In accordance with an embodiment, a method includes receiving an indication of a changed load condition or voltage characteristic of a power supply providing power to a load via an output port of the power supply in a first mode, and switching regulation of the power supply from sourcing a current to the load in the first mode to sinking the current from the load in a second mode in response to receiving the indication of the changed load condition or voltage characteristic. Sinking the current from the load in the second mode includes controlling the power supply to transfer energy from the output port of the power supply to an input port of the power supply.