'external power supply' is correct and can be used in written English.
You can use it when referring to an external device that provides power for another device. For example, "The laptop requires an external power supply to turn on."
It comes with an external power supply that can be replaced without opening the machine.
The device uses four AA batteries and, like all units I tested, comes with an external power supply.
Most described the external power supply as an annoyance rather than a benefit, getting in the way and heavy when travelling.
But then the tsunami struck, which knocked out the emergency generators (the external power supply had been stopped by the earthquake).
Experimental artificial hearts have also been implanted, but these require a cumbersome external power supply and long-term survival rates are not known.
This year rebels in Syria posted video online of a portable missile-launcher rigged to an external power supply for target acquisition.
This power amplification results from the conversion of the energy stored in an external power supply to an output energy in the load circuit of the electron device.
Instead, there is a fixed internal lithium-ion battery that is recharged by plugging its external power supply into an electrical outlet or by plugging the device into the U.S.B. port of a PC or Mac.
When a positive voltage is applied to the anode (or plate), electrons emitted from the heated cathode flow to the plate and return to the cathode through an external power supply.
With this tool members of Dr Palanker's team can "tile" the affected area with as many chips as is necessary.Unlike some existing chip systems, this one does not need an external power supply (though the glasses themselves need batteries).
No external power supply, that makes sense.
