Abstract: A converter power supply uses a resonant primary circuit connected to a transformer and switches driving current pulses to the resonant primary circuit in phase with and substantially over the duration of the positive and negative half cycles during drive conditions, and clamps to allow the natural resonant current to decay in magnitude substantially over the duration of the positive and negative half cycles during clamping conditions. The decisions to drive or to clamp are made on half-cycle of the naturally resonating current. An algorithmic relationship creates the maximum alternation of drive and clamp conditions to achieve the desired level of power regulation. A configuration of current switches drives the primary winding and charges a resonator capacitor during one half cycle of the resonant current, and during the other half cycle the capacitor is discharged to drive in the other direction. The power supply is particularly useful for energizing an x-ray tube.