Highly Resonant Wireless Power

Summary

This chapter focuses on the loosely coupled highly resonant wireless energy transfer solution, based on the AirFuel standard. The wireless power transformer has a leakage inductance that can be significantly larger than the magnetizing inductance due to the low coupling factor. To overcome the leakage inductance, the wireless power coil‐set is tuned on‐resonance using either series, shunt, or a combination of series and shunt capacitors. Unlike radio frequency systems with fixed impedance loading, wireless power amplifiers need to operate with variable impedance loading and concurrently exhibit high operating efficiency. The figure of merit is a popular method to quickly evaluate various power devices and can also be adopted for wireless power amplifier topologies. The switching family of amplifier topologies are the only ones that can operate at high enough efficiency for use as a wireless power amplifier. The gallium nitride transistors powered the amplifiers without the need for a heatsink.