The input voltage in the above simulation is 6.8V. The major drawback of this type of circuit is the power dissipation. Components101 is a resource dedicated for electronics design engineers, covering product news, analysis and articles on latest electronics components., Copyright 2021 Components101. If the full voltage appeared on the output, then it could damage many of the ICs that are in the circuit being supplied. So voltage more than 5V will damage the microcontroller. Most power supplies use an over-voltage protection circuit to prevent damage to the electronic components. If this occurs, then the full unregulated input voltage would appear in the output of the voltage regulator. For example, maximum overvoltage that can happen or can be applied as a supply voltage can be 13V. All rights reserved. Below circuit diagram for overvoltage protection is built using Zener diode and PNP transistor. Power supply circuits The R1 and D2 are two components protecting the output from over-voltage protection. All the latest articles, projects, new product reviews, and competitions, Discuss ideas with our professional engineering community, Software created to help you in your design process, A collection of resources to help speed up your design process, Get help from trusted 3rd parties with your design and build process, A collection of materials to help students and professionals alike. In this conduction, no current flows through the Zener diode because its breakdown voltage has not been reached and no current flows into the gate of the thyristor and it remains off. When over-voltage protection is required for switch mode power supplies, SMPS the clamp and crowbar techniques are less widely used because of the power dissipation requirements and the possible size and cost of the components. With the Zener diode voltage chosen to be slightly above the maximum rail voltage, under normal conditions it will not conduct. Zener diodes have a power rating. In this technique, the voltage remains regulated and the cost of this circuit is very less when compared with other methods. When the V1 reaches 6.8V, the output will be protected. Figure 1. As Q1 conducts less it reduce the output voltage hence maintains the output voltage constant. Check out these pages on our website: 2. For our example discussed above it is 50mA. Hence, Q1 does not allows the current to flow through it and protect the Load from exceeded voltage. It can be done by two methods. To be specific, a 5.1V Zener diode blocks current to flow in reverse direction up to 5.1V If the voltage across the Zener diode is more than 5.1V, it allows the current to pass through it. The disadvantage of the circuit is that you may not find the exact value of Zener diode, so choose one which have the nearest rating to your preset value. 1. This circuit disconnects the output when the voltage exceeds the preset level. Omron's G8PM DC Automotive PCB Relay is a high load automotive relay for motor/resistive control. When implementing this, it is necessary to incorporate a sense loop that is outside the main IC regulator - many switch mode regulators and DC-DC converters use a chip to achieve the majority of the circuit. It will work fine during an over voltage situation. Check our Supplier Directory. Meaning, unlike a fuse, a Zener diode does not get damaged even during an overvoltage condition. For the above example in Pspice, the Zener voltage is 6.8V. The R1 and D2 are two components protecting the output from over-voltage protection. Zener Voltage Regulator Circuit: This method regulates the input voltage and protects the circuit from over voltage by supplying a regulated voltage,but itdoesn't disconnect the output part when voltage exceeds the safety limits. This short circuit can also be used to blow a fuse or other element, taking the power off the voltage regulator and isolating the unit from further damage. 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A Zener diode follows the same diode theory, which blocks the current flow in the reverse direction. Op Amp circuits Power supply electronics overview This is how a Zener diode is effective to save the connected circuit from an overvoltage situation, also when the voltage goes back to less than 6.8V, he circuit will work normal again as shown in the previous step. Every circuit design operates at various voltage levels, with 3.3V, 5V, and 12V being the most common voltage levels for a digital circuit. This enables the series pass transistor to regulate the output voltage adequately. Other than the load current, biasing current is required by Zener diodes. Voltage limiting: PSU specs The above schematic has an input voltage, which is V1. The thyristor can be linked back to a fuse which blows and isolates the regulator from having any further voltage placed upon it. Transistor design The below points will help you in selecting the right value and part number for the Zener diode. In such instances, it is possible to choose a near value of the Zener diode. Any value above the maximum operating voltage can be fatal for any circuits or components. In practice, however, it will behave as a regular diode and block less than 5.1V The image below is a simulation of the spice circuit of Zener diode protection. Most power supplies designed for very reliable operation of high value equipment will incorporate some form of over-voltage protection to ensure that any power supply failure does not result in damage to the equipment being powered. They can fail in many ways and one particularly worrying possibility is that the series pass element, i.e. A very common and cost-effective solution is to use a Zener Diode Over Voltage Protection Circuit. 4. Figure 2. They offer some form of overvoltage-protect (OVP) circuit to detect and then quickly pull down the overvoltage. A 5.1V Zener diode blocks current to flow in the opposite direction up to 5.1V If the voltage is greater than 5.1V through the Zener diode, it allows the current to pass through it. In such cases, a close value of the Zener diode can be chosen. In this case, the D2, 1N4099 is a 6.8V Zener diode. OVP protection using Zener diodes is the easiest and simple process to protect devices from overvoltage. For example, a standard computer SMPS system will work at six different levels of voltage, namely 3.3V, 5V, and 12V. In this case, the D2, Let's see how the above circuit acts as a, Now, the input voltage is 7.5V, which is more than the 6.8V. Amphenol RF offers fixed length FAKRA-to-FAKRA assemblies featuring the popular RG-58 and RG-174 cables. Cornell Dubilier's THA/THAS Thinpack offers high energy density in a low-profile design. As per the ohm's law, the resistor value will be = 6.2V / 0.060 A = 103R As with many electronic techniques there are several ways of implementing a particular capability. Thus, the output is 6.785V which is close to the 6.8V. Let's further raise the input voltage and create a situation of overvoltage. Different voltage levels will be used to power different types of components, in these cases, if a low power component is powered with a high voltage, the component will get permanently damaged. You can check out the video at the bottom of this page for the complete simulation explanation. With a perfectly blended team of Engineers and Journalists, we demystify electronics and its related technologies by providing high value content to our readers. The way in which switching regulators operate is very different, but there are circumstances in which the full output could appear on the output of the power supply. Now when the voltage exceeds the preset value the Zener diode starts conducting, which connects the base of Q2 to ground and turns ON the Q2. Different voltage levels will be used to power different types of components, in these cases, if a low power component is powered with a high voltage, the component will get permanently damaged. Let's increase the input voltage further and create an overvoltage situation. Meaning, unlike a. Return to Circuit Design menu . Power management bus: PMbus In these cases, if a low-power device is operated by a high voltage, the component will be permanently impaired if various voltage levels are used to power different types of components. Linear power supply The output is still 6.883V now. We will always receive an output voltage less than or equal to the rating of the Zener diode. There are several different techniques that can be used, each with its own characteristics. Some power supplies may not incorporate over-voltage protection and these should not be used for powering expensive equipment - it is possible to do a little electronic circuit design and to develop a small over-voltage protection circuit and add this on as an extra item. It is the voltage value that will serve as a close circuit for the Zener diode and protect the load from overvoltage. Often some decoupling in the form of a small capacitor is placed from the gate of the thyristor to ground to prevent sharp transients or RF from the unit being power from getting on to the gate connection and causing a spurious trigger. Consider the below image, where we need over-voltage protection for Microcontroller. Therefore, the Zener diode power rating will be equal to Zener diode voltage, ties the total current that will flow through the diode. But every design is unique and it is also common for a circuit to have more than one operating voltage. Circuit diagram for Overvoltage Protection using Zener Voltage Regulator is given below: The preset voltage value of the circuit is the critical value over which either the supply is disconnected or it wont allow any voltage above that value. Therefore, more than 5V could damage the microcontroller. If the voltage is more than 5.1V, the Zener will pass the current and control the voltage up to 5.1V. The voltage remains regulated in this technique and the cost of this circuit is much lower compared to other techniques.Although, surely, there are disadvantages to this sort of circuit. In this circuit, the Zener diode is chosen so that its voltage is above the normal operating voltage of the output, but below the voltage where damage would occur. The above circuit is simulated using cadence pspice. Op Amp basics It can transfer the current and regulate the voltage up to 5.1V if the voltage is more than 5.1V. The microcontroller can be anything that has a maximum rating of 5V across the IO pins. Omron's G8PM DC Automotive PCB Relay is a high load automotive relay for motor/resistive control. Here in this circuit, Zener Diode and Bipolar Transistor are used for automatic overvoltage protection. The major drawback of this type of circuit is the, TPP 180 and TPI 180 Medical and Industrial AC/DC Power Supplies, THA/THAS, Thinpack, Aluminum Electrolytic Capacitors, K78 Series Non-Isolated DC/DC Switching Regulator, 7-Channel DMOS Transistor Array for Industrial and Agricultural Automation, High Performance 750V SiC FET Portfolio with Low RDS Designed for Onboard Chargers and IT Power Supplies, Programmable Power Management IC with Various Protection Functions Optimized for Automotive Applications. In other words, a Zener diode does not get fried even during an overvoltage state, unlike a fuse.To pick different overvoltage margins in the above circuit, any other Zener diodes with different values such as 3.3V, 5.1V, 9.1V, 10.2V can be used. Typically thyristors, i.e. A Zener Voltage Regulator protects the circuit from overvoltage and also regulates the input supply voltage. Therefore, the total current, plus the Zener diode biasing current, should be equal to the load current. Zener diodes are mostly the first choice to protect the circuit from an overvoltage condition.