13.56MHz 50W Load-Independent Synchronous Class E Rectifier using GaN devices for Space-Constrained Applications

This paper presents the design and implementation of a load-independent synchronous Class E rectifier to enable fast and efficient wireless charging in space-constrained applications such as drones and laptops. Load-independent operation allows Class E circuits to maintain zero-voltage switching (ZVS) and a inherently regulated output voltage for any load value without the need for tuning or replacement of components. Load-independent operation also the allows Class E rectifiers to have a constant input reactance that does not vary with loading and coupling. This feature allows the rectifier to present a real impedance to the transmitter side and therefore allows the complete system to operate without detuning of the inverter or the wireless link. Operating at MHz switching frequencies is now possible with the availability of wide-bandgap devices such as GaN resulting in low profile, power dense converters to be realised. Here we present the design process and implementation of a 13.56 MHz 50W load-independent synchronous Class E rectifier using GaN devices for a wireless charging system operating at 13.56 MHz. The derivation of the switching signal and the circuitry to achieve this will also be discussed and initial experimental results will be presented.