What are the different functions of magnetic ring inductor in three circuits?

Magnetic ring inductor is one of the commonly used electronic components in the circuit. It can form an LC filter network with capacitor C, form a freewheeling circuit with diode in the step-down circuit, and can also be used in the LC resonant circuit. The following briefly introduces the application of magnetic ring inductor in the circuit.

1. Form LC filter circuit with capacitor

Magnetic ring inductor can pass DC and block AC. Since the inductive reactance of magnetic ring inductor is closely related to the AC frequency, the higher the frequency of magnetic ring inductor, the greater the inductive reactance. In the LC filter circuit, the magnetic core inductor is the most common circuit structure of the switching power supply. The inductor and capacitor have a filtering effect. The AC ripple distortion in the circuit will be filtered out by the inductor, and the capacitor C has a filtering effect, which can make the back-end output smoother. This type of magnetic ring inductor is generally used in the application of switching power supply or high-power power supply.

2. Used in DC/DC step-down circuit

The input range of DC/DC step-down chip is wide and the conversion efficiency is high, while the DC/DC step-down chip is generally composed of inductor, capacitor, diode, etc. to complete the circuit principle. The magnetic core inductor is a common DC/DC power chip in the DC/DC step-down circuit. The inductor and the diode form a freewheeling function here. When the internal MOS tube is turned on, the inductor stores energy; when the internal MOS tube is turned off, the energy stored in the inductor supplies power to the load. This is also the most common PWM step-down principle at present.

3. Used in LC resonant circuit

LC can form parallel resonance or series resonance, which is generally called frequency selection. Among many input frequencies, only those that are consistent with resonance can pass. This type of circuit is often used in applications such as radios and smart TVs. When designing the LC resonant circuit, a lot of calculations must be performed to determine the optimal parameters of the magnetic ring inductor and capacitor.

The magnetic ring inductor is a coil containing a magnetic ring. Because the electromagnetic coil has an inductive reactance to the alternating current after the power is turned on, it forms an electronic component-an inductor. The inductance value of the inductor ranges from a few micrometers to tens of millihenries. Originally, the inductor can be formed by only using coils, but in order to increase the inductance and reduce the volume and line resistance, a ferrite core with little eddy current damage is added. For example, if a 1 microhenry electromagnetic coil is added with a core with a magnetic permeability of 100, the inductance is theoretically increased by 100 times to 100 microhenries. But in fact, how much the actual increase is not only related to the magnetic permeability, but also to the shape of the core. Generally, the core inductance of tens of millihenries is mostly used in high-frequency AC circuits. The inductance in AC circuits under hundreds of Hz will be above hundreds of millihenries. It is no longer suitable to use a core, but it is changed to microcrystal, permalloy, or even silicon steel sheet, which increases the volume and weight. In areas where the inductance quality Q is required to be very high, no iron core is added!