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UPS Circuit – Easily Build Emergency Backup Battery Systems

Power outages can occur in any setting. Also, a battery voltage can go below the required levels. In such scenarios, a battery backup is imperative. But you cannot have a stock of numerous acid batteries. Instead, you need a reliable backup power source. An uninterruptible power supply (UPS) is necessary for such a scenario. It ensures that all electronic equipment that requires constant input voltage keeps running. But how does a UPS circuit operate? We are going to expound on this. We’ll further elaborate on how it effectively substitutes actual mains power. Thus, keep reading for more insights. 

1. How does the UPS Circuit Work?


Figure 1: A UPS

A UPS circuit works by providing instant power when utility mains power is unavailable. The working of the circuit is primarily dependent on the UPS circuit that you are using.

Ideally, the UPS circuit is different from a generator or other standby emergency power systems, and the systems will require manually switched on. 

Instead, the UPS circuit will give instantaneous power. It features connected batteries for small energy users and generators for high-power users, and the batteries are paramount in supporting an immediate power supply.  

Usually, the UPS circuit will provide power for approximately 15 minutes, and the time is sufficient to allow proper shutting of electrical equipment like computers. Hence, a UPS is imperative in protecting electrical gadgets and systems that cannot withstand abrupt power disruptions. 

2. Type of UPS Circuit

A Consultant Controls a UPS

Figure 2: A Consultant Controls a UPS

There are three main kinds of UPS systems. Thus, choose the type that suits your power needs. They include standby, double-conversion, and line-interactive. 

Offline Standby

The offline standby is the most straightforward backup UPS Product. When there is a power issue, the UPS will change to a battery backup power. Typical power issues include a blackout, sag, or a voltage surge. 

When there are any issues in the input power source, the UPS will first change to DC power. The UPS has an AC inverter that changes the current to AC electric power. Such a UPS also gives adequate power to everyday electronic gadgets.


The UPS will solve a minute power disturbance without shifting to battery mode. It features an autotransformer that regulates voltage changes. Voltage changes, in case, include blowouts and swells. 

The power kit can serve low-end servers, ordinary components, and gaming systems, among other sophisticated gadgets. 

A UPS unit

Figure 3: A UPS unit. 

Online/Double Conversion

The power conditions of the incoming input do not matter for this UPS. Irrespective of its form, the UPS will give clean electric power. 

Like the offline standby type, this type first changes input AC power to DC. Again, it converts the DC power to AC. 

All UPS systems can be on DC power throughout. Hence, most feature no transfer time as they don’t need to change to DC power. Such UPS systems are ideal for high-end servers and other sophisticated gadgets. 

3. 4 Simple Uninterruptible Power Supply (UPS) Circuits

A 230V UPS System

Figure 4: A 230V UPS System

We’re going to discuss four central UPS circuits that you can create with  12-V Lead-acid batteries. 

Simple UPS using a Single IC

A UPS in Battery Mode

Figure 5: A UPS in Battery Mode

You can build this circuit using standard components. While it’s of simple build, it can effectively run a wide array of output devices. There are two main parts of this circuit. First, there is a UPS Inverter part and the battery design part.

At the inverter stage, there are several components. They include 20K, two 1K, and two 20 ohm resistors. Others are capacitors, IC SN74LVC1G132, IC 4017, IC 7085, and a transformer. 

Note that the value of the capacitor and resistor will determine the rate of the oscillator’s operation. The input is a square wave in the circuit, and hence, the output will also be a square wave. 

The other critical section is the automatic battery charger stage. For optimal performance of the charger system, an accurate battery charger design is imperative. 

Single Transformer UPS for Inverter and Battery Charging

For this circuit, one transformer is enough to provide sufficient charge to the battery banks. In the course, one of the cardinal components is the MOSFET, and it features a reverse high-power diode for providing battery power. Hence, there is no need to use additional diodes. 

IC 555 Based UPS Circuit

UPS Batteries

Figure 6: UPS Batteries 

You can also create a simple UPS capable of fulfilling a variety of applications with pulse wave modulation (PWM). Note that IC 555 is cardinal in the creation of PWM pulses.

Assembling the system will also not cost you a lot as it requires simple and cheap components. 

How do you make such electrical circuits? It all involves prompting the output electronic components to switch depending on the applied PWM pulses. The action will, in turn, drive the transformer to create an AC output current. Note that this current resembles a typical AC sine wave.

This circuit’s critical parts include a 3V Zener diode and other diodes such as  1N4148, 1N4007, and 1N5402. Other critical components include transistors, capacitors, and an IC 4049. Also, expect to find a transformer.

The most critical component is the IC 555. Hence, it is the reason we are using the IC to refer to the emergency power system. 

The system also features an automatic battery charger circuit part. 

1kva UPS Design

Universal Inverters

Figure 7: Universal Inverters

The other standard UPS circuit is this design which provides a constant voltage to run a 1000-W device. Typically, it is a high voltage system. As a result, it does not require a transformer. Like the other systems we have discussed above, this system has two sections. One is the inverter part, and the other is the battery charger section. 

On the battery section, there are relays. They are responsible for shifting the batteries to charging mode when AC input is present. When the mains power goes off, the relays will turn the batteries to inverter mode. 


As we have highlighted in the article, a UPS circuit is essential. We have covered several UPS circuit designs. 

As you choose the one to settle for, professional judgment is imperative. Consult an expert for legal advice on the proper UPS for your power needs. 

Also, talk to us in case of any query, and we will assist you to our level best. 

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Emma Lu
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