電解電容作為開關(guān)電源的重要元件，對其性能的要求也越來越高，電解電容廠家針對電解電容器的一個(gè)較為重要的特性--高頻低阻抗化進(jìn)行展開闡述其對開關(guān)電源的重要性。

　　As an important component of switching power supply, electrolytic capacitor has higher and higher requirements for its performance. In this paper, the importance of electrolytic capacitor to switching power supply is described, which is an important characteristic of electrolytic capacitor high frequency and low impedance.

　　盡管開關(guān)頻率有所不同，但是開關(guān)電源的輸出整流濾波電容器的作用基本相同，主要是通過利用濾波電容器吸收開關(guān)頻率及其高次諧波頻率的電流分量而濾除其紋波電壓分量。

　　Although the switching frequency is different, the function of the output rectifier filter capacitor of the switching power supply is basically the same. The ripple voltage component is filtered by absorbing the current component of the switching frequency and its higher harmonic frequency by using the filter capacitor.

　　對于中小輸出功率開關(guān)電源的工作頻率除少數(shù)因價(jià)格限制而仍采用20~40kHz外，大多數(shù)均在50kHz以上；DC/DC電源模塊大多在300kHz以上；大功率開關(guān)電源的開關(guān)頻率受主開關(guān)（一般采用IGBT）的開關(guān)速度限制而一般在20~40kHz。

　　For medium and small output power switching power supply, the operating frequency is more than 50 kHz except for a few which are still used 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 limited by the switching speed of main switch (generally using IGBT), but it is generally 20 ~ 40 kHz.

　　在開關(guān)電源輸出端用的濾波電容，與工頻電路中選用的濾波電容并不一樣，在工頻電路中用作濾波的普通電解電容器，其上的脈動(dòng)電壓頻率僅有100Hz，充放電時(shí)間是毫秒數(shù)量級，為獲得較小的脈動(dòng)系數(shù)，需要的電容量高達(dá)數(shù)十萬微法，因而一般低頻用普通鋁電解電容器制造目標(biāo)是以提高電容量為主，電容器的電容量、損耗角正切值以及漏電流是鑒別其優(yōu)劣的主要參數(shù)。

　　The filter capacitor used at the output end of switching power supply is different from the filter capacitor used in power frequency circuit. The pulse voltage frequency of ordinary electrolytic capacitor used as filter in power frequency circuit is only 100Hz, and the charge and discharge time is in the order of millisecond. In order to obtain a small pulse coefficient, the capacitance required is as high as hundreds of thousands of Micromethods. Therefore, ordinary aluminum electrolysis is used in low frequency The main purpose of vessel manufacturing is to improve the capacitance. The capacitance, loss tangent and leakage current are the main parameters to identify the advantages and disadvantages.

　　在開關(guān)穩(wěn)壓電源中作為輸出濾波用的電解電容器，由于大多數(shù)的開關(guān)電源工作在方波或矩形波的狀態(tài)，含有及其豐富的高次諧波電壓與電流，其上鋸齒波電壓的頻率高達(dá)數(shù)十千赫，甚至數(shù)十兆赫，它的要求和低頻應(yīng)用時(shí)不同，電容量并不是主要指標(biāo)，衡量它好壞的則是它的阻抗頻率特性，如圖所示。

　　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, as shown in the figure.

　　47μF/350V鋁電解電容器的阻抗頻率特性

　　Impedance frequency characteristics of 47 μ f / 350V aluminum electrolytic capacitor

　　由圖可知，隨著頻率的升高，容抗下降、感抗上升，容抗等于感抗并相互抵消時(shí)的頻率為鋁電解電容器的諧振頻率，這時(shí)的阻抗最低，僅剩下ESR。如果ESR為零，則這時(shí)的阻抗也為零；頻率繼續(xù)上升，感抗開始大于容抗，當(dāng)感抗接近于ESR時(shí)，阻抗頻率特性開始上升，呈感性，從這個(gè)頻率開始以上的頻率下電容器時(shí)間上就是一個(gè)電感。

　　In this case, when the frequency of the reactance and capacitance of the electrolytic capacitor increases, the frequency of the remaining reactance is equal to that of the resonant capacitor. If the ESR is zero, then the impedance is zero; if the frequency continues to rise, the inductive reactance begins to be greater than the capacitive reactance. When the inductive reactance is close to the ESR, the impedance frequency characteristic starts to rise and is inductive. From this frequency, the capacitor is an inductance in time.

　　由于制造工藝的原因，電容量越大，寄生電感也越大，諧振頻率也越低，電容器呈感性的頻率也越低。這就要求它在開關(guān)穩(wěn)壓電源的工作頻段內(nèi)要有低的等效阻抗，同時(shí)，對于電源內(nèi)部，由于半導(dǎo)體器件開始工作所產(chǎn)生高達(dá)數(shù)百千赫的尖峰噪聲，亦能有良好的濾波作用，一般低頻用普通電解電容器在10kHz左右，其阻抗便開始呈現(xiàn)感性，無法滿足開關(guān)電源使用要求。

　　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.

　　用于開關(guān)穩(wěn)壓電源輸出整流的電解電容器，要求其阻抗頻率特性在300kHz甚至500kHz時(shí)仍不呈現(xiàn)上升趨勢。電解電容器ESR較低，能有效地濾除開關(guān)穩(wěn)壓電源中的高頻紋波和尖峰電壓。而普通電解電容器在100kHz后就開始呈現(xiàn)上升趨勢，用于開關(guān)電源輸出整流濾波效果相對較差。

　　The output impedance of the rectifier is not required to rise even at 500KHz. The ESR of electrolytic capacitor is low, which can effectively filter out the high frequency ripple and peak voltage in the switching power supply. However, the common electrolytic capacitor begins to show an upward trend after 100kHz, so the filtering effect of the output rectifier of switching power supply is relatively poor.

　　通過實(shí)驗(yàn)可發(fā)現(xiàn)，普通CDII型中4700μF,16V電解電容器，用于開關(guān)電源輸出濾波的紋波與尖峰并不比CD03HF型4700μF,16V高頻電解電容器的低，同時(shí)普通電解電容器溫升相對較高。當(dāng)負(fù)載為突變情況時(shí)，用普通電解電容器的瞬態(tài)響應(yīng)遠(yuǎn)不如高頻電解電容器。

　　Through the experiment, it can be found that the ripple and peak of common cdii 4700 μ F, 16V electrolytic capacitor used in switching power supply output filtering is not lower than that of cd03hf 4700 μ F, 16V high frequency electrolytic capacitor, and the temperature rise of common electrolytic capacitor is relatively higher. When the load is sudden change, the transient response of ordinary electrolytic capacitor is much worse than that of high frequency electrolytic capacitor.

　　開關(guān)電源為了高效率而提高了工作頻率的高頻化，特別是小型高輸出開關(guān)電源中輸入濾波用電容器要求高紋波性，輸出端低阻抗化。要使輸出濾波用電容器在高頻下低阻抗化，必須降低等效串聯(lián)電阻。

　　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.