Patent ID: 8004113

Claim:
An apparatus for operating a portable electronic device, comprising: a voltage converter having an input and an output, wherein the input is capable of being coupled to a solar power source and the output is capable of being coupled to a portable electronic device, and wherein the voltage converter is configured to convert solar power received from the solar power source to power the portable electronic device; and a controller coupled to the voltage converter to monitor power drawn at the output of the voltage converter based on an average amount of current drawn by the portable electronic device and a voltage of the portable electronic device, wherein the controller controls the voltage converter to adjust output power in response to the monitored power, wherein the controller is configured with a current-voltage relationship characteristic of the solar power source, the characteristic specifying voltage operating points for the solar power source, the voltage operating points including stable operating points indicating a stable mode for the solar power source and unstable operating points indicating an unstable mode for the solar power source, the solar power source in the unstable mode collapsing with a constant current and a sharp drop of voltage, wherein the controller causes the solar power source to operate in the stable mode to allow the solar power to reach a maximum power indicated in the characteristic without the solar power source operating in the unstable mode, wherein the controller determines whether the solar power source generates the maximum power based on the monitored power, and wherein the controller maintains the solar power source in the stable mode within a predetermined range indicated in the characteristic, the predetermined range including a voltage threshold to prevent the sharp drop of the voltage of the solar power source.