Mini UPS System: Power Backup Solution for Small Electronics


In today’s fast-paced society, where our reliance on electronic gadgets has reached unprecedented levels, unexpected power disruptions and fluctuations can lead to significant inconveniences. An innovative solution has emerged—an incredibly efficient and portable power backup system. It is the introduction of a remarkably compact device that discreetly ensures a continuous power supply for our electronics during unforeseen power outages or unwelcome voltage instabilities. This ingenious creation, a Mini UPS, efficiently safeguards against disruptions by providing a temporary power source. Its user-friendly attributes and affordable pricing have contributed to its widespread adoption for personal and professional applications. Unquestionably, the seamless operation of our interconnected electronic companions hinges on this discreet but indispensable technology, guaranteeing uninterrupted performance.

This article explores a compact power solution, a mini UPS (Uninterruptible Power Supply) system, underscoring its importance and critical components. We delve into its operational aspects, including the circuit diagram, system setup, advantages, and applications across various scenarios. The article highlights the merits of the mini UPS as a portable and condensed device that offers backup power to electronic equipment during voltage fluctuations and power disruptions.

A UPS, short for uninterruptible power supply, ensures a continuous and uninterrupted power supply to connected devices. Unlike generators that require startup time, a UPS provides instantaneous and steady electricity. When faced with a power outage or similar interruptions, delivering uninterrupted power to essential devices such as computers and servers becomes crucial. This, in turn, helps prevent data loss and other issues arising from abrupt power failures.

To exemplify the system, please refer to Figure 1, which depicts a Mini UPS System.
To exemplify the system, please refer to Figure 1, which depicts a Mini UPS System.

The purpose of a mini UPS revolves around providing reserve power to devices during power disruptions. Comprised of a battery that stores DC power, it supplies AC power when needed. This device proves highly valuable to individuals who require uninterrupted operation of their electronic devices during power outages. By utilizing a micro UPS, users can have peace of mind knowing their devices will continue to function seamlessly during power disruptions.

Many electronic devices require an uninterruptible power supply (UPS) to maintain functionality during power outages. This micro UPS circuit serves precisely that purpose, delivering uninterrupted power to DC-powered instruments operating at 12V, 9V, and 5V. With this circuit in place, users can confidently rely on their devices to remain operational despite power interruptions. When the primary power source falters, the secondary battery seamlessly takes over the load, ensuring a smooth transition without interruptions or delays. Providing 12V, 9V, and 5V operating voltages, this adaptable power supply unit can effectively serve as a workstation power source.

Critical Components of a Mini UPS Circuit Board

A compact uninterruptible power supply (UPS) is a vital tool, discreetly ensuring continuous power supply in unforeseen electricity disruptions. Comprising crucial elements, the focal point lies on the battery component, acting as the main for its seamless operation.

1. Battery

The battery provides backup power to the connected devices during a power outage. In a power disruption, the Mini UPS system would be ineffective without the battery. As a result, ensuring the proper condition and ample capacity of the energy source to sustain the connected devices for the required duration becomes crucial.

2. The Charging Circuit

Whenever the primary power source becomes accessible, the circuit responsible for replenishing the energy levels becomes highly significant. Ensuring proper regulation of the battery charging process is essential to achieve optimal performance and avert potential harm. The purpose of the regulation procedure is to carefully monitor the charging process, preventing the risk of excessive charging that could harm the energy source. The battery can be effectively charged through careful modulation of the charging process, guaranteeing both its longevity and peak performance.

3. The Inverter Circuit

The primary objective of the inverter circuit is to transform the direct current (DC) voltage from the rectifier or battery back into the alternating current (AC) voltage necessary to power the critical load. This procedure ensures a consistent and uninterrupted power supply to the essential burden. The absence of the inverter circuit would render the double conversion process inadequate, rendering the critical load vulnerable to power interruptions. Hence, the inverter circuit is crucial in upholding the system’s reliability and effectiveness. By converting AC to DC and then back to AC, employing filtering techniques in the process, disruptive occurrences like spikes, sags, surges, and electrical noise are eliminated, resulting in a clean output with a pure sine waveform.

4. The Control Circuit

Control circuits are an indispensable component of electronic systems, regulating and guiding the flow of electrical signals within an electronic device. In the case of a miniature uninterrupted power supply (UPS) system, the control circuit operates as the system’s central processing unit or “brain.” Its primary function revolves around closely monitoring the primary power source, the charge level of the energy source, and the system’s power requirements. When a power interruption is detected, the control circuit activates the switching mechanism, allowing for seamless power transfer from the main supply to the energy source, ensuring uninterrupted system operation.

Understanding the Working of Mini UPS

The process of operating a Mini UPS is relatively simple. It comprises a set of components: a battery, charger, and inverter. When the power supply is present, the battery is charged, and the inverter converts the DC power from the battery into AC power. This converted AC power is then supplied to the electronic device. In case of a power interruption, the Mini UPS automatically switches to battery power, ensuring the uninterrupted operation of the electronic device. The duration of battery backup for the Mini UPS depends on the battery capacity and the power consumption of the electronic device. This device is indispensable for individuals relying on electronic devices for work or recreational activities. It guarantees the security and functionality of the electronic device during power outages or fluctuations by delivering a consistent and uninterrupted power supply.

Design 1 Circuit Diagram

As for electrical engineering, voltage level conversion plays a crucial role. A standard step-down transformer provides a 12V AC output in this scenario. Following this, diodes D1 and D2 are utilized to rectify this voltage. Capacitor C1 supplies steady and uninterrupted direct current (DC) to the battery and the other circuit components. This ensures the battery is charged effectively and the circuit operates without fluctuations or disruptions. When the primary power source is turned on, diode D3 becomes forward-biased, enabling the battery to be charged. Resistor R1 is responsible for limiting the charging current. A voltage comparator containing a potentiometer (VR1) with a value of 10k and a transistor (T1) can signify the voltage level. This arrangement permits accurate voltage measurement. The VR1 has been precisely calibrated to ensure that the LED1 is presently in the ‘off’ state. When the battery is fully charged, the LED1 indicator illuminates to indicates a voltage of 12 volts.

Figure 2 12V Mini UPS Circuit Diagram
Figure 2 12V Mini UPS Circuit Diagram

System Setup

This circuit is intended to provide an uninterruptible power supply (UPS) for 12V, 9V, and 5V DC-powered devices with a maximum current of 1A. In the event of a power outage, the reserve battery will immediately assume the burden without any spikes or delays. It may also be used as a power supply for a workstation, providing 12V, 9V, and 5V operating voltages. The circuit disconnects the load instantaneously when the battery voltage falls below 10.5V to prevent a severe discharge. LED1 is used to signify the battery’s voltage level after a complete charge. Miniature white LEDs (LED2 and LED3) are utilized as emergency lighting, particularly during power outages at night.

In the event of a power outage, the reverse bias of diode D3 and forward bias of diode D4 allows for seamless transfer of the load to the battery without any delay. To prevent the battery from deep discharging, a cut-off circuit is implemented when the voltage of the battery or input voltage drops below 10.5V. The cut-off circuit is comprised of three components: resistor R3, zener diode ZD1 (with a voltage rating of 10.5V), and transistor T2. Transistor T2 conducts when the voltage exceeds 10.5V. This causes the negative polarization of its base, which is determined by the combination of R3, VR2, and ZD1. When the voltage falls below 10.5V, the zener diode ceases to conduct, and the base voltage of transistor T2 becomes positively charged. When the device enters the ‘cut-off’ mode, the output stage’s current flow is effectively stopped. The voltage regulator circuitry uses a preset VR2 (22k) to modulate the voltage below 0.6V, allowing T2 to function correctly. This regulation mechanism is only activated when the voltage surpasses 10.5V.

In the presence of mains power, the 12V, 9V, and 5V output voltages are readily available to power the designated load. When the primary power source is unavailable, the output voltages can only power the load if the battery is entirely charged. LED1 glows to signify this. The battery is partially set, producing a limited output of 9 and 5 volts, respectively. Note that no result will be produced if the voltage falls below 10.5V. It is crucial to observe that when the UPS system is in battery mode, the work at terminal A may fluctuate between 10.5V and 12V if the battery voltage varies between 10.5V and 13V. Users of the UPS system must be aware of the possible output variations that may occur during battery mode operation.

A, B, and C are the three output nodes of the circuit under consideration. These nodes are controlled by two integrated circuits (IC1 and IC2) and a zener diode. A’s output provides 12V, while B’s and C’s outputs provide 9V and 5V, respectively. The emergency light has ultra-bright white LEDs, specifically LED2 and LED3, and current limiting resistors R5 and R6. The light can be manually activated and deactivated through switch S1. The circuit’s construction is executed on a versatile printed circuit board (PCB) that can be utilized for various purposes. Sufficient space has been provided between the multiple components to prevent any overlapping. Heat sinks have been effectively implemented for the transistor T2 and regulator ICs to dissipate heat, specifically the 7809 and 7805 models.

After completing all necessary adjustments, the circuit can be connected to the battery and transformer. This will effectively activate the mini UPS system, allowing it to function as intended. The course employs a 12V, 4.5Ah UPS battery as its power source.

Design 2 Circuit Diagram

A basic and user-friendly 12V mini uninterruptible power supply (UPS) serves as a valuable device for offering emergency power to electronic gadgets during power disruptions. It relies on a 12V battery and effectively energizes appliances like routers, modems, and other low-energy electronic devices. This UPS is intelligently engineered to seamlessly transition to battery power whenever the primary power supply encounters an outage, ensuring uninterrupted operation of connected devices. Its setup is straightforward, and it presents a cost-efficient option for individuals seeking a dependable backup power solution for their electronic equipment. Provided below is a circuit diagram depicting a fundamental UPS configuration that can supply both 12V unregulated and 5V regulated DC power.

Figure 3 Simple Mini UPS Circuit Diagram
Figure 3 Simple Mini UPS Circuit Diagram

System Setup

This uninterruptible power supply (UPS) design is simple and can be easily implemented. Transformer T1 is used to convert the main voltage to 12V AC. After the voltage is stepped down, it is rectified using a bridge referred to as B1. In electronic circuits, the rectified signal is commonly smoothed using a capacitor. In this case, capacitor C1 is employed for this purpose. The smoothing process eliminates any undesirable fluctuations or noise present in the signal. The capacitor acts as a filter, letting in just the desired frequencies while filtering out the unwanted ones. This results in a more constant and steady signal that may be used for analysis or processing. Capacitors are commonly used in electrical design for signal smoothing, which guarantees the precise and reliable operation of electronic equipment.

Diode D3 allows electricity from the wall outlet to charge the battery, while diode D5 gives juice to the regulator IC. Both 12V and 5V DC are available at the output terminals. Diode D4 allows the battery to provide energy to the regulator IC and the 12V DC terminal in the event when main power source is cut off. In battery mode, diode D3 blocks current in the opposite direction, protecting the battery and electronics from harm. This feature is essential for the gadget to continue working as intended. Filters like capacitors C2 and C3 are essential to electrical circuits. These filters are used to scrub the circuit of any extraneous signals or noise. Passive components like capacitors can be used to store energy in an electric field. They are frequently implemented in electrical circuits to mitigate noise and regulate voltage swings. C2 and C3 are signal-filtering capacitors that keep the circuit running smoothly by blocking out noise. The absence of these filters increases the risk of interference and circuit failure. As a result, components such as capacitors C2 and C3 are crucial to ensuring the reliable operation of electrical circuits.

Advantages of Mini UPS Circuit Board

Mini UPSs are designed to respond immediately to power outages or surges, ensuring an uninterrupted power supply to connected devices. This instantaneous power delivery eliminates any lag or downtime, providing a seamless transition and preventing disruptions to the devices’ operation. When an emergency occurs, having a mini-UPS may dramatically increase both your productivity and the safety of your computer. They supply the attached desktop computer with power without interruption, which prevents the machine from shutting down unexpectedly. The mini UPS versions provide emergency power to allow you some additional time so that you may preserve any data that has not yet been saved and safely shut down your device without causing any damage.

In addition, it prevents electrical burnouts in your device in the event of excessive power or electrical surges. Additionally, these mini-UPS systems offer excellent portability due to their lightweight and compact design. This portability allows you to transport them to your house and attach them to any device without any problem.

Mini uninterruptible power supplies (UPSs) generally demand minimal upkeep. Once correctly set up and linked, they can operate dependably without regular maintenance or interference. This feature renders them exceedingly convenient and trouble-free alternatives for supplying backup power to various devices. Users can dedicate their attention to tasks without concerns about continuous maintenance obligations.

Figure 4 PCB Display
Figure 4 PCB Display

Applications in Various Settings

Typically, a mini UPS (Uninterruptible Power Supply) system is used to provide backup power for DC-powered low-power devices and equipment. Here are some frequent uses for a 12V mini UPS system:

  • A Mini UPS can power home networking equipment, including routers, modems, switches, and Wi-Fi access points. It maintains your internet connection during power disruptions, allowing you to stay connected.Figure 5 Applications of Mini UPS
  • Numerous security systems, such as surveillance cameras, motion detectors, and alarm systems, are powered by DC. During power outages, a mini UPS can provide reserve power to keep these systems operational, ensuring continuous monitoring and protection.
  • If you have a home automation system such as smart door locks, intelligent lighting controllers, or motorized draperies, a mini UPS can keep these devices powered during power outages, preserving the functionality of your home automation system.
  • Small electronic devices and appliances, such as portable speakers, projectors, mini refrigerators, and charging stations, typically operate on 12V power.

Thanks to a little UPS that will keep them charged, you can keep using them even if the main power supply goes down. They are convenient for mobility setups, such as camping trips, outdoor events, and remote workstations. They help charge electronics like cell phones, portable fans, and LED lights when camping.

Efficient Operation and Maintenance Techniques

To ensure optimal performance and longevity of batteries, it is crucial to employ efficient operation and maintenance methods. Battery management plays a vital role in maintaining the durability and performance of your devices. Adhering to specific charging and discharging guidelines is necessary to achieve this goal. Additionally, there are a few key points to consider for extending the life of your battery.

Firstly, using the charger that came with your device is recommended, as using third-party chargers may harm the battery and shorten its lifespan. It’s also not a good idea to fully charge or totally discharge your battery. Instead, keep the battery between 20% and 80% of its capacity to extend its useful life. Protecting your equipment from high heat is also recommended. Both high and low temperatures can negatively affect a battery’s performance. Therefore, maintaining your appliance at an ambient temperature and avoiding exposure to direct sunlight environments.

Monitoring and Testing the Mini UPS System

The Mini UPS system is designed to provide backup power during power disruptions. However, if the system fails to activate during a power outage, it may be due to a faulty connection, insufficient battery charge, or incorrect configuration. Regular testing helps identify these issues, and troubleshooting steps involve checking links, verifying battery charge levels, and evaluating system settings.

· Battery Failures

Battery failures can occur for various reasons, such as aging, improper charging, or environmental factors. However, to control or prevent battery failures, regularly check the battery status and conduct tests to ensure optimal performance. Moreover, with time, batteries lose their capacity and become less reliable. Create a battery replacement schedule based on manufacturer recommendations or performance degradation, and replace aging batteries promptly.

· Circuit Overload

A Mini UPS system is designed to handle a specific load capacity. A circuit overload can occur if the connected devices draw more power than the UPS can provide. To control or prevent circuit overload, carefully calculate the power requirements of all connected devices to ensure they are within the UPS system’s capacity.

· Inverter Malfunctions

The inverter in a Mini UPS system converts DC power from the batteries into AC power for connected devices. Inverter malfunctions can lead to a loss of power supply. Follow the manufacturer’s recommended maintenance procedures and keep the UPS system’s firmware current. Regular maintenance can prevent issues related to outdated software or internal components. Also, ensure the connected devices are compatible with the Mini UPS system’s inverter specifications. Incompatibility can strain the inverter and potentially cause malfunctions.


The Mini UPS system is a compelling power backup option for portable devices, protecting them from power interruptions and voltage fluctuations. Mini UPS circuit boards consist of various components, including the battery, charging circuit, inverter circuit, and control circuit, all working harmoniously to ensure dependable operation and safeguard connected electronics. These portable uninterruptible power supply (UPSs) are battery-operated and can recharge whenever mains power is present. At the same time, an inverter transforms the DC power from the battery into AC power that can be used by the attached electronics. These small UPSs’ electronic boards offer a number of benefits, such as a rapid reaction to power outages, protection from data loss and device damage, and ease of maintenance. Portable and mobile setups, together with smaller electronic devices, home networking gear, security systems, and home automation systems all make use of them. Using the manufacturer-recommended charger, avoiding overheating the unit, and keeping an eye on the battery’s status are all simple ways to get the most out of your tiny UPS system and extend its useful life. A reliable power source requires constant monitoring and testing to detect problems as soon as they arise. For tiny equipment, the mini UPS system provides a reliable and cost-effective means of maintaining constant power during outages.


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