US Patent 7969043 Power management systems with multiple power sources

An electronic system includes a plurality of primary power sources operable for powering a load and charging a secondary power source, and a power management unit coupled to the plurality of primary power sources and the secondary power source. The power management unit is operable for selectively directing power of each of the primary power sources to the load according to a power requirement of the load. The power management unit is further operable for directing power of the secondary power source to the load if the power requirement of the load exceeds a total power capacity of the plurality of primary power sources.