Optimization of Communication Techniques for Efficient WPT

In wireless power transfer systems, control relies on a communication loop between receiver and transmitter, a key factor for ensuring efficiency and reliability. In mobile devices, this loop is typically implemented through load modulation at the receiver, while the transmitter employs frequency-shift keying (FSK) by varying the full-bridge frequency. A common architecture combines load modulation with a buck converter for battery charging; however, the magnetic component of the buck results in a bulky implementation, making it unsuitable for compact form factors. Fixed-ratio switched-capacitor (SC) converters represent a promising alternative, providing higher power density and reduced size. Yet, their use disrupts the conventional load modulation mechanism, raising new challenges for the communication feedback path. This work presents a modeling approach for the regulation channel from the portable device to the charging station and proposes an optimized strategy compatible with fixed-ratio converters. The concept has been experimentally validated on a MagSafe-based prototype, demonstrating a communication system capable of sustaining high signal levels over a wide operating range with a load of up to 25 W.