CONTROL CIRCUIT FOR UNINTERRUPTIBLE POWER SUPPLY

摘要

A circuit for generating control signals used in detecting a power failure in an uninterruptible power supply in which the A.C. signals of the power supply are examined to output a first signal representing the zero crossing of the A.C. signals. This first signal is used to reset an oscillator whose output clock signals are synchronized with the frequency of the A.C. signals by a phase lock loop circuit. The clock output of the phase lock loop circuit operates a counter whose output count is used to address a programmable read-only memory which outputs binary bits to a digital-to-analog converter which in turn outputs a full wave rectified sine wave operating at the system frequency which is used as a reference to detect the occurrence of a power failure in the main source of A.C. power signals. A second control signal is generated indicating a power failure condition which is used in switching an inverter into the power supply for supplying A.C. signals to a load.