Overview of switching power supply protection circuit technology
The quality index for evaluating switching power supply should be based on the principle of safety and reliability.
Under the condition that the electrical technical indexes meet the requirements of normal use, in order to make the power supply work safely and reliably in harsh environment and sudden failure, a variety of protection circuits must be designed, such as soft start against surge, protection circuits against overvoltage, undervoltage, overheating, overcurrent, short circuit, phase loss, etc. 2.
Several protection circuits commonly used in switching power supply 2.
1 anti-surge soft start circuit the input circuit of switching power supply mostly adopts capacitor filter rectifier circuit. At the closing moment of the incoming power supply, since the initial voltage on the capacitor is zero, the capacitor will form a large surge current at the moment of charging, especially the high-power switching power supply, which adopts a filter capacitor with a large capacity to make the surge current reach more than 100A A.
When the power supply is connected, such a large surge current will often cause the input fuse to burn out or the contact of the closing switch to burn out, and the rectifier bridge will be damaged; Light will also make the air switch not close.
The above phenomena will cause the switching power supply to fail to work normally. Therefore, almost all switching power supplies are equipped with soft start circuits to prevent surge current to ensure the normal and reliable operation of the power supply. 2.
2 overvoltage, undervoltage and overheating protection circuit, the harm caused by overvoltage and undervoltage of the incoming power supply to the switching power supply is mainly manifested in the damage of the device due to the voltage and current stress beyond the normal use range, at the same time, the electrical performance index cannot meet the requirements due to damage.
Therefore, the upper and lower limits of the input power supply should be limited, so overvoltage and undervoltage protection are adopted to improve the reliability and safety of the communication power supply.
Temperature is * an important factor affecting the reliability of power supply equipment.
According to the analysis of relevant data, every time the temperature of electronic components rises by 2 ℃, the reliability decreases by 10 ℃, and the working life when the temperature rises by 50 ℃ is only 1/6 of that when the temperature rises by 25 ℃. In order to avoid damage caused by overheating of power devices, overheating protection circuit also needs to be set in switching power supply.
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