13.56MHz High Power Half-Bridge GaN-HEMT Resonant Inverter Achieving 99% Power Efficiency

High-power inverters with high frequency have been required for progressing technologies such as wireless power transfer (WPT) and plasma processing. Recently, gallium nitride high electron mobility transistor (GaN-HEMT) is getting lots of attention from the viewpoint of fast switching ability and low power consumption. However, GaN-HEMT inverters are difficult to be operated in over several kW because of its low drain-source breakdown voltage. In other words, the conventional half-bridge GaN-HEMT inverter can output high power only for the small load resistance less than several- Ω. This paper overcomes this difficulty by implementing an impedance conversion network in the prior stage of the series resonator. The proposed topology realizes not only high-power from low drain-source voltage but also the sine wave output with very low harmonics. 3kW output to 50Ω load at 13.56MHz is theoretically designed, and verified by computer simulations. And also, the experimental prototype using GaN-HEMTs achieves the high efficiency of 99.43% at 13.56MHz and 471W.