Abstract: The addition of gate bias resistors substantially balances the voltage across any number of series-connected FETs, while the feedback control of the gate-source voltage of one FET controls the current through all of the FETs. In this way, the thermal load and voltage stress are substantially balanced for series connected FETs operating in active linear mode (partially on), enabling operation at voltages much higher than the individual ratings of low cost, readily available FETs. Alternatively, series-connecting FETs for active-mode operation is thermally equivalent to paralleling because the FET heat load is practically uniform, enabling operation at much higher current. This concept is extended to a series connection of FETs that can block, pass, and/or limit alternating load current with the voltage applied across all the FETs being either polarity or alternating polarity. We provide analysis, practical design considerations, and simulation results.

Abstract: Fuel cell power systems and methods of operating fuel cell power systems are described. According to one aspect, a fuel cell power system includes a fuel cell configured to generate electrical energy; switch mode power conditioning circuitry configured to electrically condition the electrical energy generated by the fuel cell, wherein the switch mode power conditioning circuitry comprises a controller configured to monitor an electrical status of the fuel cell and to adjust the conditioning of the electrical energy using the switch mode power conditioning circuitry responsive to the monitoring, wherein the controller is configured to provide a pulse width modulated control signal to control the switching of the switch mode power conditioning circuitry and to vary a duty cycle of the control signal to adjust the conditioning of the electrical energy using the switch mode power conditioning circuitry.

Abstract: Fuel cell power systems and methods of operating fuel cell power systems are described. According to one aspect, a fuel cell power system includes a fuel cell configured to generate electrical energy; switch mode power conditioning circuitry configured to electrically condition the electrical energy generated by the fuel cell, wherein the switch mode power conditioning circuitry comprises a controller configured to monitor an electrical status of the fuel cell and to adjust the conditioning of the electrical energy using the switch mode power conditioning circuitry responsive to the monitoring, wherein the controller is configured to provide a pulse width modulated control signal to control the switching of the switch mode power conditioning circuitry and to vary a duty cycle of the control signal to adjust the conditioning of the electrical energy using the switch mode power conditioning circuitry.

Abstract: Fuel cell power systems, direct current voltage converters, fuel cell power generation methods, power conditioning methods and direct current power conditioning methods are provided. According to one aspect of the invention, a fuel cell power system includes a plurality of terminals adapted to couple with a load; a fuel cell configured to convert chemical energy into direct current electrical energy having a variable voltage potential; and a converter coupled intermediate the fuel cell and the terminals, the converter being configured to convert the direct current electrical energy having the variable voltage potential into direct current electrical energy having a substantially constant voltage potential.