What is an inductor?

Inductors, also known as Inductors, Coils, and Chokes, are components that can convert electrical energy into magnetic energy and store it. The structure of an inductor is similar to that of a transformer, but it has only one winding. An inductor has a certain inductance, which only hinders changes in current

If the inductor is in a state where no current is flowing through it, it will try to block the flow of current through it when the circuit is turned on.

If the inductor has current flowing through it, it will try to maintain the current when the circuit is disconnected.

1. Inductor material

① Coil: The main materials are

Silver - mainly used in multilayer inductors

Copper – mainly used in wirewound inductors

② Core: The main constituent materials are

Alumina ceramic - mainly used for high-frequency inductors, does not contain iron elements, and has a magnetic permeability of almost 1 (the magnetic permeability of non-ferromagnetic materials is similar to the vacuum magnetic permeability 4π×10^(-7)H/m , that is, relative magnetic permeability 1), mainly plays the role of fixing the coil

Nickel-zinc ferrite - the most widely used material in power inductors, meeting a wide frequency range of use

Manganese-zinc ferrite - magnetic permeability > nickel-zinc ferrite, used less frequently, becoming increasingly rare as the switching frequency increases

Rail aluminum alloy - magnetic rings and one-piece inductors are widely used

Iron powder core - commonly used in magnetic rings and used in low-frequency circuits

③ Sleeve Cover: Shielded Power Inductor will contain a shielding cover, the main materials of which are

Nickel-zinc ferrite - the most commonly used, generally used with magnetic cores of the same material

Manganese-zinc ferrite - often used in shielding cases for NR type inductors in recent years

④ Terminal

Silver - > Nickel plating > Tin plating - mostly used in designs where the electrode terminals and the magnetic core are integrated

Copper - > Nickel plating > Tin plating - mostly used in assembly designs where the electrode terminals and the magnetic core are separated

2. Classification of inductors:

(1) If inductors are classified according to their uses, they mainly include the following:

① High frequency inductor (RF Inductor)

High frequency inductors are also called radio frequency inductors and RF inductors. They mainly refer to inductors used in radio frequency circuits or signal lines.

It is made of insulated wires (such as enameled wires, yarn-covered wires, etc.) and is mainly composed of a skeleton, windings, shields, packaging materials, magnetic cores or iron cores, etc.

The core of this type of inductor usually appears white because the common core material is "aluminum oxide", the most common ceramic material

Main characteristics of high frequency inductors:

· High efficiency, fast speed, low consumption and environmental protection

· Can be used for high frequency signal lines

· Air-core coil: High-frequency inductors are essentially air-core coils - the coil is wound around a core made of "alumina" ceramic material. The main function of the core is to fix the coil, making the overall structure stable and resistant to deformation. Give the inductor high-frequency characteristics

· Small size: High-frequency inductors only need to pass a small current (electrical signal), so they are generally very small in size, and the trend will become smaller and smaller in the future.

· High precision: Since there is no ferrite core, its inductance properties are generated only by its own coil, and the tolerance of the inductance is relatively easy to control. Because it is most often used as a matching circuit for radio frequency signals, if the tolerance is too large, it may cause good and bad signals, or even signal loss. Its accuracy - the inductance tolerance is basically within ±5%, or even within ±1%

At present, high frequency inductors are widely used in life, such as:

· Mobile phones, pagers and GPS products

· Oscillators, crystal oscillator circuits and RF transceiver modules

· Wireless LAN, Bluetooth module, communication equipment

From Murata

② Power Inductor

Refers to an inductor used for power supply current, an inductive element specially designed to withstand larger currents and high power

The design principle of power inductors is to minimize DC resistance while ensuring the inductance value, thereby reducing power loss and improving conversion efficiency.

Power inductors usually adopt the structure of planar rectangular coils. The materials and manufacturing techniques used in the conductors will affect the amount of current they can withstand. For example, the smaller the resistivity of the conductor material, the greater the load-bearing capacity in the same area.

The working principle of power inductors is based on the principle of electromagnetic induction. When current passes through the inductor coil, a magnetic field is generated, thereby realizing the transmission and storage of electrical energy.

In DC circuits, inductive components can reduce high-frequency signal interference and make the DC output of the circuit more stable.

In AC circuits, inductive components can block or delay changing signals, reduce the impact of high-frequency interference, and ensure the stability of the circuit.

In addition, power inductors can also be used in power circuits to form a low-pass filter to limit the current in the circuit and protect other components from being damaged by overload.

In mounting technology, power inductors can be either active components or passive components. Ferrite is usually used as the core material and copper wire is used as the coil material. It has high magnetic permeability and good heat dissipation performance.

Characteristics of power inductors:

· Dark color: Most core materials are black or brown. The main reason is that the main component of common core materials is "ferrite", that is, "iron oxide"

· The coil is wound around a "magnetic core": a magnetic core containing "ferrite" is inserted into the center of the coil, which enhances its inductance properties and increases the inductance value

· Larger size than general high-frequency inductors: In order to pursue low loss and high current, thicker coils are often used, so there are many larger-sized power inductors; however, in recent years, due to the pursuit of miniaturization in mobile phones and other fields, design, various inductor brand manufacturers are also working hard to update the design to reduce the size as much as possible while meeting customer requirements.

· Low precision: Contrary to high-frequency inductors, the inductance properties are enhanced and the inductance value is increased due to the insertion of ferrite cores and the addition of ferrite shields. However, some new logistics tolerances will be added, including but not limited to: dimensional tolerance of the ferrite core itself, assembly position tolerance, material permeability tolerance, etc., making its accuracy more difficult to control than high-frequency inductors.

Its precision-inductance tolerance is basically above ±10%, and even the tolerance of some small inductance values reaches ±30%. Although the accuracy is low, its usage scenarios often do not require high accuracy.

Power inductors can be divided into:

· Shielded Power Inductor

· Un-Shielded Power Inductor

The main differences are as follows:

③ Ferrite Bead

The full name of magnetic beads is ferrite beads, which is also a type of inductor. Under the guidance of customer demand, the materials and structure are specially adjusted to show a variety of impedance frequency characteristics.

Ferrite material is an iron-magnesium alloy or an iron-nickel alloy. This material has high magnetic permeability. It can minimize the capacitance between the coil windings of the inductor at high frequency and high resistance.

Ferrite materials are usually used at high frequencies because at low frequencies they are mainly inductive, resulting in very small losses on the line.

At high frequencies, they mainly exhibit reactive characteristic ratios that change with frequency.

In practical applications, ferrite materials are used as high-frequency attenuators in radio frequency circuits.

In fact, ferrite is better equivalent to a parallel connection of a resistor and an inductor. At low frequencies, the resistor is short-circuited by the inductor. At high frequencies, the impedance of the inductor becomes quite high, so that all current passes through the resistor.

Ferrite is a consumption device on which high-frequency energy is converted into heat energy, which is determined by its resistance characteristics.

Key features of Ferrite Bead:

· Filtering: used for signal lines or power lines to play the role of filtering

· Dark color: Most core materials are black or brown, because the main component of common core materials is "iron oxide"

· The coil is wound around a "magnetic core": a magnetic core containing "ferrite" is inserted into the center of the coil to enhance its inductance properties

· Diversified impedance frequency curves: Adjust material formulas and product structures to produce different impedance frequency curves to meet customer requirements

· Low accuracy: Like power inductors, due to the insertion of ferrite cores and the addition of ferrite shields, the inductance properties are enhanced and the impedance value is increased.

However, some new logistics tolerances will be added, including but not limited to: dimensional tolerance of the ferrite core itself, assembly position tolerance, material permeability tolerance, etc. This makes its accuracy more difficult to control than high-frequency inductors, but its use scenarios are often High accuracy is not required, the industry standard accuracy is ±25%

Applications of Ferrite Bead:

Ferrite Bead is mainly used for decoupling of power supply systems in radio frequency and microwave circuits, decoupling of high-speed digital circuit power supply systems, and preventing bad coupling between stages through power supplies.

This is especially obvious in small-signal multi-stage amplification circuits. In a small-signal multi-stage amplification circuit, when the signal of the subsequent stage circuit reaches a certain intensity, and the fragrance shift between stages is enough to cause the phase difference between the front stage and the subsequent stage to reach positive feedback, at this time, if the feed system cannot effectively suppress the signal Through crosstalk in the power supply system, the circuit is easily prone to self-excitation, making the circuit unable to operate normally.

If an ordinary wirewound inductor is connected in series in the power supply circuit and is coupled with a decoupling capacitor for power decoupling, the problem that is likely to arise is that the wirewound inductor itself has a self-resonant frequency. If used improperly, new interference sources will be generated. , and this interference source is sometimes latent and will only appear under specific conditions.

This will make it very difficult to resolve this type of interference.

If a small value resistor is used for decoupling, the main problem is that the resistor presents a constant value within the entire screen range. A resistor of about 10 ohms will not have a significant effect on suppressing bad coupling. The larger the resistance, the better the suppression effect, but the voltage drop across the resistor is also larger and the power consumption is also increased, which is extremely detrimental to battery-powered portable devices. Even large equipment powered by AC will create new heat sources and solve heat dissipation problems.

Ferrite Bead is undoubtedly the best choice to solve this kind of problem

First of all, the DC resistance of the Ferrite Bead is only the resistance of a section of wire, but the AC impedance characteristics it presents are dozens to hundreds of times the DC resistance. Although the impedance characteristic of Ferrite Bead that changes with frequency also has its limit point, it does not have a self-resonant frequency. Therefore, it is very effective to use in decoupling circuits

Another application of Ferrite Bead is the suppression of spikes and ringing in high-speed signal transmission. This application is commonly found in monitor cables, keyboard and mouse cables in computers.

At the end of the connection line between the computer monitor, keyboard, and mouse, there will be a cylinder that is thicker than the connection line. This cylinder is a ferrite magnetic column. The ferrite used in this application can come in various shapes. For example, the vibration-suppressing ferrite used on flat cables is a flat-pack type. Simply remove the flat cable from the flat-pack ferrite. Just pass it through the middle of the body magnetic core

It should be noted that different brands of ferrite cores are required to suppress the ringing caused by different transmission rates. The specific brand of ferrite core to be used can be determined based on the signal speed transmitted and the equivalent resistance embodied by the ferrite core.

(2) If inductors are classified according to the production process, there are mainly the following types:

①Wound inductor

The coil of a wire-wound inductor is wound around a ceramic or ferrite core. The coil is generally made of enameled copper wire.

②Multilayer inductor

The coils of the laminated inductor are printed on each layer, and the stacked layers are pressed together to form the internal coil.

③Thin film inductor

The coil of the thin film inductor is etched on the film (Film), and then the coil is attached to the ceramic base and fixed.

3.Main Inductor Manufacturers

Murata - the combination of Saw Filter + RF Inductor makes most of the original designs of RF circuits use the Murata brand

TDK - a fully enclosed link from material development to inductor production, making TDK's power inductors a representative of high reliability and performance, widely used in automotive electronics

Taiyo-Yuden - the inventor of NR inductors, realized fully automated production of power inductors

One River Electronics Ltd. has the above brands of inductors in stock. If you have purchasing needs, you can inquire for free and we can ship the same day after placing the order.

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