US Patent 9998117 Solid state resettable fuses

A resettable solid state fuse that automatically restores an interrupted circuit after an overcurrent event is cleared. The resettable solid state fuse can include one or more switching devices, such as, for example, a normally-on power semiconductor, and one or more positive temperature coefficient (PTC) resistive elements. The switching device is structured to extend the voltage rating of the resettable fuse, allowing the solid state resettable fuse to attain both a relatively elevated voltage rating and a relatively elevated electrical current rating while using a PTC resistive element. According to certain embodiments, the solid state resettable fuse can be tripped by a cascaded PTC resistive element, thereby providing a passive electronic device that can operate in the absence of electronic sensing, detection, and tripping, as well as without reliance on an auxiliary power supply.