- Thu May 21, 2009 6:19 am
This is a good thought, however, AC/DC Transformers like I assume you're talking about ("wall warts" such as cell phone chargers, electric razor chargers, various battery chargers, etc.) take only miniscule loads while plugged in with no load on them. In order to incorporate the ability for the unit to "auto shut off", you would have to have circuitry internal to the Transformer unit that is always on to sense if there is a load demand or not and then switch the unit on or off depending on the decision of the "sensing" circuit. Potentially, this sensing circuit would have a minimal draw of current like the transformer but it would most likely be the same load or more than if you just left the unit plugged in. Also, lets remember that this "sensing" circuit would always be on no matter if the transformer is being used for a device or not thus using more electricity in the long run.
Just one last note on this though...there are some transformer units that have smart functions built in for proper charging and others with a range of voltage outputs supported (such as most laptop power supplies) where the charger senses no load and this "sensing" circuit cuts off other non-essential functions but A transformer is still most likely operating the "sensing" circuit becuase it most likely will not be a AC.