The working principle of a capacitor is to store electrical energy by storing charges on the electrodes, and it is usually used together with an inductor to form an LC oscillator circuit. The working principle of metallized capacitors is that the charges will move under the force in the electric field. When there is a medium between the conductors, it will hinder the movement of the charges and make the charges accumulate on the conductors, resulting in the accumulation and storage of charges. Metallized capacitors are one of the electronic components widely used in electronic equipment, so they are widely used in DC blocking, coupling, bypass, filtering, tuning loops, energy conversion, control circuits, etc. As one of the passive components, the role of capacitors is nothing more than the following:
1. Applied to power circuits to realize the functions of bypass, decoupling, filtering and energy storage.
The following categories are detailed:
1) Bypass
Bypass capacitors are energy storage devices that provide energy to local devices, which even out the regulator's output and reduce load demand. Like a small rechargeable battery, the bypass capacitor can be charged and discharged to the device. To minimize impedance, bypass capacitors should be placed as close as possible to the power and ground pins of the load device. This is a good protection against ground potential rise and noise caused by excessively large input values. Ground bounce is the voltage drop across a ground connection when a large current spike is passed through it.

2) Remove the lotus root
To remove lotus root, also known as lotus root solution. From a circuit perspective, a distinction can always be made between the source of the drive and the load being driven. If the load CBB capacitance is relatively large, the driving circuit needs to charge and discharge the capacitance to complete the signal transition. When the rising edge is relatively steep, the current is relatively large, so the driving current will absorb a large power supply current. Due to the circuit The inductance and resistance in the circuit (especially the inductance on the pins of the chip will bounce back), this current is actually a kind of noise compared to the normal situation, which will affect the normal operation of the previous stage. This is the so-called "coupling ".

3) Filtering
Theoretically (that is, assuming that the capacitor is a pure capacitor), the larger the capacitor, the smaller the impedance, and the higher the passing frequency. But in fact, most capacitors exceeding 1μF are safety capacitors, which have a large inductance component, so the impedance will increase when the frequency is high. Sometimes it is seen that there is a large electrolytic capacitor connected in parallel with a small capacitor. The larger the capacitance, the easier it is for low frequencies to pass, and the larger the capacitance, the easier it is for high frequencies to pass through. Specifically used in filtering, a large capacitor (1000μF) filters low frequencies, and a small capacitor (20pF) filters high frequencies. Some netizens once compared the filter capacitor to a "pond". Since the voltage across the capacitor will not change suddenly, it can be seen that the higher the signal frequency, the greater the attenuation. It can be said that the capacitor is like a pond, and the water volume will not change due to the addition or evaporation of a few drops of water. It converts changes in voltage into changes in current. The higher the frequency, the greater the peak current, thereby buffering the voltage. Filtering is the process of charging and discharging.

4) Energy storage
The energy storage type safety capacitor collects the charge through the rectifier, and transmits the stored energy to the output terminal of the power supply through the converter lead. Aluminum electrolytic capacitors (such as B43504 or B43505 from EPCOS Company) with a voltage rating of 40-450VDC and a capacitance value of 220-150 000μF are commonly used. According to different power requirements, devices are sometimes connected in series, in parallel or in combination. For power supplies with a power level exceeding 10KW, generally larger pot-shaped screw-terminal capacitors are used.