Simple and low-cost switching power supply protection circuit design

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Overview:
The role of the switching power supply is becoming more and more important. In order to make the power supply work safely and reliably under sudden fault conditions, various protection circuits need to be added. A LM339 voltage comparator designed in this paper is used to complete the overvoltage and undervoltage of the switching power supply. The overheat protection circuit not only makes the protection circuit simpler, but also greatly reduces the cost.

With the development of science and technology, the relationship between power electronic equipment and their work and life is increasingly close, and electronic equipment is inseparable from reliable power supply, so switching power supply has begun to play an increasingly important role. At the same time, with the development of many high-tech, switching power supply technology is constantly innovating. The design of the switching power supply should be based on the principle of safety and reliability. Under the condition that various indicators meet the requirements of normal use, in order to make the power supply work safely and reliably under sudden failure conditions, various protection circuits need to be added to protect the switch. The power supply itself is not damaged by overvoltage or undervoltage. Whether the protection circuit is reliable or not is critical to the safe operation of the switching power supply.

In this paper, through the analysis of the working principle of the voltage protection circuit composed of the voltage protection circuit composed of the single junction transistor and the thyristor, a LM339 voltage comparator is used to complete the overvoltage, undervoltage and overheat protection circuits of the switching power supply, which makes the protection circuit more Simple, the cost is greatly reduced.

Single-junction transistor and thyristor over-voltage, under-voltage protection single-junction transistor and thyristor over-voltage and under-voltage protection circuit are connected in parallel with a thyristor at the input end of the switching power supply. When the voltage of the switching power supply is over or undervoltage for some reason, it is amplified by detection. The circuit provides a signal to the thyristor, causing the thyristor to conduct and tripping the circuit breaker for protection purposes. The protection circuit is suitable for power supply in low power applications, and when the input voltage is under voltage, since the voltage on the capacitor C cannot be abruptly changed, the charging voltage under the undervoltage still remains on, and the volume is large. Long-response, expensive high-power relays or circuit breakers.
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