US Patent 9379580 Uninterruptable power supply

An apparatus including a plurality of transformers each having a primary winding and a secondary winding where the secondary windings are connected in series, a battery, a plurality of switches, each coupled to one of the plurality of transformers, the switches intermittently closes to complete a circuit between the battery and the primary winding of the one transformer and a processor that individually activates the respective switches of the plurality of transformers in a predetermined order to generate an alternating current voltage across an output of the series connected secondary windings.