Overvoltage protection circuit design skills
Overvoltage in a circuit refers to a situation where the voltage exceeds the designed range. This anomaly can lead to damage of electronic components, system failures, or safety hazards. Therefore, understanding its causes and countermeasures is crucial for circuit design and protection.
The main causes of overvoltage in circuits include lightning strikes (lightning induction), load dump, electrostatic discharge (ESD), unstable power supply, inductive kickback, and common-mode interference. Lightning strikes can cause instantaneous high voltage (thousands to tens of thousands of volts), which can couple into devices through power lines or antennas, commonly seen in outdoor equipment, communication base stations, and power grid equipment. Load dump, on the other hand, is particularly common in automotive electronics, where sudden disconnection of the battery (e.g., removing the battery) can cause instantaneous high voltage at the generator output.
Additionally, electrostatic discharge (ESD) occurs when a charged human body or object meets a circuit, releasing a high-voltage but low-energy pulse that can damage sensitive components. Unstable power supply arises from poor-quality mains or power supplies, or large input voltage fluctuations, leading to instantaneous overvoltage. Inductive kickback occurs when inductive loads (such as inductors, motors, or relays) release reverse high voltage upon power interruption. Common-mode interference is caused by ground potential drift or poor circuit grounding, resulting in localized overvoltage.
Below, we will introduce some common overvoltage protection circuits and key design considerations.
- PNP transistor plus PNP transistor overvoltage protection circuit
- LM393 plus relay overvoltage protection circuit
- TVS diode overvoltage protection circuit
Conclusion
When we face transient surges, unstable power sources, or unexpected operations, overvoltage protection is no longer just an option; it is a critical line of defense to ensure system stability and component longevity. From simple TVS diodes to logic-controlled LM393 + relay architectures, and to analog PNP transistor designs, each solution has its unique positioning and application advantages. By understanding the principles, selection criteria, and practical techniques of various protection circuits, we are not just stacking hardware; we are building an electronic safety mechanism that “predicts risks and actively defends.” Designing overvoltage protection is not only a technical practice but also a commitment to reliability from electronic engineers.