Our mobile devices are becoming more and more wireless. While data transfer of mobile devices is already wireless, charging is typically still performed with cables. Efficient and easy-to-use wireless charging is the next major step in freeing our devices from their wired connections. Current inductive wireless charging designs work, but the receiver must be positioned very accurately on the charging pad for efficient power transfer to actually take place. Resonant wireless charging is much more forgiving of the receiver placement – as long as the receiver is placed somewhere on the resonant wireless charging pad, power transfer can be established.
Resonant wireless charging design needs more than simply an understanding of the properties of the switches. An efficient design also requires knowledge of how the magnetic system works. The central part of optimizing the wireless charging system during the design phase is applying the formula used to calculate the resistance seen by the transmitter and estimating the maximum power that can be transmitted. In addition, the coupling between the transmitter and the receiver, and the effects that the quality factors of the two coils have on the overall efficiency must be understood.