PTC is the English abbreviation for Positive Temperature Coefficient. PTC resettable fuse is to add a polymer material made conductive particles, the basic principle is that a balance of energy, When the current flows through the components to produce heat. The heat generated part of the distribution to the environment. Part of the increase in the temperature of polymer materials in the working current, The heat generated and the heat dissipation reaches the equilibrium current that can pass normally. When too much current through, Components produce a lot of heat can not be distributed in time, Resulting in polymer material temperature rise, When the temperature reaches the material crystallization melting temperature, Polymer material aggregation expansion. Blocking the conductive path composed of conductive particles, Leading to rapid rise in resistance, Limit the Large current through, And thus play a role in over-current protection.
 
        PTC resettable fuse has the following three basic laws of physics:
 
           1, Ohm's law: I = U / R
            2, Joule law: Q = 0.24 * I ^ 2 * R * t
            3, electric power: P = U * I = I ^ 2 * R
 
       By Ohm's law,When the voltage "U" applied across the load remains constant, The entire loop of the operating current "I"And the resistance value of the circuit "R" is inversely proportional to, The greater the resistance value "R"The current "I" will be smaller.
 
       By Joule's law, Current flows through the heat generated by PPTC "Q"And the current is proportional to the square of the current I, When the current I of the loop is only increased by a little, The resulting heat "Q" will increase dramatically, Once the accumulated heat inside the PPTC reaches the temperature required for its action, PPTC internal conductive path will be localized or broken, PPTC will immediately show a high resistance value, hus limiting the current of the entire loop to a very small range.
 
         By the formula of electric power,In the case of PPTC protection, at the moment:
            P Input = PRt + PRL.
             Where: P Input: Power input power
             PRt: PTC's power
             PRL: The power obtained by the load
           As a result of the restoration of the fuse protection action, Rt >> RL
            Where: Rt: PPTC resistance value
            RL: Equivalent resistance value of load (Recommended reading: PTC industry terminology explanation)
            Although the current flowing through the two is exactly the same, but: PRt (= I ^ 2 * Rt) >> PRL (= I ^ 2 * RL)
 
    Therefore: the power input power,Almost all by the PPTC to bear,The load is no longer able to get electric power,Thus achieving the purpose of protecting the load.