transformers suck (power) - they can be vampires
A transformer uses significant power even when the output is an open circuit. They're always warm.
The Dell power supply has a transformer, but apparently has circuitry to disconnect the transformer when the output is open. When I plug it in, it uses about 7 watts for a second or two (after the spike), then drops to 0.1 watt. I assume that there's some active circuit that isolates the transformer.
By the way, when shopping for usb hubs, battery chargers, phone chargers, and other items with small power bricks - buy light. If the power brick is heavy, it's probably a transformer that's always sucking power. If it's lightweight, it's probably an electronic device that isn't a vampire.
http://en.wikipedia.org/wiki/Electricity_vampire
That makes no sense. Its an open circuit then. Theorethiclaly no power should be pulled.
A transformer uses significant power even when the output is an open circuit. They're always warm.
The Dell power supply has a transformer, but apparently has circuitry to disconnect the transformer when the output is open. When I plug it in, it uses about 7 watts for a second or two (after the spike), then drops to 0.1 watt. I assume that there's some active circuit that isolates the transformer.
By the way, when shopping for usb hubs, battery chargers, phone chargers, and other items with small power bricks - buy light. If the power brick is heavy, it's probably a transformer that's always sucking power. If it's lightweight, it's probably an electronic device that isn't a vampire.
http://en.wikipedia.org/wiki/Electricity_vampire