GaN VHF Converters With Integrated Air-Core Transformers.

This paper proposes an air-core transformer integration method, which mounts the transformer straight into the multilayer printed circuit board (PCB), and maintains a proper distance between the inner transformer and other components on the top layer. The integration method reduces the PCB area significantly, ensuring higher power density. The design of the complete structure is accomplished with finite element analysis (FEA) to ensure that the unconstrained transformer magnetic field does not affect other components. It is applied to three resonant flyback converters operating at 20 MHz with Si mosfets, 30 MHz, and 50 MHz with enhancement-mode gallium nitride (eGaN) high-electron mobility transistors, respectively. The 30-MHz eGaN prototype achieves the full load efficiency of 80.1% (an increase of 1.1% compared with the 20-MHz Si prototype) and power density of 32 W/in3 at 5-V input and 5 V/ 2 W output. The 50-MHz eGaN prototype achieves the power density of 39.4 W/in3, which is 41% higher than the 20-MHz Si prototype. With the similar efficiency, the overall height of the converters in this paper is less than half of the commercial products, very suitable for low thickness and profile applications. [ABSTRACT FROM AUTHOR]