What is the purpose of using a UPS for computer?

UPS or uninterruptible power supply is commonly used for desktop computers. Laptop computers have their own built-in battery so that a UPS is not needed. You can use one for your Wi-Fi internet router for preventing loss of connectivity while browsing the internet or downloading a file from the internet. A home UPS for desktop computers usually have only a short back up time of about 15 to 30 minutes. This period allows you to save the files you were working on and prevent loss of data when there is a power outage. The UPS senses loss of mains power supply and switches to back up battery. This avoids loss of data in the random access memory or RAM.

Data stored in the RAM will be lost permanently if power supply is cut off. Even in the presence of a UPS, you have to save the files before the UPS battery is depleted. UPS prevents damage to the computer in case of sudden power outage. UPS uses a switch mode power supply or SMPS to convert the low voltage DC battery supply to a high voltage AC suitable for the desktop computer. In effect that functions as an inverter. Within the computer another SMPS provides the required DC voltage for various circuits. If you have a home inverter connected, then the function of UPS is only to prevent the transient break in power when the grid power supply fails and inverter takes over.