Patent attributes
An over-current protection device comprises a PTC device and a heating element operable to heat the PTC device. The PTC device contains crystalline polymer and metal or ceramic conductive filler dispersed therein. The PTC device has a resistivity less than 0.1 Ω·cm. The over-current protection device has the relation: It (heating)<Ih (60° C.)×10%, where Ih (60° C.) is a hold current of the over-current protection device at 60° C. when the heating element is not activated; It (heating) is a trip current of the over-current protection device when the heating element is activated to heat the PTC device. The PTC device has high hold current, thereby allowing a battery containing the device can be fast charged with a large current. In a specific situation, the heating element heats the PTC device to decrease the hold current of the over-current protection device of low resistivity, and accordingly the PTC device can trip by a small current.
