Aplikace Magnetický Korálky v EMC Design Of Přepínání Napájení Napájení Napájení
Tento článek zavádí vlastnosti z ferit korálek 2c a podle to jeho charakteristiky% 2c analyzuje a zavádí jeho důležité aplikace v EMC design z přepínání napájení napájení 2c a dává experimentální a test výsledky v napájení linka filtr.
Toto papír úvodní základní principy a charakteristiky z magnetické korálky to ilustrovat jeho důležitost v spínání napájení napájení EMC, v objednávka k poskytovat přepínat napájení napájení produkt návrháři s více a lepší volby kdy navrhování nové produkty.
1 ferit EMI potlačení komponenty
Ferrite is a ferrimagnetic material with a cubic lattice structure. Its manufacturing process and mechanical properties are similar to those of ceramics, and its color is gray-black. One type of magnetic core often used in EMI filters is ferrite material, and many manufacturers provide ferrite materials specially used for EMI suppression. This material is characterized by very large high-frequency losses. For ferrite used to suppress electromagnetic interference, the most important performance parameters are magnetic permeability μ and saturation magnetic flux density Bs. The magnetic permeability μ can be expressed as a complex number, the real part constitutes the inductance, and the imaginary part represents the loss, which increases with the increase of frequency. Therefore, its equivalent circuit is a series circuit composed of an inductor L and a resistor R, both L and R are functions of frequency. When the wire passes through this ferrite core, the formed inductive impedance increases in form as the frequency increases, but the mechanism is completely different at different frequencies.
In the low frequency band, the impedance is composed of the inductive reactance of the inductor. At low frequency, R is very small, and the magnetic permeability of the magnetic core is high, so the inductance is large, and L plays a major role, and the electromagnetic interference is reflected and suppressed; and at this time, the loss of the magnetic core is small, and the the celé zařízení je an induktor s nízká ztráta a vysoká Q charakteristika.
In the high-frequency band, the impedance is composed of resistance components. As the frequency increases, the magnetic permeability of the magnetic core reductions, resulting inactance inductance of the inductor and a reduction in inactive reactance component. However, at this time, the loss of the magnetic core increases and the resistance component increases, resulting in an increase in the total impedance. Když Vysokofrekvenční signál prochází skrz ferit, elektromagnetické rušení je absorbováno a rozptýleno v forma teplo energie.
Ferrit potlačení komponenty jsou široce použité zapnuté tištěné obvody desky, výkon vedení a data linky. If a ferit potlačení prvek je přidáno k v vstup konec of the power line of the tištěné deska, vysokofrekvenční interference může be filtrované out. ferit magnetické kroužky nebo magnetické korálky jsou speciálně použité k potlačit vysokofrekvenční rušení a hrot interference zapnuto signál vedení a výkon vedení. it also has the ability to absorbovat elektrostatický výboj puls rušení.
2. Princip a charakteristiky z magnetické korálky Když proud proud protéká skrz ten drát v jeho centrální díra, it bude bude a magnetický stopa že cirkuluje uvnitř the magnetický korálek. ferity pro EMI ovládání mělo mělo formulováno takové to to nejvíce z magnetické toku je rozptýlené jako teplo v materiál. Toto jev může být modelováno by a série kombinace of an induktor a a rezistor. jako ukázáno v obraz 2
The numerická hodnota z dva komponent je proporcionální k délka z z magnetická korálek, a délka z magnetická korálek má a významný dopad na potlačení účinek. Ta delší dlouhá délka z magnetická korálek, lepší potlačení účinek. Vzhledem k tomu, že signál energie je magneticky spojitá k k magnetická korálek, the reaktance a odpor of induktor zvýšení s zvýšení z z frekvence. Účinnost z magnetická vazba závisí na magnetická propustnost z korálek materiál relativní k vzduch. obvykle ztráta z ferit materiál to zhotoví nahoru korálek může být vyjádřeno jako a komplex množství skrz jeho propustnost relativní k vzduch.
3 Aplikace z magnetické korálky
3.1 špička supresor
The biggest disadvantage of switching power supply is that it is easy to generate noise and interference, which is a key technical problem that has plagued switching power supply for a long time. The noise of the switching power supply is mainly caused by the fast-changing high-voltage switching and pulse short-circuit current of the switching power tube and the switching rectifier diode. Therefore, using effective components to limit them to a minimum is one of the main methods of suppressing noise. Non-linear saturated inductance is usually used to suppress the reverse recovery current peak, at this time the working state of the iron core is from -Bs to plus Bs. According to the consistency of the high magnetic permeability and saturable ultra-small inductance element-magnetic beads on the freewheeling diode of the switching power supply, a spike suppressor used to suppress the peak current generated when the switching power supply is switched is developed.
Výkon Charakteristiky špičky supresory
(1) The initial and maximum indukčnost values are very high, and the nlinearita of the redudual indukčnost value after saturation is extremely unobvious. After being connected in series to the circuit, the current rises and shows high impedance instantly, which can be used as a takzvaně instantaneous impedance element.
(2) It is suitable for preventing the transient current peak signal in the semiconductor circuit, the impact excitation circuit and the accompanying noise, and it can also prevent the semiconductor from being damaged.
(3) Reziduální indukčnost je extrémně malá, a ztráta je velmi malá když obvod je stabilní.
(4) It is complete different from the performance of ferite products.
(5) As long as magnetic saturation is avoid, it can be used as an ultra-small, high-inductance inductance element.
(6) It can be used as a high-performance saturable iron core with low loss to control and generate oscillation.
The spike supresor vyžaduje the železo jádro materiál to have a higher magnetic permeability to obget a larger indukčnost; when the high square ratio can saturate the iron core, the indukčnost should drop to zero fast; the donucovací síla is small and the high frequency loss is low, otherwise the heat dissipation of the iron core will not work normally.
The účel z špička supresor je hlavně k redukce the current peak signal; reduce the noise caused by the current peak signal; prevent the damage of the switching tranzistor; reduce the switching loss of the switching tranzistor; compensate the recovery characteristics of the diode; prevent high-frequency pulse current shock excitation. Use as an ultra-small line filter, etc.
3.2 Aplikace v filtr a) Test výsledek bez magnetické korálky b) Test výsledek s magnetické korálky c) Test výsledek s L čára a magnetické korálky d) Test výsledek s N čára a magnetické korálky
Obyčejné filtry jsou složené z bezztrátové reaktivní komponenty. Jeho funkce v obvod je to reflektovat stopband frekvence zpět to signál zdroj, so this type of filter is also called a reflection filter. When the reflection filter does not match the impedance of the signal source, part of the energy will be reflected back to the signal source, resulting in an increase in the interference level. v objednávka k řešit toto nevýhoda, ferit magnetický kroužek nebo magnetický korálek rukáv může být použitý on the příchozí line of the filter, and the eddy current loss of the high-frequency signal by the ferite ring or magnetic bead can be used to convert the high-frequency component into heat loss. Therefore, the magnetic ring and magnetic beads actually absorb high-frequency components, so they are some called absorption filters.
Different ferite suppression components have different optimal suppression frequency ranges. General, the higher the permeability, the lower the frequency suppressed. In addition, the larger the volume of the ferrite, the better the suppression effect. When the volume is constant, the long and thin shape has better suppression effect than the short and thick one, and the smaller the inner diameter, the better the suppression effect. Nicméně, in the case of DC or AC bias current, there is still the problem of ferite saturation. The larger the cross-section of the suppression element, the less likely it will be saturated, and the greater the bias current it can withresist.
Based on the above principles and characteristics of magnetic beads, it is applied to the filter of switching power supply, and the effect is obvious. From the test results, it can be seen that the application of magnetic beads is significantly different. It can be seeen from the experimental results that due to the influence of the switching power supply circuit, structural layout, and power, sometimes it has a good suppression effect on differential mode interference, sometimes it has a good suppression effect on common mode interference, and sometimes it does not have a suppression effect on interference but increases noise interference.
Když EMI absorbující magnetický kroužek/magnetický korálek potlačuje diferenciální-režim interference, the current value passing through it is proportional to it volume, and the imbalance between the two causes saturation, which reduces the performance of the component; when suppressing common-mode interference, the two wires (positive and negative) of the power supply pass through a magnetic ring at the same time, and the effective effective signál je a diferenciální-mód signál. Jiný lepší metoda v the use of the magnetic ring is to make the wire passing through the magnetic ring repeated wound some times to increase the inductance. According to its suppression principle of electromagnetic interference, its suppression effect can be reasonably used.
Ferrit potlačení komponenty měly by instalovány blízko k zdroj of rušení. For the input/output circuit, it should be as close as possible to the inlet and outlet of the shielding case. for the absorption filter composed of ferite magnetic ring and magnetic beads, in addition to choosing lossy materials with high magnetic permeability, attention should also be paid to its application occasions. jejich odpor k vysokofrekvenční komponenty v vedení je asi ten to stovky z Ω, so jeho role v vysokoimpedance obvody je není zřejmé. On the contra, it will be very effective in low-impedance obvody (takové jako napájení distribuce, napájení nebo rádio frekvence obvody).
