According to an embodiments, a power supply device includes: a first voltage generator that operates to output a first voltage; a second voltage generator that operates to output a second voltage higher than the first voltage; a third voltage generator that, from the second voltage generated by the second voltage generator, operates to generate a third voltage equal to the first voltage and to output the third voltage therefrom; and a selector that operates to select as an output whichever has a higher voltage from the output of the first generator and the output of the second generator, wherein each of the output of the second voltage generator and the output selected by the selector are supplied to a load.