Abstract: The present application relates to a class of switching power supplies, which use a resonant isolation stage (typically LLC) fed directly or via a diode bridge from the line. Extension of the range of available gain values over frequency without material loss of efficiency is facilitated by usage of additional resonant elements. This capability allows the devices to provide narrow-range inputs to secondary-processing circuits, with the ability to achieve power factor correction if required. The conversion architecture is also compatible with optimal usage of energy storage elements suitable for use with switching power supplies.