穿心电容滤波器的分类和特点

穿心电容滤波器的分类和特点

穿心电容滤波器是一种三端电容，但与普通的三端电容相比，由于它直接安装在金属面板上，因此它的接地电感更小，几乎没有引线电感的影响，另外，它的输入输出端被金属板隔离，消除了高频耦合，这两个特点决定了穿心电容具有接近理想电容的滤波效果。

滤波器的内部电路形式分为很多种类型，利用铁氧体磁珠和电容按照不同的电路结构组合起来，可以构成C、LC、Pi、T型等滤波电路。这些电路提供了不同的滤波特性。滤波器的器件越多，通带与阻带之间的过渡带越短，插入损耗越大。下面我们就来了解下这些类型的特点和应用。

C型滤波器，单电容结构。是一种避免高频对地的噪音干扰的低自感应装置,适用于信号线滤波和直流电源线滤波，适合应用于高阻抗源和高负载的场合。

LC型滤波器，这是款带有电感元件和电容元件的EMI滤波器。不同的安装方式(方向)可以分别用于源阻抗高、负载阻抗低，或源阻抗低、负载阻抗高的场合。

Pi型滤波器，是由两个电容元件和在两个电容元件之间的一个电感元件组成。 比C型，LC型结构提供更好的高频滤波性能。适用于源阻抗和负载阻抗都高，并且对干扰抑制性能要求高（插入损耗）的场合。 

T型滤波器，由两个电感元件和一个电容元件组成。它和Pi 型滤波结构相似，但没有Pi型滤波器应用广泛,适用于源阻抗和负载阻抗都低，并且对干扰抑制性能要求高（插入损耗）的场合。

Classification and characteristics of through-core capacitor filters

The feedthrough capacitor filter is a three-terminal capacitor, but compared with the ordinary three-terminal capacitor, because it is directly mounted on the metal panel, its grounding inductance is smaller and there is almost no effect of the lead inductance. The input and output are separated by a metal plate, which eliminates high-frequency coupling. These two characteristics determine that the feedthrough capacitor has a filtering effect close to the ideal capacitor.

The internal circuit form of the filter is divided into many types. The combination of ferrite beads and capacitors according to different circuit structures can form filter circuits such as C, LC, Pi, and T. These circuits provide different filtering characteristics. The more filters there are, the shorter the transition band between the passband and the stopband, and the greater the insertion loss. Let us understand the characteristics and applications of these types.

Type C filter, single capacitor structure. It is a low self-inductive device that avoids high frequency ground noise interference. It is suitable for signal line filtering and DC power line filtering. It is suitable for high impedance sources and high loads.

LC filter, this is an EMI filter with inductive and capacitive elements. Different installation methods (directions) can be used in situations where the source impedance is high and the load impedance is low, or the source impedance is low and the load impedance is high.

The Pi-type filter is composed of two capacitive elements and an inductive element between the two capacitive elements. Compared to C-type, LC-type structure provides better high-frequency filtering performance. It is suitable for occasions with high source impedance and load impedance, and high requirements on interference suppression performance (insertion loss).

The T-type filter consists of two inductive elements and one capacitive element. It is similar to the Pi-type filter structure, but it is not widely used without the Pi-type filter. It is suitable for occasions with low source impedance and load impedance and high interference suppression performance (insertion loss).