### Performance classification and selection of patch fuse

If the chip fuse has high requirements, the film process is usually used, and the very low internal resistance value is more suitable for overcurrent protection, such as surge. Computer peripherals, mobile phones and other communication equipment, digital cameras, monitors, batteries are commonly used.

SMD fuses are classified and managed according to performance, and can be divided into: fast fuse, slow fuse and enhanced melting heat energy.

SMD fuses can be divided into disposable SMD fuses and SMD self-recovery fuses. Disposable SMD fuses must be replaced after protection. After self-recovery fuse protection, power failure can be automatically repaired and can be recycled. However, when buying chip fuses, what issues should you pay attention to?

The editor proposes to select the chip fuse according to the following aspects: normal current, fusing current, open circuit voltage, short circuit current, inrush current, and operating temperature.

Short-circuit current: Everyone calls the maximum current value that flows when the circuit is short-circuited as the short-circuit current. For a variety of chip fuses, the rated short-circuit capacity is standard, you must pay attention to the selection of chip fuses not to make the short-circuit current exceed the rated short-circuit capacity. If a chip fuse with a small short-circuit capacity is selected, it may cause the chip fuse to crack or cause a fire accident.

Amount of inrush current: Observe the waveform of inrush current (inrush current waveform), and use I2t value (Joule integral value) to measure its energy. The amount of inrush current and frequency are different, and the harm to the chip fuse is also different. The ratio of the I2t value of the inrush current to the single-pulse fuse I2t value determines the frequency of the anti-impulse current of the chip fuse.

Normal current: the premise everyone must understand, how much normal current flows through the chip fuse in the circuit used. Generally speaking, you should set a derating amount in advance, and then choose according to the following basic principles: That is, the normal current amount must be lower than the product of the rated current and the derating factor.

Amount of fusing current: According to the standard of UL specification model, chip fuse should blow quickly under the condition of twice the rated current. But in most. Under slaughter conditions, in order to ensure stable fusing, we recommend that the amount of fusing current should be greater than 2.5 times the rated current. In addition, when the fusing time is important, you must refer to the fuse performance chart provided by the manufacturer to make a decision.

Open circuit voltage: The open circuit voltage should normally be selected to be lower than the rated voltage. For example, when a chip fuse with a rated voltage of DC24V is used in an ACl00V circuit, it may ignite the chip fuse or split the dangerous wire.