Abstract
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.
Highlights
The proliferation of mobile and wearable devices is making its power management troublesome, and under this circumstance, wireless power transfer (WPT) has gained attention as an up-and-coming technology to charge these devices
There is a growing interest in the use of WPT by magnetic resonance coupling [1,2,3,4,5,6,7,8] in day-to-day applications because of its broader transmission range compared with electromagnetic induction [9], higher transmission efficiency and relatively low impact on the human body compared with microwaves [10] and laser [11]
Since rigid coils were mostly used in WPT via magnetic resonance coupling, it was difficult to be installed into environment and flexible objects in the living space
Summary
The proliferation of mobile and wearable devices is making its power management troublesome, and under this circumstance, wireless power transfer (WPT) has gained attention as an up-and-coming technology to charge these devices. Since rigid coils were mostly used in WPT via magnetic resonance coupling, it was difficult to be installed into environment (e.g., utensils and furniture) and flexible objects in the living space. This study proposes a practical method that automatically controls the capacitance value of external capacitors to counter the efficiency drop caused by the shape change of flexible coils. We propose a method of resonance compensation by automatic control of the capacitance value of external capacitors according to changes in the shape of flexible coils. The two main contributions of this paper are as follows: First, it offers an automatic resonance compensation system that maintains a high transmission efficiency despite changes in the coil shape in WPT via magnetic resonance coupling using flexible coils. We demonstrated via actual experiments that the proposed system is able to maintain a level of transmission efficiency nearly as high as that of the ideal resonant state, while it shows enough control responsiveness
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