Resonant converters may be operated according to selected working modes to achieve voltage doubler or non-voltage doubler functions. Embodiments may be based on two-phase resonant converters. Embodiments may implement primary side switching, secondary side switching, or both, to achieve the selected working modes and voltage doubler and non-voltage doubler function. Embodiments are suitable for applications requiring wide input and output voltage ranges, such as low-voltage charging circuits for personal electronic devices, and high voltage charging circuits for electric vehicles.