[quote=@Lucidnonsense]
<Snipped quote by Willy Vereb>

Solsys Network also uses conversion power, though at this point in time not something they could mount on a toothbrush, Im thinking the smallest generators would be the size of a car engine. 
[/quote]Q-Fabs in the Federation tend to make issues with miniaturization rather negligible.
There are exceptions, though. Like the extensive machinery required to contain and gather power from vacuum so truly small scale use is just counterintuitive.