Simultaneous Wireless Power and Data Transmission Based on Unsymmetrical Current Waveforms With Duty Cycle Modulation

Yan Zhou,Peng Dong,Zijian Zhang,Yihan Chen,Liang Huang

doi:10.1109/access.2020.2966664

Abstract

This paper proposes an active-clamped inverter (ACI) with duty cycle modulation for achieving simultaneous wireless power and data transmission (WPDT). The proposed method adjusts harmonic amplitudes by changing the duty cycle of the inverter, as a means to encode information alongside power using a shared wireless channel. This method generates a variable unsymmetrical current waveform corresponding with different duty cycles. By controlling the duty cycle, simultaneous power and data transfer can be achieved by using the fundamental and harmonic components respectively. The ACI is designed to operate in continuous current mode to reduce the variation of harmonic components, even under no load conditions. A simple ACI containing two switches is proposed to generate unsymmetrical current waveforms with a high efficiency and high circuit quality factor Q. Two communication methods are developed to balance the power transfer capability and signal-noise-ratio (SNR). Various separation distances and loads are tested, with experimental results showing the proposed system can achieve simultaneous power and data transfer across a shared channel in an inductive wireless power transfer.

Highlights

Wireless power and data transfer technologies are used in many special applications
This paper proposes a single-ended active-clamped inverter (ACI) to produce an unsymmetrical waveform to achieve simultaneous wireless power and data transmission
Based on (6), Fig. 6 shows that the predicted values and experimental results at three typical duty cycles fit very well under different separation distances. These experiments show that duty cycles will affect the capabilities of the wireless power transfer significantly, agreeing with Fig. 5

Summary

INTRODUCTION

Wireless power and data transfer technologies are used in many special applications. For example, some medical implants, such as pacemakers and cochlear implants [1], [2], need to transfer power and data simultaneously. Based on a symmetrical waveform, novel WPDT methods using fundamental components to transfer power, and harmonics to transmit data have been previously proposed [22], [23]. A full-bridge converter can produce a symmetrical waveform to achieve WPDT, but it contains four switches. This paper proposes a single-ended active-clamped inverter (ACI) to produce an unsymmetrical waveform to achieve simultaneous wireless power and data transmission. Various unsymmetrical triangular current waveforms can be formed in Lp, corresponding to different duty cycles. The fundamental frequency of the triangular current waveform equals the SRF of Ln and Cn in the power receiving circuit. The selected harmonic frequency equals the SRF of Ls and Cs in the signal receiving circuit. Since the discontinuous current mode for an ACI does not exist, the values of the harmonics in (6) remain constant even under no load conditions

EQUIVALENT CIRCUITS OF THE PROPOSED SYSTEM

EXPERIMENTAL RESULTS

CONCLUSION