How does a PoE/12 V camera work?

[pschmehl]

I can't seem to find the answer to this anywhere. Some cameras have both a PoE connector and a 12 V connector. From my reading, it appears that most PoE switches/injectors provide 48 V. So, how do these cameras work when using PoE? Do they step down the voltage to 12 V? Do they use an internal power supply to manage the increased voltage? I thought a device that works on 12 V would not be able to handle 48 V.

 

[nayr]

https://en.wikipedia.org/wiki/DC-to-DC_converter

Internally they dont even run off 12v, likely 3.3v.. but the high voltage is required to get DC any distance without giant copper wires.

power circuits will handle 48v input and output it onto a 12v rail, that will then again be regulated down to 5v, 3.3v for chip level logic, and even sometimes down to 1.6v but thats usually for very low power applications.

also read: https://en.wikipedia.org/wiki/Power_over_Ethernet