field is too large, the impedance of the magnetic beads will be adversely affected.

The reason for the use of chip magnetic beads and chip Inductance: whether the use of chip magnetic beads or chip inductance is mainly applied. Chip Inductor must be used in the resonant circuit. The use of chip magnetic beads is the best choice to eliminate unwanted EMI noise. Chip magnetic beads and Chip Inductor applications: Chip Inductor: RF and wireless communication, information technology equipment, radar detector, automotive electronics, cellular phone, pager, audio equipment, PDAs (Personal Digital Assistant), wireless remote control system, and low-voltage power supply module. Chip magnetic beads: Clock generation circuit, filtering between analog circuit and digital circuit, I/O input/output internal connector (such as serial port, parallel port, keyboard, mouse, long distance telecommunications, local Area Network (LAN), RF circuit and vulnerable logical equipment, filtering out high-frequency conduction interference, computer, printer, video recorder (VCRs) in the power supply circuit ), emi noise suppression in television systems and mobile phones.

Selection of magnetic beads

1. The unit of the magnetic beads is Ohm rather than Hunter. Pay special attention to this. Because the unit of the magnetic beads is nominal according to the impedance produced at a certain frequency, the unit of impedance is also ohm. Datasheet of magnetic beads generally provides characteristic curves of frequency and impedance, which are generally based on 100 MHz. For example, 1000r @ 600 MHz means that the impedance of magnetic beads is equivalent to ohm at MHz.

2. A common filter is composed of zero-loss reactive components. Its function in the line is to return the impedance band frequency back to the signal source. Therefore, this type of filter is also called a reflection filter. When the reflected filter does not match the signal source impedance, some of the energy is reflected back to the signal source, resulting in an enhancement of the interference level. In order to solve this problem, ferrite magnetic ring or magnetic beads can be used in the inlet of the filter to convert the high-frequency component into heat loss by using the eddy current loss of high-frequency signal by using the zihuan or magnetic beads. Therefore, magnetic rings and magnetic beads are used to absorb high-frequency components. Therefore, they are also called absorption filters.

Different ferrite suppression elements have different optimal suppression frequency ranges. The higher the permeability, the lower the inhibition frequency. In addition, the larger the volume of ferrite, the better the inhibition effect. At the time of accumulation, the longer and finer shapes are better than the shorter and coarse shapes, and the smaller the inner diameter, the better the inhibition effect. However, in the case of DC or AC Partial flow, there is still the problem of ferrite saturation. The larger the cross section of the suppression element, the less saturated it is, and the larger the allowable partial flow.

When EMI absorption magnetic ring/magnetic beads suppress differential mode interference, the current value is proportional to its volume. The imbalance between the two causes saturation, reducing the performance of components, the two wires (plus and minus) of the power supply pass through a magnetic ring at the same time. The effective signal is a differential mode signal, and EMI absorption is not affected by magnetic ring/magnetic beads, however, common-mode signals show a large amount of inductance. Another good way to use the magnetic ring is to repeat the wires that pass through the magnetic ring several times to increase the inductance. It can be used properly based on its suppression principle of electromagnetic interference.

Ferrite suppression elements should be installed near the interference source. For the input/output circuit, try to be close to the inlet and outlet of the shielding shell. In addition to the consumable materials with high permeability, the absorption filter composed of the inner body magnetic ring and the magnetic beads should be used. Their resistance to high-frequency components in the line is about 10 to several hundred Ω, so it does not play a significant role in high-impedance circuits. On the contrary, it will be very effective in Low-Impedance Circuits (such as power distribution, power supply, or RF circuits.
Conclusion
Ferrite is widely used in EMI control because it can degrade at a high frequency and make the low frequency pass through without any obstacles. Magnetic rings/magnetic beads used for EMI absorption can be made into various shapes and are widely used in various occasions. For example, the PCB can be added to the DC/DC module, data cable, and power cord. It absorbs high-frequency interference signals on the road, but does not generate new zero poles in the system, and does not damage the stability of the system. It is used in combination with the power filter, which can well supplement the shortcomings of the high-frequency end Performance of the filter and improve the filtering characteristics in the system.