Compact High Efficiency GaN-based PPU

Busek proposes to develop a low-cost, lightweight Hall Effect Thruster (HET) Power Processing Unit (PPU) at targeted 1kW/kg power density with more than 97% efficiency. The proposed PPU solution adopts advanced GaN power MOSFETs and PCB based planar magnetics technology to enable high switching frequency operation. Reduced headcount of magnetics, semiconductors and associated driver integrated circuits will allow for significant size reduction of all passive components to support ultra-high power density designs. This innovation will further miniaturize HET PPUs from today’s state-of-art by an anticipated 30% in volume and mass, with cost reductions exceeding 50% versus SOA solutions.The unique advantages of the proposed system can be summarized in three parts. First, the system utilizes a novel single-core multi-port circuit topology which integrates all the PPU subsystems through a single stage power conversion using a single multi-winding transformer. This significantly reduces system volume, weight, and cost. Second, the power flow control for each subsystem is fully independent regardless of power stage sharing. Each subsystem has its own phase shift control to regulate the desired output voltage and current. Third, the proposed PPU circuit topology is essentially a soft-switching DC-DC converter which can ensure zero-voltage-switching operation for all the switching devices. The proposal adopts the advanced GaN power MOSFETs and PCB based planar magnetics technology to enable high switching frequency operation, which supports a 30% size reduction of magnetics and other passive components in the high-efficiency and high-power density design.In Phase II Busek will characterize the breadboard PPU with sub-kilowatt Hall thrusters and develop a proto-flight brass-board level unit using GaN devices. At the conclusion of Phase II, Busek will deliver a PPU to NASA for additional characterization testing.