What Is an Uninterruptible Power Supply？

An uninterruptible power supply (UPS) can use a battery to provide backup power for other AC electrical equipment when the utility power fails.

Uninterruptible power supplies fall into two categories: The first is called a standby or offline UPS. Under normal circumstances, a standby UPS acts as a kind of electrical middleman. It plugs into a wall outlet and distributes AC power from that outlet to other electrical devices connected to it. In addition to distributing power, UPS units often provide surge protection, but an uninterruptible power supply doesn't really work until after a power outage! Once it detects that the current fluctuates downwards or stops flowing, the power inverter of the backup UPS turns on immediately to convert the DC power in the battery to AC power to provide backup power to the equipment under the protection of the UPS.

The second type of uninterruptible power supply is called a continuous or online UPS. The functionality of a continuous UPS is much more complex than that of a backup UPS. Instead of distributing AC power from a wall outlet like a backup UPS, a continuous device runs the device powered by its battery, which is then continuously charged. A continuous UPS does not need to switch it to battery mode, which means there is no time delay in the event of a utility power outage. Therefore, continuous UPSs are mainly used in situations where critical data or extremely sensitive components are handled.