Probably it is not possible but I will ask anyway.
My laptop (Dell Inspiron 15) stands on cooling pad, which is connected on the D3100 USB port. If I turn of the laptop the fan in cooling pad turns off. But after a few seconds fan starts to work again as D3100 has its own power source. So I also have to disconnect D3100 from the power or disconnect cooling pad from the D3100 to turn off the fan in the cooling pad.
Is there anyway to tell D3100 to turn off power from USB ports when there is no connection with laptop?
And of course I could connect the cooling pad to the laptop. But that is what D3100 should be for.