Ferrite magnetic rings mainly include nickel zinc ferrite magnetic rings and manganese zinc ferrite magnetic rings, which have strict differences in frequency of use. Nickel zinc ferrite magnetic rings are suitable for suppressing high-frequency electromagnetic interference; Manganese zinc ferrite magnetic rings are suitable for suppressing low-frequency electromagnetic interference.

The higher the magnetic permeability of ferrite, the greater the impedance at low frequencies and the smaller the impedance at high frequencies. According to different requirements, different processes can be selected to manufacture magnetic rings. Magnetic rings have different impedance characteristics at different frequencies, generally having very low impedance at low frequencies, and the impedance exhibited by magnetic rings increases sharply with the increase of signal frequency.

The function of magnetic rings:

Function 1: For ferrites used to suppress electromagnetic interference, the most important performance parameters are magnetic permeability μ and saturation magnetic flux density Bs. Its equivalent circuit is a series connection of inductance and resistance, and the values of the two components are proportional to the length of the magnetic bead. When the wire passes through the ferrite core, the inductive impedance formed increases with the increase of frequency. High frequency current dissipates internally in the form of heat.

Function 2: In the low-frequency range, impedance is composed of inductive reactance. At low frequencies, R is very small and the magnetic permeability of the core is high, resulting in a large inductance value, with L playing a major role. Electromagnetic interference is reflected and suppressed, resulting in less loss of the magnetic core. The entire device is a low loss, high-Q inductive component. In the high-frequency range, impedance is composed of resistive components. As the frequency increases, the magnetic permeability of the magnetic core decreases, resulting in a decrease in inductance and reactance components. At this point, the loss of the magnetic core increases, the resistance component increases, and the total impedance increases. When high-frequency signals pass through ferrite, electromagnetic interference is absorbed and dissipated in the form of thermal energy.

Function three: The magnetic ring absorbs high-frequency components, also known as an absorption filter. Ordinary filters are composed of lossless reactive elements, also known as reflection filters. When the impedance of the reflection filter does not match the signal source, a portion of the energy will be reflected back to the signal source, resulting in an increase in interference level. To address this drawback, ferrite beads can be used on the input line of the filter to convert high-frequency components into thermal losses by utilizing their eddy current losses on high-frequency signals.