Circuits and methods for providing a “bootstrap” power supply for level-shifter/driver (LS/D) circuits in a FET-based power converter. In a first embodiment, linear regulators and a bootstrap capacitor provide a bootstrap power supply for level-shifter/driver circuits in each tier of a multi-level FET-based power converter. In a second embodiment, floating charge circuits and bootstrap capacitors provide an improved bootstrap power supply for level-shifter and driver circuits in each tier of a multi-level FET-based power converter. More particularly, a floating charge circuit configured to be coupled to an associated bootstrap capacitor includes a first sub-circuit configured to pre-charge the associated bootstrap capacitor when coupled and a second sub-circuit configured to transfer charge between the bootstrap capacitor and a bootstrap capacitor coupled to an adjacent floating charge circuit.