capacitor Related Articles

Ⅰ IntroductionAs we all know, capacitors have always played a very important role in electronic circuits. They are responsible for the coupling of signals in electronic circuits, the differentiation of volt-ampere characteristics in RC circuits, such as integration, the "channel" in oscillating circuits, bypass and power filter, etc. Aluminum electrolytic capacitor is made of anodized aluminum foil, corroded cathode aluminum foil and electrolytic paper in the middle, then impregnated with working electrolyte and sealed in aluminum shell. CatalogⅠ IntroductionⅡ Common problems of electrolytic capacitor  2.1 Why can't an aluminum electrolyte capacitor withstand reverse voltage?  2.2 What are the similarities and differences between nonpolar capacitance and polar capacitance?  2.3 What will happen when a polar capacitor is reversed?  2.4 The reverse connection of the polar capacitor will explode. Does it mean that it can't be directly connected to the AC power supply?  2.5 If the polarity capacitor is reversed, why is it short-circuited?  2.6 Why does the resistivity of electrolytic capacitor become smaller when the positive and negative poles are reversed?  2.7 Why can we only use a nonpolar capacitor in a pure AC circuit?  2.8 What is electrolytic capacitance?  2.9 The characteristics of electrolytic capacitors are as follows  2.10 What are the similarities and differences that cannot be ignored between polar and nonpolar capacitors in performance, principle and structure?Ⅲ SummaryⅣ FAQ Ⅱ Common problems of electrolytic capacitor2.1 Why can't an aluminum electrolyte capacitor withstand reverse voltage?Due to the polarity of electrolytic capacitors, it is necessary to pay attention to the correct connection of positive and negative electrodes in use, otherwise, not only the capacitors can not play a role, but also the leakage current is very large. In a short time, the inside of the capacitors will heat up, damage the oxide film, and then damage.  As shown in the figure, the basic structure of the aluminum electrolytic capacitor is composed of an anode, aluminum layer attached to the insulating medium, cathode aluminum layer of the receiving electrode and the real cathode composed of electrolyte. The electrolyte is soaked in the paper between the two aluminum layers. Aluminum oxide layer is plated on the aluminum layer, which is very thin compared with the voltage applied on it, and it is easy to be broken down, leading to capacitor failure. The alumina layer can withstand the forward DC voltage. If it bears the reverse DC voltage, it is easy to fail in a few seconds. This phenomenon is called the "valve effect", which is why the aluminum electrolytic capacitor has polarity. If both electrodes of the electrolytic capacitor have an oxide layer, the non-polar capacitor will be formed.Many articles report the mechanism of the threshold phenomenon of the reverse voltage of the aluminum electrolytic capacitor, which is called the hydrogen ion theory. When the electrolytic capacitor bears the reverse DC voltage, that is, the cathode of the electrolyte bears the positive voltage while the oxide bears the negative voltage, The hydrogen ions gathered in the oxide layer will pass through the medium and reach the boundary between the medium and the metal layer, and then they will be converted into hydrogen. And the expansion force of the gas causes the oxide layer to fall off. Therefore, the current flows directly through the capacitor after breaking through the electrolyte, and the capacitor fails. This DC voltage is very small. Under the reverse DC voltage of 1 ~ 2V, the aluminum electrolytic capacitor will immediately fail due to the hydrogen ion effect in a few seconds. On the contrary, when the positive voltage is applied to the electrolytic capacitor, the negative ions are concentrated between the oxide layers. Because the diameter of the negative ions is very large, they can not break through the oxide layer, so they can withstand higher voltage.2.2 What are the similarities and differences between nonpolar capacitance and polar capacitance?Are nonpolar capacitors the same as nonpolar electrolytic capacitors? Most kinds of capacitors are nonpolar, only the electrolytic capacitors have polarity. Among them, there are very special nonpolar electrolytic capacitors. Compared with ordinary capacitors, electrolytic capacitors have a larger capacity, lower price and smaller volume than other capacitors, but electrolytic capacitors generally have polarity, and their working reliability, withstand voltage, temperature resistance, dielectric loss and other indicators are not as good as other capacitors.The so-called non-polar electrolytic capacitor is actually the back-to-back packaging of two identical electrolytic capacitors. This kind of capacitor has large loss, low reliability and low voltage withstand, which can only be used in a few occasions with low requirements.2.3 What will happen when a polar capacitor is reversed?If the capacitance capacity is very small, the withstand voltage is very high, and the working voltage is low, there will be nothing wrong with the reverse connection. If the capacity is slightly large (above 100uF) and the withstand voltage is close to the working voltage, the capacitance can just work for nearly 10 minutes, then it will bulge and burst.2.4 The reverse connection of the polar capacitor will explode. Does it mean that it can't be directly connected to the AC power supply?It can't be connected to the AC power supply, because the polar capacitor is designed to be used in the DC power supply for filtering, and there is special material inside the polar capacitor, which can not bear the backpressure. If it is connected to the AC power supply, it will breakdown reversely or explode.2.5 If the polarity capacitor is reversed, why is it short-circuited?The internal structure of the polar capacitor is divided into the positive electrode, a dielectric layer and the negative electrode. The dielectric layer has the property of unidirectional conduction. Of course, the dielectric layer of the product will not play the role of insulation after being connected reversely, and the capacitor will be short-circuited. 2.6 Why does the resistivity of electrolytic capacitor become smaller when the positive and negative poles are reversed?It involves the principle of electrolytic capacitor. When the positive electrode of the capacitor is connected positively, a very thin oxide film (alumina) will be formed as the dielectric. When the negative electrode of the capacitor is connected reversely, H2 will be produced without forming the oxide film, and the other electrode will not form the oxide film which can be used as the dielectric due to different materials. 2.7 Why can we only use a nonpolar capacitor in a pure AC circuit?In the circuit of DC voltage superposing AC signal, if we can ensure that the lowest voltage after superposing will not become negative, we can use a capacitor with polarity. In the case of the same capacity, the volume and cost of the polar capacitor are far less than that of the nonpolar capacitor, so when we need a larger capacity, the volume of the capacitor is a big contradiction. We usually replace non-polar capacitors with polar ones, which not only solves the volume problem but also reduces the cost. Large capacitance can filter the AC signal with a lower frequency and above, while small capacitance can only filter the signal with higher frequency and above. 2.8 What is electrolytic capacitance?Electrolytic capacitor is a kind of capacitor. Its medium is coated with electrolytes. It can be divided into positive and negative electrodes and cannot be connected wrongly. The capacitance is composed of two metal poles and the insulating material (medium) sandwiched between them.2.9 The characteristics of electrolytic capacitors are as follows①The capacitance per unit volume is dozens to hundreds of times larger than other kinds of capacitance.②Rated capacity can easily reach tens of thousands of μ for even several F, but it is not as good as double electric layer capacitance.③The price is much lower than other kinds because the components of electrolytic capacitors are ordinary industrial materials, such as aluminum. The equipment for manufacturing electrolytic capacitors is also common industrial equipment, which can be mass-produced at a relatively low cost. Electrolytic capacitors are usually made up of metal foil (aluminum/tantalum) as the positive electrode, and the insulating oxide layer (alumina/tantalum pentaoxide) of metal foil as the dielectric. The negative electrode of aluminum electrolytic capacitor is composed of thin paper/film or electrolyte polymer soaked in electrolyte, the negative electrode of the tantalum electrolytic capacitor is usually manganese dioxide. As both of them use electrolytes as the negative electrodes, the electrolytic capacitor gets its name. The polar electrolytic capacitor usually plays the role of power filter, decoupling, signal coupling, the time constant setting, DC isolation and so on in the power circuit or IF and LF circuits. It can't be used in an AC power circuit. When it is used as a filter capacitor in the DC power circuit, its anode (positive) should be connected with the positive end of the power voltage, and the cathode (negative) should be connected with the negative end of the power voltage. It can't be reversed, or it will be damaged. 2.10 What are the similarities and differences that cannot be ignored between polar and nonpolar capacitors in performance, principle and structure? Polar capacitance is a kind of electrolytic capacitance. It consists of two electrodes formed by the anode aluminum foil and the cathode electrolyte. A layer of aluminum oxide film produced on the anode aluminum foil is used as the dielectric of capacitance. As a result of this structure, it has polarity. When the capacitance is directly connected, the aluminum oxide film will remain stable due to the electrochemical reaction. When the reverse connection is made, the aluminum oxide layer will become thinner, which makes the capacitor easy to be broken down and damaged.  Therefore, we must pay attention to the polarity of the electrolytic capacitor in the circuit. Ordinary capacitors are nonpolar. We can also connect two anodes or cathodes of electrolytic capacitors in series to form nonpolar electrolytic capacitors. ①The same principleThey both store and release charges.The voltage on the plate shall not change suddenly. (voltage here refers to the electromotive force of charge accumulation) ②Different mediaWhat's the medium? It's the material between the two plates of the capacitor. Most of the polar capacitors use electrolytes as a dielectric material, and the capacity of the polar capacitor is larger than that of the same volume. In addition, the capacity of the same volume of polar capacitance produced by different electrolyte materials and processes will be different. The withstand voltage of the capacitor is closely related to the dielectric materials used. There are also many dielectric materials for non-polar capacitance, most of which are metal oxide film, polyester and so on. The reversibility or irreversibility of dielectric determines the use environment of polar and nonpolar capacitors. ③Different performance.Performance and maximization of requirements are the requirements for use. If a metal oxide film capacitor is used for filtering in the power supply part of the TV set, and the capacity and withstand voltage of the capacitor should meet the requirements of filtering, a power supply must be installed in the shell. For a filter, only the polar capacitance can be used, which is irreversible. The positive terminal must be connected to the high potential terminal and the negative terminal to the low potential terminal. Generally, when the electrolytic capacitance is more than 1 microfarad, it is used for coupling, decoupling, power filtering, etc. Most of the nonpolar capacitors are below 1 microfarad, which participates in resonance, coupling, frequency selection, current limiting, etc. Large capacity and high withstand voltage capacitors are usually used for reactive power compensation, motor phase-shifting and frequency conversion power supply phase-shifting. There are many kinds of nonpolar capacitors. ④Different capacityFor capacitors of the same volume, when the medium is different, the capacity is also different. ⑤Different structureWe can use capacitors of any shape without considering the tip discharge. The polar capacitance is usually round, and there are few polar capacitances of square type. There are many shapes of nonpolar capacitors, including tube type, deformed rectangle, sheet type, square type, circular type, combined square type and circular type, and of course there are intangible ones. Here intangible refers to distributed capacitance.The distributed capacitance in HF and IF devices should not be ignored. The function is the same. The main difference is their capacity. Due to the influence of material structure, the capacity of non-polar capacitance is relatively small, generally below 10uF, while the capacity of polar capacitance is usually large. When filtering the power supply, you have to use a polar capacitor of large capacity. Ⅲ SummaryOne of the basic principles of circuit design is to require the designer to fully understand and master the real components. The components used should be standard parts, general parts, and the most common models on the market (the better the versatility of components, the easier the procurement, the larger the supplier's output, and the lower the procurement cost). For the components used in the drawings, if the materials can only be obtained by customization, the cost is certainly not low. If you can't get the customized material, this design is wastepaper. In addition, large capacitance is suitable for filtering low-frequency signals and small capacitance for filtering high-frequency signals. However, decoupling is only one function of capacitance. Different kinds of capacitance have different characteristics and usages. This aspect has a lot to do with experience. It is impossible to achieve it quickly. It can only be accumulated through practice. Ⅳ FAQ1. Which capacitor gives a long-term service: ceramic capacitors or aluminum and tantalum electrolytic capacitors?Electrolytics have a limited lifetime, 10,000 hours at high temps.Tantalums are really good capacitors, until they short out, whenever they feel like it.Ceramics tend to live the longest. 2. Why is aluminum used in electrolytic capacitors?Aluminum has been found to be among ideal materials for electrolytic capacitors due to the following reasons—1) It easily forms a thin oxide layer with a high dielectric constant.2) This layer can be formed in a wide range of thicknesses to suit different applications.3) The aluminum oxide layer can be formed and can withstand high voltages exceeding 400 V. Other materials Tantalum/ Niobium can only take small voltages of below 25 V. 4) Aluminum can be made into foil/ plate / formed into shape. In yesteryears, it was common to use shapes of this metal mechanically formed into different shapes.5) These properties allow high capacitor values for low and high voltages in small size.6) Most amenable to convenient manufacturing processes like winding, punching, forming (oxidation).7) Most abundant material on earth, hence very cheap.There are hardly any other materials that have these properties. 3. What is the role of aluminum electrolytic capacitors?Aluminum electrolytic capacitors are polarized capacitors because of their anodization principle. They can only be operated with DC voltage applied with the correct polarity. Operating the capacitor with the wrong polarity or with AC voltage leads to a short circuit and can destroy the component. 4. What happens if the electrolytic capacitor backward?Electrolytic capacitors are polar by nature and have positive and negative terminals clearly marked. If the polarity is reversed while connecting, the dielectric in the form of an oxide layer is damaged. A heavy current flows, a large amount of heat is generated, and the capacitor is damaged. 5. How do you determine the polarity of the Aluminium electrolytic capacitor?If the case is insulated, you can try applying a small bias voltage (3-5V) to the capacitor in each direction (through a current-limiting resistor of 100K or so) and see which direction allows the least current; this will be the correct polarity of the capacitor. 6. What are aluminum electrolytic capacitors used for?Especially aluminum electrolytic capacitors are used in many applications as decoupling capacitors to filter or bypass undesired biased AC frequencies to the ground or for capacitive coupling of audio AC signals. Then the dielectric is used only for blocking DC. 7. How long do aluminum electrolytic capacitors last?Today's aluminum electrolytic capacitors have a longer shelf life, usually around 2 years, as compared to their predecessors. For aluminum electrolytic capacitors, the changes in ESR, capacitance, and leakage current are caused by the chemical reactions between the aluminum oxide film and the electrolyte. 8. How do you read an electrolytic aluminum capacitor?The value of the capacitor is denoted in picofarads for ceramic, film, and tantalum capacitors, but for aluminum electrolytic capacitors the value is denoted in microfarads. For small values the letter R is used to denote a decimal point, e.g. 0R5 is 0.5, 1R0 is 1.0 and 2R2 is 2.2, etc. 9. How are aluminum electrolytic capacitors made?Aluminum electrolytic capacitors are made by layering the electrolytic paper between the anode and cathode foils and then coiling the result. The process of preparing an electrode facing the etched anode foil surface is extremely difficult. Due to this process, the electrolyte essentially functions as the cathode. 10. What are aluminum capacitors used for?Aluminum electrolytic capacitors (electrolytic) are widely used in power supply applications requiring high capacitance in energy-dense, small-volume packages having very low equivalent series resistance (ESR). 

What is a capacitor? Capacitor, a electronic component to hold charges, represented by the letter C. It composes of two metal electrodes between a layer of insulating dielectric. When a voltage is applied between the two metal electrodes, the charge is stored on the electrode, so the capacitor is an energy storage electrical part. Any of two conductors that are insulated and close to each other form a capacitor. In addition, the parallel plate capacitor consists of the electrode plate and the dielectric of the capacitor.  Capacitor is one of the widely used electronic components in electronic equipment. It is widely used in stopping DC and alternating AC, coupling, bypass, filtering, tuning loop, energy conversion, control and so on. Capacitor is different from capacitance. The capacitance is the basic physical quantity, the symbol C, the unit is F (Farah).   A video introducing basic knowledge of capacitors Catalog   I. Capacitor characteristics II. Functions of capacitor in electrical circuits III. How to use capacitors? IV. Capacitor types V. Capacitor volume VI. Charge and discharge of a capacitor VII. Matters needing attention when using capacitors VIII. Common fault of capacitor and treatment method FAQ   I. Capacitor characteristics  - It has the ability of charge and discharge, preventing DC current from passing through, allowing AC current to pass through.  - During the charge and discharge process, the charge on the bipolar plate accumulates, that is, the voltage is set up, therefore, the voltage on the capacitor will not change abruptly. Charging: two plates with the same amount of dissimilar charge, each plate with the absolute value of the charge is called capacitor volume. Discharging: positive and negative charges at both ends of capacitors are neutralized through conductors. During discharge, there is a transient current on the wire. Capacitor charge  - The capacitive reactance of capacitors is inversely proportional to frequency and capacity. When analyzing the capacitance, the frequency and capacity of the contacting signal must be analyzed. Formula of parallel plate capacitor The dielectric constant of vacuum εr=1, k is a constant of hydrostatic power, s is the positive area of two plates, and d is the distance between two plates. Explanation: the electric field in the parallel plate capacitor is uniform electric field. II. Functions of capacitor in electrical circuits In DC circuits, the effect of a capacitor is equivalent to a open circuit. Capacitors are one of the most commonly used electronic components to store charge. Capacitors are used in electronic circuits as low-pass, high-pass and band filters. A filter is a circuit that allows current and voltage of a specified frequency and waveform to pass through. A capacitor's reactance is inversely proportional to frequency. By controlling or changing the reactance, you can control the frequency allowed through the circuit. Capacitors also play a significant role in high-speed switching logic circuits. Such circuits' voltage level, which should be steady, can change with current fluctuation, thereby introducing noise or error signals. Decoupling capacitors are built into circuits to stabilize the current, minimizing noise signals. The effect of capacitor links with the structure of itself. The simplest capacitors are made up of polar plates at both ends and insulating dielectric (including air) at the middle. After electrification, the plate is charged, forming a voltage (potential difference), but the entire capacitor is non-conductive because of the intermediate insulation. However, the condition is that the critical voltage (breakdown voltage) of the capacitor is not exceeded. We know that any substance is relatively insulated, and when the voltage at both ends of the material increases to a certain extent, the material can conduct electricity. We call this voltage a breakdown voltage. When the capacitor is broken down, it is not an insulator. However, in AC circuits, the direction of the current changes with time, that is, this change has functional relation. The charging and discharging process of capacitors is time-dependent, and at this time, a varying electric field is formed between the plates, and this electric field is a function of the change with time. In fact, the current passes between capacitors in the form of an electric field. III. How to use capacitors? As a relatively common electronic component, capacitors have a wide range of uses. The following content gives you a brief introduction to the 9 most common scenarios where capacitors are used: Stopping DC, bypass (decoupling), coupling, filtering, temperature compensation, timing, tuning, rectifier, and energy storage. 1.Stopping DC: the function is to prevent the passage of DC and allow the AC to pass through. DC blocking capacitor 2. Bypass (decoupling): it provides a low impedance path for some parallel components in AC circuits.       Signal input and output   3. Coupling: as a connection between two circuits, AC signals are allowed to pass and transmitted to the next stage of the circuit. Coupling capacitor circuit model Capacitor as coupling component The purpose of using capacitor as coupling part is to transmit the front stage signal to the next stage, and to separate the influence of the DC of the former stage on the latter stage, so that the circuit is simple to debug and its performance is stable. The amplification of AC signal without capacitor will not changed, but the work points at all levels need to be redesigned. Because of the influence of the front and back stages, to debug at working points is very difficult and can hardly be realized at multistage. 4. Filtering: this is very important for the circuit, the capacitor behind the CPU is having this function basically. Impedance formula(filtering circuit) That is, the larger the frequency f, the smaller the impedance Z of the capacitance. At low frequency, the capacitance C can pass smoothly because of the large impedance Z, and at high frequency, the capacitance C is very small because of the impedance Z, which is equivalent to shorting the high frequency noise to the GND. 5. Temperature compensation: it improves the stability of the circuit by compensating for the influence of other components on the temperature adaptability.   Temperature compensation Analysis: because the capacity of the timing capacitor determines the oscillation frequency of the horizontal oscillator, the capacity of the timing capacitor must very stable and does not change with the humidity in the environment. Therefore, the capacitors with positive and negative temperature coefficients are used for temperature complementation. When the operating temperature increases, the capacity of Cl is increasing, while the capacity of C2 is decreasing, and the total capacity of two capacitors is the sum of the two capacitors after parallel connection. Because one capacity is increasing and the other is decreasing, the total capacity is basically stable. Similarly, when the temperature decreases, the capacity of one capacitor decreases while the other increases, and the total capacity is basically unchanged, which stabilizes the oscillation frequency and realizes the purpose of temperature compensation. 6. Timing: the use of capacitors in conjunction with resistors to determine the time constant of the circuit. Capacitor and resistor(timing) Inputting signal from low to high, after buffer 1 then input RC circuit. The characteristics of capacitor charging make the B point signal not change immediately with the input signal, but there is a gradual process of increasing. When it becomes larger to a certain extent, the buffer 2 flips over, resulting in a delay jump from low to high at the output end. 7. Tuning: having systematic tuning to circuits which related to frequency, such as cell phones, radios, and televisions. System tune Because the resonant frequency of the oscillation circuit is a functional relation of lc. It is fond that the ratio of maximum to minimum resonant frequency varies with the square root of capacitance ratio. Here the capacitance ratio refers to the ratio of the capacitance at the minimum reverse bias voltage to the capacitance at the maximum reverse bias voltage. Therefore, the tuning characteristic curve (bias voltage and resonant frequency) is basically a parabola. 8. Rectifier: switch on or off a semi-closed conductor component at a predetermined time. Rectification Filtering wave form 9. Energy storage: storage of electrical energy for release when necessary. For example, camera flashlights, heating devices, etc. (some capacitors now store energy at levels close to lithium batteries; a capacitor can store electricity as one-day power for a mobile phone.   IV. Capacitor types According to the analysis and statistics, capacitors are divided into the following 10 categories: 1. According to the structure: solid capacitor, variable capacitor and fine-tuned capacitor. 2. Classified by electrolytes: organic dielectric capacitor, inorganic dielectric capacitor, electrolytic capacitor, electrothermal capacitor and air-spaced capacitor. 3.According to the usage: high-frequency bypass  capacitor, low-frequency bypass  capacitor, filtering capacitor, tuning capacitor, high-frequency coupling capacitor, low-frequency coupling capacitor, small capacitor. 4. According to the different materials: ceramic capacitor, polyester capacitor, electrolytic capacitor, tantalum capacitor, advanced polypropylene capacitor etc. 5. High frequency bypass: ceramic capacitor, mica capacitor, glass film capacitor, polyester capacitor, glass-glazed capacitor. 6. Low frequency bypass: paper capacitor, ceramic capacitor, aluminum electrolytic capacitor, polyester capacitor. 7. Filter: aluminum electrolytic capacitor, paper capacitor, composite paper capacitor, liquid tantalum capacitor. 8. Tuning: ceramic capacitors, mica capacitors, glass film capacitors, polystyrene capacitors. 9. Low coupling: paper capacitor, ceramic capacitor, aluminum electrolytic capacitor, polyester capacitor, solid tantalum capacitor. 10. Small capacitors: metallized paper capacitor, ceramic capacitor, aluminum electrolytic capacitor, polystyrene capacitor, solid tantalum capacitor, glass-glazed capacitor, metallized polyester capacitor, polypropylene capacitor, mica capacitor. V. Capacitor volume Since capacitors are a container for storing charges, there is a problem of capacity. In order to measure the capacity of capacitors to store charges, the capacity is determined. A capacitor must store a charge under the action of an applied voltage. The amount of charge stored in different capacitors under voltage may also different. According to the international standard, when the capacitor is subjected to a 1V DC voltage, the value is the charge that can store in the the capacitor (that is, the electric quantity per unit voltage), which is expressed by the letter C. The basic unit of capacitance is the Farah (F). At 1V DC voltage, if the capacitor stores the charge is 1 Coulomb, the capacitance is set at 1 farah, and Farah is represented by the symbol F, 1 F=1 Q/ V. In practical application, the capacitance of capacitors is often much smaller than that of 1F, and is often used in smaller units, such as mF, μF, nF, pF, etc. The relationship between them is as follows:   1F=1000mF1mF=1000μF1μF=1000nF1nF=1000pF1F=1000000μF1μF=1000000pF VI. Charge and discharge of a capacitor When the capacitor is connected to the power supply, under the action of the electric field force, the free electron connected with the positive electrode of the capacitor moves through the power supply to the plate connected to the negative electrode of the power supply. The positive electrode is positively charged because of the loss of the negative charge; the negative electrode is negatively charged because of gaining negative charge. The positive and negative plates have the same charge size and the opposite sign, so the charge moves in a fixed direction to form a current. Due to the repulsive effect of the same charge, the initial current is maximum, and then decreases gradually. During the process of charge movement, the charge stored on the electrode plate of the capacitor increases continuously. When the voltage Uc between two poles of capacitor is equal to the power-supply voltage U, the charge stop moving. The current I=0, switch closed, through the wire connection, the capacitor plate charge neutralized. When K is closed, on the one hand, the positive charge of the capacitor C can be neutralized on the negative electrode; on the other hand, the negative charge of the negative electrode can also be moved to the positive electrode. The charge gradually decreases, the apparent current decreases and the voltage decreases to zero. VII. Matters needing attention when using capacitors Because the two poles of the capacitor have the residual charge, it is necessary to release the charge at first, otherwise the electric shock will occur easily. When dealing with the faulty capacitor, the circuit breaker and the upper and lower disconnector of the capacitor set should be opened first, and if the fuse protection is adopted, the fuse tube should be removed first. At this time, although the capacitor set has discharged  itself, there will still be part of the residual charge, therefore, it is necessary to carry out manual discharge. When discharging, the grounding end of the ground wire and the grounding grid should be fixed first, then the capacitor should be discharged with the grounding rod several times until there is no spark and discharge sound, and finally the ground wire is fixed again. Meanwhile, it should also be noted that if the capacitor has internal breakage, fuse failure or poor lead contact, there may be residual charges between the two poles, which will not be released during automatic discharge or manual discharge. Therefore, the operation or maintenance personnel should wear insulating gloves before contacting the faulty capacitor, and use a short line to connect the two poles of the fault capacitor to make it discharge. In addition, the capacitor with series connection should be discharged separately. VIII. Common fault of capacitor and treatment method (1) When the capacitor explodes, the power should cut off immediately and extinguish the fire with sand and dry-firefighter. (2) When the capacitor fuses, it shall report to the dispatch and open the circuit breaker of the capacitor after obtaining the consent. When the power supply is cut off to discharge it, external checks are carried out, such as whether there are flashover marks on the outside of the casing, whether the casing is deformed, the oil leakage and the short circuit of the earthing device, etc., and the insulation resistance between the poles and the ground is measured. Check whether the capacitor set connection is complete, firm, lacking of phase phenomenon. If not found fault phenomenon, it can be replaced after the investment. If the insurance still melts after power transmission, the faulty capacitor should be withdrawn and the rest should be power on. If the circuit breaker tripped at the same time as the fuse, at this time, don’t connect power supply. After the above inspection has been completed, the insurance must be replaced. (3) The circuit breaker of the capacitor tripped and the shunt safety was not broken, the capacitor should be discharged for three minutes before checking the power cable of the circuit breaker current inductor and the outside of the capacitor. If no anomaly is found, it may be due to external fault bus voltage fluctuations. After inspection, it may be put on trial; if not, a comprehensive test of the protection should be carried out. Through the above inspection, the test, if still can not find the reason, it is necessary to act according to the system, the capacitor is gradually tested. No trial test shall be made until the cause has been found.   FAQ   1. What is a capacitor used for? A capacitor (originally known as a condenser) is a passive two-terminal electrical component used to store energy electrostatically in an electric field. The forms of practical capacitors vary widely, but all contain at least two electrical conductors (plates) separated by a dielectric (i.e., insulator).   2. What is capacitor and how it works? In a way, a capacitor is a little like a battery. Although they work in completely different ways, capacitors and batteries both store electrical energy. ... Inside the capacitor, the terminals connect to two metal plates separated by a non-conducting substance, or dielectric.   3. When should you use a capacitor? Power Supply Smoothing. This is the easiest and very widely used application of a capacitor. ... Timing. If you supply power to a capacitor through a resistor, it will take time to charge. ... Filtering. If you pass DC through a capacitor, it will charge and then block any further current from flowing.   4. What is capacitor and its types? The most common kinds of capacitors are: Ceramic capacitors have a ceramic dielectric. Film and paper capacitors are named for their dielectrics. Aluminum, tantalum and niobium electrolytic capacitors are named after the material used as the anode and the construction of the cathode (electrolyte).   5. Are capacitors AC or DC? When we connect a charged capacitor across a small load, it starts to supply the voltage (Stored energy) to that load until the capacitor fully discharges. Capacitor comes in different shapes and their value is measured in farad (F). Capacitors are used in both AC and DC systems (We will discuss it below).   6. What is the principle of capacitor? A capacitor is a device that is used to store charges in an electrical circuit. A capacitor works on the principle that the capacitance of a conductor increases appreciably when an earthed conductor is brought near it. Hence, a capacitor has two plates separated by a distance having equal and opposite charges.   7. Are capacitors dangerous? Capacitors may store hazardous energy even after the equipment has been de-energized, and may build up a dangerous residual charge without an external source. "Grounding" capacitors in series, for example, may transfer (rather than discharge) the stored energy.   8. What type of capacitor should I use? The general rule is always use a capacitor with a higher working voltage than the circuit it is used in. This is of particular importance in power supply circuits with high value electrolytic capacitors. The working voltage should always exceed the peak working voltage of the circuit by a minimum of 20%.   9. What is capacitor and its applications? Capacitor is a basic storage device to store electrical charges and release it as it is required by the circuit. Capacitors are widely used in electronic circuits to perform variety of tasks, such as smoothing, filtering, bypassing etc…. One type of capacitor may not be suitable for all applications.   10. Do capacitors change AC to DC? No, capacitor cannot convert AC to DC. Capacitor can add DC to AC so that zero reference of AC signal can be changed, in other words capacitor works as level shifter.   11. Can Capacitors store AC? Capacitors do not store AC voltage - it stores voltage. It's rated to handle 450 VAC; that means it can withstand an AC voltage being applied to it. In other words, the capacitor is non-polar (it has no positive or negative lead). Polar (or polarized) capacitors are best known as "Electrolytic" capacitors.   12. What is the difference between a capacitor and a battery? A battery is an electronic device that converts chemical energy into electrical energy to provide a static electrical charge for power. Whereas a capacitor is an electronic component that stores electrostatic energy in an electric field.   13. How much current can a capacitor handle? A 3.5V charger will charge the capacitor up to 3.5V only. You need a higher voltage DC source to charge the capacitor to higher potential. Remember, in your case, 100V is the maximum which capacitor can handle.   14. What happens when a capacitor fails? During a failure, half of the capacitor could fail open, which would result in overall capacitance being lost. Or half of the capacitor could fail short, which would result in the overall capacitance being halved.   15. Does type of capacitor matter? Yes, the type of capacitor can matter. Different types of capacitor have different properties. Some of the properties that vary between capacitor types: a. Polarised vs unpolarised b. Max voltage c. Equivalent Series Resistance (ESR) d. Lifetime (electrolytics are particularly bad in this case) e. Physical size (e.g. a 100,000 uF ceramic capacitor would be HUGE!) f. Tolerance of capacitance (again, electrolytics are bad here, often being +/- 20%

The solid-state capacitor is called a solid-state aluminum electrolytic capacitor. The biggest difference between it and ordinary capacitors (i.e. liquid aluminum electrolytic capacitors) lies in the use of different dielectric materials. The dielectric materials of liquid aluminum capacitors are electrolyte, while the dielectric materials of solid capacitors are electroconductive polymer materials.   Electronic Basics #14: Capacitors Catalog I. Solid State Capacitor Introduction II. Solid State Capacitor Advantages III. Solid State Capacitor Types IV. Advantages and Disadvantages of Solid Capacitors FAQ   I. Solid State Capacitor Introduction   In view of the many problems of liquid electrolytic capacitance, the solid aluminum electrolytic capacitor has emerged as the times require. Since the 1990s, solid conducting polymer material has been used as cathode instead of electrolyte for aluminum electrolytic capacitor, which has achieved great development. The conductivity of conductive polymer materials is usually 2 ~ 3 orders of magnitude higher than that of electrolytes.    The application of aluminum electrolytic capacitors can greatly reduce the ESR and improve the features of temperature frequency, what’s more, because of the good processability of polymer materials, it is easy to be packaged. All greatly promote the development of aluminum electrolytic capacitance.   On the market, there are two types of aluminum electrolytic capacitors: organic semiconductor aluminum electrolytic capacitors (OS-CON) and polymer conductor aluminum electrolytic capacitors (PC-AC) (PC-CON).    The structure of an organic semiconductor aluminum electrolytic capacitor is similar to that of a liquid aluminum electrolytic capacitor; both are packaged in straight-pin and vertical configurations.   The difference is the cathode material of solid aluminum polymer electrolytic capacitor using the organic semiconductor extract, which can effectively solve the tough problems of electrolyte evaporation, leakage, flammability, and so on. Also, a solid aluminum polymer patch capacitor is a unique structure formed by combining the characteristics of aluminum electrolytic capacitance and tantalum capacitance.   Like liquid aluminum electrolytic capacitors, solid aluminum polymers are mostly in the form of patches. The film of polymer electrode with high conductivity is deposited on alumina as cathode, carbon, and silver as an extraction electrode, which is similar to the structure of solid tantalum electrolytic capacitance.     II. Solid State Capacitor Advantages   （1）With high stability, the solid aluminum electrolytic capacitor can work stably in a high-temperature environment, and improve the performance of the motherboard directly. At the same time, it is suitable for power filters because of its stable impedance in a wide temperature range, provides a stable and abundant power supply effectively, especially in overclocking.    Solid-state capacitors can work at high temperatures and maintain various electrical properties. The capacitance changes less than 15% in the whole temperature range, which is obviously superior to the liquid electrolytic capacitance. Meanwhile, the capacitance of solid-state electrolytic capacitor is independent of its working voltage, so it can work stably in the environment of voltage fluctuation.   （2）The solid-state aluminum electrolytic capacitor has an extremely long service life (over 50 years). It longer than the liquid aluminum electrolytic capacitance. And it will not be broken down, nor need to worry about liquid electrolyte drying and leakage affecting the stability of the motherboard. Solid-state electrolytes do not expand or even burn as liquid electrolytes do at high temperatures. Even if the temperature of the capacitor exceeds its limit, it just melts, which does not cause the capacitor metal shell to burst, so it is very safe.    The working temperature has a direct effect on the life of electrolytic capacitance. Advantages of its electrolyte make a longer service life than liquid electrolytic capacitor under different temperature conditions.   （3）Low ESR(Equivalent Series Resistance) and high mA rms are important indexes of capacitance. The lower the ESR, the faster the charge and discharge speed of capacitance. It directly affects the decoupling performance of the microprocessor power supply circuit, which is more obvious in high-frequency circuits. Therefore, it can be viewed the biggest difference between solid-state electrolytic capacitance and liquid capacitance.   Solid aluminum electrolytic capacitance with the lower ESR and energy dissipation under high power operation conditions can fully absorb the high amplitude voltage between the power lines in the circuit and prevent its interference to the system. When the CPU changes from a low power state to a full load state, the transient (generally less than 5 milliseconds) power required for this CPU switch comes from the CPU power supply circuit, at this moment, the high peak current can be output instantly by the high-speed charge-discharge characteristic of the solid-state capacitor, which can guarantee sufficient power supply and ensure the CPU to work stably.     III. Solid State Capacitor Types     According to the medium, capacitors can be divided into inorganic dielectric capacitors, organic dielectric capacitors, and electrolytic capacitors three categories.   1. Inorganic dielectric capacitors: including familiar ceramic capacitors and mica capacitors, we will often see ceramic capacitors on the CPU. Ceramic capacitors have excellent comprehensive properties and can be used in GHz-class UHF devices, such as CPU/GPU, thus its price is also very expensive.   2.Organic dielectric capacitors: such as thin-film capacitors, which are often used in loudspeakers with their precision, high temperature, and high-pressure resistance.   3. Electrolytic capacitors: known as aluminum capacitors. The traditional method of classifying electrolytic capacitors is based on anode materials, such as aluminum, tantalum, or niobium. However, this method of judging capacitance performance based on the anode is out of date. At present, the key to determine the performance of electrolytic capacitance lies not in the anode, but in the electrolytic, cathode. According to the classification of cathode materials, electrolytic capacitors can be divided into electrolyte, manganese dioxide, TCNQ organic semiconductors, solid polymer conductors, and so on.      IV. Breif Analysis of Advantages and Disadvantages of Solid Capacitors   The dielectric of liquid electrolytic capacitors is liquid electrolyte: liquid particles are very active at high temperatures and have a low boiling point relative to the internal pressure of the capacitor, making it easily explosible. The solid-state capacitance is made of polymer dielectric: at high temperatures, the particle growth and behavior of solid particles are lower than that of liquid electrolytes, and its boiling point will reach 350 degrees Celsius, making it almost impossible to burst.    The ESR of solid-state capacitance in high-frequency operation is shown to be very weak, and the conductivity is very fine. It has the properties of lowering impedance and producing less heat, which is the most obvious between 100KHz and 10MHz.   Traditional electrolytic capacitance is easily influenced by the operating environment's temperature and humidity, and it is less stable at high and low temperatures. The ESR of the solid capacitance can be as low as 0.0040.005 ohms between minus 55 and 105 degrees Celsius, but the electrolytic capacitance varies with temperature.   In terms of capacitance values, liquid capacitance would be lower than the indicated capacitance value below 20 degrees Celsius, and the lower the temperature, the lower the capacitance value. At minus 20 degrees Celsius, capacitance decreases by around 13%, and at minus 55 degrees Celsius, capacitance decreases by 37%. Since solid capacitance decreases by less than 5% at minus 55 degrees, solid state capacitors are guaranteed not to be harmed by lower temperatures. The low-frequency response of solid-state capacitance is not as good as electrolytic capacitance.     In other words, a motherboard with all-solid-state capacitance is not the most reasonable. Whether solid or electrolytic capacitors, their main function is to filter clutter, so long as the capacity and quality of capacitance can reach certain requirements, it can also ensure a stable operation. Solid-state capacitors at 105C have the same lifetime as electrolytic capacitors for 2000 hours.    When the temperature drops, their lives increase, but the solid-state capacitors increase even more. In general, the operational temperature of the capacitor is 70 degrees or less. In addition, the service life of solid-state capacitance can last 23 years, almost six times than the electrolytic capacitance. Compared with electrolytic capacitors, the capacity of electrolytic capacitors is much larger than that of solid capacitors at the same volume and voltage.     At present, solid capacitors are mostly used in the CPU power supply of computer motherboard, but the capacity redundancy is very little, it is necessary to improve the switching frequency of the part of the CPU power supply. Both solid and electrolytic capacitors will have the problem of capacity attenuation in the process of use. However, although the capacity of the circuit board with solid-state capacitance fluctuates slightly, the power supply will appear ripples, which will cause the CPU to work improperly.     Therefore, the lifetime of the solid-state capacitor is very high theoretically, but not in practice. Maintenance when using solid-state capacitor computer board: the power supply part of the CPU is often connected with multiple capacitors, so the solid-state capacitance will not have deformation, explosive slurry, leakage, etc. There is no way to determine which one is out of order basically. Therefore, in maintenance, one of them is often removed (no matter good or bad), and a large-capacity capacitor can be replaced (often with electrolytic capacitance). This method can usually solve the problem quickly.      In theory, the lifetime of the solid-state capacitor is very long, but there will still be a lot of faults in the process of practical use. At present, it seems that most motherboards with overclocking as the selling point put forward by many manufacturers will use solid-state capacitors. But it is not the capacitance that determines the performance of the CPU. The design of the circuit, the development of BIOS, the quality of the CPU itself, and the heat dissipation measures may determine the success or failure of the CPU.   FAQ   1. What is a solid state capacitor? The full name of a solid capacitor is a conductive polymer aluminum electrolytic capacitor, also called a polymer aluminum capacitor. It is currently the highest level of capacitor products. The dielectric material of the solid capacitor is a functional conductive polymer, which can greatly improve the product.   2. Are Solid Capacitors better? Solid capacitors have a higher tolerance not only for higher temperatures, but they also perform better with higher frequencies and higher current than electrolytic capacitors. ... Because there is less impedance at higher frequencies, solid capacitors are more stable and generate less heat than electrolytic capacitors.   3. How do you read a solid state capacitor? If you have a capacitor that has nothing other than a three-digit number printed on it, the third digit represents the number of zeros to add to the end of the first two digits. The resulting number is the capacitance in pF. For example, 101 represents 100 pF: the digits 10 followed by one additional zero.   4. What do you need to know about solid state capacitors? Solid-state capacitors have already gone down the altar. Many common electronic and digital products use these products in large quantities. The solid-state capacitors are similar to the common aluminum electrolytic capacitors, some are replaceable, and there is a solid capacitor, sheet, for Replace the common tantalum capacitor.   5. Which is the best electrolytic capacitor for motherboard? Solid aluminum electrolytic capacitors can directly improve the performance of the motherboard. At the same time, it is suitable for power supply filtering due to its stable impedance over a wide temperature range. It can effectively provide a stable and abundant power supply, which is especially important in overclocking.   6. How do you read a solid state capacitor? If you have a capacitor that has nothing other than a three-digit number printed on it, the third digit represents the number of zeros to add to the end of the first two digits. The resulting number is the capacitance in pF. For example, 101 represents 100 pF: the digits 10 followed by one additional zero.   7. What is the average lifespan of a capacitor? Design lifetime at rated temperature. Manufacturers of electrolytic capacitors specify the design lifetime at the maximum rated ambient temperature, usually 105°C. This design lifetime can vary from as little as 1,000 hours to 10,000 hours or more.   8. What metals are capacitors made of? There are three different anode metals in use for electrolytic capacitors: Aluminum electrolytic capacitors use a high-purity etched aluminium foil with aluminium oxide as dielectric. Tantalum electrolytic capacitors use a sintered pellet (“slug”) of high-purity tantalum powder with tantalum pentoxide as dielectric.   9. When should you use a capacitor? Capacitors are widely used in electronic circuits for blocking direct current while allowing alternating current to pass. In analog filter networks, they smooth the output of power supplies.   10. How do I choose the right size capacitor? You mainly need to look at 2 values: the voltage and the capacity -both are written on most capacitors-. For example, if you are going to charge a capacitor with 24V, you need to make sure your capacitor will support that voltage; so you'll need a capacitor for at least 25V (plus error margin).       You May Also Like Operational Amplifier(OP Amp) Tutorial Instructions of Common problems in the Application of Inverter About Operational Amplifier LM358: 24 Classical Circuits DIY Community:  DIY Capacitor Flux Capacitor - Back TO The Future

Maxim Integrated is a company specializing in semiconductor interface, digital signal processor, analog signal chain, communication IC, power supply and battery management, etc. In the past twenty years, Maxim has developed ICs with high reliability, working in the extended temperature range for industrial applications. Now, they also offer products with current and voltage protection, reducing the devices' demand for space and power consumption with excellent performance indicators. CatalogsI MAX7409 / MAX741O / MAX7413 / MAX7414II MAX847 / MAX769III MAXl674 / MAXl675 / MAXl676IV MAX3875V MAX2105VI MAX3690VII MAX4539 / MAX4540VIII MAX7400 / MAX7403IX MAXl710X MAX668 / MAX669XI MAX254BXIII MAX2663 / MAX2671 / MAX2673Intro Integrated circuits (ICs) are a keystone of modern electronics, in this article we will disguss some kinds of ICs in Maxim Integrated. They are the heart and brains of most circuits. They are the ubiquitous little black "chips" you find on just about every circuit board. Unless you’re some kind of crazy, analog electronics wizard, you're likely to have at least one IC in every electronics project you build, so it's important to understand them, inside and out.An IC is a collection of electronic components ——resistors, transistors, capacitors, etc. ——all stuffed into a tiny chip, and connected together to achieve a common goal. They come in all sorts of flavors: single-circuit logic gates, op amps, 555 timers, voltage regulators, motor controllers, microcontrollers, microprocessors, FPGAs…the list just goes on-and-on.Embedded computing is based on microcontroller design and provides fixed function operation control. Embedded computing originated from industrial control applications, and has been widely used in consumer electronics, medical treatment, and even communications. Maxim provides real-time clock, security authentication, interface IC and sensor solutions for these markets,which makes it an important supplier in the industry.  What is IC chip and how does an IC work I Space and power saving 5th order filter IC---MAX7409/MAX741O/MAX7413/MAX7414New 5th order Bessel, Butterworth Switched-Capacitor Low Pass Filters series products, uMAX-8 pins and DIP package. MAXIM's proprietary uMAX package, which is 80% smaller than the 8-pins DIP package, makes it the industry's smallest 5-order switched capacitor filter. MAX7409/MAX7410 works at +5V, MAX7413/MAX7414 works at +3V and both devices draw only 1.2mA of supply current. Low price, small size and low power consumption make this kind of filter extremely suitable for price sensitive portable devices requiring DAX post-filtering or anti-aliasing applications.The MAX7409/MAX7413 Bessel filters have the characteristics of low overshoot, fast establishment and linear phase response, and the MAX7410/MAX7414 Butterworth filters have the flatest band-pass response. The four kinds of chips are all fixed frequency response, and the design tasks of filter is simplified to selecting clock frequency.The angular frequency can be tuned from 1Hz to 15 kHz by the clock at a rate of 100 times the clock/rotation angle. Two modes of clock operation, one is a self-contained clock of an external capacitor, another is an external clock which could strictly control the cut-off frequency. They have a very low output misalignment (±4 mV) and can be further regulated via an offset adjustment pin. Figure 1. Typical application circuit of MAX7409/MAX741O/MAX7413/MAX7414 II Power management ICs for communication equipment---MAX847/MAX769The MAX847/MAX769 DC-DC converter produced by MAXIM Company of USA has the characteristics of low voltage operation, high conversion efficiency and synchronous rectification. It is suitable for the low power digital radio communication system with 1 to 3 batteries, such as two-way paging, GPS receiver and so on, ensuring the cut-in voltage is as low as 0.87V and the quiescent current is 37 μA (the outage current is 2 μA).The built-in synchronous rectifier eliminates the external Schottky diode, meanwhile the conversion efficiency is increased to 90% , and for MAX847, an output current exceeding 50mA may be provided when power is supplied with a single battery. When two batteries are supplied, the MAX769 with function of boost/buck conversion could provide an output current over 90mA. Both chips can digitally adjust the output voltage through a serial interface compatible with SPI, which ranges from 1.8 V to 4.9 V whit an adjustable interval of 100 mV. The no-load current is only 13 μA.The MAX769 is similar to the MAX847 except that it contains a buck/boost DC-DC converter (for 2-cell or 3-cell inputs) rather than a boost-only converter (for 1-cell inputs). Both MAX847 and MAX769 include a multichannel ADC for battery monitoring. Three low noise Linear Regulator outputs for various uses (3V analog, 2.85V logic, and 1V receiver.  Both chips are 28-pin QSOP packaged. Figure 2. Typical application circuit of MAX847 Figure 3. Typical application circuit of MAX769 III Compact and efficient DC-DC converter IC with very low power supply current---MAXl674/MAXl675/MAXl676The MAX1674/MAX1675/MAX1676 DC-DC converter chip can provide up to 94% conversion efficiency. They available in small 8 or 10-pin uMAX package, and the static current is only 16 μA. The built-in synchronous rectifier not only improves efficiency but also eliminates the using of  external Schottky diodes, resulting in smaller dimensions and lower costs.The MAX1674 has a current-limiting of 1A, and the MAX1675 has a current-limiting of 0.5A, allowing the use of very small inductors. The MAX1676 has an optional current-limiting and minimizes the EMI due to an elimination of inductive oscillations. All chips have built-in N channel MOSFET with 0.3Ω and with a pin-selectable output voltage of 3.3V or 5V. The output voltage can also be adjusted in the range of 2 V to 5.5 V using the divider resistance. The input voltage ranges from 0.7 V to VOUT and the cut-in voltage can be as low as 1.1 V. Other features include: efficiency up to 94% when the output current is 200mA, built-in low voltage detection and 0.1 μA shutdown mode. IV Clock recovery and data retiming IC---MAX3875MAX3875 is a compact, low power clock recovery and data retiming chip for 2.488GbpsSDH／SONET systems. The fully integrated PLL can extract the synchronous clock from the serial NRZ input data which is retimed by the recovery clock. The clock and data output of the chip are compatible with the differential PECL and the additional 2.488Gbps serial input is used for loopback test of the system. It can also provide unlock monitoring signal of a TTL level.MAX3875 can be used as regenerator or terminal receiver in 0C-48／STM-16 transmission system. Insert jitter characteristics are higher than any SONET/SDH specification. The single supply is from 3.3V to 5V and when power is 3.3V, the power loss is less than 400mW in the full temperature range from -40 ℃ to 85 ℃.MAX3875 is available in 32-pin TQFP package.Figure 4. Typical application circuit of MAX3875 V Digital DBS direct-conversion tuner IC---MAX2105It is designed for the application of Direct Broadcast Satellite (DBS) TV set-top box. Compared with the structure based on intermediate frequency, the cost of the system is greatly reduced because of the use of direct frequency conversion structure. MAX2105 is supplied by a single power supply of 5V and the input signal frequency ranges from 950MHz to 2150MHz, tuned directly from L band to baseband by broadband I/Q down converter.The MAX2105 internal circuit includes a low noise amplifier with AGC, two down conversion mixers, an oscillating buffer with a 90° orthogonal generator, a prescaler and a baseband amplifier. The range of AGC gain adjustment is 41 dB, and the minimum power of input signal is -60 dB. Since the range of AGC gain adjustment is reduced, MAX2105 can use high gain external LNAs to obtain better noise coefficient, and can also provide a automatic baseband drift correction.MAX2105 is available in 28-pin SO package.Figure 5. Typical application circuit of MAX2105 VI SDH/SONET 8:1 serializer with clock synthesis and TTL inputs---MAX3690The MAX3690 serializer is powered by 3.3V only with a 200mW power consumption. Ideal for converting 8-bit-wide, 77Mbps parallel data to 622Mbps serial data in SDH / SONET system. Other applications include Add/Drop Multiplexers, Digital Cross-Connects.The clock and data input of MAX3690 is TTL logic level, serial data output is 3.3V PECL logic level. A fully integrated PLL synthesizes an internal 622Mbps serial clock from a low-speed crystal reference clock (77.76MHz, 51.84MHz, or 38.88MHz). An unlocked output of a TLL level can be used to indicate whether the PLL is working properly.MSX3690 is available in 32-pin TQFP packages.Figure 6. Functional diagram of MAX3690 VII Single 8-channel and dual-4 channel multiplexer ICs with precision resistance networks---MAX4539/MAX4540The single-8 channel MAX4539 and the dual-4 channel MAX4540 are a kind of multiway switch with calibration function (calibrating multiplexer), which is suitable for system self-testing and precision type MAX4540. Their built-in precision resistive partial voltage networks can provide accurate reference voltage of V+／2、5／8(V+ -V-)、15VREF/4096 and 4081VREF/4096 (Where VREF is external reference voltage).The MAX4539/MAX4540 have enable inputs and address latching. When power supply working at 5V or ±5V, the digital input has a 0.8V/2.4V logic threshold that guarantees compatibility with TTL/CMOS.The MAX4539/MAX4540 are available in small 20-pin DlP, S0, and SSOP packages, both of which can operate in a single supply of +2.7V to 12V or a duplicate supply of ±2.7V to ±6V. The on resistance (maximum 100 Ω) of the same device matches within 12Ω, and Each switch can handle Rail-to-Rail analog signals.The off leakage current is 1nA at TA = +25°C and 10nA at TA = +85°C.Functional diagram of MAX4539Figure 8. Functional diagram of MAX4540 VIII 8th-Order, lowpass, elliptic, switched-capacitor filters---MAX7400／MAX7403MAX7400/MAX7403 is a newly developed 8th-order, lowpass, elliptic, switched-capacitor filters by MAXIM Company of USA. The cut-off frequency ranges from 1Hz to 10kHz, and only draw 2mA of supply current. With a single power supply of 5 V, it is ideal for low power anti-aliasing and post-filtering of D/A converters. They feature a shutdown mode that reduces the supply current to 0.2μA.MAX7400 devices provide a sharp roll-off with a 1.5 transition ratio and 80 dB of stop-band rejection, while the MAX7403 devices provide a sharper roll-off of 1.2 transition ratio and 58 dB of stop-band rejection. For the both filters, the low output offset of ±4 mV can be adjusted via an offset adjustment pin.The internal switching operation of the filter can be controlled by an internal clock of an external capacitor or an external control to obtain a more accurate angular frequency. The fixed frequency response greatly simplifies the design, which only needs to set the clock frequency according to the desired angular frequency. MAX7400 and MAX7403 filters are available in 8-pin SOIC and plastic DIP packages.Figure 9. Typical application circuit of MAX7400/MAX7403 IX High-speed, digitally adjusted step-down controllers fornotebook CPUs---MAXl710The MAX1710/MAX1711 step-down controllers are intended for core CPU DC-DC converters in notebook computers. They feature a triple-threat combination of ultra-fast transient response, high DC accuracy, and high efficiency needed for leading-edge CPU core power supplies. Maxim's proprietary Quick-PWMTM quick-response, constant-on-time PWM control scheme handles wide input/output voltage ratios with ease and provides 100ns "instant-on" response to load transients while maintaining a relatively constant switching frequency.High DC precision is ensured by a 2-wire remote-sensing scheme that compensates for voltage drops in both the ground bus and supply rail. An on-board, digital-to-analog converter (DAC) sets the output voltage in compliance with Mobile Pentium Ⅱ CPU specifications. The MAX1710 achieves high efficiency at a reduced cost by eliminating the current-sense resistor found in traditional current-mode PWMs. Efficiency is further enhanced by an ability to drive very large synchronous-rectifier MOSFETs.Single-stage buck conversion allows these devices to directly step down high-voltage batteries for the highest possible efficiency. Alternatively, 2-stage conversion (stepping down the +5V system supply instead of the battery) at a higher switching frequency allows the minimum possible physical size. MAXl710 is available in Small 24-Pin QSOP Package.Figure 10. Typical application circuit of MAX7400/MAX1710 X Boosting DC-DC controllers with power levels of 20W---MAX668/MAX669The MAX668/MAX669 constant-frequency, pulse-width modulating (PWM), current-mode DC-DC controllers are designed for a wide range of DC-DC conversion applications including step-up, SEPIC, flyback, and isolated-output configurations. Power levels of 20W or more can be controlled with conversion efficiencies of over 90%. The 1.8V to 28V input voltage range supports a wide range of battery and AC-powered inputs. An advanced BiCMOS design features low operating current (220µA), adjustable operating frequency (100kHz to 500kHz), soft-start, and a SYNC input allowing the MAX668/MAX669 oscillator to be locked to an external clock.DC-DC conversion efficiency is optimized with a low 100mV current-sense voltage as well as with Maxim's proprietary Idle ModeTM control scheme. The controller operates in PWM mode at medium and heavy loads for lowest noise and optimum efficiency, then pulses only as needed (with reduced inductor current) to reduce operating current and maximize efficiency under light loads. A logic-level shutdown input is also included, reducing supply current to 3.5µA.The MAX669, optimized for low input voltages with a guaranteed start-up voltage of 1.8V, requires boot-strapped operation (IC powered from boosted output). It supports output voltages up to 28V. The MAX668 operates with inputs as low as 3V and can be connected in either a bootstrapped or non-bootstrapped (IC powered from input supply or other source) configuration. When not bootstrapped, it has no restriction on output voltage. Both ICs are available in an extremely compact 10-pin µMAX packages.Figure 11. Typical application circuit of MAX669Figure 12. Functional diagram of MAX668/MAX669 XI Low cost and small size RS-232 transceiver---MAX254BMAX254B is a complete electrically isolated RS-232 interface developed by MAXIM Company in USA. It is suitable for the system with demanding cost and size. It is mainly aimed at equipment in which noise, high transient voltage and highland potential damage or communication interference maybe occur.  XII High-performance laser driver---MAX3867The MAX3867 is a complete, single +3.3V laser driver for SDH/SONET applications up to 2.5Gbps. The device accepts differential PECL data and clock inputs and provides bias and modulation currents for driving a laser. The synchronizing input latch can be bypassed if a clock signal is not available.An automatic power control (APC) feedback loop is incorporated to maintain a constant average optical power over temperature and lifetime. The wide modulation current range of 5mA to 60mA and bias current of 1mA to 100mA are easy to program, making this product ideal for use in various SDH/SONET applications.The MAX3867 also provides enable control, a programmable slow-start circuit to set the laser turn-on delay, and a failure-monitor output to indicate when the APC loop is unable to maintain the average optical power. The MAX3867 is available in a small 48-pin TQFP package as well as dice.Figure 13. Functional diagram of MAX3867 XIII High linearity upconverters---MAX2663／MAX2671／MAX2673The MAX2663/MAX2671/MAX2673 miniature, low-cost, low-noise upconverters are designed for low-voltage operation and are ideal for use in portable consumer equipment. Signals at the IF input port are mixed with signals at the local oscillator (LO) port using a double-balanced mixer. These upconverters operate with IF input frequencies between 40MHz and 500MHz, and upconvert to output frequencies as high as 2.5GHz.These upconverters offer a wide range of supply currents and output intercept levels to optimize system performance. Supply current is essentially constant over the specified supply voltage range. Additionally, when the devices are in a typical configuration with VSHDN-bar=0, a shutdown mode reduces the supply current to less than 1μA.The MAX2663/MAX2671 family of upconverters are offered in the space-saving 6-pin SOT23 package. For applications requiring balanced IF ports, choose the MAX2673 upconverters in the 8-pin μMAX package.Figure 14. Typical application circuit of MAX2663／MAX2671／MAX2673   

Warm hints: The word in this article is about 2500 and  reading time is about 12 minutes. Summary In the power system, in addition to the traditional harmonic sources, such as electric arc furnace and frequency converter, the nonlinear loads such as new energy access and charging pile may produce a lot of harmonics. In order to prevent harmonic from further affecting the power grid, accurate monitoring and timely treatment of harmonic level in power grid is a necessary step. The correct measurement of harmonic content in power grid is the basis of monitoring and governance. This paper mainly introduces some basic  knowledge about capacitor voltage transformer including the capacitor voltage transformer symbol; testing; working principle; capacitive voltage transformer VS inductive voltage transformer and etc. Article core capacitor voltage transformer Abbreviation CVT English name capacitor voltage transformer Category Power Subject Power engineer compose Capacitive voltage divider and medium voltage transformer Field Energy         Catalogs I. What is Capacitor Voltage Transformer( CVT)3.1 Insulation Resistance Measurement1.1 The Composition of CVT3.2 Capacitance Measurement1.2 CTV Judgment of Common Anomalies3.3 Pressure Swing Ratio Test1.3 CVT Equivalent Circuit Model3.4 Polar MeasurementII.Terminal Sign of Capacitive Voltage TransformerIV.Working Principle of Capacitive Voltage Transformer （CVT)III.Capacitor Voltage Transformer TestingV.Capacitive Voltage Transformer VS Inductive Voltage TransformerⅥ. FAQ  Introduction I. What is Capacitor Voltage Transformer( CVT) 1.1 The composition of CVT 一、The capacitive voltage transformer is mainly composed of a capacitor voltage divider and a medium voltage transformer. The capacitor divider is made up of porcelain bushing and series capacitors installed in it. The porcelain bushing is filled with insulating oil that keeps 0.1MPa positive pressure, and steel bellows are used to balance different environments to maintain oil pressure. The capacitor divider can be used as a coupling capacitor to connect the carrier device. The medium voltage transformer is composed of a transformer, a compensating reactor, a lightning arrester and a damping device installed in a sealed tank, and the space on the top of the tank is filled with nitrogen. The primary windings are divided into main windings and fine tuning windings, and a low loss reactor is connected in series between one side and one winding. Due to the capacitance and the inherent nonlinear impedance of the capacitor voltage transformer sometimes cause Ferroresonance in capacitor voltage transformer, thus suppressing resonant damping device, damping device is composed of a resistor and reactor, connected across the two windings, normally the damping device has very high impedance, when iron magnetic resonance caused by overvoltage in medium voltage transformer affected before the reactor is saturated only resistive load, the oscillation energy will soon be reduced. 1.2 CTV Judgment of common anomalies (1)The secondary voltage fluctuation. The two connection is loose, the distributor is not grounded or the carrier coil is not connected. If the damper is a fast saturable reactor, it may be improper parameter matching. (2)The Secondary voltage is low. Its connection is bad and the electromagnetic unit failure or the capacitor unit C2 is damaged. (3)The secondary voltage is high.The capacitance unit C1 is damaged and the ground end of the partial voltage capacitor is ungrounded. (4)The oil level of the electromagnetic unit is too high. The next capacitance unit is leaking oil or electromagnetic unit into the water. (5)There is a different sound in the transportation. Bolt loosening of reactor or medium pressure rheostat in electromagnetic unit. 1.3 CVT equivalent circuit model Under the condition of steady state, the whole CVT equivalent circuit can be regarded as a linear system, which compensates the stray capacitance of reactor C. The influence of the primary stray capacitance C: of the intermediate transformer at the high frequency can not be ignored. CVT intermediate transformer core can be regarded as linear segments in the magnetization curve, ignoring the core magnetizing inductance, one or two intermediate transformer side leakage resistance reduction to compensation reactor.   II.Terminal sign of capacitive voltage transformer · A single phase transformer with a two - time winding   It represents a single-phase transformer with two times winding. A represents the primary winding terminal of capacitive voltage transformer, and N represents the primary winding grounding terminal of voltage transformer. A represents the two winding terminal terminal of a capacitive voltage transformer, and N represents the first winding grounding terminal of the voltage transformer. · Single phase transformer with two two times windings   It represents a single-phase transformer with two two times windings, A represents the primary winding terminals of capacitive voltage transformers, and N represents the primary winding grounding terminals of voltage transformers. 1A and 2A represent the two winding terminals of the capacitive voltage transformer, and 1n and 2n represent the primary winding grounding terminals of the voltage transformer. · A single phase transformer with two two windings with a tap A single phase transformer with two taps and two winding is represented. A represents the primary winding terminal of capacitive voltage transformer, and N represents the primary winding grounding terminal of voltage transformer. 1A1, 1A2, 2a and 2A2 respectively represent the two winding terminals of the capacitive voltage transformer, and 1n and 2n represent the primary winding grounding terminals of the voltage transformer. · A single phase transformer with a residual voltage winding and two two times windings   It represents a single-phase transformer with a residual voltage winding and two two winding. The A represents the primary winding terminal of capacitive voltage transformer, and N represents the primary winding grounding terminal of voltage transformer. 1A1, 1A2, 2a and 2A2 respectively represent the two winding terminals of the capacitive voltage transformer, and 1n and 2n represent the primary winding grounding terminals of the voltage transformer. Da and DN represent the residual voltage terminal.   Detail III. Capacitor Voltage Transformer Testing 3.1 Insulation resistance measurement The insulation resistance should be measured by the main capacitor, the partial voltage capacitor and the one or two winding insulation resistance of the intermediate transformer. 3.2 Capacitance Measurement The purpose of the test is to determine whether the capacitance of the voltage divider has a change, and the capacitor is insulated without water and dampness.   3.3 Pressure swing ratio test The test transformer exerts high voltage as far as possible. Due to the rise effect in the test, the high voltage voltage must be measured at the high voltage end. The voltage transformer used must be level 0.1 or above to ensure the accuracy of the test results. After the voltage is applied at the high voltage side, the voltage of the low voltage side is measured in turn on the two side and in the auxiliary side, and the voltage ratio is compared with the pressure ratio of the nameplate. 3.4 Polar measurement The purpose of polar measurement is to check the mark of the nameplate. Test method: using DC method, CAR instantaneous addition of 1.5V battery power "+", "-" with "N", respectively, with a multimeter or mA DC or mV meter, pay attention to the polarity put right, A1, A0 "+" X1, XD "-" pointer in the power supply to the deflection of the "+" direction; open to "-" deflection. The test of polarity and pressure variable ratio of windings is usually done in hand over and after overhaul.   IV. Working Principle of Capacitive Voltage Transformer （CVT) There is a video about CVT:   This vidoe explained How Capacitor Voltage Transformer CVT works.Capacitor potential transformer concept is explained.What is high voltage measurement using capacitor type voltage transformer is explained. How to measure high voltage? Educational tutorial on electrical engineering 126 by G K Agrawal. The basic part of the capacitive voltage transformer is the capacitor voltage divider, and it also includes the electromagnetic parts such as the intermediate transformer, the compensating reactor, the damper and so on. Its principle connection is shown in the following picture,the picture shows capacitor voltage transformer wiring diagram capacitance divider is composed of main capacitor C1 and voltage divider capacitor C2 series. Without considering the electromagnetic part, the voltage is divided by capacitance. The voltage on C2 is the following formula: K is the partial voltage ratio. When the two ends of the C2 are connected to the two load, due to C1, C2 The basic part of the capacitive voltage transformer is the capacitor voltage divider, and it also includes the electromagnetic parts such as the intermediate transformer, the compensating reactor, the damper and so on. Its principle connection is given below.   The capacitor voltage divider is composed of the main capacitor C1 and the partial voltage capacitor C2 in series, without considering the electromagnetic part, then the voltage is divided according to the capacitance inverse ratio, and the voltage on the C2 is:   In this formula,K is the ratio of partial pressure When the two ends of C2 are connected to two loads, the larger capacitance internal impedance is due to the existence of C1 and C2, which makes UC2 smaller than the capacitance partial voltage. The larger the load current is, the greater the error is. In order to reduce the capacitance internal impedance, a compensatory reactor L can be connected in series, and the UC2 is not related to the load as much as possible. In fact, because the capacitor has loss, the reactor also has resistance, so that the internal impedance can not be zero, so when the load changes, there will always be error. In order to further reduce the effect of load current, the measuring instrument is connected to the divider after the intermediate transformer TV is boosted. When the two side transformer short circuit occurs, the resistance in the circuit and the total reactance reactor L after compensation are very small, several times the short-circuit current may reach the rated current, will produce a very high voltage resonance in L and C2, in order to prevent overvoltage caused by the breakdown of insulation in capacitor C2 parallel at both ends of the discharge gap F1. Capacitor voltage transformer with capacitance and nonlinear inductance (e.g. TV magnetizing inductance etc.), when the transformer side suddenly close or receive two side and eliminate the impact of sudden short circuit, overvoltage in the transient process may cause nonlinear inductor saturation, which excite ferroresonance overvoltage, such as harmonic 1/3 resonant.  Because the resistance is very small, the resonance will last for a long time, which will cause damage to voltage transformers, instruments and relays, and may lead to incorrect operation of the protective devices. Therefore, the damping resistance RD or damper is often installed on the two side of the capacitive voltage transformer to consume the resonant energy as soon as possible to suppress the ferroresonance. For a common capacitive voltage transformer, a resonant damper is used. It is the capacitance and the inductor in parallel and then added to the damping resistance. In UHV power grid, a capacitive voltage transformer often uses a fast saturation type damper, which is composed of a fast saturation reactance and a damping resistor.     Analysis V. Capacitive Voltage Transformer vs Inductive Voltage Transformer Inductive Voltage Transformers (IVT), are used for voltage metering and protection in high voltage network systems. They transform the high voltage into low voltage adequate to be processed in measuring and protection instruments secondary equipment, such as relays and recorders). A Voltage Transformer (VT) isolates the measuring instruments from the high voltage of the monitored circuit. VTs are commonly used for metering and protection in the electrical power industry. It’s a standard transformer available in the market for step-up or step-down voltages. The advantage is it can be used for high load current and provides isolation.   However,as we mentioned in the above,capacitor voltage transformer is a specialized circuit whose purpose is to convert a high voltage AC signal to lower voltage, usually used with very high input voltages, and a large ratio between input and output voltage. It's usually only used in cases where you're trying to extract a very small amount of power from a high-power circuit, usually for monitoring the high-power circuit. Its advatage is economical but there is no galvanic isolation.   Ⅵ. FAQ 1. What is the function of capacitor voltage transformer?A capacitor voltage transformer (CVT), also known as capacitor-coupled voltage transformer (CCVT), is a transformer used in power systems to step down extra high voltage signals and provide a low voltage signal, for metering or operating a protective relay.   2. Why is CVT used?One of the advantages of a CVT is its ability to continuously change its gear ratio. This means that no matter what the engine speed it, it is always performing at its peak efficiency. CVTs often offer better fuel economy as a result, especially when driving in the city. ... This is because the transmission never shifts.   3. What do you understand CVT and CCVT?Capacitor Voltage Transformer (CVT) or Capacitor Coupled Voltage Transformer (CCVT) is a switchgear device used to convert high transmission class voltage into easily measurable values, which are used for metering, protection, and control of high voltage systems.   4. Why are capacitors used in transformers?At too high common mode frequencies, the inevitable capacitive coupling in the transformer will cause some of the common mode signal on the input to show up as signal on the output. The capacitor provides a more serious connection to ground for AC, while the resistor only a weak connection for DC to avoid ground loops.   5. Why is CVT hated?Because CVTs tend to lock an engine into a specific RPM, generally a high and noisy RPM, making the whole experience very hard on the ears. Also, CVTs are generally tuned for fuel economy rather than performance, and most of the magazines out there are wannabe racecar drivers.   6. What is the function of capacitor voltage transformer?A capacitor voltage transformer (CVT), also known as capacitor-coupled voltage transformer (CCVT), is a transformer used in power systems to step down extra high voltage signals and provide a low voltage signal, for metering or operating a protective relay.

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