Abstract: An aircraft device power supply is capable of connecting to either an AC or a DC power bus provided on an aircraft. When connected to an aircraft's AC power bus, an AC power signal is EMI-filtered, stepped down in voltage to the same voltage as that of the DC power bus, and then rectified. When connected to an aircraft's DC power bus, a DC power signal is EMI-filtered before it is merged with the rectified AC power signal via an AC/DC switchover subcircuit. The output of the AC/DC switchover subcircuit is input to a power factor correction subcircuit which outputs a boosted DC voltage, regardless of which of the AC or DC aircraft power buses is connected to the power supply. A step down converter reduces the boosted DC voltage to a lower, system voltage which may then be further reduced or modified, as appropriate for device to be powered.