Wireless Power Transmission Using LC Cancellation

In recent years, research on wireless power transmission technologies has been attracting more attention after MIT introduced the magnetic resonance technology in 2007. Wireless power transmission technology enables flexible comfortable supplying energy needs to electric devices. However, the wireless power transmission technologies that use the magnetic field resonance method have various problems. This method has been uniformly investigated from different directions. Therefore, it is difficult to understand the principle for such new technology phenomenon. Much of the research is often focused on the efficiency between resonators. Moreover, the relationship between the internal resistance and efficiency is not clear. Furthermore, the efficiency at high output power is not well understood. Practically, adding an internal resistance as an equivalent of both of rectifier and inverter losses is important for efficiency calculations. Even if the wireless power transmission has high efficiency, it is not suitable for practical use if the output power rating is very small. In this study, at first, the drawbacks of using the electromagnetic induction method for wireless power transmission are described in detail. Then, we indicate that we can increase the transmission power in accordance to the principles of the LC cancellation by using the resonance phenomenon even at a small coupling coefficient. After that, the difference between the overall efficiency considered of entire system and the transmission efficiency between the resonators is clearly distinguished. Then a theoretical formula has been developed for the overall efficiency and the output power in terms of the characteristic impedance. Finally, the theoretical results are compared with the experimental results and discusses in detail.