Closed-loop Adaptive Transcutaneous Wireless Power Transfer System for Implantable Sensors

Abstract

Even though inductively-coupled wireless power transfer system has been significantly developed in the past few decades for implantable sensors, the efficient and continuous transfer of power still remains as a challenge as the distance and alignment vary over time. A scheme for adaptively regulating the transferred power within a certain range instead of delivering a constant power is proposed in this paper. The proposed design is implemented using a standard $0.5\ \mu m$ CMOS process and it utilizes the Load-shift Keying (LSK) technique to sense the variations in the distance and alignment between the transponder and the receiver implant. In the proposed power regulation scheme, the DC voltage output of the rectifier is regulated within a threshold window by changing the supply voltage of the class-E power amplifier (PA) at the transmitter side. Based on the voltage regulation, the proposed adaptive system transmits 2.25 mW to 13.5 mW of power over a distance range of 1 to 8 mm. The simulation result of the proposed scheme shows a 14.89% efficiency improvement compared to the system without the adaptive control mechanism.