Could a blown voltage regulator still supply electricity?
I'm building a very tiny form factor transformerless power supply with 5 V output.


Oh-oh. This could be bad.


  I was wondering if I could use a voltage regulator as a fuse ...


No. You can't predict whether the device will fail open-circuit or short-circuit. The design would not be designed to "fail safe".


  I've heard that normal fuses are temperature sensitive that's why I want to use a voltage regulator as a fuse.


The principle of operation of a fuse is thermal. As the current increases the fuse wire temperature increases. At some current for a certain time the fuseewire will melt and the output will be disconnected. This is an extremely simple and well-proven technology that is guaranteed to fail safe.



Please, please be careful with this project and have the sense to walk away from it if you realise that you do not have the expertise required. The output must be considered to be at mains voltage. The project seems pointless when you can purchase a 5 V, 2 A mobile phone charger with full mains isolation so cheaply.