Under voltage protection circuit and over voltage protection circuit are the most important circuits in a power supply. They are used to protect the equipment from damage or failure by over or under voltages. The articles below explain these circuits in detail with examples as well as applications of them.


Under and over voltage protection circuits are necessary for your power supply to protect itself from overvoltage and undervoltage situations. The main purpose of these circuits is to ensure that the device does not get damaged when it has been overloaded or can’t handle the load that you have put on it. In this article, we will discuss both types of protection in detail along with their respective working principles and implementation methods.

Under Voltage Protection Circuit: An under voltage protection circuit will prevent a device from becoming damaged by drawing too much current from its source (generally an alternator). When this happens, there may be some damage to internal components inside the device like resistors which can lead to overheating or even catching fire if left unchecked for long enough periods of time without proper cooling being provided by other means such as air conditioning systems installed nearby; however if these systems fail due lack maintenance then all sorts of problems arise including fires happening outside due lack oxygen supply needed by humans who live there too!

Under Voltage Protection

Under voltage protection is to prevent the voltage from dropping below a certain value. It may be required to protect the circuit from damage and ensure that it can operate at its normal capacity.

Working of Under Voltage Protection Circuit

Under voltage protection circuit is a type of over current protection circuit that prevents the occurrence of electrical short circuits. Under voltage protection circuits are used in all types of power supplies, including battery chargers, inverters and electric motors. The main purpose of this protective measure is to prevent damage due to excessive current flowing into the system which might lead to overheating or fire hazard. When there is too much current flowing through an object then it becomes vulnerable because it cannot withstand such high level of load without getting damaged thereby resulting in permanent damage and loss in its performance capacity.

Over Voltage Protection

An under voltage protection circuit is used to protect the load from over voltages. Undervoltage protection circuits are designed in such a way that they protect the load from under and over voltages.

Undervoltage Protection Circuits

An under voltage protection circuit is used to protect the load from over and under voltages by providing a DC potential drop across anode, cathode or both electrodes at all times within specified limits (normally less than 10%).

Working of Over Voltage Protection Circuit

The over voltage protection circuit is used to protect the circuit from over voltage. If a high voltage is applied on your power supply, it can damage your components and cause damage to other parts of the system. This is why you need an Over Voltage Protection Circuit in place so that no harm comes from this kind of situation!

Applications of Under & Over Voltage Protection Circuits

Under and over voltage protection circuits are used in the protection of electrical equipment. The main applications include:

  • Protection of electrical equipment, such as transformers and generators.
  • Protection of electrical substations.
  • Protection of electric motors, generators and hydraulic pumps that produce high voltages or currents under normal operating conditions but fail to protect against excessive voltage surges during transient events like lightning strikes or power outages (e.g., brownouts).

The above article aims to explain the under and over voltage protection circuits.

Under and over voltage protection circuits are used to detect and protect against under and over voltage conditions. These circuits can be found in applications such as power supply, battery charging etc., where there is a need for both safety and reliability of equipment.

Undervoltage Protection Circuit: If the input voltage falls below the set point value then this circuit will operate as an open-collector NPN transistor (Q2). The output will drive Q1 forward so that it makes current flow through R3 which provides resistance to the base current drawn by Q1 (see Figure 1). This causes current from source S2 through R4 which discharges R5 capacitor C5 through ZDETs FETs Q6 & 7 until its voltage reaches its set point value Vref again before turning into collector mode again after approximately 50ms (see Figure 2).


We have discussed the working of under voltage and over voltage protection circuits. These are important to protect electrical equipment from damage due to short circuit or overload.