fast blow fuse vs circuit breaker

　　PPTC can be used for fast charging protection of lithium batteries

　　Lithium batteries are currently high-energy density and lightweight batteries, but due to their highly active chemical properties, they require additional charge and discharge protection circuits for safety protection. The key component of the charge discharge protection circuit, Mosfet, also has a certain rate of short-circuit failure. If the production of lithium batteries is not large, this effect will not be reflected. However, the demand for lithium batteries is very high, and in the face of such a huge shipment volume, even with a probability risk of 1ppm, there is an average of 5600 dangerous events that may occur per year.

　　So, in addition to the main protection circuit, add a secondary protection to further reduce the risk. In secondary protection components, generally only one component is used, including disposable fuses, PPTC self recovery fuses, and temperature fuses. Previously, using PPTC did not require regular fuses, and using regular fuses did not require PPTC. Due to the fact that various protective components are not fully superior, a situation has emerged where multiple components coexist to meet different application needs.

　　However, with the rapid popularity of smartphones and the increasing capacity of mobile phone batteries, there is a demand for fast charging. Currently, there are multiple standards such as OPPO Vooc standard, Qualcomm's QC 2.0 standard, and MTK's Pump Express Plus standard that have emerged worldwide. In the case of fast charging, the current in the first 30 minutes will be very high, usually reaching around 3A.

　　Under the high current surge 30 minutes before fast charging, accompanied by heating and temperature rise, the competitive situation of secondary protection components for lithium batteries will be changed, replaced by a cooperative mode: PPTC self recovery fuse and disposable fuse form a protection combination.

　　PPTC self-healing fuses and disposable fuses can complement temperature protection and overcurrent protection. PTC has temperature protection function, but due to its high temperature reduction ratio, it has a relatively large specification, which weakens its overcurrent protection ability, and PTC operates slowly. Disposable fuses are not sensitive to temperature and cannot provide temperature protection, but their temperature reduction ratio is also very low. Therefore, smaller current specifications can be selected, which have stronger overcurrent protection capabilities and much faster action speed.

　　The protection scheme of PPTC self recovery fuse and disposable fuse will be safer than a single component. Because combining two components together is equivalent to adding another layer of protection in addition to the secondary protection, it adds another layer of safety to the lithium battery, further significantly reducing the risk factor.

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