UPS systems can be classified into three main categories:
Brity Ning
Laptop battery | battery charger| UPS |portable power station | OEM factory | --Manufacturer&Vendor
1. Offline/standby
When AC-line voltage is present, a relay bypasses the inverter, which then remains off. The battery charger operates to maintain full charge. If the AC power fails, the relay switches the UPS output over to the inverter, which starts up after a short interruption of 10 to 20 ms to take over the emergency power supply.
2. Line-interactive
Similar to the offline UPS, but with an AC mains conditioning function to regulate the AC output to compensate for low and high-line input voltages and ensure a more stable output voltage. The system is a combination of line conditioner and offline UPS.
3. On-line/double-conversion
The AC input is converted to DC when the battery is charged and then converted back to AC so that if the AC line fails, the system seamlessly switches to battery power and the output power continues without interruption. Such systems provide a stable and clean AC output under all conditions, but there is an inherent loss of efficiency in the conversion stages. More sophisticated systems are able to mitigate this by partially bypassing the two conversion stages during AC line operation so that only a small portion of the power flows through them. If AC input fails, the inverter stage can take the full load without interrupting the output.