A Closed-loop Ultrasonic Wireless Power Transfer System with Constant Output Voltage

Ultrasonic wireless power transfer (UWPT) is a reasonable method to power loads in enclosed metal container. For the existing open-loop UWPT system, the output voltage varies with different loads. In this paper, a closed-loop UWPT system with constant output voltage for different load resistances is proposed. Two pairs of piezoelectric transducers with different resonant working frequencies are adopted, for which one pair is used for power transfer and another is used for voltage signal feedback. PI control algorithm is used to dynamically adjust the PWM duty of the boost circuit, which is able to regulate the input voltage of the high-frequency inverter. As a result of which, the output voltage of the system can be kept constant when the load resistance varies. The experiment validates the proposed system.