Automatic Resonance Compensation for Efficient WPT via Magnetic Resonance Coupling Using Flexible Coils

With the recent proliferation of mobile and wearable devices, wireless power transfer (WPT) has gained attention as an up-and-coming technology to charge these devices. In particular, WPT via magnetic resonance coupling has attracted considerable interest for day-to-day applications since it is harmless to the human body and has relatively long transmission distance. However, it was difficult to be installed into environment (e.g., utensils and furniture) and flexible objects in the living space since the use of flexible coils leads to the decrease in transmission efficiency due to the collapse of the resonance caused by coil deformation. Therefore, this study proposes an automatic resonance compensation system that automatically compensates the inductance variation caused by coil deformation using a circuit that can electronically control the equivalent capacitance (a capacity control circuit), and thereby maintains the resonant state. An experiment was conducted to verify whether the efficiency was maintained when the coil deformed. The results indicated a transmission efficiency nearly as high as that of the ideal resonant state as well as a highly responsive control, and therefore, the proposed system has a good potential for use in real-world applications.