An uninterruptible power supply includes a first power converter, a second power converter, and a DC-to-AC converter coupled to the first power converter and the second power converter. The first power converter includes a first AC-to-DC converter and a transformer having a primary winding coupled to the input and the output, and a secondary winding coupled to the first AC-to-DC converter. The first power converter is configured, during a first mode of operation of the UPS, to provide a first portion of the AC input power as the AC output power via the primary winding and convert a second portion of the AC input power into DC power via the first AC-to-DC converter. The second power converter includes a second AC-to-DC converter and is configured to convert the AC input power into DC power via the second AC-to-DC converter during a second mode of operation of the UPS.