Subsystem-level efficiency analysis of a wireless power transfer system

In this paper, a mid-power 13.56 MHz wireless power transfer (WPT) system is used as an example to discuss the relationship between the overall system and each subsystem. There are four subsystems discussed, including a power amplifier, a pair of resonant coils, a rectifier, and an electronic load. The paper evaluates the system performance under different mutual inductances in two cases. One is a simple WPT system without a rectifier, and the other with the rectifier. It is found that the existence of rectifier introduces more power reflection, especially when strong coupling occurs. The analysis in this paper can guide the design of an optimal load and input impedance matching network. Finally, the theoretical analysis is validated by experimental results.