Patent ID: 7531916

Claim:
A system for powering a direct-current electrical load, comprising: a fuel cell stack configured as a primary power device for producing electrical power in response to the supply of fuel and oxidant; said fuel cell stack having a cell potential that varies in response to load changes; a first protection circuit coupled to said fuel cell stack; a fuel cell output current sensor coupled to said first protection circuit; a fuel cell output voltage sensor coupled to said first protection circuit; a first protection circuit output voltage sensor coupled for sensing the output voltage from said first protection circuit; an energy storage device (ESD) coupled to said first protection circuit and configured for providing current to the load when the fuel cell stack produces less current than the load requires; wherein said ESD is selected from the group consisting of a supercapacitor, an ultracapacitor, and a battery; wherein said first protection circuit regulates current supplied to said ESD, and reduces current supplied to said ESD in response to detecting a current level from said fuel cell output current sensor which exceeds an adjustable predetermined threshold; wherein said first protection circuit ceases conduction in response to said fuel cell output voltage sensor detecting that fuel cell output voltage is below a predetermined threshold; wherein said first protection circuit limits the voltage applied to said ESD in response to the output of said first protection circuit output voltage sensor; a second protection circuit coupled to said enemy storage device (ESD) and configured for outputting a fixed voltage driving the electrical load of the system; an ESD output current sensor coupled to said second protection circuit; an ESD output voltage sensor coupled to said second protection circuit; a second protection circuit output voltage sensor coupled for sensing the output voltage from said second protection circuit; wherein said second protection circuit controls the amount of current being supplied from said ESD to the load in response to detecting current level from said ESD output current sensor; wherein said second protection circuit ceases conduction in response to the ESD output voltage sensor detecting a low voltage condition below a predetermined threshold; wherein said second protection circuit limits the voltage applied to the load in response to detecting a low voltage condition from said second protection circuit output voltage sensor.