What is an inductor?

An inductor is an electronic component. The inductor we usually refer to actually an inductor device.

Inductors, resistors and capacitors are the three major electronic components in PCB circuits.

It can store magnetic energy and generate an electromotive force to resist changes in current when the current changes.

2. Principle of Inductor

The principle of electromagnetic induction

Inductance operates based on Faraday's Law of Electromagnetic Induction.

When there is an electric current flowing through a wire, a magnetic field is generated around the wire.

If the current changes, the magnetic field will also change. According to Faraday's Law of Electromagnetic Induction, the changing magnetic field will generate an induced electromotive force in the wire.

Inductance utilizes this phenomenon to store and release energy.

For example, a simple coil inductance. When the current starts to increase from zero, the magnetic field around the coil gradually strengthens.

The coil will induce an electromotive force to resist the increase of the current. This induced electromotive force has a direction opposite to the direction of current increase, just like a "resistance".

When the current stabilizes, the magnetic field also stabilizes, and the induced electromotive force disappears. If the current decreases, the magnetic field weakens,

and the coil will generate another induced electromotive force to resist the decrease of the current. At this time, the direction of the induced electromotive force is opposite to the direction of the current decrease.

The relationship between magnetic flux and inductance

The magnitude of an inductor can be described by the relationship between magnetic flux and current.

Magnetic flux (Φ) refers to the total number of magnetic lines passing through the coil.

The inductance (L) is defined as: when the current flowing through the coil is I, the magnetic flux generated in the coil is the ratio of the current. Its formula is L = Φ/I.

The unit of inductance is henry (H). The greater the inductance, the stronger the resistance of the coil to changes in current.

For example, a coil with an inductance of 1 henry will generate an induced electromotive force of 1 volt across its terminals when the current changes at a rate of 1 ampere per second.

2. Types of Inductors

By installation method classification

Plug-in inductor: An inductor used for SMT surface mounting.

Surface mount inductor: An inductor designed for plug-in installation

By size packaging classification

4532 inductor: Inductor size 4.5*3.2*2.8mm

1211 inductor: Inductor size 12.5 * 10.8 * 6.5 mm

1608 inductor: Inductor size 6.6*4.45*2.92mm

2920 inductor: Inductor size 28*25*20.5mm

....

By model classification

UU inductor: A very cost-effective type of plug-in common-mode inductor, commonly used in LED lighting circuits.

PQ inductor: It is a series of common-mode inductors formed by winding on flat wires.

NR inductor: Also known as magnetic gel inductor

EP inductors: A series of inductors mainly used in digital amplifiers. They come in various sizes and may be designed with two inductors integrated together.

According to the appearance of the process

I-beam inductor: A type of plug-in inductor with an appearance resembling an I-beam.

Magnetic gel inductor: An inductor sealed around the coil with magnetic gel.

Integral molded inductor: An inductor formed by pressing materials such as iron powder or carbonyl powder.

Hollow coil inductance: An inductance directly formed by winding the coil.

Magnetic ring inductor: The magnetic core is in a circular shape and it is an inductor.

Flat-wound inductor: An inductor formed by winding a flat coil. It is characterized by a large current, capable of reaching several hundred amperes.

By application classification

Automobile inductors: Inductors that comply with the IATF quality certification for automobiles

Digital power amplifier inductor: A specific type of inductor used in digital power amplifiers

Power inductor: Used in various power circuits

Energy storage inductor: Used in some energy storage application devices

Boost inductor: The inductor used in the boost circuit

Low-frequency inductor: Mainly operates in low-frequency circuit environment

High-frequency inductor: It is an inductor used in high-frequency circuits.

3. Applications of Inductance

Filtering circuit

In the power circuit, inductors are often used in combination with capacitors to form a filtering circuit. For example, at the output end of a DC power supply, an inductor and a capacitor form a low-pass filter.

The inductor has a greater impedance to high-frequency signals, while the capacitor has a smaller impedance to high-frequency signals.

When high-frequency noise in the power supply passes through the filtering circuit, the inductor will impede the passage of the high-frequency noise,

and the capacitor will short-circuit the high-frequency noise to the ground, thereby making the output DC voltage more stable and reducing the ripple.

2. Oscillation Circuit

The inductor plays a crucial role in oscillation circuits. For instance, in an LC oscillation circuit, the inductor (L) and the capacitor (C) form a resonant circuit.

When the circuit starts to operate, the capacitor charges, and the electric field is stored in the capacitor.

When the capacitor discharges, current flows through the inductor, and the magnetic field is stored in the inductor.

Then the inductor converts the magnetic field energy into electric field energy, allowing the capacitor to be charged again.

This mutual conversion of electrical and magnetic energy generates oscillation signals. These oscillation signals can be used to generate clock signals.

For example, in electronic watches, the oscillation signals generated by the LC oscillation circuit, after being processed through frequency division and other steps, can drive the rotation of the second hand, minute hand, and hour hand.

3. Signal Coupling and Impedance Matching

In communication circuits, inductors can be used for signal coupling. For instance, in a transformer-coupled amplification circuit, the magnetic coupling between the primary coil and the secondary coil is achieved through an inductor,

allowing signals to be transmitted from one circuit to another. Additionally, inductors can also be used for impedance matching.

In radio frequency circuits, the impedance of the antenna and the impedance of the circuit often do not match. Inductors can be combined with capacitors to form a matching network,

enabling the antenna to effectively receive and transmit signals and reducing signal reflection losses.