Feed Through Capacitor EMI Ceramic Capacitor,EMI filter

Description

Feed Through Capacitor EMI Ceramic Capacitor

Feed Through Capacitor EMI Ceramic Capacitor, which is “electromagnetic” and “interference”.

The so-called “interference” refers to the two-layer meaning that the performance of the device is reduced after interference and the interference source that interferes with the device. The first layer of meaning such as thunder and lightning makes the radio produce noise, the motorcycle screen is driving around, snowflakes appear on the TV screen, and the radio sound is heard after picking up the phone. These can be referred to as “BC I” “TV I” “Tel I” , These abbreviations have the same “I” (interference) (BC, TV, Tel) followed by “electromagnetic”. If the charge is static, it is called static electricity. When different potentials move in unison, an electrostatic discharge occurs, generating a current, and a magnetic field is generated around the current. If the direction and magnitude of the current continue to change continuously, electromagnetic waves are generated. Electricity exists in various states, and we call these states collectively electromagnetic.

What is an EMI filter
The EMI mentioned here is the English abbreviation of Electro Magnetic Interference, which is the electromagnetic interference filter. It is a passive filter composed of inductance and capacitance. It allows the low-frequency useful signals to pass through smoothly, while suppressing high-frequency interference. This filter is a new type of component that has been popularized and applied in recent years. It can effectively suppress grid noise, improve the anti-interference ability of electronic equipment and the reliability of the system. It can be widely used in electronic measuring instruments, computer room equipment, switches Power supply, measurement and control system and other fields.
The feedthrough capacitor 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 influence of the lead inductance. In addition, its input and output The ends are isolated by a metal plate, eliminating high-frequency coupling. These two characteristics determine that the feedthrough capacitor has a filtering effect close to that of an ideal capacitor.

What is a feed-through capacitor
The capacitors used in EMI filters are generally ceramic capacitors. Due to their physical structure, such ceramic capacitors are also called feedthrough capacitors. The self-inductance of feed-through capacitors is much smaller than ordinary capacitors, so the self-resonant frequency is very high. At the same time, the feed-through design also effectively prevents high-frequency signals from going straight from the input
Connect to the output. This combination of low-pass and high-impedance provides excellent suppression in the 1GHz frequency range. The simplest through-core structure is one (C type) or two capacitors (Pi type) composed of internal and external electrodes and ceramics. The capacity of this capacitor can be from 10pF to 2uF, and the operating voltage can reach 2000VDC. Tubular feedthrough capacitors, because of their coaxiality, will not produce significant self-resonance even at 10GHz.
The medium of the feed-through capacitor is a ceramic medium, and the capacity of the ceramic capacitor will change with the change of the ambient temperature. This change in capacity will affect the filter cut-off rate of the filter. The rate of temperature change of the capacitance of the ceramic capacitor is determined by the ceramic medium itself. Therefore, it is very important to choose an appropriate ceramic medium.

Feed Through Capacitor EMI Ceramic Capacitor classification

1) Chip filter
There are two types of patch type and lead type, small size, can be used for surface mounting, saving PCB space and installation time.
2) Resin sealed package filter
This filter is divided into two types according to different installation methods: welded and threaded.Installed, the circuit structure has C type, L type, LC type, Pi type, T type To choose.
3) Glass sealed package filter
Use glass package, suitable for harsh environment, high filtering performance, widely usedIn the fields of aviation and aviation. Circuit structure has C type, LC type, Pi type, T type And double T.
4) Filter array
The filter array is a combination of multiple welding filters, which can be selected according to customer requirements Select multiple filters with different filter characteristics or the same filter characteristics, welded on the same bottom On the board, a standard array interface is formed, and the cable can be plugged in when connected.It is very convenient to use.
5) Filter connector
The filter connector is to add a filter to the standard connector. Filter connector With I / O interface, it can provide good electromagnetic interference suppression effect. Filter Company The connector has various forms such as D type and round shape, which can be docked with the standard connector.
6) Power filter
The power filter is used in the power supply system of the circuit, which can suppress the transmission through the power line.The electromagnetic interference that leads to the circuit can also suppress the interference generated by the circuit and feed back to the power supply Power supply is the most economical choice to solve EMI problems.