Abstract: A galvanically isolating circuit for converting input voltage which is in a first potential to an output variable which is in a second potential. The circuit is characterized by a first input terminal and a second input terminal for receiving the input voltage in the first potential, and a first output terminal and a second output terminal in the second potential for generating the output variable. The circuit is further characterized by a serial capacitance section for providing galvanic isolation between the input terminals and the output terminals, first polarity switching means, which are arranged to operationally connect the input terminals to the serial capacitance section by periodically reversing the polarity, and second polarity switching means, which ate arranged to operationally connect the serial capacitance section to output terminals by periodically reversing the polarity, in synchronism with the first polarity switching means.