Application selection of conventional aluminum electrolytic capacitors

1. Advantages and disadvantages of aluminum electrolytic capacitors:

Advantages: It has obvious advantages such as easy access to large capacity, high withstand voltage, low price, etc. It is commonly used in the input and output filter circuit of the power supply.

Disadvantages: afraid of high temperatures. Because the electrolyte of the aluminum electrolytic capacitor is in a liquid state, the core heats up or the ambient temperature is high, which will cause the electrolyte to volatilize, and the long-term high temperature causes the electrolyte to dry out.

2. Application notes for aluminum electrolysis in power circuit

(1) Prevent halogen corrosion

Aluminum electrolytic capacitors are very sensitive to chlorine, bromine, etc. If halogen-containing fluxes, cleaning agents, fixatives, and fumigants are used, halides may penetrate the inside of the capacitor through the sealing rubber plug, which may easily cause corrosion of the capacitor anode. The acceleration capacitor fails after power-on. Therefore, the halogen component of the relevant sensitive preparations used in the production process must be strictly controlled.

(2) Control of the storage environment and periodic activation

It is necessary to control the storage environment and time of the electrolytic capacitors, and periodically perform power-on energization. After aluminum electrolysis is stored in a high temperature environment for a long time, a chemical reaction occurs between the capacitor anodized film and the electrolyte, resulting in a drop in withstand voltage and an increase in leakage current. When the power is suddenly turned on and the capacitor voltage is close to the rated voltage, it may cause overvoltage failure or excessive leakage current, resulting in overheating failure.

Corresponding to the single capacitor, especially the high voltage capacitor, it needs to be activated after long-term storage. It is recommended to connect the 1kΩ protection resistor in series and gradually pressurize it to the rated voltage for about 1 hour, so that the capacitor anodized film can be repaired and the leakage current returns to normal. .

(3) Reasonably lay out the components on the PCB to keep the aluminum electrolytic capacitor away from the heat source

(4) According to the product characteristics, select the solid capacitor.

For example, in the application of low voltage and high current output, use aluminum solid capacitors. Aluminum solid capacitors have extremely low ESR and high ripple current capability, making them ideal for low-voltage, high-current rectification and filtering applications.