| 摘要 |
<p>The present invention provides a method and apparatus for alternating current (AC) power failure detection. The method includes amplifying an AC power waveform, where the amplified waveform is asserted when the AC power waveform is in a vicinity of a zero-crossing and negated at all other times; initiating a counter when the amplified waveform is asserted; and determining if the counter equals or exceeds a reference number, where the counter being equal or exceeding the reference number indicates an AC power failure. The present invention converts an AC power signal to a near digital signal, where the near digital signal is asserted when the AC power signal is in the vicinity of a zero-crossing and negated at all other times. When the near digital signal is asserted, a counter in a controller begins counting, and ends the counting when the near digital signal is negated. If the counter equals or exceeds a reference number before the near digital signal is negated, then a failure of the AC power signal is detected. A signal indicating the AC power failure is then output by the controller to initiate power down operations. By measuring the length of time the AC power signal remains in the vicinity of a zero-crossing, a failure of the AC power can be detected earlier than with conventional methods. This allows more time to perform power down operations.</p> |
