This is a usb powersupply for iphone or samsung.

5Volt USB power supply

this is the 5voltĀ  power supply once opened. You can see the capacitor to the left, in the middle is the coil and to the right the usb plug

5Volt USB power supply

The plug, the yellow part is a transformer and the usb plug on the right

The standing parts are capacitors that are here to stabilize the voltage