Do not despise small capacitance oh. His role is very large, do you see any use of his electronic products do not. Where there is a bad use, die ugly, so first of all introduce the role of capacitance.
As one of the passive components of the capacitor, its function is the following:
1- applies in the power supply circuit, realizes the bypass, the Lotus root, the filter and the energy storage aspect capacitance function.
The following categories detail:
Filtering is an important part of the capacitance. Used in almost all power circuits. Theoretically (that is to say, the capacitor is a pure capacitor), the larger the capacitance, the smaller the impedance, the higher the frequency. But in fact more than 1uF of capacitors are mostly electrolytic capacitors, there is a large inductance component, so the higher the frequency of the impedance will increase.
Sometimes you will see a large capacitance of electrolytic capacitor in parallel with a small capacitor, at this time the large capacitor, low frequency, small capacitance Qualcomm. The function of the capacitor is to pass high resistance, low frequency. The greater the capacitance, the more easily through the low frequency, capacitance, the greater the more easily through.
Specifically used in filtering, large capacitance (1000uF) filter low-frequency, small capacitance (20pF) filter high-frequency. There has been a netizen to filter capacitance compared to “pond.” Because the capacitor at both ends of the voltage will not mutate, it can be said that the higher the signal frequency attenuation is larger, it is very image of the capacitor like a pond, will not be added or evaporated by a few drops of water caused by the change. It converts the change in voltage to the change of current, the higher the frequency, the greater the peak current, thus buffering the voltage. Filtering is the process of charging and discharging.
The bypass capacitor is a storage device that provides energy for the local device, which can make the output of the voltage stabilizer more homogeneous and reduce the load demand. Like a small rechargeable battery, the bypass capacitor can be recharged and discharged to the device. To minimize impedance, the bypass capacitor should be as close to the load device as possible to the power supply of the foot and foot. This is a good way to prevent ground potential elevation and noise caused by too much input value. A ground bomb is a voltage drop that is connected to the ground through a large current burr.
3) to the Lotus root
To the Lotus root, also known as the Solution Lotus. From the circuit, it is always possible to differentiate between the source of the drive and the load being driven. If the load capacitance is relatively large, the driving circuit to the capacitor charging, discharge, in order to complete the signal jump, in the rise along the steeper, the current is relatively large, so that the current will absorb a large power supply current, due to the inductance in the circuit, resistors (especially the chip tube on the foot of the inductor, will produce a rebound), the current relative In the normal case is actually a noise, will affect the normal work of the front level. This is the coupling. The decoupling capacitor is a function of a battery, which satisfies the change of the current of the driving circuit and avoids the coupling interference between them. The combination of the bypass capacitor and the decoupling capacitor will be easier to understand.
The bypass capacitor is also to go to the Lotus, but the bypass capacitor generally refers to high-frequency bypass, that is, to high-frequency switching noise to improve a low impedance relief channel. High-frequency bypass capacitors generally relatively small, according to the resonant frequency is generally 0.1u,0.01u, and the coupling capacitance is generally larger, 10uF or greater, according to the distribution of the circuit parameters, as well as the driving current changes in size to determine. The bypass is the interference of the input signal as the filter object, and decoupling is the interference of the output signal as the filter object, to prevent the interference signal back to the power supply. This should be their essential difference.
4) Energy Storage
The energy storage capacitor collects the electric charge through the rectifier and transmits it to the output end of the power supply through the converter lead. The voltage rating of 40~450VDC, capacitance value of 220~150 000uF between the aluminum electrolytic capacitor (such as Epcos Company’s B43504 or B43505) is more commonly used. According to different power requirements, the device will sometimes use series, parallel or combination of the form, for power level more than 10KW power supply, usually the larger size of the tank-shaped spiral terminal capacitor.