With the development of the times and the advancement of technology, there are more and more electronic products. Among them, there is an important component in electronic products, the magnetic ring. Today, the editor will take you to understand it.
It is a commonly used anti-interference component in electronic circuits, which has a good suppression effect on high-frequency noise. It is generally made of ferrite material (Mn Zn). Magnetic rings have different impedance characteristics at different frequencies. Generally, the impedance is very small at low frequencies, and as the signal frequency increases, the impedance exhibited by the magnetic ring sharply increases. As we all know, the higher the signal frequency, the easier it is to radiate (to buy a high-quality computer case, it is also necessary to reduce electromagnetic leakage). However, most signal lines do not have shielding layers, so these signal lines become good antennas to receive various chaotic high-frequency signals in the surrounding environment. These signals are superimposed on the originally transmitted signal and may even change the useful signal originally transmitted. Under the action of the magnetic ring, normal and useful signals can pass through well, while high-frequency interference signals can be effectively suppressed, and the cost is low. So it's not surprising that people see plastic lump shaped integrated magnetic rings on monitor signal cables, USB connection cables, and even high-end keyboards and mice.
Number of turns selection
Passing the entire cable through a ferrite magnetic ring forms a common mode choke, and the cable can also be wound around the magnetic ring a few times as needed. The more turns there are, the better the suppression effect on interference at lower frequencies, while the suppression effect on noise at higher frequencies is weaker. In practical engineering, the number of turns of the magnetic ring should be adjusted according to the frequency characteristics of the interference current. Usually, when the frequency band of the interference signal is wide, two magnetic rings can be placed on the cable, each with a different number of turns, which can simultaneously suppress high-frequency interference and low-frequency interference. From the mechanism of the common mode choke coil, the larger its impedance, the more obvious its interference suppression effect. The impedance of the common mode choke coil comes from the common mode inductance Lcm=jwLcm. It is not difficult to see from the formula that for a certain frequency of noise, the larger the inductance of the magnetic ring, the better. But the actual situation is not like that, because there are parasitic capacitors on the actual magnetic ring, which exist in parallel with the inductor. When encountering high-frequency interference signals, the capacitance impedance of the capacitor is small, which short circuits the inductance of the magnetic ring, thereby rendering the common mode choke ineffective.
Magnetic ring inspection method
1: The appearance of the magnetic ring can be visually inspected under normal lighting conditions.
2: The external dimensions of the magnetic ring are inspected using a vernier caliper with an accuracy of 0.02mm under normal lighting conditions.
3: The comprehensive factor of the magnetic ring is measured using a CF-3A magnetic ring sorter, with an excitation current set at 2.5A and a frequency of 40KHz.
4: The inductance of the 4-turn magnetic ring is measured using a YD2810D LCR digital bridge at a frequency of 1 KHz.
5: The induced electromotive force of the magnetic ring is measured under specified conditions using the "UI100 High Frequency Power Source" and "UI9720 Magnetic Material Dynamic Analysis System".
6: The Curie point of the magnetic ring is measured using a YD2810D LCR digital bridge and a precision oven.
The above is a brief understanding of magnetic rings by the editor, hoping to bring some thoughts to everyone.