Patent ID: 7057868

Claim:
A method of protecting a fuel cell of a power circuit from damage caused by reverse current into the fuel cell caused by a faulty diode, the power circuit powering an electric motor of a vehicle for propelling the vehicle, comprising: providing one or more contactors in the power circuit that open to prevent current from flowing therethrough and close to allow current to flow therethrough; measuring the voltage across the diode to determine if the diode is in a good condition or a fault condition; causing the one or more contactors to be closed if the diode is in a good condition so that current flows from the fuel cell through the diode and the contactor to the electric motor to propel the vehicle; and causing at least one of the one or more contactors to be opened if the diode is in a fault condition so that current does not flow through the contactor, protecting the fuel cell from damage caused by reverse current through the diode and into the fuel cell, wherein measuring the voltage across the diode to determine if the diode is in a good condition or a fault condition includes inverting the voltage across the diode with an impedance buffer, comparing the inverted voltage to a reference voltage with a threshold detector, and determining that the diode is in a good condition if the inverted voltage is greater than the reference voltage and determining that the diode is in a fault condition if the inverted voltage is less than the reference voltage.