I have recently put together a DIY bench power supply using a DPS5015 from Rui Deng and an old laptop power supply. Everything seems to be working fine except for a small amount of current leaking to earth even when the output is turned off.
I noticed this when I was testing after assembly. I was connecting an LED to the binding posts and noticed that if I was holding one leg of the LED it would light up when the other leg touched the binding post.
Now where I start to get confused is that the laptop power supply that I’ve repurposed has no earth connection and should therefore be floating. I believed this would mean leakage to earth was not possible as there was no return path for the current. I’ve confirmed the current is AC 50 Hz(I live in Australia with 50 Hz mains). Measuring the current straight to earth I get 148 uA. Current through my body is 133 uA. Current through my body with my feet insulated is 34 uA.
So my main questions are how can current leak to earth from a power supply that is not earth referenced and why does current still flow when not even connected to earth.
Am only a hobbyist just learning and would really love to understand what’s going on. Does this represent a safety risk? Are there any changes that can be made to reduce this effect/improve any safety factors?
Thanks in advance.