EMI filter is one kind is mixed by inductance what capacitance comprises is low connect filter, it can make the useful signal of low frequency successful pass, and have inhibition to high frequency interference. The action of EMI filter, main body is the following now two respects: 1, the to equipment influence of high frequency interference in controlling alternating current network; 2, control device (especially power source of high frequency switch) the interference to alternating current net. Filter of EMI power source is electronic equipment the first selection tool that design engineer control conducts electromagnetism interference and radiation electromagnetism interference.

 

 

1, carapace of metal of filter of EMI power source and box carapace must assure good surface contact, had received ground wire;

2, line of input of filter of EMI power source, output line must pull open a distance, avoid by all means is collateral, lest reduce filter efficiency;

3, jumper of filter of EMI power source is beautiful with choosing double skeining thread, it can remove a part effectively signal of high frequency interference.

 

Popularly, to filter of EMI power source we care its groovy function and frequency domain to control function only. And to EMI line filter, because transmission line itself can generate certain electromagnetism interference, so test signal can produce certain attenuation necessarily. At this moment, we are about to undertake to its time domain transmits the test on function. Because of the influence as a result of distributinging parameter of inductance distributinging capacitance and circuit, its are high frequency paragraph a frequency character either linear, must pass a test, adjust parameter of yuan of parts of an apparatus and filter structure ceaselessly, the wrong standard with gaining satisfaction, in all the model inserts loss character curve. EMI filter installation is in rectification module is exterior, the test is in rated load (be fully loaded with) the conducted interference that reachs half load condition to fall. The end that such doing is the effect that does not suffer the condition such as the ground connection, radiate inside machine when the parameter of each yuan of parts of an apparatus that optimizes EMI filter, exclude other factor easily, get best EMI filter.

 

To inserting a needle through same filter wave, the frequency of square wave is taller, its harmonic signal will be jumped over by what filter wave inserts needle attenuation big, criterion the weaveform of square wave rises reach decay time to will grow more. Same, undee to same frequency, insert a needle through filter wave, value of look of its filter wave is greater, the rate of delay of hasten of square wave rise time is older.

 

Power source filter designs the passive filter that comprises to reach inductance by resistor, capacitance only commonly, did not resemble the active component of transistor and so on. The upper part of power source filter receives power source, power source end has in all modular inductance, namely 2 lines of power source are depended on same direction is circled on core, on power supply cord if have in all modular question mark, its are in in all the magnetic field that modular inductance produces is met addition, because this has bigger impedance, and mark of wrong standard question is in in all the magnetic field that modular inductance produces will be mutual and quits, because this can have flowed in all modular inductance. The electric current that power source has shed basically is wrong standard, but above also may noise appears with differring modular form, if want to restrain wrong standard noise, need uses wrong standard inductance additionally, or it is each photograph has individual inductor.