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1、TECHNICALNOTESANDGUIDELINESProfessional achievements value专业成就价值铝电解电容器的基本概要铝电解电容器的基本概要铝电解电容器的基本概要铝电解电容器的基本概要1-1.电容器的基本原理电容器的基本原理可以用图 1 来描述当在两个正对的金属电极上施加电压时，电荷将根据电压的大小在介质表面被储存起来。Q=CVQ:电量(C)V：电压(V)C:电容量(F)CF， 称为电容器的电容量,可以由电极面积 Sm2， 介质厚度 tm以及相对介电常数“”通过下式来表示:C=0s/t0：介质在真空状态下的介电常数(=8.85xl012F/M)铝氧化膜的相对介电
2、常数为 78要想获得更大的容量，可以通过增加表面积 S 或者减少其厚度 t 来获得。表 1 列出了电容器中常用的几种典型的介质的相对介电常数，在很多情况下，电容器的命名通常是根据介质所使用的材料来决定的，例如：铝电解电容器、钽电容器等。虽然铝电解电容器非常小，但它具有相对较大的电容量，因为其通过电化学腐蚀后，电极箔的表面积被扩大了，并且它的介质氧化膜非常薄。图 2 是铝电解电容器的切面示意图。TECHNICALTECHNICALTECHNICALTECHNICAL NOTESNOTESNOTESNOTES1General Description of Aluminum Electrolytic
3、 Capacitors1-1 The Principle of CapacitorThe principle of capacitance can be presented by the principledrawing as Fig1. When a voltage is applied between the metalelectrodes placed opposite on the surfaces of a dielectric.Electric charge can be stored proportional to the voltage.Q=CVQ: Quantity of e
4、lectricity(C)V: Voltage (V)C: Capacitance (F)C F ,called the capacitance of capacitor, is expressed by thefollowing expression with the electrode area S m2, the electrode spacing t m and the dielectric constant of dielectric“” :C= 0s/t 0 0 0 0:Dielectric constant in vacuum (=8.85xl012F/M) The dielec
5、tric constant of an aluminum oxide film is 7 to 8. Largercapacitances can be obtained by enlarging the electrode area Sor reducing t.Table 1 shows the dielectric constants of typical dielectrics usedinthecapacitor.Inmanycases,Capacitornamesaredeterminedbythedielectricmaterialused,forexample.aluminum
6、 electrolytic capacitor, tantalum Capacitor, etc.Although the aluminum electrolytic Capacitor is small, it has alarge capacitance. It is because the electrode area is roughenedby electrochemical etching, enlarging the electrode area andalso because the dielectric is very thin. The schematic crosssec
7、tion of the aluminum electrolyticCapacitor is as in Fig.2TECHNICALNOTESANDGUIDELINESProfessional achievements value专业成就价值1-2 电容器的等效电路电容器的等效电路图可由下图 3 表示R1：电极和引出端子的电阻R2：阳极氧化膜和电解质的电阻R3：损坏的阳极氧化膜的绝缘电阻D1：具有单向导电性的阳极氧化膜C1：阳极箔的容量C2：阴极箔的容量L：电极及引线端子等所引起的等效电感量1-3 铝电解电容器的结构1-2Equivalent Circuit of the CapacitorT
8、he electrical equivalent circuit of the aluminum electrolyticCapacitor is as presented in Fig.3R1: Resistance of terminal and electrodeR2: Resistance of anode oxide film and electrolyteR3: Insulation resistance because of defective anodic oxide filmD1: Oxide semiconductor of anode foilC1: Capacity o
9、f anode foilC2: Capacity of cathode foilL:Inductance caused by terminals, electrodes, etc.1-3 Structure of aluminum electrolytic CapacitorTECHNICALNOTESANDGUIDELINESProfessional achievements value专业成就价值TECHNICALNOTESANDGUIDELINESProfessional achievements value专业成就价值1-5 基本参数和术语1-5-1 电容量阳极箔电介质部分的容量可以用
10、下列公式进行计算：阴极箔也有一个容量（Cc） ，它的电介质是利用形成电压生成的氧化层，或在储存期内自然生成的（一般为 1 伏或小于 1 伏 l）。根据铝电解电容器的结构Ca 和 Cc 是串联在一起的，因此，其容量可用下列公式得出：标准的容量允许误差范围为20% (M)，但是也可以生产容量允许误差为l0% (K)的特殊用途的电容器，铝电解电容器的容量会因温度和频率不同而变化，因此，测试频率按标准设为 120Hz，温度设定为 20。1-5-2 Tan（损耗角正切）在等效电路中， 等效串联电阻 ESR 同容抗 l/之比称之为 Tan。Tan =RESR/ (l/)= C RESR其中：RESR=ES
11、R (120 Hz) =2TTf f =120HzTan随着测量频率的增加而变大，随测量温度的下降而增大。1-5-3 等效串联电阻(ESR)等效串联电阻(ESR)是与电容相串联的、代表电容器所有电阻损耗的一个电阻值。ESR 源于电极箔、电解液、引线的电阻和它们之间的连接电阻。ESR 随温度上升而下降，在低频区也随频率的上升而降低。1-5-4 阻抗(Z)：在特定的频率下，阻碍交流电通过的电阻就是所谓的阻抗(Z)。它与容量和电感所对应的容抗和感抗有关，也与等效串联电阻 ESR 有关。具体表达式如下：1-5 Basic parameters and terms1-5-1 Capacitance:Th
12、e capacitance of the dielectric portion of the anode aluminum foil canbe calculated with the following formula:The cathode foil has a capacitance (Cc) that uses the oxide layer, whichformed by the forming voltage or formed naturally during storage (generally lV or less), as a dielectric. According t
13、o the construction of aluminumelectrolytic capacitors, Ca and Cc are connected in a series. Therefore, thecapacitance can be determined by the following formula:The standard capacitance tolerance is 20%(M); however, capacitors witha capacitance tolerance of 10%(K), etc. are also manufactured for spe
14、cialusage. The capacitance of aluminum electrolytic capacitors changes withtemperature and frequency of measurement, so the standard has been set toa frequency of 120Hz and temperature of 20.1-5-2Tan (tangent of loss angle or dissipation factor):TheTan is the ratio of the resistive component (RESR)
15、to thecapacitive reactance (l/C) in the equivalent seriescircuit.Tan= RESR/ (l/)= C RESRwhere: RESR=ESR (120 Hz) =2TTf f =120HzTheTan shows higher values as a measuring frequency increases and ameasuring temperature decrease.1-5-3 Equivalent series resistance (ESR)The equivalent series resistance (E
16、SR) is a single resistance representingall of the ohmic losses of the capacitor and connected in series with thecapacitance. ESR is from resistance of the electrode foils, the electrolyte, theleads and each connection.The ESR declines with increasing temperature, and also declines steadilywith increasing frequency at low frequencies .1-5-4 Impedance (Z):The impedance is the resistance which opposes the flow o
