A new type of fuse to avoid melting shell and surge failure in switching power supply

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A new type of fuse to avoid melting shell and surge failure in switching power supply [Copy link]

        In recent years, independent switching power supplies and power modules have become an indispensable part of our lives and work. With the explosive growth of mobile phones, communication products, and small household appliances, according to statistics, the average number of independent switching power supplies used by each household is more than 5, and more than half of them are powered on for a long time without plugging in or out. (Such as independent power supply router power supply, display power supply, lamp power supply, air purifier power supply, etc. and various household appliances with power modules),,,,,, and with the trend of miniaturization and high power of switching power supplies gradually strengthening, and the increase in the number of household appliances used in households, abnormal conditions such as micro short circuits inside switching power supplies have caused serious safety accidents such as product fires. Therefore, in the primary safety circuit of the switching power supply or power module, choosing a good fuse is crucial to the quality of the case application. This can not only reduce the failure of cold machine surge and hot machine lightning surge, but also prevent the phenomenon of melting shell in the application, protecting personal safety and property safety. Analysis of the structure of existing fuse resistors: Huawei 5V/1A European charger, Meizu 5V/2A charger, Xiaomi 5V/2A Indian charger, Bull 5V/2A charger, Bull Cube plug strip, Xiaomi plug strip, etc. were randomly selected from the chargers on the market for semi-short circuit testing, simulating the micro-short circuit state of electrolytic capacitors. All the above chargers were tested without melting shell phenomenon, and the surge resistance of the switching power supply in cold and hot states was also strong. However, in the case of micro-short circuit, the fuse resistor or NTC of some other brands of chargers all had high-heat melting shell. Their structures are divided into 3 types, among which the conventional, fast-melting type and high-lightning-resistant type are the following A-type structure, the semi-short circuit wire-wound fuse resistor is the following D-type structure, and the full short circuit temperature fuse resistor is the following T-type structure, among which the D-type structure is based on the conventional resistor structure with multiple functional fuse layers added and special alloy wires updated, and the T-type structure is based on the conventional resistor structure with temperature fuse elements added.

Among the above three structures, type A has no ability to protect against melting shells when a micro-short circuit occurs, type D has the ability to partially protect against melting shells, and type T can completely prevent the risk of melting shells. In the cases we tested, the Bull socket and charger both use full short-circuit resistors, and the Mijia socket uses half short-circuit resistors.

Safety requirements are constantly upgrading Through case analysis and disassembly testing, it is not difficult to find that with the different design cases of switching power supplies, the selection methods of fuse resistors vary greatly. But in the final analysis, a good selection will greatly improve the performance, safety, and reduction of volume and weight of the switching power supply. Moreover, due to the large flexibility of the performance design of the fuse resistor, the new safety requirements of many cases can be solved from the new fuse resistor. Finally, as an old driver in the component industry, I hope that every switching power supply is safe, powerful and stable. In fact, not only switching power supplies, but all electronic product solutions can ensure safety and stability.