Wireless Power Transfer Receiver With Adjustable Coil Output Voltage for Multiple Receivers Application

In this paper, a receiver that can adjust the output voltage of a coil is proposed to simultaneously charge as many receivers of different couplings as possible. One large coil of traditional receiver is split into two small coils while the total coil volume is kept constant. The receiver has three output modes: half-voltage, same-voltage, and boosted-voltage modes. First, the boosted-voltage mode can produce an receiver (RX) coil voltage that is ~60% higher than the traditional receiver with an identical coil volume. It is useful for low-coupling and low-transmitter (TX)-output condition. Second, the half-voltage mode protects the semiconductor devices from overvoltage by outputting half of the traditional receiver with identical volume. It is necessary for high-coupling and high-TX-output condition with otherwise high voltage stress. Finally, the same-voltage mode produces the same coil voltage as that of the traditional receiver. Due to the mode selection, a relatively constant RX coil voltage can be maintained under both high-coupling and low-coupling conditions. This enables a single TX to charge both the strongly coupled RX and the weakly coupled RX simultaneously. In the experiment, the proposed 30-W receiver can operate across 1.9-7.5 cm, whereas the conventional receiver is restricted to 3.5-5.5 cm.