High Power Constant Current Class EF2 GaN Power Amplifier for AirFuel Magnetic Resonance Wire-less Power Transfer Systems

This paper presents the constant current Class EF2 power amplifier (PA) for magnetic resonance WPT with GaN devices, where the current output of the Class EF2 PA remains almost constant when the load impedance varies. The solution enables power transfer coil load of the WPT system to simultaneously support multiple devices and naturally supply the power demanded by receiver with open loop. The design methodology of Class EF2 PA will be discussed in detail, followed as a customer solution design for WPT. The Class EF2 PA can deliver 150W CW power at 6.78MHz, with 94% efficiency at 70V before EMI filter.