The capacitance in design of EMC of switch power source is analysed characteristicly
[introduction] the effect that a lot of electron architects know to filter wave capacitance rises in power source, but on the filter wave electric capacity that uses in end of output of switch power source, as different as the filter wave capacitance that chooses in labour frequency circuit, the general set up an electric circuit that uses the wave that make filter in labour frequency circuit solves capacitor, the pulsatile voltage frequency on its is only 100 hertz, filling discharge time is millisecond amount class, to obtain lesser pulsatile coefficient, the capacitance of need is as high as tens of 10 thousand small ways, consequently general low frequency electroanalysises with common aluminium capacitor is made, the target is with rising capacitance is given priority to, value of tangent of horn of the capacitance of capacitor, loss and leakage current are the main parameter that differentiates its actor bad.
What output filter wave uses regard as to electroanalysis in switch regulated power supply capacitor, the frequency of toothed wave voltage on its is as high as tens of kilohertz, even tens of megahertz, differ when its requirement and low frequency application, capacitance is not main index, the impedance that those who weigh its stand or fall is it one frequency is characteristic, ask it is in the working frequency of switch regulated power supply paragraph inside should have low impedance, in the meantime, in-house to power source, because semiconductor device begins working place to produce the aiguille noise that is as high as hundreds kilohertz, can have favorable filter wave effect, general low frequency solves capacitor to be controlled in 10 kilohertz with average report, its impedance begins to present sensibility, cannot satisfy switch power source to use a requirement.
Appropriative of switch regulated power supply is high frequency aluminium electroanalysises capacitor, it has 4 to carry stature, positive electrode is aluminous piece two end part derivative the anode that serves as capacitor, negative pole is aluminous piece two end also part derivative as negative pole. The electric current of regulated power supply is being carried of capacitance from 4 end flow into, through capacitance interior, again from another is carrying flow direction load; The electric current that returns from load also loses end to flow into from a of capacitance, lose end from power source of another flow direction that lose end again.
Because 4 upright capacitance have good high frequency character, the pulsatile heft that it outputs voltage to reduce and restrained switch aiguille noise to provide very advantageous measure.
High frequency aluminium electroanalysises the form that capacitor still has much core, it divides aluminum foil into shorter a certain number of paragraphs small, with much more derivative a shunt-wound join in order to reduce the resistor component in capacitive reactance, in the meantime, the data that uses low resistance rate serves as derivative terminal with screw, bear in order to enhance capacitor the ability of big electric current.
Fold a capacitance to also be called without feeling capacitance, electroanalysis commonly the fuse of capacitor roll into is cylindrical, inductance of equivalent series connection is bigger; Fold the structure of a capacitance and book similar, the magnetic flux way that because of flowing electric current produces is opposite and be offsetted, reduced the numerical value of inductance consequently, have more good high frequency character, this kind of capacitance makes set prescription body commonly, facilitate fixed, still can reduce appropriately constitute machine bulk.
In addition, still one kind mixes 4 end the 4 end that fold a photograph couple fold a type high frequency electroanalysis capacitor, it is integrated both advantage, high frequency character is much better.