A power supply, including a primary pre-converter, coupled to supplying mains, configured to receive an AC voltage at low frequency and output a high DC voltage, and further configured to receive the high DC voltage and to output the alternating current; a primary converter, disposed on a primary side of the power supply, coupled to the high DC voltage from the primary pre-converter; an isolating transformer to receive the high frequency AC voltage and output a high frequency secondary AC voltage, and to receive a high frequency secondary AC current and to output primary high frequency AC current; and an output converter, on a secondary side of the power supply, wherein the output converter is configured to receive high frequency AC voltage from the isolating transformer and to output a DC voltage of a first or second polarity to an output, and wherein the output converter is configured to receive DC current of a first or second direction from the output and to output a high frequency AC current to the isolating transformer.