I am using this large 24V power brick (rated for 9.2A) to power a small circuit (an arduino controlling some RGB LED strip, drawing less than 0.5A).
If I physically pull the plug out of the wall, the circuit runs on the transformer's stored energy for about a second before shutting down, which makes sense to me.
If the power supply has been plugged in for a long time, and I switch it off at the wall outlet, then the circuit continues to run for a very long time-- more than an hour-- before shutting down. But if I physically pull the plug, it still shuts down in a second or so.
- The switch on the wall socket is working correctly (tested with a desk lamp), and as I understand it, this switch interrupts the 240VAC live conductor.
- The power supply connects to the live, ground and neutral conductors on the AC side, and on the DC side provides a +24V and an AC ground connection
- Because I use an Apple laptop, I know the ground and neutral wires in my home are not at the same voltage
So, where is this circuit getting its power from when the live AC is disconnected?