automotive blade fuse colours.fuse PPTC for overcurrent protection in photovoltaic street light controllers)

　　Due to the fact that the intelligent control part of this new type of LED explosion-proof light is completed through RS485 serial communication, it was found in practical applications that the 485 interface chip is easily burned out. After analysis, overvoltage protection was not done properly, so TVS tube was selected as the overvoltage protection circuit, and it was found that it is still easy to be burned out by lightning.

　　When I was in a state of exhaustion, I saw an overcurrent protection scheme using a self recovery fuse TVS tube. The experiment was successful, greatly improving the reliability of the explosion-proof lamp. I didn't expect to use a self recovery fuse PPTC in series at port 485, and then connect TVS in parallel to complete the task. There is no simpler solution than this method.

　　The self restoring fuse PPTC is an overcurrent protector, also known as a ten thousand fuse, also known as a self resetting overcurrent protector or a polymer self restoring fuse. When it operates normally, it has low resistance. When the RS485 port of the explosion-proof lamp encounters high voltage input or lightning, it will trigger the conduction of the TVS to generate a large current, which will cause the self restoring fuse to suddenly change into a high resistance, limiting the current passing through the TVS and achieving the purpose of protecting the TVS and 485 circuits.

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