Diodes are commonly used in overvoltage protection circuits to safeguard electronic devices from voltage spikes or surges that could damage them. These voltage spikes can occur due to various reasons, such as lightning strikes, sudden power surges, or electromagnetic interference. The diode acts as a one-way valve for electrical current, allowing it to flow in one direction but blocking it in the opposite direction.
There are two primary types of diodes employed in overvoltage protection circuits:
Zener Diodes: Zener diodes are specifically designed to work in the reverse breakdown region, where they maintain a constant voltage across their terminals once a certain "Zener voltage" is reached. When the voltage across the Zener diode exceeds its breakdown voltage, it starts conducting in reverse bias, allowing excessive current to flow through it. This helps to regulate the voltage and protect the connected circuitry from high voltages. Zener diodes are often used to clamp the voltage at a safe level.
Transient Voltage Suppression (TVS) Diodes: TVS diodes, also known as surge protection diodes, are designed to handle transient voltage spikes by rapidly conducting when the voltage exceeds a certain threshold. When the voltage surge occurs, the TVS diode provides a low impedance path for the excessive current, diverting it away from the sensitive components. TVS diodes respond very quickly to voltage spikes, providing an effective means of overvoltage protection.
In an overvoltage protection circuit, the diode is connected in parallel with the device or circuit to be protected. When the voltage exceeds the safe threshold, the diode starts conducting, providing an alternative path for the excess current to flow. This prevents the voltage from rising beyond a certain level, protecting the connected components from potential damage.
It's important to note that while diodes provide effective overvoltage protection, they are not a complete solution for all overvoltage scenarios. Additional protective measures, such as fuses, transient voltage suppressors, and proper grounding, may also be used in combination with diodes for comprehensive overvoltage protection in sensitive electronic systems.