Selection of electrolytic capacitor for power adapter

　　As power adapters have lower and lower ESR requirements for output rectifier filter capacitors, electrolytic capacitor manufacturers are forced to try to make cheaper and lower ESR electrolytic capacitors. At the same time, the working temperature of power adapters is getting higher and higher, and the requirements The maximum operating temperature of the output rectifier filter capacitor is also getting higher and higher, from the past 85 ℃ to 105 ℃ or even higher temperature: with the improvement of the reliability of other electronic components, it has always been an electrolytic capacitor with a short board in the reliability of electronic circuits. It seems to be more restrictive of the reliability and service life of the power adapter, so long-life output rectifier filter electrolytic capacitors. The current high-frequency and low-ESR electrolytic capacitors generally have a lifespan of more than 2000. 6000 lifespans are also very common and commonly used, and even appear The high-frequency and low-ESR electrolytic capacitors with a life of 10000h provide a strong guarantee for the reliability and life of electronic circuits and power adapters. In other words, electrolytic capacitors may no longer be the shortcomings of power adapters.

　　Why is it said that it is an electrolytic capacitor instead of using other types or dielectric capacitors? The reason is simple, this is the price. Among many capacitors, the volume of electrolytic capacitors is relatively one of the smallest, and the more important thing is that they are at the same rated voltage. Under the condition of capacitance, electrolytic capacitors are the cheapest.

　　Because of this, most power adapters choose electrolytic capacitors for output rectification filter capacitors.https://powerstation-gf.com/prodcuts/SPS-001-wall-mounted-home-energy-storage_283.html

　　The first step in selecting an electrolytic capacitor for output rectification and filtering is to select its rated voltage. Among the various parameter selections of the capacitor, the selection of rated voltage is relatively simple, as long as the rated voltage is slightly higher than the working voltage.

　　For example, when the output voltage is a 5V power adapter, you can choose a rated voltage of 6.3 or 10v; there is no need to choose a rated voltage of 16V or above. The reason is simple, the rated voltage is high, the volume is large, and the cost is high.

　　When outputting 12V power adapter, you can choose a rated voltage of 16V or 25V.

　　Selection of capacitance

　　The choice of capacitance will depend on two factors, the minimum capacitance requirement and the ripple current requirement.

　　1. Select the capacitance according to the minimum capacitance requirement

　　The minimum capacitance requirement is to ensure that the flyback power adapter does not cause low-frequency self-oscillation due to the low capacitance of the output finishing filter capacitor. If a low ESR electrolytic capacitor is used, generally you can choose to output an average current per ampere with a capacitance of 1000µF.

　　If you use polymer electrolytic capacitors or ceramic capacitors, you can choose to output an average current of 400µF per ampere.

　　2. Select the capacitance according to the actual ripple current flowing through the capacitor

　　Since the ripple current that the electrolytic capacitor can withstand is relatively low, if you want the electrolytic capacitor to withstand the ripple current generated by the flyback power adapter, you need to choose a relatively large capacitance to meet the current requirements.

　　Under normal circumstances, each 1000F can withstand the ripple current generated by the average output current of 1A (usually 1.2A or slightly higher).

　　Selection of the highest working temperature and life

　　The choice of output rectifier filter capacitor always needs to consider the cost of the capacitor. If there are no special requirements, the cheaper the better.

　　Relatively speaking, electrolytic capacitors with a low maximum operating temperature are cheaper than those with a high maximum operating temperature; similarly, for the same maximum operating temperature electrolytic capacitors, it is inevitable that the long life is more expensive than the general life. Therefore, if the flyback power supply The adapter has no special requirements on the life of the output rectifier filter capacitor and the maximum operating temperature. 85℃/2000h products can be used, which is the cheapest. The 85℃/2000h products are the lowest grade products in China.

　　If the working temperature of the power adapter is relatively high, or even very high, you need to consider choosing an electrolytic capacitor of 105°C. If a longer life is required, you need to choose an electrolytic capacitor with a suitable life according to your needs. For example, 6000h, etc.

　　Selection of electrolytic capacitor for power adapter

Read recommendations:

350W power amplifier power supply

6W adapter

The Exporter Charger 5W Made In Shenzhen Perfection For Audio And Video Using Without USB Port

Do you really understand laptop batteries and power adapters?

Hardware EMC specifications that power adapter engineers must know