Abstract: An interruptible power supply can supplant a primary power source with a secondary power source such as a battery when the primary power source fails. The supply has a switching device, an inverter and a pair of output terminals. The inverter is coupled to the output terminals. The inverter can couple electrical energy from the battery to the pair of output terminals. The switching device is responsive to the presence of electrical potential at the primary power source for coupling and decoupling the primary power source or the secondary power source to the output terminals. The switching device can also provide a current path from the primary source to the output terminals, which bypasses the inverter. A force commutation device responds to the voltage at the primary power source for driving the switching device, causing it to decouple the primary power source from the output terminals.

Abstract: A high-efficiency, low-cost D.C. to A.C. electronic inverter generates sinusoidal ouptut voltage(s) by utilization of an oscillator and divider circuitry that generates extremely precise symmetrical control signals. These control signals cause a push-pull amplifier comprising power switch drive transistors to periodically alternately energize power switches comprising two banks of matched output transistors, that in turn generate high current inputs to a ferro-resonant transformer. The transformer is tuned to provide the desired output sinusoidal voltage.The inverter incorporates unique overload and short-circuit protection electronics that prevent catastrophic destruction of the power switch drive transistors as well as the power switch transistors. Furthermore, to maximize the inverter's efficiency, the power switch driving circuit receives electrical energy from the ferro-resonant transformer in order to insure deep saturation of the power switch transistors.