Seven notes of patch fuse

时间:2019-11-14 丨 预览:448 人次
SMD fuses are mainly used in electronic products such as digital cameras, notebook computers, and smart phones. From traditional glass tube fuses to miniature fuses and chip fuses, due to differences in product technology, the choice of focus is different. The selection of chip fuses involves the following factors:


  1. The normal operating current of the circuit. The operating current through the fuse should not exceed 70% of the rated current of the fuse.

  2. Pulse, inrush current, inrush current, starting current and circuit transients. SMD fuses pay special attention to the following facts: due to the small process size, the impact resistance of chip fuses is much smaller than that of glass tube fuses or other bulky fuses with the same rated current, so it can be overcurrent protectors according to ptc if possible;

  3. The magnitude of the overload current and the minimum and maximum time of the circuit overload current. Usually must use oscilloscope test and theoretical calculation to determine the magnitude of overload current. The basic requirements of the fuse should not be damaged without damage (for example, when there is an inrush current), and must be opened at an appropriate time. (For example, when there is an overload current that needs to be cut off);

  4. resistance. The resistance of the chip fuse has a certain effect on some circuits: if a fuse with an excessive internal resistance is installed in some circuits, it will affect the number of circuits of the circuit, thereby making the circuit unable to work normally;

  5. The ambient temperature of the fuse. When applying chip fuses to portable equipment, please consider the temperature rise of the chip fuse, that is, reduce the rated current of the fuse. The ambient temperature of the fuse should be within the specified operating temperature range. When the ambient temperature around the fuse exceeds 25 ° C, it should be degraded by referring to the temperature decrease curve;

  6. Apply voltage to the fuse. Usually, chip fuses are used in portable equipment, and the operating voltage of the circuit is usually not high. As long as the rated voltage of the chip fuse is higher than the working voltage of the circuit, it can be used with confidence;

  7. SMD fuse product certification. For example, to export to North America, you must have UL or CSA certification. Products currently exported to Europe must also comply with the RoHs Directive EU;