But actual coil circles the not complete semmetry that make, can bring about the generation of inductance of the leakage that need a standard. Signal electric current or source current are in way of outdated of two winding midstream is opposite, the flux of generation is mutual and quits, choke presents low impedance. In all modular noise electric current (the disturbance current that includes ground annulus road to cause, also be in call fore-and-aft electric current) stream via the direction when two winding identical, the flux of generation is the same as to addition, choke presents tall impedance, rise to restrain thereby in all the action of modular noise.

 

In all modular inductance is a two-way filter essentially: Want filter to go up except line on one hand in all modular electromagnetism interference, want to restrain itself not to give out electromagnetism interference outwards again on the other hand, avoid to affect the regular job of other electron equipment below same electromagnetism environment.

 

In all modular choke can transmit wrong standard signal, the wrong standard signal with dc and very low frequency can be passed, and to high frequency in all modular noise presents very big impedance, so it can be used restrain in all modular electric current is annoyed.

 

Choke is used in power supply cord to input end commonly.

 

Working principle

 

 

In all modular inductance choke is a substantial in the equipment such as power source of switch power source, transducer, UPS. Its job principle: When working electric current has shed two to be circled to contrary coil, produce two magnetic field H1 that offset each other, H2, right now working electric current basically suffers coil ohm resistor and the working frequency that can ignor to issue the damp of small leakage inductance. When if have interference,signal has shed coil, coil presents a tall impedance namely, produce very strong damp result, achieve attenuation to disturb signal action.

 

In all the filter wave circuit of modular inductance, la and Lb are in all modular inductance coil. These two coil are circled on same core, v/LIT all over the ground number and phasic identical (circle make retrorse) . Such, when circuit medium normal electric current flows classics in all when modular inductance, electric current is in inphase retrorse magnetic field produces in circling the inductance coil that make and offset each other, the effect that right now normal signal electric current basically suffers coil resistor (with a few damp that cause because of leakage feeling) ; Should have in all modular report pursues 2 graphs 3 stream when shedding longitudinal circle, as a result of in all of modular electric current with tropism, the generation inside can online circle is the same as to magnetic field and the inductance that increases coil, make coil expression is tall impedance, produce stronger damp result, with this attenuation in all modular electric current, achieve the goal of filter wave.

 

 

In fact, circuit of this filter wave one termination violates a source, another termination is disturbed equipment, criterion La and C1, lb and C2 form two groups low connect filter, can make on circuit in all modular EMI signal is controlled go up in very low n. This circuit can be restrained already external EMI signal is passed into, the EMI signal that when attenuation circuitry oneself works, can generate again, reduce EMI effectively to disturb intensity.

 

A kind when home produces small-sized in all modular inductance, use high frequency noise to restrain countermeasure, in all the model clutchs streamline to encircle a structure, question mark not damply, volume is minor, use convenient, have a balance to spend beautiful, use convenient, high quality wait for an advantage. Use extensively in double balance transformer of diapason device, much frequency, impedance transformer, balance reachs lopsided changeover transformer. . . Etc.

 

Still one is plant in all modular filter inductance / EMI filter inductance uses ferrite magnetic core, crewel is circled, noise restrains countermeasure beautiful, gao Gongmo noise is restrained and signal of noise of low wrong standard is restrained, signal of noise of low wrong standard controls interference source, be out of shape hard in high speed signal, volume is minor, have a balance to spend beautiful, use convenient, high quality wait for an advantage. The IEEE1394 line that uses the USB route that controlling noise of electronic equipment EMI, personal computer and peripheral equipment, DVC, STB extensively, liquid crystal shows signal of face plate, low-pressure differential. . . Etc.

 

Thrust loss character

 

 

In all modular choke thrusts loss character is the impedance character that plays in interference spectrum by its will measure.

 

When frequency limits is 0.01~1MHZ, impedance basically depends on coil inductance L.

 

When frequency limits is 1~10MHZ, impedance basically depends on CK of winding distributinging capacitance.

 

It is when frequency limits ” when 10MHZ, impedance and winding capacitance, advocate loop inductance, leakage inductance and caustic of magnetism core iron and the parallel circuits that cupreous caustic place comprises are concerned (ZS is equivalent impedance) .

In all the application of modular choke

 

Filter of a confusion of voices of curb of 1. switch power source

 

2. power supply cord and line are electrostatic noise filter

 

The faze of spoke blackberry lily such as 3. transformer and ultrasonic device is restrained implement

 

Leakage feels and differ modular inductance

 

the inductance model to ideal, after coil is circled, all magnetic flux are centered inside the center of coil. But normally coil of form of circumstance runner band won’t wind full a week, or circle make not close together, such meetings cause the leak of magnetic flux. In all modular inductance has two winding, meantime has quite large space, can produce magnetic flux leak so, form wrong standard inductance. Accordingly, in all modular inductance also has proper wrong standard to disturb attenuation ability commonly.

 

In the design of filter, we also can use leakage sense. If be in common filter, install only in all modular inductance, use in all the wrong standard inductance with the leakage feeling right amount generation of modular inductance, remove the inhibition of pair of wrong standard electric current. Sometimes, increase artificially even in all the leakage inductance of modular choke, increase amount of wrong standard inductance, in order to achieve better filter wave result.

 

Magnetism bead

 

Magnetism bead is special the high frequency noise that goes up at restraining line, power supply cord and aiguille interference, still have the capacity that absorbs electrostatic pulse. Magnetism bead is to be used draw ultrahigh frequency signal, circuit of a few RF, PLL, oscillating circuit, contain circuit of ultrahigh frequency memory (DDR SDRAM, RAMBUS) need to input a part to add magnetism bead in power source, and inductance is a kind of harbour can component, use in LC oscillating circuit, in the filter wave circuit of low frequency, its apply frequency limits to exceed wrong 50MHZ rarely.

 

The function of magnetism bead basically is to eliminate structure of consist in transmission line (circuit) medium RF noise, RF energy is overlay the composition of communication sine wave on dc transmission n, dc composition is the useful signal of need, and the electromagnetism interference that energy of radio frequency RF is no use however is transmitted along circuit and radiation (EMI) .

 

Want to eliminate these signal energy that do not need, use a formula the part that magnetism bead acts high frequency resistor (attenuator) , this parts of an apparatus allows dc signal to pass, and filter divides communication signal. Normally high frequency signal is 30MHz above, however, low frequency signal also can get a type the influence of magnetism bead.

 

The unit of magnetism bead is ohmic, is not Hunter, this want special attention. Because the unit of magnetism bead is the impedance that arises in some frequency according to it,come nominal, the unit of impedance also is ohmic. General meeting offers the characteristic graph of frequency and impedance on the DATASHEET of magnetism bead, it is a standard with 100MHz commonly, for instance 1000R@100MHz, the meaning is in namely 100MHz frequency when the impedance of magnetism bead is equivalent to 600 ohm.

 

Want to choose magnetism bead correctly, must notice the following:

 

1, how much is the frequency limits of the signal that does not need;

 

2, who is noise source;

 

3, the noise attenuation with how old need;

 

4, what is ambient conditions (temperature, volts d.c. , structural intensity) ;

 

5, how much are circuit and laden impedance;

 

6, whether the space is on PCB board place magnetism bead.

 

The equivalent circuit of magnetism bead is equivalent to taking block to be restricted wave implement, the noise that nods to a certain frequency only has remarkable inhibition, the need when using reckons a confusion of voices nods frequency beforehand, so that choose proper model. To the circumstance that frequency inaccuracy is decided or cannot foretell, magnetism bead is improper.

 

Before 3 impedance frequency curves that offer through surveying manufacturer can be judged. In impedance curve 3 curves are very important, namely resistor, inductance and total impedance. The biggest impedance and below low frequency and dc signal attenuation uses up hidebound magnetism bead model. Piece type magnetism bead fall in too big volts d.c. , impedance character can be affected, additional, if working temperature rise is exorbitant, exterior perhaps magnetic field is too big, the impedance of magnetism bead can be affected adversely.

 

 

Magnetism bead and inductance

 

Use a formula magnetism bead still is a type inductance still basically depend on applying. In syntonic circuit need uses a type inductance. And when need eliminates the EMI noise that does not need, use a formula magnetism bead is first-rate choice. To PCB of model, several compound board, model, number, ground suggests to part, nod ground connection together again finally, if use connection of 0 Europe resistor.

 

Inductance is store can component, and magnetism bead is energy changeover (use up) parts of an apparatus, radio frequency interference is used up with caloric form, achieve the goal of EMC, commonly used enter the mouth at line and power supply cord, restrain high frequency interference and aiguille interference. Inductance is multi-purpose at loop of wave of power source filter, side overweight checks conductibility interference; Magnetism bead is multi-purpose at signal loop, basically use at EMI respect, restrain electromagnetism radiate to disturb. Magnetism bead is used draw ultrahigh frequency signal, resemble circuit of a few RF, PLL, oscillating circuit, contain circuit of ultrahigh frequency memory (DDR, SDRAM, RAMBUS) need to input a part to add magnetism bead in power source, inductance is a kind store can component, use in LC oscillating circuit, medium the filter wave circuit of low frequency, its apply frequency limits to exceed 50MHz rarely.