One, the fundamental of capacitance

 

Capacitance, with inductance, resistor together, it is electronics 3 big basic and passive parts of an apparatus; The function of capacitance is with electric field can the form stores electric energy.

 

It is in order to make the same score andante capacitor exemple, simple introduction issues the ultimatum of capacitance

 

 

Institute of as above plan is shown, on the metallic flat that is apart from closer, mutual parallel in two (dielectric is between flat) to load a volts d.c. ; After stability, the metallic flat that is linked together with voltage anode will present the positive electrical charge of certain amount, and the negative electric charge that the metallic flat that is linked together with voltage negative pole will present to be measured equally; Such, a static electric field can be formed between two metals flat, so capacitance is with electric field can the form stores electric energy, the charge volume that store is Q.

 

The charge volume Q that capacitance stores and voltage U and oneself attribute (namely capacitance value C) is concerned, namely Q=U*C. According to academic derivation, the capacitance formula of smooth andante capacitor is as follows:

 

 

Ideal capacitance interior is medium (Dielectric) , without free charge, impossible generation charge is mobile namely electric current, is so ideal capacitance how connect communication?

 

Connect communication

 

Voltage can form an electric field in capacitance interior, and alternating voltage is handed in with respect to meeting generation change electric field. According to the law of complete electric current in maxwell equation group:

 

 

Namely the electric field of electric current or change can produce magnetic field, maxwell is ε(∂E/∂t) definition displacement electric current, it is an equivalent electric current, representing the change of electric field. (Electric current represents current density here, namely J)

 

Set alternating voltage to be sine change, namely:

 

Actual displacement electric current is equal to current density to multiply with the area:

 

 

So the capacitive reactance of capacitance is 1/ωC, when frequency is very tall, capacitance capacitive reactance will be very small, connect namely high frequency.

 

Next graphs are the parallel that uses ANSYS HFSS to emulate board the change of the electromagnetism field of capacitor interior.

 

Cross section electric field changes (GIF uses a figure, should click seemingly examine)

 

 

Vertical section magnetic field changes (GIF uses a figure, should click seemingly examine)

 

 

That is to say when capacitance is connecting communication, in-house electric field and magnetic field are in mutual changeover.

 

Lie between dc

 

Volts d.c. does not change along with time, ε(∂E/∂t) of displacement electric current is 0, dc heft cannot be passed.

 

Model of equivalent of practical electric capacity

 

The character of practical electric capacity dispute is ideal, have effect of a few parasitism; Accordingly, need represents practical electric capacity with a relatively complex model, commonly used equivalent model is as follows:

 

 

● because medium is not absolutely insulation, put in the electric capacity with particular move; Accordingly, any capacitance are existing leakage current, express with equivalent resistor Rleak;

The lead of ● capacitor, electrode has fixed resistor rate, dielectric is put in certain interpose report loss; These loss are unified express with ESR of resistor of equivalent series connection;

The lead of ● capacitor is put in the inductance with particular move, be in high frequency when the impact is bigger, express with ESL of inductance of equivalent series connection;

● is additional, any medium are existing phenomenon of certain electric hysteresis, it is capacitance is after fast discharge, disconnect suddenly voltage, capacitance can restore partial charge volume, with circuit of series connection RC expresses.

 

Most moment, basically pay close attention to the ESR of capacitance and ESL.

 

Quality factor (Quality Factor)

 

With inductance, can define the quality factor of capacitance, namely Q value, namely of capacitance store of power and loss power than:

 

Qc=(1/ωC)/ESR

 

Q value is more important parameter to high frequency capacitance.

 

From syntonic frequency (Self-Resonance Frequency)

 

As a result of the existence of ESL, made a syntonic circuit together with C, its resonance frequency is capacitance from syntonic frequency. Be in from syntonic frequency before, the impedance of capacitance increases as frequency and decrescent; Be in after syntonic frequency, the impedance of capacitance increases as frequency and decrescent, present sensibility; Following plan institute show:

 

The EMK042BJ332MC-W norms book of graph out Taiyo Yuden

 

2, the craft of capacitance and structure

 

According to capacitance formula, the size of capacitance is concerned besides the dimension with capacitance, the dielectric constant with dielectric (Permittivity) is concerned. The function of dielectric is affecting the performance of capacitance, different medium applies to different workmanship.

 

The performance of commonly used medium is comparative, the documentation of a technology of OK and referenced AVX.

 

AVX Dielectric Comparison Chart

 

The workmanship of capacitance basically can divide it is 3 kinds big:

 

● filmy capacitance (Film Capacitor)

● electroanalysises capacitance (Electrolytic Capacitor)

Capacitance of ● pottery and porcelain (Ceramic Capacitor)

 

2.1 filmy capacitance (Film Capacitor)

 

Film Capacitor is translated normally in home for filmy capacitance, but with Thin Film craft it is different. To distinguish, the individual thinks direct translation is bit better for velar capacitance.

 

Filmy capacitance is to pass the plastic film winding that contains two metal electrode to become cylindrical, enclose finally shape; Because its medium is plastic material normally, also call plastic film capacitance; Its interior structure pursues as follows roughly be shown:

 

 

Original intent comes from Yuweiji 100 divisions

 

Filmy capacitance basis the making craft of its electrode, can divide it is two kinds:

 

Tinsel film capacitance (Film/Foil)

 

Tinsel film capacitance, add a thin tinsel on plastic film directly, it is aluminum foil normally, as electrode; This kind of craft is relatively simple, electrode is convenient and derivative, OK at circumstance of big electric current applying.

 

Metallization film capacitance (Metallized Film)

 

Metallization film capacitance, through vacuum deposit (Vacuum Deposited) craft forms a very thin metal face in the surface of plastic film directly, as electrode; Because electrode ply is very thin, can circle make more the capacitance of high capacity; But because electrode ply is thin, apply to circumstance of small electric current only.

 

Metallization film capacitance has the function of ego rehabilitate namely, if capacitance interior has puncture to damage,nod namely, avalanche effect can produce in caustic disadvantage, aerification metal will form surface of an aerification gather in caustic disadvantage, short circuit disappears, attaint is nodded by repair; Accordingly, reliability of metallization film capacitance is very high, invalidation of nonexistent short circuit;

 

Filmy capacitance has two kinds of winding methods: Have feeling circle a law to be before winding, down-lead has been together repeatedly with in-house electrode; Without feeling wind a way circling after making, can use aureate wait for craft, become the in-house electrode of two end panel an area repeatedly, can obtain lesser ESL so, should high frequency performance is higher; In addition, still one kind folds a layer model without feeling capacitance, structure and MLCC are similar, performance is better, SMD of facilitating make it is enclosed.

 

 

The medium material of the earliest filmy capacitance is to use paper dip to note in oil or olefin, ci of English D” Fei Jielade invented 1876; Working voltage is very tall. Multi-purpose now plastic material, namely high polymer polymer, according to its medium material different, basically have the following kinds:

 

 

Using most filmy electric capacity is polyester film capacitance, cheaper, because its dielectric constant is taller, what dimension can do is lesser; It is polypropylene film capacitance next. Other data still has get together 4 fluorine ethylene, polystyrene, polycarbonate is waited a moment.

 

The characteristic of filmy capacitance can accomplish high capacity namely, tall compression; But as a result of craft reason, its dimension is done very hard small, apply at strong report circuit normally, for example industry of electric power electron; Basically be to grow this sample:

 

Cut pursues at High Power Capacitors For Power Electronics – AVX

 

2.2 electroanalysis capacitance (Electrolytic Capacitor)

 

Electroanalysis capacitance is to use a metal to serve as positive pole (Anode) , form film of oxidation of a metal to serve as medium in the surface; Next wet or the electrolyte of solid state and metal serve as cathode (Cathode) . Electroanalysis electric capacity has polarity mostly, if the metal of cathode side, also have an oxidation film, do not have polarity namely electroanalysis capacitance.

 

Of the metal that the basis uses different, at present only should 3 kinds electroanalysis capacitance:

 

Aluminium electroanalysises capacitance (Aluminum Electrolytic Capacitors)

 

Aluminium electroanalysises capacitance should be to use the most extensive electroanalysis capacitance, the cheapest, its are basic following plan institute show the structure:

 

 

Aluminium electroanalysises the making craft of capacitance is like below a few paces roughly:

 

● above all, aluminum foil can etch through report (the means of Etching) , form a very rough surface, increased the surface of electrode to accumulate so, can increase capacitance;

Method of ● repass chemistry oxidizes positive pole, form an oxidation layer, as medium;

● next, one is added to electroanalysis between zincous aluminum foil and cathode aluminum foil paper serves as segregation, pressure close circle make;

● is final, add note electrolyte, electroanalysis paper can absorb electrolyte, enclose shape.

 

Of use electrolyte wet aluminium electroanalysises capacitance application is the widest; The advantage is capacitance big, rated voltage is tall, cheap; Weakness is apparent also, it is life bad, ESR mixes character of shorter, temperature ESL is bigger. To hardware development, need has avoided to design, below the circumstance that asks in contented function, petty gain is the largest dominant position.

 

Next graphs are base beautiful (the aluminium of Kemet) electroanalysises capacitance product, can see aluminium electroanalysises roughly the characteristic of capacitance.

 

 

Aluminium electroanalysises capacitance also has the solid state material such as polymer of use manganese dioxide, electric high polymer to do electrolyte; Polymer aluminium electroanalysises the structure of capacitance pursues as follows roughly be shown:

 

 

Polymer aluminium electroanalysises the ESR of capacitance is lesser, look watch is stable, transient state has been answered; Because be solid state, fight those who pound type of oscillatory ability specific humidity to be close friends; Can make lesser SMD enclose. Of course, wet aluminium electroanalysises capacitance also can do SMD to enclose, it is long mostly nevertheless such:

 

 

And polymer aluminium electroanalysises of capacitance enclose long such:

 

 

Tantalum electroanalysises capacitance (Tantalum Electrolytic Capacitors)

 

Tantalum (N) of phoneticize T ǎ electroanalysises capacitance application is most should be to use manganese dioxide to do solid state electrolyte, basically grow such:

 

 

Solid state Tantalum electroanalysises capacitance interior structure pursues as follows roughly be shown:

 

Documentation of technology of Vishay of original intent out

 

Tantalum capacitance and aluminium electroanalysis capacitance comparing, in at tantalum oxide (2 Tantalum of 5 oxidation) dielectric constant compares aluminous oxide (2 aluminium of 3 oxidation) tall many, so identical bulk, tantalum capacitance capacity should electroanalysis than aluminium of capacitance should big. Tantalum capacitance life is longer, electric performance is more steady.

 

Tantalum capacitance is advantageous also with polymer of electric high polymer (Conductive Polymer) does electrolyte, structure and go up graph capacitance of manganese dioxide Tantalum is similar, change manganese dioxide electric polymer namely; The electrical conductivity of electric polymer is taller than manganese dioxide, such ESR are met lower.

 

Still have wet tantalum electric capacity additionally, the characteristic exceeds leakage current of high capacity, tall compression, small direct current namely, basically use at military affairs and spaceflight domain. Wet tantalum capacitance basically grows such:

 

Cut pursues at Vishay technology documentation

 

Niobium electroanalysises capacitance (Niobium Electrolytic Capacitors)

 

Niobium electroanalysises capacitance and Tantalum electroanalysis capacitance is similar, it is niobium and its oxide replace tantalum; Niobium oxide (5 oxidation 2 niobium) dielectric constant compares tantalum oxide (5 oxidation 2 Tantalum) taller; The performance of niobium capacitance is more steady, reliability is higher.

 

AVX has product of niobium capacitance series, exterior of capacitance of manganese dioxide Tantalum is yellow, and niobium capacitance exterior is orange red, roughly long such:

 

 

Electroanalysis capacitance contrast is expressed, data originates Vicki 100 divisions, offer reference only.

 

 

Capacitance of 2.3 pottery and porcelain (Ceramic Capacitor)

 

Capacitance of pottery and porcelain is with pottery and porcelain material regards medium as material, material of pottery and porcelain has a lot of kinds, dielectric constant, stability has different, apply to different situation.

 

Capacitance of pottery and porcelain, basically have the following kinds:

 

Ceramics capacitance (Ceramic Disc Capacitor)

 

The main good point of ceramics capacitance can be able to bear or endure namely high pressure, use as normally bring compasses electric capacity, can be able to bear or endure 250V alternating voltage. Following plan institute show its exterior and structure:

 

 

Multilayer capacitance of pottery and porcelain (Multi-layer Ceramic Capacitor)

 

Multilayer capacitance of pottery and porcelain, namely MLCC, piece shape (of Chip) multilayer capacitance of pottery and porcelain is the capacitance type that makes dosage the biggest on the world at present, its standardization is enclosed, size is small, apply to automation high density to stick a production.

 

 

Author, namely myself designs advocate board, the picture that oneself take, added artistic effect; Cite without mark and the picture of provenance and content, myself is drawn or great majority is gotten, remain little to may forget to add cursorily; The picture that mark cites, very much more I am machined afresh, be translated for example or a few pieces of graphs go all out together to wait a moment, tool very earthy EXCEL+ check scheme.

 

Multilayer following plan institute show the internal composition of capacitance of pottery and porcelain:

 

SMD MLCC For High Power Applications – KEMET of original intent out

 

Multilayer following plan institute show technological process of production of capacitance of pottery and porcelain:

 

 

As a result of multilayer porcelain of agglomeration of need of pottery and porcelain is changed, form unifinication structure, so down-lead (what Lead) encloses is multilayer capacitance of pottery and porcelain, also cry alone stone (Monolithic) capacitance.

 

Also introduce craft of overmuch layer pottery and porcelain and Thin Film technology in talking about inductance. Thin Film technology is compared in function or technology control respect advanced, the OK and accurate report function that controls parts of an apparatus and physical function. Accordingly, performance of Thin Film capacitance is better, value of the smallest look can accomplish 0.05pF, and tolerance can accomplish 0.01pF; Than normally MLCC is close friends a lot of, resemble the GJM set of Murata, value of the smallest look is 0.1pF, tolerance is 0.05pF normally; Accordingly, thin Film capacitance can be used at asking to compare tall RF domain, AVX has Accu-P® series.

 

The classification of medium of pottery and porcelain

 

According to EIA-198-1F-2002, main component is medium of pottery and porcelain 4 kinds:

 

● Class I: Have temperature to compensate medium of characteristic pottery and porcelain, its dielectric constant mostly inferior, do not exceed 200. It is medium of suitable report sex normally (Paraelectric) , below temperature, frequency and bias voltage, dielectric constant is stabler, change is minor. Loss is very small also, dissipation factor is less than 0.01.

 

 

Property is the stablest, application is most is C0G capacitance, namely NP0. NP0 is the code name that provides in IEC/EN 60384-1 standard, namely Negative Positive Zero, express to losing error namely with N and P.

 

Because dielectric constant is low, the look value of C0G capacitance is lesser, can accomplish 0.1uF greatly most, 0402 enclose have 1000pF only greatly most normally.

 

● Class II, III: Among them, temperature character A-S belongs to Class II, dielectric constant thousands of the left and right sides. Temperature character T-V belongs to Class III, dielectric constant is highest and OK to 20000, the performance that can see Class III is more flabby calm. According to the classification of IEC, class II and III belong to the 2nd kind, medium of tall dielectric constant. Resembling X5R and X7R is Class II capacitance, go applying in power source in Ou more, and Y5V attributes Class III electric capacity, performance is not quite steady, the individual feels application is not much now.

 

 

Because the look value of Class II and III capacitance is highest,can accomplish hundreds of UF, but as a result of medium of tall dielectric constant, it is ferroelectricity medium mostly (Ferroelectric) , temperature stability is poor. In addition, ferroelectricity medium, below dc bias voltage dielectric constant can drop.

 

Talking about inductance in one article, introduced hysteresis of ferromagnetism medium existence, when in-house magnetic field is worth certainly more than, can produce magnetism saturation phenomenon, bring about magnetism conductance to drop; Same, put in electric hysteresis phenomenon to ferroelectricity medium, when in-house electric field is worth certainly more than, can produce electric saturation phenomenon, bring about dielectric constant to drop.

 

Accordingly, when the dc bias voltage when Class II and III capacitance is worth certainly more than, capacitance can drop apparently, following plan institute show:

 

 

● Class IV: The craft that make and normally material of pottery and porcelain is different, grain of in-house pottery and porcelain is outside a very thin oxidation layer, and core is conductor. The capacitance size of this kind of type is very large, but puncture tension is very little. Because the performance of this kind of capacitance is not steady, loss is high, was washed out already basically now.

Capacitance type sums up a watch

 

 

Still have a kind of super electric capacity, it is a capacity particularly big, can replace batteries to regard power supply as equipment, also can cooperate to use with batteries. Super capacitance charges rate is rapid, can charge discharge out and out, and the voltage that can fill, want not to exceed rated voltage only. Application is more also now, a lot of towns of domestic have super electric capacity dynamoelectric bus; There also still is application on some electrons product, for example on recorder of a few drive a vehicle, can last power supply a few days.

 

3, the application of capacitance and type selecting

 

Type selecting of parts of an apparatus, collect pertinent information from the norms book of parts of an apparatus namely actually, whether does judgement satisfy the requirement of the design of the product and application.

 

3.1 overviews

 

Capacitance serves as store can component, can store energy. After exterior power source disconnects, capacitance is likely also and electrified. Accordingly, safe clew is very necessary. Interior of some electrons equipment can stick a high-pressured danger, had dismantled the monochrome television engine in the home in one’s childhood, after ravelling, saw a high-pressured danger is stuck on picture tube, there is a doubt in those days, did not insert power source to you also can have maximum pressure? After the job, had torn open adapter of a few power source, by electric aftertaste boundless ……

 

 

Recursive subject, capacitance store can OK make following application:

 

● stores energy can be become power source, for example super capacitance;

● memory data, application is very wide. Trends breaks sexual memory easily (DRAM) uses data of compositive capacitance array memory namely, capacitance fills report is 1, putting report is 0. The use amount of the memory in all sorts of mobile phones, computer, server is very large, accordingly, memory industry can serve as the vane of the Information Industry.

 

In addition, capacitance still can use as:

 

● is time: Capacitance fills discharge to need time, can use do timer; Still can make delay time circuit, the commonnest is restoration of electrify delay time; A few time chip are like NE556, can generate trigonometry wave.

● syntonic source: Comprise LC resonance circuit together with inductance, generation secures the signal of frequency.

 

Use capacitance to know the low frequency of high frequency, block, character that lies between dc, capacitance still can use as:

 

Power source goes Ou

 

Power source goes Ou should be the application with the widest capacitance, of all sorts of CPU, SOC, ASIC all round, the reverse side placed much electric capacity, the purpose maintains the stability of power supply voltage namely.

 

Above all, in DCDC circuit, need chooses right input electric capacity and output electric capacity to reduce voltage ripple. Need computation gives relevant parameter.

 

 

In addition, when job resembling IC, the working electric current of the quarter need when differring is different, accordingly, also need to go in great quantities Ou capacitance, will make sure working voltage gets stability.

 

Coupling is lain between straight

 

When designing circuit, below some circumstances, hope to transmit communication signal only, do not hope to transmit dc signal, can use series connection capacitance to come at that time coupling signal.

 

For example multistage amplifier, to prevent dc to slant buy is affected each other, calculation of static work place is complex, capacitance coupling is used between class normally, jobs of such each class static state order OK and independent analysis.

 

For example such high speed of PCIE, SATA is serial signal, also use capacitance to undertake communicating coupling normally.

 

Bypass filter wave

 

Bypass, the communication signal that just as its name implies will not need namely guides the earth. Filter wave also is a meaning actually. In circuit of microwave radio frequency, the design of all sorts of filter needs to use electric capacity. In addition, resemble EMC design, to the LED lamp that interface is in, can increase electric capacity of wave of a filter on line, can raise the dependability when ESD checks so.

 

3.2 aluminium electroanalysis capacitance

 

3.2.1 aluminium electroanalysis capacitance (wet)

 

Aluminium electroanalysises capacitance (wet) no matter be plug-in unit,still stick piece enclose, height is taller, and ESR is taller, unwell close to go at power supply is being made near IC at placing Ou, it is the input that is used at power source circuit and output electric capacity normally.

 

 

Look value

 

Get capacitance to be worth tolerance from inside norms book, normally aluminium electroanalysises the tolerance of capacitance is ±20% . Consideration is the biggest when holding value and cost of the smallest look, each parameter should satisfy design requirement.

 

Rated voltage

 

Aluminium electroanalysises capacitance applies to dc circumstance only normally, design work voltage wants at least 80% under rated voltage. To having the circuit that surge defends, its are rated surge voltage wants prep above to defend parts of an apparatus (the residual voltage that is TVS) normally.

 

For example, to the equipment of power supply of a few POE, according to 802.3at standard, working voltage is highest can amount to 57V, so the TVS clamp of the choice voltage has 90 much V, so the aluminium that chooses rated voltage 100V at least electroanalysises capacitance. Right now, also only aluminium electroanalysises the requirement that capacitance can satisfy high capacity at the same time.

 

 

Dissipation factor

 

When designing DCDC circuit, the ESR influence that outputs capacitance outputs voltage ripple, because this needs to know aluminium electroanalysises the ESR of capacitance, but most aluminium electroanalysises the norms book of capacitance gave out only dissipation factor Tanδ . Can calculate according to the following formula ESR:

 

ESR = Tanδ/(2πfC)

 

For example, when 120Hz, tanδ is 16% , and C is 220uF, criterion ESR is 965mΩ about. Visible aluminium electroanalysises the ESR of capacitance is very big, this meeting brings about output voltage ripple is very big. Accordingly, use aluminium electroanalysises when capacitance, need cooperates to use an electric capacity of shape pottery and porcelain, stand by DCDC chip to place.

 

As switch frequency and temperature elevatory, ESR can drop.

 

Rated ripple electric current

 

The ripple electric current of capacitance, the demand of the input that wants contented DCDC design and the RMS electricity that export capacitance. Aluminium electroanalysises the need of rated ripple electric current of capacitance is amended according to switch frequency.

 

 

Life

 

Aluminium electroanalysises the life of capacitance is briefer, type selecting needs to notice. And life is to mix working temperature is direct and relevant, norms book gives a product the life when highest temperature normally, for example when 105 ℃ , life is 2000 hours.

 

According to experience rule, working temperature every drop 10 ℃ , life is multiplied with 2. If the design service life of the product is 3 years, namely 26280 hours. Criterion 10*log2(26280/2000)=37.3 ℃ , so design work temperature cannot exceed 65 ℃ .

 

3.2.2 polymer aluminium electroanalysis capacitance

 

The CPU that resembles Intel parts of an apparatus of such great merit bad news, a chip the power comsumption of 80 much tile, nuclear electric current a few arrive about a hundred how, at the same time advocate frequency is very tall, high frequency composition is much. Be opposite at this moment go the demand of Ou capacitance is very high:

 

● capacitance value wants big, satisfy big electricity demand;

Electric current of ● rated RMS wants big, satisfy big electricity demand;

● ESR wants small, contented and high frequency go Ou requirement;

● look is worth stability to be close friends;

● surface post is installed, height cannot too tall, because lay the BOTTOM layer in CPU the reverse side normally, go best in order to achieve Ou effect.

 

At this moment, choose polymer aluminium to electroanalysis electric capacity is most right.

 

In addition, to frequency circuit, normally need uses coupling, go Ou capacitance, because the frequency of frequency is very low, so need uses large electric capacity, right now polymer aluminium electroanalysises electric capacity is very right also.

 

3.3 Tantalum capacitance

 

According to preamble the origin of relevant data, can discover, the main firm of tantalum capacitance is Kemet, AVX, Vishay.

 

Tantalum belongs to rarer metal, accordingly, tantalum capacitance can want than the capacitance of other type a bit more expensive. But function should electroanalysis than aluminium capacitance is close friends, ESR is smaller, loss is smaller, go Ou effect is better, leakage current is small. Next graphs are Kemet the parameter watch of capacitance of Tantalum of a solid state:

 

 

Rated voltage

 

The working voltage of capacitance of solid state Tantalum needs to fall frontal design. Voltage of normal circumstance job wants 50% under rated voltage; When high temperature environment or laden impedance are inferior, working voltage wants 30% under rated voltage. Specific fall frontal demand should ask strictly according to norms book.

 

In addition, still need those who notice tantalum capacitance to bear the circumstance of retrorse voltage, communication part is too large, may bring about tantalum capacitance to bear retrorse voltage, bring about tantalum capacitance invalidation.

 

The main failure mode of capacitance of solid state Tantalum is short circuit invalidation, can bring about circuit to misfire directly, even the risk such as on fire. Accordingly, need additional attention dependability design, lower failure rate.

 

To once invalidation, with respect to the product that can cause grave accident, the proposal does not use electric capacity of solid state Tantalum.

 

Rated ripple electric current

 

Ripple electric current has shed tantalum capacitance, because ESR existence can cause tantalum capacitance temperature rise, add environmental temperature, the rated temperature that does not exceed tantalum electric capacity and relevant fall frontal design.

 

3.4 shape are multilayer capacitance of pottery and porcelain

 

Piece shape is multilayer capacitance of pottery and porcelain should be the electric capacity with shipment the largest amount, manufacturer is more also, fasten TDK, MuRata, Taiyo Yuden like 3 days big, beautiful department had been bought by Japanese Beijing porcelain like KEMET, AVX() .

 

The comparison that 3 days of big departments do is good is to have corresponding type selecting software, have the product of all series such as inductance, capacitance and relevant parameter curve, very complete, must recommend again:

 

3.4.1Class I capacitance

 

Application of Class I capacitance is most is C0G capacitance, performance is steady, apply to resonance, match, the high frequency circuit such as filter wave.

 

The look value of C0G capacitance is very stable, do not follow outside ambient basically (frequency except) change, next graphs are Murata the dc of capacitance of a 1000pF, communication and temperature character.

 

 

Accordingly, need to pay close attention to the frequency character of C0G capacitance only normally. 3 next graphs are Murata identical enclose (0402inch) identical tolerance (the frequency character of the 10pF capacitance of 5%) is comparative.

 

 

Among them GRM is common series, GJM is tall Q cost set, GQM is high frequency series, visible GQM series is high frequency performance is better, mix from syntonic frequency Q watch is tall, the circumstance with very high demand of a few high frequency performance, can choose tolerance the product of 1% . And GRM series is cheaper, more general, for example EMC filter wave.

 

3.4.2Class II and Class III capacitance

 

Class II and Class III capacitance are medium of tall dielectric constant, performance is not steady, the span that hold a cost is big, use as normally power source goes Ou or signal bypass.

 

With Murata capacitance of a 22uF, 6.3V, X5R is exemple, correlated characteristics curve:

 

 

Look value

 

Class II and Class III capacitance, look value slants along with temperature, DC buy and AC slant buy span is bigger. Use as especially power source goes when Ou, capacitance has constant direct current to slant buy, capacitance is compared nominal the value is a lot of less, want to notice real look is worth requirement of whether contented design so.

 

Ripple electric current

 

Regard the input of DCDC and output as capacitance, can have certain ripple electricity, because the existence of ESR can cause particular temperature rise. Add environmental temperature, cannot exceed the rated temperature of capacitance, for example highest forehead spends X5R capacitance temperature is 85 ℃ .

 

Normally as a result of multilayer ESR of capacitance of pottery and porcelain is lesser, can susceptive ripple electric current is bigger.

 

From syntonic frequency

 

The capacitance existence as a result of ESL, have frequency of one each resonance. The capacitance of high capacity, from syntonic frequency inferior, have 1-2MHz only. So, to heighten the high frequency effect of power source, many Xiaorong is worth go Ou capacitance is must. In addition, very tall to switch frequency DCDC chip, should notice the input outputs capacitance from syntonic frequency.

 

ESR

 

Design DCDC circuit, need knows to output the ESR of capacitance, will calculate output voltage ripple. Multilayer the ESR of capacitance of pottery and porcelain normally inferior, about a few go to Europe of a few fine long hair.

 

3.5 bring compasses electric capacity

 

To the electronic equipment of our family expenses, final it is power supply of report of 220V communication town. Power source adapter is opposite to decrease the interference of electrified wire netting, check through relevant EMC, can increase all sorts of filter wave electric capacity. Next graphs are a simple and easy circuit sketch map:

 

 

Call X capacitance to the capacitance between L and N, the capacitance between L, N and PE or GND calls Y capacitance. Because 220V alternating current has dangerous sex, the person of can minatory person is safe, electronic product needs to satisfy relevant bring compasses level, for example the relevant test requirement of GB4943 and UL60950. Accordingly, x capacitance and Y capacitance and these tests are direct and relevant, also make bring compasses electric capacity so.

 

It is in order to refuse electric intensity test exemple, according to the standard, side of L, N is circuit, basic insulation is between need and PE or GND. Accordingly, need communicates 1.5kV to perhaps shed the compression test of 2.12kV continuously to be being added between GND in L or N, last nearly 1 minute, relevant leakage current cannot exceed a standard to provide a value during. Accordingly, bring compasses electric capacity, have quite high compression demand, shed leakage current continuously at the same time cannot too big.

 

In addition, commonly used RJ45 net mouth, to reduce EMI, commonly used to Bob-Smith circuit, following plan institute show:

 

 

The compression that can see capacitance is 2kV above, because net mouth has transformer normally, the L of 220V alternating current and N have two transformer segregation to reticle, it is double insulation, l and N arrive between reticle also should undertake intensity checks fighting report. Double insulation, normally the requirement passes communication 3kV or dc 4.24kV checks.

 

Because, install compasses capacitance to have tall compression demand, use ceramics capacitance is small-sized perhaps and normally filmy capacitance.

 

In addition, type selecting of parts of an apparatus basically asked at 2 o’clock even: The length that affirms parts of an apparatus with the structure is wide tall; Enclose parts of an apparatus to plug-in unit not a long time, can use a watch to stick parts of an apparatus entirely, can omit so the working procedure of wave crest solder.

 

Epilogue

 

The article introduced the craft structure of a few kinds of main capacitance roughly, and apply type selecting. The level is finite, careless omission of hard to avoid, welcome to point out. Be familiar with IT equipment only at the same time, do not understand the other industry such as electric power electron, war industry, still have a few so application cannot introduce related other capacitance.

 

Origin: Zhihu