The popular science | 0. 1 u F capacitance could do not want to use

滤波电容在开关电源中起著非常重要的作用,如何正确选举择滤波电容,也是出口滤波电容性选举择则每个工程技术人员都是十分钟关心性问题。 We are in the power supply filter circuit can see all kinds of capacitor, 100 uf, 10 uf, nf, 100 10 nf different values, so these parameters is how to determine? 50 hz工宽带电路中使用的普通电解电容器,其脉搏电压频率仅为100 hz,充放电时间的毫秒数量级。 为了获得更小的脉搏系数,所需的高电容量达数十万μf,因此普通低宽带铝电解电容器的主要目标是为了听听高电容量,电容器的电容量,损耗正角切值以及漏电流是鉴别其优劣的主要参数。 而开关电源中的出口滤波电解电容器,其锯齿波电压频率高我们数十khz,它们是数十mhz,这时电容量水平不是中的关键指标,握手高宽带铝电解电容优劣的标准是“阻抗- Frequency 'features, requires the open within the working frequency power supply should have the equivalent impedance of low, for the work of semiconductor devices at the same time produce high-frequency spike has good filtering effect. 普通低宽带电解电容器在10 khz左右航班开始呈现感性,无法满脚开关电源的使用要求。 而开关电源转而高宽带铝电解电容器有四个端子,正极铝片懂事两端提款权作为电容器的正极,负极铝片性两端也分各提款权作为负极。 电流从四端电容的一个正端流入,经过电容内部,再从另一个正端流向负载; 从负载阶次也从电容性电流流入一个负端,再从另一个负端流向电源负端。 由归于四端电容具有良好的高频特性,为了减少小电压的脉搏分量以及抑制开关尖峰杂讯为了提供了极有利手段。 High-frequency aluminum electrolytic capacitor and the form of multicore, the aluminum foil is divided into short segments, with multiple leads connected in parallel to minimize the impedance component of capacitive reactance. 普通猫聘用低电阻率性材料作为提款权端子,提高了电容器承受大电流的能力。 Digital circuit to run stable and reliable, the power must be 'clean' energy supplement, and must be in a timely manner, namely filtering decoupling must be better. What is a filter for decoupling, a simple say is don't need the chip current storage energy, when you need current I can timely replenish energy again. Don't talk to me said, 'the duty is not to DCDC? Yes, they can fix in low frequency, but the high-speed digital system are different. Let's look at a capacitor, capacitance effect of simple said is the storage charge. We all know to add in the power supply capacitor filter, on each chip power foot placed a 0. 1 uf capacitance decoupling. And so on, how do I see to some of the power of the chip board feet beside the capacitance is 0. Uf 1 or 0. 01 uf, what to pay attention to it. To understand the way way to understand the actual characteristics of capacitance. 理想的电容它只电荷性记忆是一个身体,即c。 And the actual manufactured capacitance is not so simple, analysis of the integrity of the power supply when we commonly used capacitance model as shown in the figure below. Figure in the ESR is the equivalent series resistance capacitance, ESL is the series equivalent inductance capacitance, capacitance C is the true ideal. The ESR and ESL is decided by the capacitance of the manufacturing process and material, can't eliminate. 那这两个东西对电路有什麽影响。 esr影响电源纹波,esl影响电容性滤波此时率特性。 We know that the capacitance of capacitive reactance Zc = 1 / C omega, inductive reactance of inductance Zl = L, omega, ω=2πf) ,实时电容性复阻抗为z = esr + jωl - 1 / jωC = ESR + j2πf L - 1/j2πf C。 可看到当频率很低改称是电容起作用,而频率高不到一定的时候电感的作用就不可忽视了,再高上改称电感就起主导作用了。 The effect of capacitance lose filtering. 所以记住,高宽带的改称电容足以是单纯电容了。 实时电容性滤波曲线了图所示。 Mentioned above is the capacitor equivalent series inductance capacitance of manufacturing processes and materials, the actual patch of ceramic capacitor ESL from several tenths of nH to nH, the smaller the encapsulation ESL. Capacitor filter curve from above we also see that is not flat, it is like a 'V', that is a frequency selective characteristics, in the time we want it to be as flat as possible ( 前级的板级滤波) And sometimes hope for it, the more the pointed the better ( Filtering or trap) 。 Impact of this feature is the capacitor quality factor Q, Q = 1 / omega CESR, ESR, the greater the Q the smaller, the curve becomes more smooth, whereas the ESR is smaller, the greater the Q, the curve becomes more pointed. 通常钽电容和铝电解有比较小的esl,而esr大,所以钽电容和铝电解模具很宽始创性语句效频围率范,前级的板级滤波非常匹配。 In the input stage of DCDC or they often larger capacity of tantalum capacitor filter. In close to the chip put some 10 uf and 0. 1 uf capacitance to decoupling, ceramic capacitor has a very low ESR. Said so much, that what we placed near the pin of the chip is 0. 1 uf回收的。 01 uf, the following list for your reference. So, later don't see what all zero. 1 uf capacitance, some high speed the zero in the system. 1 uf capacitance don't work.
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