Hall thrusters can be operated over a wide range of specific impulse while maintaining high efficiency. However S/C power system constraints on electric propulsion systems often force a choice of maximum power operation over a narrow range of specific impulse and thrust. Most spacecraft users would desire a continuous selection of thrust and specific impulse at maximum power when possible, but power supply systems currently do not exist with this level of functionality. To provide continuous Hall thruster adjustment, a power supply must be wide ranging in voltage, current, and power. In addition, the power supply system must be lightweight and efficient. The proposed work addresses these needs through a three-phase resonant power conversion strategy combined with novel frequency selective output-stage circuitry that will allow greater than 8:1 output voltage adjustment at power levels up to and beyond 100-kW. Three-phase resonant power converters utilize filter components with lower mass and size relative to single-phase converters, and demonstrated efficiencies are greater than 97%. Additionally, resonant converters operate at higher frequency, which results in extended stability when used in dynamic load situations imposed by Hall thrusters. The proposed Phase I program will develop a prototype power supply and demonstrate its functionality.