The role of the fuse is: when the fault or abnormal circuit, with the current increasing, and increase the current may damage the circuit in some important devices or expensive devices, there may even cause a fire burned circuit. If the circuit correctly placed the fuse, the fuse will be so in the abnormal current increases to a certain height and a certain time, the fuse cut off the current, so as to protect the safe operation of the circuit. The first fuse was invented more than 100 years ago by Edison, and because of its poor industrial technology, incandescent lamps were expensive, so it was originally used to protect expensive incandescent lamps.Chip self recovery fuse type selection

Fuse is mainly used in digital camera, laptop, mobile phone and other electronic products from the traditional glass tube fuse, micro fuse, fuse, due to differences in product process, their selection of the focus is slightly different. The choice of SMD fuses involves the following factors:
1. the normal working current of the circuit. The work current through the fuse shall not exceed the current rating of the fuse 75%.
2. pulse, impulse current, surge current, starting current and circuit transient value. Fuse with particular attention to a little, because the process of small size brings, the impact resistance of the fuse was far less than that of the rated current of the fuse in a glass tube fuse or other large volume.
3. the overload current of the circuit and the shortest and most time of the overload current. It is usually necessary to combine the oscilloscope test with the theoretical calculation to determine the magnitude of the overload current. The basic requirements of the fuse should not break off when not (such as when the surge current), the off time must be in the appropriate time off (such as when need to cut the current overload).
4. resistor. The resistance of chip fuse has certain influence on some circuits. If the fuse with too large internal resistance is installed in some circuits, it will affect the system number of the circuit, so that the circuit can not work properly.
5. the environmental temperature of the fuse. When chip bonding is applied to portable devices, the temperature rise of the fuse should be taken into account, that is, the reduction of the current rating of the fuse. The ambient temperature of the fuse shall be within the specified operating temperature range. When the ambient temperature of the fuse exceeds 25 degrees, the temperature reduction curve shall be used for reference.
6. the applied voltage applied to the fuse. Usually patch fuses are applied to portable devices, and the circuit operating voltage is generally not high. As long as the rated voltage of the patch fuse is higher than the working voltage of the circuit, it can be safely selected.
7. product certification. For example, exports to North America must require UL or CSA certification. At present, products exported to Europe also need to comply with the EU‘s RoHs directive, which is commonly referred to as SGS and other environmental certification.
When choosing a patch fuse, the normal working current, fault current, I2t value, environmental temperature, internal resistance and rated value shall be taken into account.
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