The working principle of the resettable fuse is the dynamic balance of energy. The current flowing through the resettable fuse generates heat due to the fuse relationship, and the generated heat is completely or partially dissipated into the environment, and the undissipated heat will increase the temperature of the component.

The temperature during normal operation is relatively low, and the heat generated and the heat dissipated are balanced. The resettable fuse is in a low resistance state and does not work. When the current flowing through the fuse increases or the ambient temperature increases, but if the balance between the generated heat and the dissipated heat is reached, the self-recovery fuse still does not work.

When the current or special ambient temperature rises again, the fuse will reach a higher temperature. If the current or ambient temperature continues to rise at this time, the heat generated will be greater than the heat released, causing the fuse temperature to rise suddenly. At this stage, a small temperature change will cause a large increase in resistance. At this time, the fuse is in a high-impedance protection state. The increase in impedance limits the current, which will drop sharply in a short time. Thereby protecting the circuit equipment from damage. As long as the heat generated by the applied voltage is sufficient to recover the heat emitted by the fuse, the element is always in an operating state (high resistance) under changing conditions. When the applied voltage disappears, the self-healing fuse can automatically recover.