Method of utilizing power transistor of fuel cell stack diagnostic system

An apparatus comprising:

• a fuel cell stack;
• a fuel cell stack diagnostic system including:
• a diagnosis control analyzer that diagnoses and analyzes a status of the fuel cell stack by measuring a current and a voltage of the fuel cell stack;
• an alternating current (AC) signal generator that generates a diagnostic AC signal in accordance with control of the diagnosis control analyzer;
• and a power transistor that is driven in response to the diagnostic AC signal outputted from the AC signal generator and includes a diagnostic AC component into the current of the fuel cell stack;
• a regenerative braking detector configured to detect regenerative braking of a fuel cell vehicle equipped with the fuel cell stack diagnostic system;
• a voltage rise determiner configured to determine whether a voltage rise due to regenerative braking of the fuel cell vehicle is a predetermined value or more;
• and
• a power transistor controller configured to control the AC signal generator so that the voltage due to the regenerative braking is discharged by the power transistor, when the voltage rise due to regenerative braking determined by the voltage rise determiner is the predetermined value or more.