Patent ID: 8901934

Claim:
A detection circuit for determining whether contacts in a high voltage (HV) contactor are stuck closed, said detection circuit comprising: a power source electrically coupled to a coil in the HV contactor; a driver switch electrically coupled to the coil in the HV contactor; a sensor electrically coupled to the coil in the HV contactor; a buffer including inputs electrically coupled across the sensor, said buffer providing a voltage signal indicative of a current flow through the sensor; and a controller configured to determine whether the contacts in the HV contactor are welded closed, said controller providing a pulse signal to the driver switch that causes a current flow through the coil for a time period less than the time necessary to close the HV contactor, said controller receiving a voltage signal from the buffer that identifies the current flow through the sensor during the pulse signal to determine whether the contacts are welded or stuck closed, where the controller compares the voltage signal from the buffer to a stored signal identifying an open HV contactor to determine whether the contacts are welded closed, including comparing a differential of the voltage signal from the buffer to a differential of the stored signal and comparing an integral of the voltage signal from the buffer to an integral of the stored signal.