Some implementations provide power management techniques for an electronic device that receives power through a USB port. The device may receive power from various different power sources such as a PC, USB hub, and various types of power adapters. To identify a type of power adapter connected to the USB port, the device's USB device controller may be reconfigured to operate in a host mode. A pull-up or pull-down may be placed on one of the D+ or D− lines of the USB port for determining whether the lines are shorted or floating. When the lines are shorted, the power source may be identified as a first type of power adapter that provides a known level of current. When the lines are not shorted, the values of the lines may be compared with known values for one or more pull-ups or pull-downs to attempt to identify other known power adapters.