The Difference Between Online and Standby UPS Power Supplies

Online UPS and backup UPS are two important types of UPS. When the device is powered off, both can provide power to the device. But the similarity ends here. The main difference between online UPS and backup UPS is that online UPS provides power through a combination of rectifiers and inverters. It provides power to both the load and the battery, allowing the battery to charge and supply power during power outages.

On the contrary, backup UPS provides AC power directly to the load by connecting the transfer switch. In the event of a power outage, the offline UPS is powered by backup batteries. Another key difference between online UPS and backup UPS is the requirement for a large radiator.

Online UPS consists of rectifiers, which directly provide power to the inverter and battery. In this way, the heat dissipation will be significant. Therefore, compared to backup UPS, online UPS requires larger radiators.

A、 Online UPS:

Online UPS consists of a rectifier, battery, and inverter, which are consistent with the AC mains and load. The AC power input to the online UPS is first sent to the rectifier circuit, and then converted into DC power by the rectifier circuit. Then, this DC power supply is used to charge the battery, which is supplied to the inverter circuit and then to the load.

There is a toggle switch, but it is always in the ON position. Therefore, at any time, the power transmitted to the load will come from a combination of rectification and inverter circuits. The main advantage of using an online UPS is that in the event of a power outage, there is no need to switch between the main power line path and the battery backup path.

1. Advantages of online UPS:

Online UPS does not require dual switching in case of power failure. In this way, the power transmitted to the load will not be interrupted.

The significant advantage of using an online UPS is that the isolation between the load circuit and the input circuit is appropriate, which helps to obtain signals with low distortion.

In an online UPS, the inverter is always in the ON state. Therefore, the power transmitted to the load will be available at any time, as the transmission time is zero.

2. Disadvantages of online UPS:

The design of online UPS is quite complex and requires large heat sinks.

Online UPS has higher power consumption because it simultaneously supplies power to battery backup and inverter circuits.

The design cost of online UPS is much higher than that of backup UPS.

B、 Backup UPS:

The backup UPS directly provides AC power to the equipment connected to the load. When power is lost, the backup UPS will change the position of the transfer switch. It connects the load to the battery backup path.

The backup UPS battery charges when AC power is available. In this case, the AC power is directly input into the load circuit, while the battery of the backup UPS is charged through the rectifier circuit

In the event of a power outage, the charged battery is used to provide DC power to the inverter, which converts the DC power to AC power and provides it to the load end.

1. Advantages of backup UPS:

Compared with online UPS, the design cost of backup UPS is very low.

The internal control of backup UPS is simple, with two paths that work at different times depending on the position of the switch.

The efficiency of backup UPS is very high because the battery backup and inverter are not always in the ON state like online UPS.

2. Disadvantages of backup UPS:

The quality of the electrical signal obtained by the backup UPS is poor because the inverter is not always ON.

In the event of a power outage, the transmission time is approximately 5ms, during which there will be no output power. Due to transmission time, there may be slight interruptions in output power.

Backup Ups provide AC power directly when available, and any spikes and surges in the input voltage are also transmitted to the output circuit.

C、 The main differences between online UPS and backup UPS are:

The key difference between online UPS and backup UPS lies in their working methods. Online UPS provides AC power through rectifier and inverter circuits when AC mains power is available. On the contrary, backup UPS directly provides AC mains power to the load circuit when there is power available.

Transmission time is a key term that distinguishes between online UPS and offline UPS. The transmission time of online UPS is zero because there is no switching between the inverter rectification path and the mains power supply path. The transmission time of the backup UPS is about 5 milliseconds.

Another significant difference between online UPS and backup UPS is that the inverter of online UPS is always in the ON state, while the inverter of backup UPS is only in the ON state when the power supply is unavailable.

The cost of online UPS is higher than that of backup UPS.

The efficiency of backup UPS is higher than that of online UPS because the inverter and rectifier circuit of backup UPS are not always in the ON state.

Conclusion:

UPS uninterruptible power supply is a device that continuously supplies power to the load circuit, even in the event of a power outage. Online UPS is an UPS that supplies AC mains power to the load circuit through rectification and inverter circuits, while also supplying power to the backup battery. The backup UPS directly provides AC power to the load circuit and only connects the inverter, rectifier, and battery backup during power outages.

Both are critical equipment for obtaining uninterrupted power. The choice of UPS to use depends solely on our application. If the transmission time of a few milliseconds is tolerable and you are seeking a lower cost UPS, then backup UPS will be the best choice.

But if the applications you are dealing with, such as medical devices, industrial, telecommunications, or even transmission times of a few milliseconds, are not feasible, then an online UPS should be used.