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| Common sense electrolytic capacitor |
| Date of issue：2018-01-09 20:50:40 see： |
| Capacitors are widely used in audio components, such as filtering, anti cross connection, high frequency compensation, DC feedback, etc. However, if we subdivide it according to its function, manufacturing materials and manufacturing methods, it can not be understood overnight. Therefore, to narrow the scope, this paper only talks about electrolytic capacitors, and only discusses the aluminum electrolytic capacitors used for power smoothing and filtering. Every audio machine needs to be powered - except for the passive front stage, since it needs power, it is necessary to "filter". Don't argue with me. Battery powered, of course, there's no need for power smoothing filtering. But the battery charging circuit also has rectification and filtering, so the filter capacitor will still exist. Now, we should use the name of electrolytic capacitor. According to my observation, except for the former stage of sonic frontiers vacuum tube in Canada, PP plastic capacitor was used as filter in high-voltage voltage stabilized circuit, all other models adopt aluminum foil dry electrolytic capacitor; therefore, it is necessary for netizens to know more about it. Facing the capacitor which acts as power smoothing filter in power supply voltage stabilizing circuit, what will you think of first? - capacity? Withstand voltage? There must be a capacity label on the package cover of the capacitor, which refers to the static capacity; there must also be a voltage withstand label, which refers to the working voltage or rated voltage. The working voltage (WV) is the absolute safety value; if the surge voltage (SV or vs for short) is surge voltage or collapse voltage; if the voltage exceeds this value, the capacitor will be drowned by waves - be careful that the capacitor will explode! According to IEC 384-4, vs = 1.15 × VR when it is lower than 315v and 1.1 × VR when it is higher than 315v. Vs is surge voltage and VR is rated voltage. The charge energy of capacitor is expressed by q = CV, q is Coulomb, C is electrostatic capacity, and V is voltage; therefore, when the voltage value is constant, increasing the electrostatic capacity can increase the charge energy. Please note that the unit of capacity of capacitor should be f (farad), but the value is too low due to too high measurement, so we often use μ F, 1F = one million μ F. In foreign countries, MF is also used to denote μ F. in fact, MF is not very appropriate, but there is no μ key on mechanical typewriters, so m is used to represent micro. With two parameters of electrostatic capacity and working withstand voltage, if you are purchasing capacitors, what will you consider next? Intuitively, it's the price. Well, this parameter is very important, and the lower the value, the better. Some people first think of brands and insist that Japanese products should not be used. They still have eight years' anti Japanese complex? American products can only rank second, while those made in Sweden or Germany come first. Well, this parameter is also very important. But when it comes to brands, we can't ignore series models, because a manufacturer will produce many different series of products, and the quality and price will be different if the series are different. OK, let's sort it out first. The parameters of power smoothing filter capacitor are known as follows: static capacity, rated working voltage, surge collapse voltage, price, brand and model series. There should not be only two or three kittens, and the size should also be very important, because it is related to the weight and pin type. Snap in is a plug-in PC board, and screen is a lock screw type. As for weight, the weight of two capacitors with the same capacity and withstand voltage, but with different brands, must be different; and the external size is more related to the chassis planning. Some capacitors are not full circle type, a bit like multi angle type. Philips and BHC have this kind of series which seems to be very advanced. Now let's sort it out again, add in the weight, the shape of the connector - there are nine parameters. Skin color? Who put it forward? It's wonderful. Because white, black, and blue plastic packages are used by manufacturers, they sometimes have certain meanings. For example, the gold lettering on black background of Japanese standard often represents advanced for audio audio audio class capacitors. What else can you think of just by appearance? The manufacturing date of 9627 is the 27th week of 1996; in recent years, it seems that the indication of manufacturing date is gradually omitted. However, the color of the skin and the printing of words are not directly related to the quality, so only the manufacturing date parameter is added. Also, don't forget the working temperature, because 105 ℃ C is more suitable for vacuum tube machines than 85 ℃. If the machine is to be placed in the south pole, it is best to choose a variety with a tolerance of - 55 ° C. The capacity error should not be omitted. When multiple parallel connection is adopted, the lower the error is, the better. Now plus the working temperature and capacity error, we have 12 parameters at hand, we should know more than 30% of the capacitor. Please don't mistakenly understand that the working temperature of the capacitor does not refer to the ambient or surface temperature - no matter how many degrees it is, the packaging plastic cover is the same. It refers to the working temperature of aluminum foil. Therefore, it is absolutely OK to select 85 ° C type for the pipe loader. As long as the capacitor is far away from the tube, it will be safe. However, several important parameters of capacitor quality only exist in the original specifications and will not be exposed on the package cover of the finished product. These important parameters are the focus of this paper. Dissipation factor loss angle The dispersion factor (DF) exists in all capacitors, and sometimes the value of DF is expressed by loss angle Tan δ. Think about the loss angle. The lower the loss angle, the better. The loss angle of plastic capacitor is very low, but the aluminum electrolytic capacitor is quite high. Whether the DF value is high or low depends on the temperature, capacity, voltage and frequency of capacitors of the same brand and series; when the capacity is the same, the higher the withstand voltage, the lower the DF value. An example is given to illustrate that for 10000 μ f capacitors of the same brand and series, the DF value of withstand voltage of 80V must be lower than that of 63v. The selection of filter capacitor in this journal will often find a higher voltage withstand, not without reason. In addition, the higher the temperature, the higher the DF value, and the higher the frequency, the higher the DF value. However, many capacitor manufacturers often do not indicate the value of dissipation factor DF in the specification, because the value is very high and difficult to see. Take Sweden RIFA as an example, its blue phe-420 series is MKP plastic capacitor, its DF value is the lowest 0.00005/the highest is 0.0008. However, the white top peh169 series aluminum electrolytic capacitors are not marked with loss angle specification. If the DF value is indicated, it may be 1.0000, with the decimal point after 1. Leakage current WOW! electric leakage! Better not. But there is no way, aluminum electrolytic capacitor in the work will produce leakage current. The leakage current is of course low, and its calculation formula is roughly: I = k × cv. The unit of leakage current I is μ a, and K is a constant, such as 0.01 or 0.03. Each manufacturer will choose different constant. However, the higher the capacitor capacity, the greater the leakage current. If you have the idea that the larger the capacity, the better the smoothing effect, this "leakage current" should also be taken into account. It can be seen from the formula that the higher the rated voltage, the greater the leakage current. Therefore, reducing the working voltage can also reduce the leakage current. However, it is not easy to reduce the leakage current of capacitor. The price of low leakage current ll series is high. I have ordered a batch of ll series capacitors with low leakage current from domestic manufacturers, and the price is higher than that of many imported capacitors. In terms of leakage current specification, aluminum electrolytic capacitor is much worse than tantalum electrolytic capacitor. Tantalum capacitor is also available in dry type and wet type, but its capacity and withstand voltage are lower. In addition to the special customization, in order to reduce the leakage current of ordinary products, we can try to increase the ratio of VS to VR. Vs is surge voltage, of course, higher than the rated voltage of VR, but the applied voltage (the real working voltage) should be lower than VR, for example, 90% of VR; it can be said that it is completely correct to find high voltage withstand type. Equivalent series resistance ESR A capacitor will produce various kinds of impedance and inductance due to its structure. The more important ones are ESR equivalent series resistance and ESL equivalent series inductance - this is the basis of capacitive reactance. Capacitors provide capacitance. Why do you need resistance? Therefore, ESR and ESL also require low... Low; but low ESR / low ESL are usually advanced series. The ESR is related to the capacity, voltage, frequency and temperature of the capacitor. When the rated voltage is fixed, the larger the capacity, the lower the ESR. Some people are used to connect several small capacitors together to form a large capacitance to reduce the impedance. The theory is that the resistance value in parallel is reduced. But if we consider the impedance of the capacitor pin solder joint, small and large, it is not necessarily a harvest. On the other hand, when the capacity is fixed, the ESR can also be reduced by using the variety with high WV rated voltage; therefore, high withstand voltage has many advantages. The influence of frequency: ESR is high at low frequency and low at high frequency; of course, high temperature can also increase ESR. The unit of series equivalent resistance ESR is m Ω. Advanced series capacitors are usually low ESR and low ESL. If the characteristics of low internal resistance and low leakage current are compared, it is easy to achieve low internal resistance, so it is very common to label the capacitance of low ESR. ESR is related to the loss angle, ESR = Tan δ / (ω × CS), CS is the capacitance. Sometimes there is Z in the specification of capacitor, which has different meaning from ESR. However, the calculation of Z is related to ESR. At the same time, the capacitive reactance and inductive reactance are also considered, which is the real internal resistance. The ESR unit of capacitance mentioned just now is m Ω, which means large capacitance. If 220 μ f small capacity capacitance, its ESR unit is not m Ω but Ω. Which capacitor has the lowest ESR? There is only one answer: Sanyo's OS organic semiconductor capacitor! Ripple current Irac The lower the dissipation factor DF loss angle Tan δ, leakage current, ESR series equivalent resistance and so on, the lower the value is, the better, but the ripple current to be mentioned is the higher the better. Especially now, we pay special attention to the large current output of the later stage amplifier. The ripple current Irac (or IAC) of the power smoothing filter capacitor is particularly prominent. The indication of ripple current Irac should have at least two specifications of low frequency and high frequency operation. The low frequency is about 120Hz and the high frequency is about 10kHz. However, there may be slight differences between different manufacturers. The ripple current is directly proportional to the frequency, so the ripple current is relatively low at low frequency. But for us audio fans, the low-frequency Irac value is important. Therefore, when purchasing capacitors, the ripple current figure is very important. In general, the ripple current of lock screw capacitor is higher than that of snap in PC board under the same brand. There was a saying that the 10000 μ F of RIFA is equivalent to 15000 μ F of other brands. Because the ripple current of most Japanese made capacitors is not high, and RIFA is particularly high, it seems that one can be used as two. German Siemens and British BHC capacitors are often superior to Japanese products in Irac. As far as I know, the largest capacitance of Irac is Siemens sikorel series capacitor, with 6800 μ f / 63v as high as 20A! If the capacitance is small, the biggest capacitance of Irac is Sanyo OS. As far as the action of the later stage amplifier is concerned, many people will believe that it will eat current at low frequency. There is a way to try: to meter DC voltage - DCV the lowest level of any emitter resistance voltage drop, the best is pointer ammeter, play records, turn the front level volume up, pay attention to the meter pointer swing, you will find that low frequency will eat current, four guitar even play will eat current! What music is most suitable for the run in post amplifier? Holst's "planetary suite" No. 1 Mars. By now you should know more than 60%. Maybe you want to ask: are there aluminum electrolytic capacitors with small size, low leakage, low ESR, low Tan δ, low error and low price, but with high ripple current and high applicable temperature range? Well... No! In recent years, aluminum electrolytic capacitors have made great progress. In the past, they were - 20% ～ + 40%, and now they are mostly + / - 20%. However, its capacity is often biased to + rather than to -. Therefore, 10000 μ F may be close to 12000 μ f in measurement. Accurate measurement of the electrostatic capacity of large capacity capacitor is something I have been trying to do for many years. There is no doubt that this kind of testing instrument is very difficult to buy. It has been made in the United States and can measure up to 99999 μ F, and can display DF value and ESR value at the same time. Moreover, the capacitance is the average value of 100Hz, 1kHz and 10kHz frequency test. This kind of instrument has appeared in the domestic market. It is sold for NT $100000 - only differential leakage current test.
At least the rated voltage is allowed to work at 15%. For example, the rated voltage of a capacitor is 50V. Although the surge voltage may be as high as 63v, I can only apply 42V voltage. Let capacitor rated voltage have more margin, can reduce internal resistance, reduce leakage current, reduce loss angle, increase life, why not do it with one stroke? I have seen the Japanese enlarger before, with a working voltage of ± 48V and a filter capacitor of 10000 μ f / 50V. Of course, it will not burn out in a short period of time, but its service life may be reduced due to a long time. Therefore, it is necessary to replace a new product or purchase a new one. Therefore, Japanese products often have the fate of "it's time to go". You can't accuse them of cutting corners. After all, business always makes profits. If you can only sell you once in your life, how can you make money? The higher the capacity, the lower the hum? The most annoying thing is that you can't get rid of the hum. Someone increased the filter capacitance and the hum was gone. I don't really believe that the hum of the amplifier is often caused by improper ground circuit, which comes from very little capacitor. However, theoretically, the higher the capacity, the better the smoothing effect of power supply. Therefore, many designers and DIY fans believe in the practice of large capacity. Therefore, many later stage amplifiers, especially Krell and mark Levinson from the United States, like to use large reservoirs and large capacitors; Dynaudio of Denmark even uses tens of thousands of μ F of capacity for the former stage expanders. As for AC & DC, they also tend to "large capacity" school, but there is still enough to stop. However, many famous factories have taken the path of low capacity. For example, amcron in the United States has a 250W × 2 professional post stage amplifier with two channels of 500W, and only two 8200 μ f small filter capacitors are used. Goldmund in Switzerland is a hi end brand. When the product is sent to various magazines for trial hearing, no commentator dares to say that it is bad. Its big back stage is the use of small capacitors. FM acoustics in Switzerland is even more expensive. A stereo can be replaced by a Benz. Its 220W × 2 professional back stage, known as dozens of a current output, I saw with my own eyes, the whole machine only uses two 10000 μ f / 100V filter capacitors. The two theories of large capacity filtering and low capacity filtering are basically opposite, but they exist in the sound circle at the same time. The low-frequency performance of the expander is no worse than that of the "big pond" one. What is the point? Irac ripple current. If you're still full of big capacity, you don't know about electrolytic capacitors! Here is a suggestion: if the low capacity filter capacitor is used in the assembled stage, high-power power transformer should be used. That is to say, "the capacitor is thinner, the transformer is fatter". This may be the secret of the sound of the amplifier. According to the detailed observation in recent years, it is much more effective to use high-power power transformer than to use large capacity filter capacitor if the later stage amplifier has good sound. A big one? How many small ones? OK, some people can't rest assured that the filter capacitor should be large μ F - is it to find a large one or use a dozen or so small ones to connect in parallel? It is also said that the use of small particles, not only can reduce the internal resistance, reaction speed will also be fast, transparency and resolution are better. Mark Levinson and Krell's posterior stage is not small and large, but who thinks it is slow, opaque and foggy? In the face of this problem, I myself have long been in a maze. As far as the case planning is concerned, it seems ideal to use multiple small capacitors in parallel. Moreover, the purchase volume is large and the price is cheap. Even the same kind of capacitor can be used in the front stage, the back stage and the integrated machine. The fate of imported machines is somewhat different from that of domestic machines. When consumers face hundreds of thousands of yuan of imported machines with multiple small capacitors, they will explain to themselves: This is very reasonable; but when facing domestic products, he may have another vicious saying: cutting corners! In terms of sound quality, there should be no absolute relationship between a large pool or a small pool, or a large or multiple small ones. Deng Xiaoping said well: regardless of the black cat and white cat, the cat that can catch mice is a good cat. Manufacturing brand is also related to quality characteristics. Some of the above-mentioned people do not use Japanese products all their life. There were two major capacitor brands in the United States, Mallory and Sprague, but now Sprague has become a famous brand because it was acquired by Nippon chemi con of Japan and the company name was registered as United chemi con / UCC. However, as long as it is still made in the United States and the outer skin is printed with made in USA, the change of trademark shall not be related to the manufacturing quality. But the outside world has whispered: UCC is worse than Sprague, what is the possibility? Once the Japanese commercial agency takes over, the marketing policy will naturally be greatly changed. In order to increase the shipment volume, the selling price must be reduced; however, the decline of false quality will also lead to the decline of quality. Ask the local agent Ruipu company that the sales volume of UCC capacitor is lower than that of Sprague, indicating that domestic manufacturers reject UCC. If we compare the specifications and characteristics of UCC and Sprague, it is a Japanese style. The size is greatly reduced. The original 40mm × 80mm is changed to 40mm × 50mm, and the price may be lower. However, with the increase of ESR and the decrease of Irac, how can it not be said that the size of the product is greatly reduced? Do you have any doubts about Japanese products? There's no way. Not only the United States, but also Germany needs Japanese funds to cooperate with Germany and Japan. Siemens and Matsushita jointly produce S + m capacitors. This is the future trend, almost inevitable. RIFA has been eaten by EVOX for a long time. EVOX is a large group with factories set up everywhere. This magazine sigend single end front stage uses 1 μ f capacitor, which is EVOX brand. Although it is imported from the United States, it has a set of products. Storage and service life Compared with the semi permanent components such as resistor, IC, transistor and plastic capacitor, the life of aluminum electrolytic capacitor is worthy of attention. One is the storage life, which is naturally related to the service life. There should be no problem in 10-20 years. Capacitors that have been stored for a long time should not be used immediately. Use power supply to age them first. Clamp the terminals and slowly adjust the power supply voltage. From low to high, the maximum voltage can be adjusted to the rated voltage of this capacitor. It is difficult to explain the working life. The so-called long life ll long life capacitor usually means that the ripple current Irac is stable. As mentioned above, the Irac of the capacitor is related to the operating temperature and frequency, for example, 10kHz, 15A at 40 ° C and 9A at 85 ° C; 15A / 9A = 1.67. This figure is the life factor of the capacitor (I think of it temporarily). The higher the number, the lower the life, and the closer the number to 1, the longer the life. If you remember correctly, 1.93 means 100000 hours, 1.85 means 200000 hours, so 167 is at least 500000 hours! However, the main function of capacitor is charge and discharge characteristics, so it is not suitable to charge and discharge frequently. There are two ways to effectively prolong the life of the capacitor: one is to reduce the number of power on and off; the other is to try to reduce the instantaneous charging current when starting up - do you understand? This has been the case for many years. Even so, if you ask: which capacitor has better sound quality? It's hard to answer. Basically, the sound performance of different brands and series of capacitors is also different. Personally, I will not "kill Japanese products without using them". As long as they are handled properly, Japanese products will not be exported to Europe and America. Elna advanced cerafine audio grade capacitor was used many years ago. Although its ESR is low, the Irac is not high. When installed on the amp, the low frequency is very thick, but the fog is heavy and not transparent enough. However, with the speed-up capacitor connected, it will suddenly become clear. Therefore, in actual assembly, remember to add a small speed-up capacitor to the main filter capacitor, which will "at least" improve the high-frequency response. What are the numbers? It is better to have a large one and a small one, with large 1 μ F and small 0.1 μ F. MKP is the minimum requirement. Sometimes the small capacitor will find little help, this may be the small capacitor is not selected. If you want to add speed-up, you are advised not to look for Wima. You are advised to try MIT ppfx-s tin foil or RTX series 0.1 μ F. While writing this article, I also pay attention to the advertisements in various magazines. The hi end new models of Krell in the United States and class'e audio in Canada all adopt Japanese Nichicon capacitor as the main power smoothing filter! But who dares say it's bad?! The former stage amplifier can't eat hundreds of ma current, so the filter capacitor is easy to choose. High wattage and high output current amplifiers are difficult to serve, and the Irac characteristics of filter capacitors should be taken into account. For filter electrolytic capacitors, there are a few points worth our attention: first, generally speaking, the Irac of Japanese products is lower than that of European and American products; second, low leakage current is more important than low ESR; third, large filter capacitors should be connected with small capacitors; fourth, high voltage capacitors should be selected as far as possible; fifth, the top-level capacitance, capacity and withstand voltage are not high, so hundreds of watts of power usually sound rough, not unreasonable 。 The author does not recommend which capacitor is the best, because as long as it is used properly, each capacitor can make a good sound. As for those who deliberately emphasize that capacitors, resistors, solders and fuses are not used by XXX brand, they are definitely laymen who do not understand the circuit structure! On the construction of aluminum electrolytic capacitor Capacitors can be roughly divided into: 1. Winding type, 2. Laminated type, 3. Electrolytic type. The electrolytic type is divided into aluminum and tantalum, and aluminum is further divided into liquid electrolyte and solid electrolyte. It is wrong to say that the liquid electrolyte is wet aluminum foil and the solid electrolyte is dry aluminum foil, because both dry aluminum foil and wet aluminum foil are liquid electrolyte capacitors. Aluminum electrolytic capacitor is made of etched high-purity aluminum foil as anode, anodized film on its surface as dielectric, and thin paper or cloth immersed in electrolyte as cathode. As the electrolyte is of suction type, it is called aluminum foil dry electrolytic capacitor. What is wet aluminum foil? Add electrolyte directly into the capacitor, such as amine borate and glycol mixture. If the capacitor is shaken by hand, the water will sound. This kind of capacitor is made by peh169 series of RIFA in Sweden. Even if it is a famous European factory, the aluminum foil used as anode is not produced by itself, but supplied by a certain company. It is like there are many watch factories in Switzerland, but only a few can make oil core. About 10 years ago, when an Italian company was unable to supply anode aluminum foil normally, the world's famous factories, such as Mallory / RIFA / Sprague or Rubycon / Philips, had to delay the delivery time. How to produce and deliver without raw materials? As for the paper soaked in electrolyte, it can not be bought in ordinary stationery shops. The largest supplier is in Malaysia. |
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