Abstract: An AC backup power system controls a power supply to selectively connect to a primary AC power source or a backup AC power source through a switching module. The switching module is controlled by a monitoring module. The monitoring module has a power monitoring unit, a first circuit switch, a second circuit switch, and a first processor. When the power monitoring unit detects an interruption of primary AC current, the first circuit switch that is normally closed is immediately turned off. The first processor then drives the switching module to connect to the backup AC power source. Once the backup AC power source reaches the zero-crossing point, the second circuit switch is turned on so that the backup AC power source provides power to the power supply. The power supply receives power at the zero-crossing point to avoid problems of sparks and coke deposition.

Abstract: An AC backup power system controls a power supply to selectively connect to a primary AC power source or a backup AC power source through a switching module. The switching module is controlled by a monitoring module. The monitoring module has a power monitoring unit, a first circuit switch, a second circuit switch, and a first processor. When the power monitoring unit detects an interruption of primary AC current, the first circuit switch that is normally closed is immediately turned off. The first processor then drives the switching module to connect to the backup AC power source. Once the backup AC power source reaches the zero-crossing point, the second circuit switch is turned on so that the backup AC power source provides power to the power supply. The power supply receives power at the zero-crossing point to avoid problems of sparks and coke deposition.