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电解电容的选型指标和重要参数
作者:红宝电容 来源:http://www.jnhongbao.com 日期:2020-08-11 09:24 浏览

  电子设备需求的不断增加,其主要的电子元器件需求量也在增加,电解电容器小型大容量化,耐纹波电流,高频低阻抗化,高温度长寿命化和更适应高密度组装成为电子设备的首选。在电解电容选型的过程中,需要注意哪些重要的参数和指标呢?

  With the increasing demand for electronic equipment, the demand for its main electronic components is also increasing. Electrolytic capacitors with small size and large capacity, ripple current resistance, high frequency and low impedance, high temperature and long life and more suitable for high density assembly have become the first choice of electronic equipment. In the process of electrolytic capacitor selection, what important parameters and indicators should be paid attention to?

  1.电容量与体积

  Capacitance and volume

  由于电解电容器多数采用卷绕结构,很容易扩大体积,因此单位体积电容量非常大,比其它电容大几倍到几十倍。但是大电容量的获取是以体积的扩大为代价的,现代开关电源要求越来越高的效率,越来越小的体积,因此,有必要寻求新的解决办法,来获得大电容量、小体积的电容器。

  Because most electrolytic capacitors adopt winding structure, it is easy to expand the volume, so the electric capacity per unit volume is very large, which is several to dozens times larger than other capacitors. However, the acquisition of large capacitance is at the cost of volume expansion. Modern switching power supply requires higher efficiency and smaller volume. Therefore, it is necessary to seek new solutions to obtain large capacity and small volume capacitors.

  2.承受温度与寿命

  Temperature and life

  电解电容器的寿命与电容器长期工作的环境温度有直接关系,温度越高,电容器的寿命越短。现在有很多种类的电解电容器的工作环境温度已经很高在环境温度为90℃,通过电解电容器的交流电流和额定脉冲电流的比为0.5时,寿命仍然为10000h,但是如果温度上升到95℃时,电解电容器即已经损坏。一般情况而言,电解电容器工作在环境温度为80℃时,一般能达到10000h寿命的要求。

  The life of electrolytic capacitor is directly related to the long-term working environment temperature of the capacitor. The higher the temperature is, the shorter the life of the capacitor is. At present, there are many kinds of electrolytic capacitors with high working environment temperature. When the ambient temperature is 90 ℃, the ratio of AC current through electrolytic capacitor to rated pulse current is 0.5, the service life is still 10000h. However, if the temperature rises to 95 ℃, the electrolytic capacitor will be damaged. Generally speaking, when the working temperature of electrolytic capacitor is 80 ℃, the life of electrolytic capacitor can reach 10000 H.

  另一方面,电解电容器的寿命还与电容器长时间工作的交流电流与额定脉冲电流的比值有关。一般说来,这个比值越大,电解电容器的寿命越短,当流过电解电容器的电流为额定电流的3.8倍时,电解电容器一般都已经损坏。

  On the other hand, the life of electrolytic capacitor is also related to the ratio of AC current to rated pulse current. Generally speaking, the higher the ratio, the shorter the life of electrolytic capacitor. When the current flowing through the electrolytic capacitor is 3.8 times of the rated current, the electrolytic capacitor is generally damaged.

  3.频率特性与阻抗

  Frequency characteristics and impedance

  对于中小输出功率开关电源的工作频率除少数因价格限制而仍采用20~40kHz外,大多数均在50kHz以上;DC/DC电源模块大多在300kHz以上;大功率开关电源的开关频率受主开关的开关速度限制而一般在20~40kHz。

  For small and medium-sized output power switching power supply, the operating frequency is more than 50 kHz except for a few which are still 20 ~ 40 kHz due to price restriction; most DC / DC power supply modules are above 300 kHz; the switching frequency of high-power switching power supply is generally 20 ~ 40 kHz, which is limited by the switching speed of the main switch.

  在开关稳压电源中作为输出滤波用的电解电容器,由于大多数的开关电源工作在方波或矩形波的状态,含有及其丰富的高次谐波电压与电流,其上锯齿波电压的频率高达数十千赫,甚至数十兆赫,它的要求和低频应用时不同,电容量并不是主要指标,衡量它好坏的则是它的阻抗频率特性。

  The electrolytic capacitor used as output filter in switching power supply, because most of the switching power supply work in the state of square wave or rectangular wave, which contains rich high-order harmonic voltage and current, the frequency of sawtooth wave voltage on the switching power supply is as high as tens of kilohertz, even tens of megahertz. Its requirements are different from those in low-frequency application. Capacitance is not the main index to measure its quality Is its impedance frequency characteristic.

  由于制造工艺的原因,电容量越大,寄生电感也越大,谐振频率也越低,电容器呈感性的频率也越低。这就要求它在开关稳压电源的工作频段内要有低的等效阻抗,同时,对于电源内部,由于半导体器件开始工作所产生高达数百千赫的尖峰噪声,亦能有良好的滤波作用,一般低频用普通电解电容器在10kHz左右,其阻抗便开始呈现感性,无法满足开关电源使用要求。

  Due to the manufacturing process, the larger the capacitance, the larger the parasitic inductance, the lower the resonance frequency and the lower the inductive frequency of the capacitor. This requires that it has a low equivalent impedance in the working frequency band of the switching power supply. At the same time, it can also have a good filtering effect for the peak noise of hundreds of kilohertz generated by the semiconductor devices in the power supply. Generally, the impedance of the common electrolytic capacitor for low-frequency use at about 10kHz begins to appear perceptual, which can not meet the requirements of switching power supply.

  开关电源为了高效率而提高了工作频率的高频化,特别是小型高输出开关电源中输入滤波用电容器要求高纹波性,输出端低阻抗化。要使输出滤波用电容器在高频下低阻抗化,必须降低等效串联电阻。

  In order to achieve high efficiency, the switching power supply improves the high frequency of the working frequency, especially in the small high output switching power supply, the input filter capacitor requires high ripple and low output impedance. In order to make the output filter capacitor low impedance at high frequency, the equivalent series resistance must be reduced.

  4.纹波电流耐受度

  Ripple current tolerance

  影响电解电容器性能的最主要的参数之一就是纹波电流问题。纹波电流对铝电解电容器的影响主要是在ESR上产生功耗使铝电解电容器发热,进而缩短使用寿命。纹波电流在ESR上产生的损耗与纹波电流有效值的平方成正比,因而随着纹波电流的增加,小时寿命曲线类似于抛物线函数曲线。

  Ripple current is one of the most important parameters affecting the performance of electrolytic capacitors. The main effect of ripple current on aluminum electrolytic capacitor is to generate power consumption on ESR, which makes aluminum electrolytic capacitor heat up, thus shortening its service life. The loss on ESR caused by ripple current is directly proportional to the square of the effective value of ripple current. Therefore, with the increase of ripple current, the hourly life curve is similar to a parabolic function curve.

  降低纹波电流的方法可以采用较大容量的铝电解电容器,毕竟大容量铝电解电容器可承受的纹波电流比小容量的铝电解电容器大;也可以采用多只小容量铝电解电容器的并联方式,还可以选用纹波电流低的电路拓扑结构。一般而言,反激式变换器产生的开关变换电流相对最大。

  To reduce ripple current, aluminum electrolytic capacitors with larger capacity can be used. After all, the ripple current that large capacity aluminum electrolytic capacitors can bear is larger than that of small capacity aluminum electrolytic capacitors; multiple small capacity aluminum electrolytic capacitors can also be connected in parallel, and low ripple current circuit topology can be selected. Generally speaking, the switching current generated by flyback converter is relatively maximum.

  随着技术日新月异的发展变化中,电解电容的发展更加趋于小型化,具有更好的频率特性、更低ESR、更低阻抗、 更低ESL,更高耐压性能、无铅化,这也是电解电容器今后的发展方向。

  With the rapid development of technology, the development of electrolytic capacitor tends to be miniaturization, with better frequency characteristics, lower ESR, lower impedance, lower ESL, higher withstand voltage performance and lead-free, which is also the development direction of electrolytic capacitor in the future.


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