Introduction
Over Voltage Protection Circuit (OVPC) is an important safety feature used to protect your electrical system from potentially dangerous voltage surges and spikes. OVPCs are installed in high-stress areas that may be vulnerable to voltage overloads, such as motor control centers, data centers, and more. The circuit works by sensing when the voltage exceeds the specified limit and shutting off the power flow before any damage can occur. This is especially useful if you live in an area with frequent lightning storms because it will protect your valuable electronics from power surges that could permanently damage them. OVPCs also help prevent fire hazards since they’re designed to quickly switch off all unnecessary electrical currents if a short occurs or too many current flows through the circuit circuitry.
Circuit Diagram
of Over Voltage Protection Circuit
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Working Explanation
of Over Voltage Protection Circuit
Electronic circuits must never be operated with an excessive supply voltage. Such a situation may be prevented with the protection circuit shown in the diagram. If the current through the IC becomes excessive, or the IC overheats, an external silicon-controlled rectifier (thyristor), Th1, is triggered, whereupon the supply voltage is short-circuited. This causes the current limiting in the power supply to be enabled or the relevant fuse in the supply to blow. Whatever the circuit is being supplied is protected.
In the diagram, the overvoltage protection comes into action when the supply voltage exceeds 5 V, but this may be set anywhere between 3.3 V and 9 V. Potential divider R1-R2 reduces the supply voltage to 1.19 V (nominal) at the ADJUST pin of IC1. As long as the level at this pin is <- 1.14 V, IC1‚ remains in standby mode and draws a current of about 70 uA.
When the potential at pin 5 rises above 1.19 V (maximum 1.24 V), IC1‚ draws a current of up to 17 A so as to pull down the supply voltage - the flag signal is then actuated. If in this situation the peak current of 17 A is exceeded, or the body temperature of the IC rises above 165 C, or when the internal shunt transistor goes into saturation, the external thyristor is triggered via pin 4 (SCR). This protects the IC itself and
ensures that the overvoltage is negated. The rating of the thyristor must, of course, be in accordance with that of the power supply. In this situation, IC1‚ shorts out its internal shunt transistor to minimize internal dissipation.
The UCC3908 is available in three different enclosures. For situations in which large supply currents flow for long periods, the TO-220 version is recommended (if necessary with a heat sink). When the load current is not large, the SO-8 version may be used. In eritoria that situation, it may even be possible to omit the thyristor, but the anticipated maximum temperature
must then be calculated very carefully.
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Conclusion
Over-voltage protection is an important feature to consider when choosing a power supply or any electrical device. Not only can it protect your hardware from being damaged by voltage spikes, but it can also prevent malfunctions that could lead to larger problems down the line. With over-voltage protection, your power supply will detect sudden increases in voltage and shut itself off to keep you and your equipment safe. This is just another way for ensuring safety in electronic device use and should be taken into consideration when selecting a power supply or other electrical equipment.