Patent ID: 6947864

Claim:
A method of testing for latent faults in a redundant DC power supply system having at least two power supplies connected to a common load via respective isolation devices, each isolation device requiring a forward voltage to be equal to a respective forward bias voltage value to be operable in a normal conductive state, the method performed by a testing system comprising: selecting as a subject for a test procedure, one isolation device and its corresponding power supply; controlling the power supplies during the test procedure to marginally vary the output voltage of at least one power supply such that a differential voltage is applied between the output of the selected power supply and the outputs of the remaining power supplies for selectively changing the conductive state of at least one isolation device to a non conductive state by reducing its forward voltage to less than its respective forward bias voltage value; measuring current through the selected isolation device; and determining whether the measured current is consistent with the existence of a fault condition in the selected isolation device.