Efficiency modeling of class-E power oscillators for wireless energy transfer

Wireless energy transfer is employed in different applications such as recharging of electrical car battery, implanted biosystems and wireless sensor network nodes. In these applications, the efficiency in the energy transfer process is a key issue, requiring careful design and correct device, circuit and system modeling. In this paper, we present accurate expressions for efficiency calculation of class-E power oscillators targeting an inductive link for wireless energy powering. The model includes the influence of the load resistance variations due to changes on the magnetic coupling between the coils of the link. Moreover, we compare the results obtained from the developed model with those obtained from simulation and measurement of a class-E power oscillator operating at 125 kHz.