A Comprehensive Comparison of MHz GaN-Based ZVS Step-Down Converters for Low Power Integrated On-Chip Applications

Non-isolated step-down converters are widely used as auxiliary power supplies. Active and passive components, excluding large magnetic components, are usually integrated in a single chip in the industry. High power density and high efficiency are always the most important requirements. High switching frequency, such as megahertz (MHz), can highly shrink the volume of passive components compared with kilohertz frequency, however, it will cause huge switching loss for hard switching converters. Zero-voltage-switching (ZVS) is able to highly reduce switching loss, especially under high switching frequency. In this paper, three ZVS buck-type converters operating at MHz frequency, including conventional buck, tapped-inductor buck and hybrid resonant buck converter, are compared. Finally, three hardware prototypes using gallium-nitride (GaN) devices with 24-48 V input and 3-A/5-V output are demonstrated and compared in terms of efficiency, size and thermal performance.