Patent ID: 8174811
Filing Date: 2012-05-08
Classification: H01M,H02H,Y02E

Abstract:
1. An overheat protection device comprising a variable resistive element for which resistance varies depending on temperature and which is a polymer PTC element, characterized in that the device further comprises a switching element which controls a current flowing through an electrical system depending on an applied voltage thereto, and a resistor having a resistance R, said electrical system comprising a secondary battery, and the variable resistive element is composed of a plurality of variable resistive elements at least some of which are electrically connected in series with each other, the variable resistive element being located on and thermally combined with a certain position of the electrical system and interrupts the current flowing through the electrical system by changing the applied voltage to the switching element when the certain position comes to be under a high temperature condition, the variable resistive element having a resistance in a high temperature state P H and a resistance in a low temperature state P L , the relationship between the resistance of the variable resistive element and the resistor being R/P L >10 and R/P H < 1/10.