Pulse Frequency Modulation of 3D Wireless Power Transfer for Capsule Endoscopy

In this article, a new attempt of utilizing pulse frequency modulation (PFM) control method to transfer power wirelessly to a pill-camera is presented. Experimental results confirm that the PFM control method surpassed the conventional phase shift control (PSC) method in terms of power loss reduction in both power converters and magnetic couplers. A 33.3% reduction in power loss and 55% gain in the overall system efficiency are recorded at maximum transmission power in a full-scale and fully functional engineering prototype. This significant improvement paves the way for the future development of wireless charging systems for humans, particularly when considering battery life. The target devices cover various health sensors, medical devices, biology, and industry applications. This article provides a complete study of proposed PFM method and comparison with conventional PSC method. The design parameters and fabrication of the engineering prototype are presented including a three-dimensional transmitting coil (3DTC) system and a one-dimensional receiving coil. The attitude information of the pill-camera is wirelessly transmitted to the controller to manipulate the magnitude and phase angle of the transmitter currents. System performance with the pill-camera in different orientations in 3DTC is measured. The advantage of using proposed control method is experimentally demonstrated and confirmed.