Uninterruptible Power Supply

UPS (Uninterruptible Power Supply) is an emergency power supply with a backup device. It is mainly used to provide sudden power supply to some devices that require high power supply stability.

When the mains power input is normal, the UPS stabilizes the mains power and supplies it to the load. At this time, the UPS is an AC voltage stabilizer, and it also charges the internal battery; when the mains power is interrupted (accidental power outage), The UPS immediately converts the DC power from the battery to continue to supply 220V AC power to the load through the inverter switching method, so that the load can maintain normal operation and protect the load software and hardware from damage. UPS equipment usually provides protection against overvoltage or undervoltage.


Uninterruptible power supply (UPS) is a system device that connects the battery (mostly lead-acid maintenance-free batteries) to the host and converts DC power into commercial power through module circuits such as the host inverter. It is mainly used to provide stable and uninterrupted power supply to a single computer, computer network system or other power electronic equipment such as solenoid valves, pressure transmitters, etc., to ensure the uninterrupted operation of these equipment and instrument. This method ensures the uninterrupted operation of these equipment and instruments to prevent computer data loss, telephone communication network interruption, or instrument loss of control.

Uninterruptible power supplies are widely used in: mining, aerospace, industry, communications, national defense, hospitals, computer business terminals, network servers, network equipment, data storage equipment, emergency lighting systems, railways, shipping, transportation, power plants, substations, nuclear power plants, fire protection Security alarm systems, wireless communication systems, program-controlled switches, mobile communications, solar energy storage energy conversion equipment, control equipment and emergency protection systems, personal computers and other fields.

Working Principle

System composition

A typical UPS system block diagram: Its basic structure is a set of rectifiers and chargers that convert alternating current into direct current, and an inverter that converts direct current into alternating current. The battery stores energy and maintains it at a normal level when the alternating current is normally supplied. In terms of charging voltage, once the mains power supply is interrupted, the battery immediately supplies power to the inverter to ensure the AC output voltage of the UPS power supply.

Connection method

  • A single UPS power supply can supply all loads, and the connection method is relatively simple.
  • The total load power requires two or more UPS power supplies. This connection method is called parallel connection without backup.
  • The total capacity of two or more UPS power supplies is greater than the total load capacity, but the system must have one more UPS power supply capacity than the total load capacity. When any UPS power supply fails, the others can still supply the entire load. This connection method is called parallel connection with backup method.
  • After the entire UPS power system fails, the mains disconnects the UPS power supply and connects the load directly without affecting the maintenance of the UPS power system.

When there is no fault in the UPS power system, the maintenance switch is opened, and the input switch and output switch are closed; when the UPS power system fails, the maintenance switch is closed, and the input switch and output switch are opened. In this way, the normal operation of the electrical load is guaranteed without affecting the online repair of UPS power system faults.