An uninterruptible power supply, comprising: an input configured to receive AC input power from an AC power source; an output configured to provide AC output power to a load; a DC power source; characterised by a first power converter coupled to the input and the DC power source, the first power converter including a first AC-to-DC converter and a transformer, the transformer having a primary winding having a first end coupled to the input and a second end coupled to the output, the transformer further having a secondary winding coupled to the first AC-to-DC converter, the first power converter configured, during a first mode of operation of the uninterruptible power supply, 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 that is different than the first portion of the AC input power into DC power via the first AC-to-DC converter; a second power converter coupled to the input and the DC power source, the second power converter including a second AC-to-DC converter, the second power converter 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 uninterruptible power supply; a DC-to-AC converter coupled to the first power converter, the second power converter, the DC power source and the output; a controller coupled to the first power converter and the second power converter, wherein the controller is configured to determine whether the AC input power is within a predefined operating range, and, in response thereto, operate the uninterruptible power supply in the first mode of operation; wherein the predefined operating range is a first predefined operating range; and wherein the controller is further configured to determine whether the AC input power is within a second predefined operating range that is different than the first predefined operating range, and, in response thereto, operate the uninterruptible power supply in the second mode of operation. an input configured to receive AC input power from an AC power source; an output configured to provide AC output power to a load; a DC power source; a first power converter coupled to the input and the DC power source, the first power converter including a first AC-to-DC converter and a transformer, the transformer having a primary winding having a first end coupled to the input and a second end coupled to the output, the transformer further having a secondary winding coupled to the first AC-to-DC converter, the first power converter configured, during a first mode of operation of the uninterruptible power supply, 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 that is different than the first portion of the AC input power into DC power via the first AC-to-DC converter; a second power converter coupled to the input and the DC power source, the second power converter including a second AC-to-DC converter, the second power converter 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 uninterruptible power supply; a DC-to-AC converter coupled to the first power converter, the second power converter, the DC power source and the output; a controller coupled to the first power converter and the second power converter, wherein the controller is configured to determine whether the AC input power is within a predefined operating range, and, in response thereto, operate the uninterruptible power supply in the first mode of operation; wherein the predefined operating range is a first predefined operating range; and wherein the controller is further configured to determine whether the AC input power is within a second predefined operating range that is different than the first predefined operating range, and, in response thereto, operate the uninterruptible power supply in the second mode of operation.