Miniature fuses are mainly used in digital cameras, notebook computers, mobile phones and other electronic products. From traditional glass tube fuses to miniature fuses, due to different product technologies, their selection focuses are slightly different. The choice of miniature fuse touches on the following elements.
Method and steps for selecting miniature fuse.
(1) the normal working current of the circuit shall not exceed 75% of the rated current of the fuse;
(2) Pulse, pulse current, surge current, starting current and circuit transient value. Micro fuses pay special attention to this point. Due to small-scale technical reasons, the impact resistance of miniature fuses is much lower than that of other large fuses with the same rated current.
(3) The size of overload current and the shortest and longest time of overload current in the circuit generally need to be judged by oscilloscope test and theoretical calculation. The basic requirement of fuse is not to interrupt at any time, but to interrupt in time;
(4) The resistance of miniature fuses has certain influence on some circuits: if fuses with excessive internal resistance are installed in some circuits, the system parameters of the circuits will be affected and the circuits will not work normally;
(5) As for the ambient temperature of the fuse, the temperature rise of the fuse, that is, the decrease of the rated current of the fuse, should be considered when using the miniature fuse for portable equipment. The ambient temperature of the fuse shall be within the specified working temperature range. When the ambient temperature around the fuse exceeds 25℃, the temperature shall drop according to the temperature drop curve.
(6) The applied voltage applied to the fuse is generally used for portable equipment. The working voltage of the circuit is generally not high. As long as the rated voltage of the miniature fuse is higher than the working voltage of the circuit, it can be safely elected.
(7) Product certification. If exported to North America, it must pass UL or CSA certification. At present, the products exported to Europe need to meet the RoHS directive of the European Union, which is generally called SGS and other environmental certification;
