Compared with the traditional silicon steel transformer power supply, the switching power supply (power adapter) has high utilization efficiency and low cost. It is now more and more widely used in various industries and is simple and convenient to use.  

However, there are some products on the market, many products, if overloaded or overcurrent, will cause transformer heating, more serious burn out the transformer insurance, now portable transformers generally use glass fuse, or directly use a 100 ohm The resistor is used for protection. Although it can protect the transformer, such protection is one-time. After the burnout, the problem must be solved by replacing the fuse.

If the load current of the switching power supply is too large or short-circuited, the self-recovery fuse immediately becomes high resistance, and the current does not pass, and the fault can be automatically restored once the fault is removed, which greatly facilitates the use. This application is a development trend.