從事電子元器件行業(yè)的人員經(jīng)常會聽到電解電容失效的問題，那么如何避免電解電容失效的問題呢？這就需要我們清楚的知道電解電容失效的原因以及在電路設(shè)計過程中注意的問題。
People engaged in electronic components industry often hear the problem of electrolytic capacitor failure, so how to avoid the problem of electrolytic capacitor failure? This requires us to know clearly the cause of electrolytic capacitor failure and the problems in the circuit design process.
1.鋁電解電容為什么會失效呢?
Why does aluminum electrolytic capacitor fail?
2.鋁電解電容失效與哪些因素有關(guān)?
What factors are related to the failure of aluminum electrolytic capacitor?
3.電解電容壽命如何計算?
How to calculate the life of electrolytic capacitor?
讓我們依次來解答以上的問題。
Let's answer the above questions in turn.
1.鋁電解電容為何失效?
Why aluminum electrolytic capacitors fail?
這個問題還得提下鋁電解電容的構(gòu)造。
The construction of aluminum electrolytic capacitors should also be mentioned.
通用型鋁電解電容器的基本結(jié)構(gòu)是箔式卷繞型的結(jié)構(gòu)，陽極為鋁金屬箔，介質(zhì)是用電化學(xué)方法在陽極金屬箔表面上形成的閥金屬氧化膜Al2O3，陰極則為多孔性電解紙所吸附的工作電解質(zhì)。
The basic structure of general aluminum electrolytic capacitor is foil winding structure. The anode is aluminum foil, the medium is valve metal oxide film formed on the surface of anode metal foil by electrochemical method, and the cathode is working electrolyte adsorbed by porous electrolytic paper.
通俗理解，電容都是由兩個導(dǎo)電板并排放到一起就構(gòu)成了。正極是鋁(陽極箔)，中間介質(zhì)是不導(dǎo)電的氧化鋁(陽極氧化膜)，負極就是電解液了。
Generally understood, the capacitor is composed of two conductive plates and discharged together. The positive electrode is aluminum (anode foil), the intermediate medium is non-conductive alumina (anodic oxide film), and the negative electrode is the electrolyte.
電解電容失效，主要原因就出在了這個電解液上了。這個電解液自己會分解產(chǎn)生氣體，也會與氧化膜發(fā)生化學(xué)反應(yīng)產(chǎn)生氣體。當然，正常使用情況下，這個速率是非常慢的，不然豈不是沒法用了。
Electrolytic capacitor failure, the main reason for this electrolyte. The electrolyte itself will decompose to produce gas, and will react with the oxide film to produce gas. Of course, under normal use, this speed is very slow, otherwise it can't be used.
所以，電解壽命的長短，主要決定于這個電解液，啥時候電解液沒了，電容也就失效了。
Therefore, the life of electrolysis is mainly determined by the electrolyte. When the electrolyte is gone, the capacitor will fail.
2.鋁電解電容失效影響因素
Influencing factors of aluminum electrolytic capacitor failure
鋁電解電容失效速度與電解液的揮發(fā)速度有關(guān)，而揮發(fā)的速度主要取決于溫度。電解電容內(nèi)部的溫度，取決與環(huán)境溫度和紋波電流。
The failure rate of aluminum electrolytic capacitor is related to the evaporation rate of electrolyte, which mainly depends on the temperature. The internal temperature of electrolytic capacitor depends on the ambient temperature and ripple current.
如果是用在電源紋波比較小的場合，那么電解電容的溫度就主要由環(huán)境溫度決定了。
If it is used in the case of small ripple of power supply, then the temperature of electrolytic capacitor is mainly determined by the ambient temperature.
如果是用在在紋波電流比較大場合，電解電容的ESR是不能忽略的，比如用在開關(guān)電源里面，因為ESR的存在，電解電容會主動發(fā)熱。
If it is used in the field with large ripple current, the ESR of electrolytic capacitor can not be ignored, such as in switching power supply, because of the existence of ESR, the electrolytic capacitor will actively heat up.
其實如果翻開電容規(guī)格書，我們也可以看到電解電容有個參數(shù)叫做最大紋波電流。
In fact, if we open the capacitance specification, we can see that electrolytic capacitor has a parameter called maximum ripple current.
以某廠的電解電容為例
Taking the electrolytic capacitor of a factory as an example
主要注意的是，這個紋波電流為有效值Irms。
It is important to note that the ripple current is RMS.
3.鋁電解電容壽命計算
Life calculation of aluminum electrolytic capacitor
溫度升高， 化學(xué)反應(yīng)速率( 壽命消耗) 增大， 一般來說， 當所處環(huán)境溫度每上升10℃ ，化學(xué)反應(yīng)速率(K 值) 將增大 2-10 倍，即電容工作溫度每升高 10℃ ，電容壽命減小一倍，電容工作溫度每下降 10℃ ，其壽命增加一倍。
Generally speaking, when the ambient temperature increases by 10 ℃, the chemical reaction rate (k value) will increase by 2-10 times, that is, every 10 ℃ increase in the working temperature of the capacitor, the life of the capacitor will be doubled, and the life of the capacitor will be doubled when the working temperature of the capacitor decreases by 10 ℃.
Lo為電解電容工作最高溫度對應(yīng)的壽命，一般來說電解電容規(guī)格書都會有相應(yīng)的參數(shù)。
Lo is the service life corresponding to the highest working temperature of electrolytic capacitor. Generally speaking, the specifications of electrolytic capacitor will have corresponding parameters.
需要注意的是，各個廠家的壽命計算公式不盡相同，不過也都是相近的。在設(shè)計電路時，通過公式計算出的壽命可以做一個大致的參考。
It should be noted that the life calculation formulas of different manufacturers are not the same, but they are all similar. In the design of the circuit, the life calculated by the formula can be used as a general reference.
由此我們可以得出以下結(jié)論：很多電解電容在最高溫度工作時，壽命只有2000小時(0.2年)，所以必須考慮壽命問題。溫度每升高10攝氏度，電解電容壽命下降一半。溫度，紋波電流都是影響電解電容的重要因素。
Therefore, we can draw the following conclusion: when many electrolytic capacitors work at the highest temperature, the service life is only 2000 hours (0.2 years), so we must consider the life problem. When the temperature increases by 10 ℃, the life of electrolytic capacitor decreases by half. Temperature and ripple current are important factors affecting electrolytic capacitor.