In recent years, the high-voltage power supply industry in China has experienced rapid growth, with a significant improvement in production quality. As a crucial component of these systems, the protection circuit plays an essential role in ensuring safe and stable operation. The protection circuit not only safeguards the internal components but also protects the high-voltage power supply and connected electrical devices. It helps extend the lifespan of the equipment and provides a safer working environment for operators. Therefore, designing an effective protection circuit is of great importance.
The overall circuit structure of a high-voltage power supply typically includes several key sections: an auxiliary power supply, an inverter unit, a pulse oscillation control unit, a voltage doubler rectifier unit, a high-voltage measurement unit, and a protection unit. The output voltage of such a system is usually very high, often exceeding 25kV. A well-designed protection circuit is placed between the voltage doubler rectifier and the high-voltage measurement unit to prevent damage caused by overvoltage conditions. This ensures the longevity of the system and enhances the safety of the users during experiments.
The thyristor-relay overvoltage protection circuit is designed to monitor and respond to voltage fluctuations. The circuit includes a sampling section, an LM358 comparator, a thyristor, and a relay. The sampling voltage is sent to the non-inverting input of the LM358, while the inverting input is connected to a reference voltage of 5V. When the sampled voltage exceeds this threshold, the LM358 outputs a high signal, triggering the thyristor to conduct. This, in turn, activates the relay and lights up an LED, indicating that the protection mechanism is engaged.
The thyristor-relay overvoltage protection circuit works by using the LM358 to compare the sampled voltage against a set reference. If the voltage goes beyond the safe limit, the circuit locks into a protective state, ensuring that the high-voltage system is disconnected from the source. This prevents potential damage to the equipment and reduces the risk of electrical hazards.
In summary, when the output voltage of the DC power supply exceeds 25V, the sampling voltage rises above 5V, causing the LM358 to output a high level. This activates the thyristor through the relay, which then turns on the LED as a visual indicator. Once triggered, the thyristor remains in the conducting state, effectively isolating the system until the voltage returns to a safe range. This design offers a reliable and efficient method of overvoltage protection in high-voltage power supplies.
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