### Selection method of patch fuse

There are many series of fuses in the electronic component market, among which are chip fuses. This series of fuses are used more in the factory, and less used by individual users.

According to industry experts, SMD fuses are a new variety with relatively high skill content in the small-scale fuse occupation. SMD fuses can be divided into SMD current fuses and SMD self-recovery fuses. The one-time fuse needs to be replaced after maintenance. Since the power is restored after the fuse is restored, it can recover itself and can be used repeatedly.

SMD fuse products can be divided according to performance. The categories are: fast fuse, slow fuse and enhanced melting heat energy.

If the chip fuse is required, the film process is generally used, and the ultra-low internal resistance is suitable for overcurrent maintenance, such as surge. Computer peripheral products, mobile phones and other communication equipment, digital cameras, monitors, batteries are commonly used. Manufacturers who can produce with this type of skills have certain plans.

It is recommended to select chip fuses according to the following aspects:

1. We call the value of the current flowing when the circuit is short-circuited as the short-circuit current. Regarding various fuses, the extra breaking capacity is regular. We must take care not to make the short-circuit current exceed the extra breaking capacity when selecting fuses. If a fuse with a small breaking capacity is selected, it may rupture the fuse or cause a fire.

2. Observe the waveform of the impulse current (pulse current waveform), and use the I2t value (Joule integral value) to calculate its energy.

The size and frequency of the inrush current are different, and the impact on the fuse formation is also different. The ratio of the I2t value of the inrush current to the I2t value of the single pulse fuse determines the number of times the fuse withstands the inrush current.

3. The size of the normal current flowing through the fuse in the circuit used. Under normal circumstances, we have to set a derating amount in advance, and then choose according to the following criteria: That is, the normal current must be less than the product of the extra current and the derating factor.

4. According to the rules of the UL specification, the fuse should blow quickly at an extra current of 2 times. But in most cases, in order to ensure reliable fusing, we recommend that the fusing current should be greater than 2.5 times the additional current. If other fusing moments are important, you must also refer to the fuse characteristic diagram provided by the manufacturer to make the judgment.

5. The open circuit voltage should generally be selected to be less than the extra voltage. For example, when a fuse with an additional voltage of DC24V is used in an AC100V circuit, it may ignite the fuse or rupture the fuse.

With the miniaturization and patching of electronic components, fuses have also become smaller and more widely used, and there are more people asking where patch fuses are used. In fact, the chip fuse has already played an important role in the overcurrent maintenance of computers and peripheral interfaces, flat-screen TVs, mobile phones, automotive electronic circuits and battery packs.