In a DC circuit, a capacitor is the equivalent of a circuit breaker. A capacitor is a component capable of storing an electrical charge and is one of the most commonly used electronic components.
It starts with the structure of the capacitor. The simplest capacitor is composed of pole plates at both ends and an insulating dielectric (including air) in the middle. When energized, the pole plates are charged, creating a voltage (potential difference), but the entire capacitor is non-conductive because of the insulating substance in the middle.
However, such a situation is under the condition that the critical voltage (breakdown voltage) of the capacitor is not exceeded.
However, in AC circuits, because the direction of the current changes as a function of time. And the process of charging and discharging a capacitor is time-dependent, and at this time, a changing electric field is formed between the pole plates, and this electric field is also a function of time. In fact, the current passes between the capacitors in the form of an electric field.
1) Bypass
A bypass capacitor is an energy storage device that provides energy to the local device, which evens out the output of the regulator and reduces the load demand. Like a small rechargeable battery, the bypass capacitor can be charged and discharged to the device. To minimize impedance, the bypass capacitor should be placed as close as possible to the supply power pin and ground pin of the load device. This is a good way to prevent ground potential elevation and noise caused by excessive input values. The ground potential is the voltage drop at the ground connection when passing through a high current burr.
2) Decoupling
Decoupling, also known as decoupling. In terms of circuit, it can always be distinguished as the source of the driver and the load being driven. If the load capacitance is relatively large, the driver circuit to charge and discharge the capacitor, in order to complete the signal jump, when the rising edge is steeper, the current is larger, so that the drive current will absorb a large supply current, due to the circuit inductance, resistance (especially the chip pin inductance) will produce a rebound, this current is actually a noise relative to the normal situation, will affect the normal work of the front stage normal operation, which is called “coupling”.
The decoupling capacitor is a “battery” to meet the current variation of the driving circuit, avoiding mutual coupling interference and further reducing the high frequency interference impedance between the power supply and the reference ground in the circuit.
Combining bypass capacitor and decoupling capacitor will be easier to understand. The bypass capacitor is actually decoupled as well, only the bypass capacitor generally refers to high-frequency bypass, that is, to provide a low-impedance drain path for high-frequency switching noise.
High-frequency bypass capacitor is generally small, according to the resonant frequency is generally taken as 0.1