DC-to-5-MHz Wide-Output-Bandwidth High-Power High-Fidelity Converter

Advances in power electronics have made it possible to achieve high-power levels, e.g., reaching GW in grids, or alternatively high output bandwidths, e.g., beyond MHz in communications. Achieving both simultaneously, however, remains challenging. Various applications, ranging from efficient multichannel wireless power transfer to cutting-edge medical and neuroscience applications, demand both high power and wide bandwidth. Conventional inverters can achieve high power and high quality at grid or specific frequency ranges but lose their fidelity when reaching higher output frequencies. Resonant circuits can yield a high output frequency but only a narrow bandwidth. We overcome these hardware challenges by combining gallium-nitride (GaN) transistors with modular cascaded double-H bridge circuits and control that can manage typical timing and balancing issues. We developed a compact embedded control solution that includes an improved look-up-table digital synthesizer and a novel adaptive-bias-elimination nearest-level modulation. This solution effectively solves the conflict between a high power level and high output bandwidth and can, in principle, be scaled in both dimensions, in contrast to previous approaches. Our prototype exhibits a frequency range from dc to 5 MHz with less than 18% total voltage distortion across the entire frequency spectrum while achieving a power level of 5 kVA. We demonstrated applications of the system by sweeping the output frequency and two channel-mixing trials, which included a practical magnetogenetics-oriented stimulation pulse as well as a communications message example.