Different ferrite materials have different optimal suppression frequency ranges, which are related to permeability. The higher the permeability of the material, the lower the optimal attenuation frequency; conversely, the lower the permeability of the material, the higher the attenuation frequency. Therefore, manganese-zinc ferrite is more suitable for low frequencies, such as 30MHz and below. Nickel-zinc ferrite is more suitable for high frequencies, such as 30MHz to 200MHz or higher.
1.Application on PCB Circuit Boards
The interference on PCB circuit boards mainly comes from digital circuits, whose high-frequency switching current generates a strong interference between the power line and the ground line. The power line and signal line will emit the high-frequency noise generated by the digital circuit switching in the form of conduction or radiation. A commonly used method to suppress interference is to add decoupling capacitors between the power supply and ground to short-circuit high-frequency noise. However, the use of decoupling capacitors alone sometimes causes high-frequency resonance, creating new interference. Adding ferrite interference suppression beads at the entrance of PCB circuit board traces can effectively attenuate high-frequency noise.
2.Application on Power Lines
Power lines can transmit interference from external power grids and switching power supply noise to the lines of equipment. Designing ferrite interference suppression cores at the power outlet and the power inlet of the PCB circuit board can not only suppress the transmission of high-frequency interference between the power supply and the PCB circuit board, but also suppress the mutual interference of high-frequency noise between PCB circuit boards.
3.Application on Signal Lines
Ferrite anti-interference cores can also be used on signal lines to suppress noise transmission between components or devices. However, the impedance of signal lines is generally greater than that of power lines, so the suppression effect of interference will not be as obvious as on power lines.
Due to the different compositions and application purposes of ferrite materials, there are generally the following different requirements for ferrite core materials:
(1) Application in low-level signals. Ferrite materials are required to have low loss, good stability, and little change over time and temperature. Main applications include high-Q inductors, common-mode inductors, broadband matching pulse transformers, radio transmission antennas, etc.
(2) Application in power supply. Ferrite materials are required to have high magnetic flux density and low loss at operating frequencies and temperatures. Main applications include switching power supplies, magnetic amplifiers, DC-DC converters, power line filters, trigger coils, and battery charging transformers.
(3) Application in radio frequency interference suppression. Ferrite materials are required to have high impedance. They are mainly used to suppress parasitic oscillations in lines and attenuate unwanted signals in transmission lines.