1. Concept
A capacitor, as the name implies, is a container for storing electricity, similar to a battery, but with a smaller capacity. Capacitor is the storage of electricity. When the power supply is turned off, the stored electricity can still be used for short-term power supply, so as to avoid the impact of short-term power failure on the circuit.
The circuit as shown in the figure below:
This is a simple LED circuit. When we press the button, the light bulb will be charged. After releasing the button, the light bulb will turn off. Press and release the button quickly, and the LED light bulb will continue to flash. Then we add a capacitor.
The modified circuit diagram is shown above, this time we quickly press and release the button again, and the LED bulb will always be on. This is because the capacitor charges when the button is pressed and discharges when the button is released, briefly providing power to the load.
2. Basic parameters
Here we take electrolytic capacitors as an example to introduce several common parameters:
The first is the maximum withstand voltage value. The capacitor in the figure is 16V, which means the maximum withstand voltage is 16V.
The second is the capacity. The capacity of the capacitor is farad. The capacity of the capacitor in the figure is 2200 microfarads (μF).
The last is the temperature resistance level. The maximum working temperature of the capacitor in the figure is 105°C.
Common capacitor types are as follows:
In the schematic diagram, each capacitor is generally represented by the following symbols:
3. Working principle
The capacitor is composed of two conductive metal plates, and the middle of the two metal plates is filled with an insulator such as ceramics.
Capacitor charging process:
Connect the capacitor to the positive and negative poles of the power supply. Due to the potential difference, the first stage of the capacitor will gather many electrons. When there is no potential difference, that is, when the voltages on both sides are equal, the electrons will no longer flow, and the charging is completed. The electrons stored on this pole of the capacitor are the capacitor storage. of electric energy.
The discharge process of the capacitor:
When the capacitor is fully charged, the voltage in the capacitor exists at this time, and the electrons need to flow from the negative electrode to the positive electrode to discharge. Due to the insulator of the middleman, if an external load is connected at this time, the short-term power supply can be completed.
4. Application scenarios
Based on the above theory, capacitors have the ability to supply power for a short time after a sudden voltage change. Therefore, the main uses of capacitors are filtering, energy storage, and direct traffic isolation.