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The full name of the magnetic bead is a ferrite bead filter (the other is a magnetic bead made of amorphous alloy magnetic material), which is an anti-interference element. Its function of filtering is mainly to eliminate the RF existing in the transmission line structure (circuit). Noise, RF energy is the AC sine wave component superimposed on the DC transmission level, the DC component is the desired useful signal, while the RF RF energy is useless electromagnetic interference transmission and radiation (EMI) along the line. Power line denoising is a common application scenario of magnetic beads. The editor of Shuokai Electronics will summarize a few points for you. When denoising power lines, the selection points of magnetic beads:
First, you need to know the operating frequency of the switching power supply.
Generally speaking, the radiated EMI noise generated by the power supply is usually less than 100MHz-300MHz. Therefore, magnetic beads with a peak frequency less than 300MHz should be selected for low-frequency magnetic beads.
Second, you need to know the working current of the power supply.
For those magnetic beads placed on switches or non-DC signals, it is usually necessary to convert the rms value of the AC signal to select the rated current of the magnetic beads. The rated current value is also the biggest selection point for the magnetic beads of the power line.
Third, in the case of meeting the design requirements of the layout space, you should try your best to choose large-sized magnetic beads.
Fourth, DCR is also a very critical parameter for denoising magnetic beads with power lines.
Especially for battery-powered portable devices, magnetic beads with small DCR should be used as much as possible to improve power efficiency.
Fifth, the impedance curve of the magnetic beads should be as flat as possible.
In this way, the high-order harmonic noise of the power supply can be filtered out to the greatest extent possible.
In addition to power line denoising, chip beads have many more applications: clock generation circuits, filtering between analog circuits and digital circuits, I/O input/output internal connectors (such as serial ports, parallel ports, keyboards , mouse, long-distance telecommunications, local area network), between radio frequency (RF) circuits and susceptible logic devices, filtering high-frequency conducted interference in power supply circuits, computers, printers, video recorders (VCRS), television systems and mobile phones. EMI noise suppression.