Patent ID: 7521823
Filing Date: 2009-04-21
Classification: H02J,H02M

Abstract:
1. A method of detecting a failure of a DC power system included in an uninterruptible power supply (UPS), the method comprising acts of: sampling a voltage provided by the DC power system; comparing at least two samples to determine whether the voltage provided by the DC power system is decreasing; adjusting in a first direction, based on a result of the act of comparing, a value that corresponds to an accumulated amount of time during which the voltage provided by the DC power system is less than a threshold voltage and is decreasing; adjusting the value in a second direction, based on the result of the act of comparing, to account for an amount of time during which the voltage provided by the DC power system is less than the threshold voltage and is increasing; and generating a signal indicating that the DC power system has failed if the value reaches a predetermined value.