Abstract
In the conventional wireless power transfer (WPT) using magnetic resonance coupling, power transfer efficiency (PTE) exhibits a peak only at a matched distance between transmitter (Tx) and receiver (Rx). That is, it rapidly degrades if the distance deviates from the matched distance. In order to achieve high PTE over a wide range of the distance, automatic range-adaptation technique is proposed in this work by using multi-loop technique and tunable matching circuit with digital capacitors. For automatic range adaptation, the microcontroller unit (MCU) in Rx runs an algorithm to find optimum loop and capacitance for best PTE based on the received power. Tx and Rx are synchronized by using low power Bluetooth wireless communications. Instead of the conventional relays, microelectromechanical system (MEMS) switches with low loss and high isolation are employed to minimize the power dissipation. The entire WPT system automatically maximize PTE with the distance, achieving high PTE of 80.5% at 30 cm and 29.7% at 100 cm.
Highlights
Magnetic resonant coupling technique allows an efficient wireless power transfer (WPT) up to a few meters, which can overcome the problem of the limited operating range of the magnetic induction technique
It is based on the fact that input impedance of magnetic resonant WPT is matched to the system impedance only at a specific distance and varies according to the distance
We propose an automatic range-adaptive WPT which is compact and low-power consuming, using microcontroller unit (MCU), microelectromechanical system (MEMS) switch, digital capacitors, and Bluetooth module
Summary
Magnetic resonant coupling technique allows an efficient wireless power transfer (WPT) up to a few meters, which can overcome the problem of the limited operating range of the magnetic induction technique. Energies 2018, 11, 1789 be adjusted according to the distance by changing the orientation or the distance between loop and coil [5] This method requires a mechanical tuning using motors for automatic adaptation which leads to the increase of DC power consumption and system complexity. WPT has been introduced to improve the range adaptation [13] by the authors’ group of this paper, where four loops with different size were employed, and only one loop was selected according to the distance It adjusts the coupling factor between the coil and loop such that the variation of input impedance with distance is dramatically reduced. We propose an automatic range-adaptive WPT which is compact and low-power consuming, using microcontroller unit (MCU), MEMS switch, digital capacitors, and Bluetooth module It is well-suited for the practical applications.
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