What are Inductors?

Inductor is an element that can convert electrical energy into magnetic energy and store it. The structure of an inductor is similar to a transformer, but with only one winding. The inductor has a certain inductance, it only hinders the change of current. If the inductor is in a state where no current is passing, it will try to prevent the current from flowing through it when it is on; if it is in the state, it will try to maintain the current when the circuit is off. Inductors are also called chokes, reactors, and dynamic reactors.

Inductor

The most primitive inductor was 1831

The inductor is generally composed of a skeleton, a winding, a shield, a packaging material, a magnetic core or an iron core.

1. Skeleton Skeleton refers to the stent for winding coils. Some of the larger fixed or adjustable inductors (such as oscillating coils, choke coils, etc.) are mostly surrounded by enameled wire (or gauze covered wire) on the skeleton, and then the core or copper core, iron core, etc Installed in the inner cavity of the skeleton to increase its inductance. The skeleton is usually made of plastic, bakelite,

The inductor can be made of a conductive material coiled magnetic core, typically a copper wire. The magnetic core can also be removed or replaced with a ferromagnetic material. A core material with higher magnetic permeability than air can tightly confine the magnetic field around the inductive element, thereby increasing the inductance. There are many types of inductors, most of which are made of outer enamel coated wire around ferrite spools, and some protective inductors place the coil completely inside the ferrite. The core of some inductive elements can be adjusted. This can change the size of the inductor. Small inductors can be etched directly on the PCB, using a method of laying spiral tracks. Small value inductors can also be used to manufacture transistors.

The characteristics of an inductor are exactly the opposite of those of a capacitor.

Two types of inductance measurement

Inductors in the circuit mainly play the role of filtering, oscillation, delay, notch, etc., as well as filtering signals, filtering noise, stabilizing current, and suppressing electromagnetic interference. The most common role of an inductor in a circuit is to form an LC filter circuit together with a capacitor. Capacitors have the characteristics of blocking DC and AC, while inductors have the function of blocking DC and AC. If the DC power with many interference signals is passed through the LC filter circuit, then the AC interference signal will be consumed by the inductor into thermal energy. When a relatively pure DC current passes through the inductor, the AC interference signal in it will also become magnetic induction. And thermal energy, the higher frequency is most likely to be impedance by the inductor, which can suppress the higher frequency interference signals.

Inductors have the characteristics of preventing the passage of alternating current and the passage of direct current. The higher the frequency, the greater the coil impedance. Therefore, the main function of the inductor is to isolate, filter, or form a resonant circuit with capacitors, resistors, and so on.

SMD inductors are electromagnetic induction elements wound with insulated wires. Belongs to commonly used inductive components. The role of the chip inductor: DC resistance to AC. This is a simple statement. Isolate the AC signal, filter it or form a resonant circuit with capacitors, resistors, etc. The role of tuning and frequency selection inductors: the inductor coil and capacitor can form an LC in parallel. Tuning the circuit. Any current of the chip inductor in the circuit will generate a magnetic field, and the magnetic flux of the magnetic field will act on the circuit.

When the current through the chip inductor changes, the DC voltage potential generated in the chip inductor will prevent the current from changing. When the current through the inductive coil increases, the self-inductive electromotive force generated by the inductive coil is in the opposite direction to the current, preventing the increase of the current, and at the same time converting a part of the electrical energy into a magnetic field that can be stored in the inductor; when the current through the inductive coil decreases, The self-inductive electromotive force is in the same direction as the current, preventing the reduction of the current, and simultaneously releasing the stored energy to compensate for the reduction of the current. Therefore, after the inductive filtering, not only the load current and voltage ripples are reduced, the waveform becomes smooth, but the conduction angle of the rectifier diode is increased.

The role of the inductor 1: the color ring inductor has a current blocking effect: the copper core in the color ring inductor coil is always resistant to the current change in the coil. The color ring inductor has a blocking effect on the AC current used in the circuit. The size of the blocking effect is called the inductive reactance XL, and the unit is ohm. The relationship between it and the inductance L and the alternating current frequency f is XL = 2fL. The color ring inductor can be mainly divided into high-frequency choke coil and low-frequency choke coil.

The role of the inductor 2: the color ring inductor has the function of tuning and frequency selection: the color ring inductor and the electrolytic capacitor in parallel can form an LC tuning circuit. When the color ring inductance is resonant, the inductive reactance and capacitive reactance of the circuit are reversed, that is, the natural oscillation frequency f0 of the circuit is equal to the frequency f of the non-AC signal. Then the inductive reactance and capacitive reactance of the circuit are also equal. Generally, it is not very high, and the color ring inductor used in the circuit is generally relatively stable.
The role of the inductor 3: The maximum of the color ring inductor is mainly used to screen signals, filter noise, stabilize current, and suppress electromagnetic interference.

The main parameters

The main parameters of the inductor are

The inductance is calculated as follows:

1. Inductance is an energy storage element, and magnetic beads are energy conversion (consumption) devices; ^[1]

2. Inductors are mostly used in power supply filtering circuits, and magnetic beads are mostly used in signal circuits for EMC countermeasures.

3. Magnetic beads are mainly used to suppress electromagnetic radiation interference, while inductors are used to focus on suppressing conductive interference. Both can be used to deal with EMC and EMI problems; the two ways of EMI, namely, radiation and conduction, are different. The approach uses different suppression methods, the former uses magnetic beads and the latter uses inductance;

4. Magnetic beads are used to absorb ultra-high frequency signals. Like some RF circuits, PLLs, oscillating circuits, including ultra-high-frequency memory circuits (DDRSDRAM, RAMBUS, etc.), magnetic beads must be added to the power input part, and inductance is a kind of Energy storage element, used in LC oscillation circuit, low-frequency filter circuit, etc., its application frequency range rarely exceeds 50MHZ;

5. Inductance is generally used for circuit matching and signal quality control, and general connection and power supply connection. Use magnetic beads where the analog and digital grounds are combined. Magnetic beads are also used for signal lines.

The size of the magnetic beads (to be precise, the characteristic curve of the magnetic beads) depends on the frequency of the interference wave that needs to be absorbed by the magnetic beads. Magnetic beads are high frequency resistance, low resistance to DC, high resistance to high frequency. Because the unit of the magnetic bead is nominal according to the impedance it produces at a certain frequency, the unit of impedance is also ohm. Magnetic bead datasheets are usually accompanied by frequency and impedance characteristics. Generally, 100MHz is used as the standard, such as 2012B601, which means that at 100MHz, the impedance of the magnetic beads is 600 ohms.