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-$\Omega$. 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 $50\Omega$ 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.