In the selection of magnetic beads, magnetic beads - the main points selection rule Inductive knowledge

by:Thermistor-Mov     2020-06-22
This article mainly introduced the magnetic beads point selection and selection rules, this article word count 1050 words, read the full text to 10 minutes. Magnetic beads type magnetic beads are mainly used for EMI differential mode noise, he dc resistance is small, has a high impedance under high frequency, usually said the 600 r refers to the 100 MHZ detection frequency impedance values. Selection of magnetic beads should follow two aspects: one is the status of the integrated operational noise interference; Second, must through the current size. To get a general idea of noise intensity and frequency, the frequency impedance curve of different magnetic beads is different, we need to choose when the choice high impedance frequency magnetic beads in the center of the noise of the class. Noise interference of persons to be high impedance of some, is not to say that the impedance is higher, the better, by the same token, the impedance, the higher the DCR is, the greater the loss of effective signals. Usually no clear is calculated and selected benchmark, specific should see application results, the values in r - 120 600 r is very practical. Should then look through the current size, if used in the power cord part to choose the rated voltage of the specifications of the larger, used in signal is usually rated voltage demand is not high. Other rated voltage, the smaller the greater the magnetic beads are usually impedance. The selection of magnetic beads to done in accordance with the actual situation. As for the 3. 3 3 v, 300 ma, power supply, regulations. 3 v may not be less than 3. 0V。 So the dc resistance of magnetic beads DCR should be lower than 1 r, this usually select 0. 5 r, avoid parameter fluctuations. Magnetic beads selection rules of magnetic beads relationship with frequency, is refers to a particular specifications of the magnetic beads have a reduced frequency points, in this frequency impedance value is large, and the other will get low frequency impedance. Normally is not zero, impedance values have only small. Magnetic beads to many frequencies are useful, but there will be high and low points. Usually the rated voltage of magnetic beads is smaller, the higher the impedance can be done, near the power supply and choose the rated voltage is higher than the high output current of the magnetic beads. The main points of the magnetic beads selection 1, how much is useless signal frequency range; 2, who is noise source; 3, need how much noise attenuation; 4, environmental conditions ( Temperature, dc voltage, structure intensity) ; How much is 5, circuit and load impedance; 6, whether there is space enough space on the PCB PCB board placed magnetic beads; 7, various types of magnetic beads, manufacturers should have performance indicators, especially the relationship between impedance and frequency of magnetic beads curve; 8, there are several holes on some magnetic beads, can promote parts with transmission line through the impedance ( Through the magnetic beads several times square) Weakened, but the increase in high frequency noise ability is not so ideal as expected, can choose the method of series multiple magnetic beads; 9, ferrite magnetic materials, are caused by excessive current magnetic saturation, permeability. The structure of large current filter should be chosen specially designed magnetic beads, note the cooling way; 10, ferrite beads, not only with the power supply circuit in filtering the high frequency noise ( Can be used as dc and ac output) , also can be applied to other integrated operational amplifier, the volume can be very small. Especially in the digital circuit, given that the pulse signal with high order harmonic frequency is very high, the key of circuit of high frequency radiation is the root cause, so it can play in this kind of situation the role of magnetic beads; 11, ferrite beads also applied in signal cable noise filtering; 12, when choosing magnetic beads must be wary of the magnetic beads flow, usually also do derating processing, should consider when used in the power supply circuit dc resistance affect pressure drop. Link address: this paper label: inductance type magnetic bead on an article: power inductors, the classification of the power inductor advantages under the action of an article: patch capacitance naming, encapsulation, internal structure, production process
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