We have more than one set of joy con controllers, and I found charging the controllers on the Switch (while docked) to be a bit of a pain. The Switch dock has two USB ports, so we bought two of these so we can charge 4 sets of controllers at a time. Beware that charing 4 devices off one USB port may take some time (depending on the amount of charge in the controllers). USB is typically 5v at about 2 amps (10 watts), so charging 4 controllers can take some time. It took about 7 hours to initially charge our brand new joy con controllers. Also, moving the Switch in/out of the dock will disrupt the power to the USB ports, so the charging lights on this device will turn red while it synchronizes the charging cycle. No this device does not come with a power supply. It would have been nice, but not a deal breaker for us since we just plug it into the Switch. Yes the USB cord is permanently attached to the charging block, but we never move our Switch dock or charging blocks (so again not a deal breaker for us). Overall we're very pleased. The controllers slide in/out of the charger easily, and it does what it needs to do.