Introduction to the functions and common applications of magnetic ring inductors

Inductor is one of the commonly used components in circuit design. It can form an LC filter network with capacitor C, form a freewheeling function with diodes in the buck circuit, and can also be used in LC resonant circuits. The following introduces common applications of inductors.

1. Use capacitors to form a liquid crystal filter circuit

It is well known that inductors can pass DC and resist AC, because the inductance of inductors has a great relationship with the AC frequency. The higher the frequency, the greater the inductance. As shown in the figure below, it is the most commonly used circuit structure for switching power supplies, and inductors and capacitors play a filtering role. The AC ripple in the circuit will be filtered by the inductor and the capacitor C, making the back-end output smoother. This is usually used in switching power supplies or high power applications.

2. Used in DC/DC buck circuits

The DC/DC buck chip has a wide input range and high conversion efficiency. The circuit principle of the DC/DC buck chip is generally realized by inductors, capacitors and diodes. As shown in the figure below, it is an ordinary DC/DC power chip, in which the inductor and diode constitute the freewheeling function.

When the internal MOS tube is turned on, the inductor stores energy; when the internal MOS tube is turned off, the inductor can power the load. This is also the most commonly used PWM step-down principle at present.

3. Used in LC resonant circuit

LC can form series resonance or parallel resonance, also called frequency selection, that is, among many input frequencies, only those consistent with the resonant frequency can pass. This circuit is often used in broadcasting, television and other applications. When designing an LC resonant circuit, a lot of calculations are required to determine the optimal parameters of inductance and capacitance.

A magnetic ring inductor is a coil with a magnetic ring. Because the coil has an inductive reactance to alternating current after being energized, it constitutes an electronic component-inductor! Its inductance value ranges from zero point zero to ten millisin. Originally, only coils can constitute inductance, but in order to increase inductance and reduce the volume and DC resistance of the wire, a ferrite core with the smallest eddy current loss is added. For example, if a magnetic core with a magnetic permeability of 100 is added to a coil of 1 micron, the inductance theoretically increases 100 times to 100 micron. But the actual increase is not only the magnetic permeability, but also related to the shape of the magnetic core (in addition to the ring, there are also cylindrical, square, bar, Wangzi, mouth-shaped, etc.). High-frequency AC circuits generally use magnetic core inductors below tens of millimeters. The inductance of AC circuits below a few hundred hertz is above a few hundred millimeters-enjoy. It is not suitable to use magnetic cores, microcrystalline, slope film alloy, or even silicon steel sheets! The volume and weight are much larger! Do not add iron cores where the inductance quality Q is extremely high.

Inductor components are mainly used in resonant circuits, bandpass filters and bandstop filters. According to the design requirements, the circuit consists of a tuning circuit, a frequency selector, a notch filter, a filter, a high-frequency and medium-frequency transformer, an anti-interference circuit, a damping circuit, a spark extinguishing circuit, an energy storage circuit, a bridge, etc. Commonly used for filtering and anti-interference!

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