1. Overcurrent protection: automatic power cut when the current is too large, to prevent damage caused by the circuit and case of exceeding the rated current.
2, over voltage protection: it is to prevent overvoltage or electrostatic discharge damage to electronic components, are widely used in telephones, fax machines and all kinds of electronic systems products such as high-speed transport interface, especially the electronic communications equipment, how to avoid because of the abnormal voltage or electrostatic discharge and cause harm to electronic equipment loss is particularly important.
3, over temperature protection, temperature protection components from commercialization to now, has passed a jia, over temperature protection components widely used in the temperature have special requirements, such protection components in accordance with the actuation principle can be divided into chemical actuator type, low temperature alloy actuator type, including chemical actuation type main characteristics of the products is can be low temperature type product, but the structure is relatively complex, high cost;Low-temperature alloy actuation is mainly a low-temperature fuse with a larger diameter, which must ensure that the heat generated by rated current will not cause the fuse to melt. This low-temperature fuse is generally adjusted by adjusting the proportion of elements such as tin, copper, silver, bismuth and indium.
4, thermal over-current protection: in recent years, with the application of ascension, pure temperature protection function, can not meet the rapid electrical appliances, motor, motor and the demand of the 3 c product safety protection, thus developed can meet again because of the abnormal temperature, electric current and voltage cases at the same time to monitor and timely protection components, and the rise of the sample components mainly for lithium ion battery and lithium polymer battery for most applications.
: 5, through the pressure with the complication of modern electronic products, for the protection of the component using request also is increasing day by day, such as the protection of the comprehensive, limited reserved space, etc., as these requirements are put forward, to protect the component sector set off a combination packaging heat wave, as mentioned above through the thermal protection is a combination of encapsulation, but most current through the combination of voltage protection packaging products that is still in development stage, has not yet mature commercial product to market.
The over-current protection devices mainly include disposable fuse, self-recovery fuse, fusing resistance and circuit breaker, among which, the most important is self-recovery fuse. The following are the key points of PTC self-recovery fuse selection:
1. The holding current should be slightly larger than the user's normal working current.
2. Vmax shall be greater than or equal to the maximum working voltage of the user.
3. Imax shall be greater than the maximum fault short circuit current.