A Monolithic GaN-IC With Integrated Control Loop for 400-V Offline Buck Operation Achieving 95.6% Peak Efficiency

Gallium nitride (GaN) transistors enable efficient and compact high-voltage power converters. In the state-of-the-art enhancement mode GaN-on-Si technology, a 650-V power transistor is formed as a lateral structure enabling monolithic integration with a driver and analog control circuits on one die. Offline power converters show a trend toward a higher level of integration, shifting from monolithic silicon (CMOS) to various integration levels in GaN technology. In this article, a monolithic, self-biased GaN buck converter for offline operation is presented, supporting both 110- and 230-V ac line voltage and providing up to 29-W output power. The converter shows a superior efficiency of 95.6 % and a very high level of integration in a 650-V p-GaN gate e-mode GaN-on-Si technology. Analog design techniques for GaN integration, such as an auto-zero comparator and a high-voltage supply regulator, are discussed. Experimental results of stand-alone circuit blocks and the full buck converter confirm the viability of monolithic GaN integration as a path toward compact and efficient offline power converters.