Capacitively Coupled Power Transfer Research Articles

Full-Duplex Communication on the Shared Channel of a Capacitively Coupled Power Transfer System

This paper proposed a novel wireless power transfer system with full-duplex communication on a shared channel for capacitively coupled power transfer systems. For the analysis of power and signal transmission, a frequency-domain model of the power and signal channels is established. Based on this model, the signal transfer characteristic of the channel and the influence of power flow on the signal channel are analyzed. Moreover, to ensure the power and signal transfer without unacceptable interference or attenuation, a parameters selection method of the communication channel is developed. In addition, an interference suppression strategy by taking the interference from the ipsilateral channel into consideration is proposed. To suppress the interference effectively, an estimation of the ipsilateral channel output signal is made. Then, the signal from the opposite channel is demodulated by removing the estimated values of the interference. Both simulation and experimental results showed have proven the correctness and effectiveness of the proposed wireless power and signal transfer method. Finally, it has demonstrated that the designed channel can transfer 100 W of power, and a full-duplex communication can be well achieved with different data rates in two directions when both two data rates are set within 200 kb/s.

Power transfer using portable surfaces in capacitively coupled power transfer technology

Capacitively coupled power transfer (CCPT) uses electrostatic mechanism to deliver power from a stationary transmitter to a mobile receiver. The authors study various aspects of this technology including physical limitations that are encountered to increase power transfer. They characterise the impact of input voltage, dielectric area, and permittivity of the dielectric material in realisation of CCPT system. It is observed that the peak voltage and VA ratings of the capacitors are affected by the choice of the aforementioned parameters. Air as a dielectric medium leads to low power density. A high permittivity material instead of air dielectric can be used to improve power density. This strategy will make the CCPT technology non-contactless, because a physical contact exists between the transmitter and receiver. However, this contact is different from an ohmic contact. A high power density CCPT system is realised using ceramic dielectric surfaces. Issues encountered in system realization are discussed including automatic resonant frequency tracking. Detailed mathematical models under resonance and off-resonance operation are proposed. The models are validated using simulations and experimental results. A low cost multilayer ceramic capacitor (MLCC) based high power-density transfer surface is realised. Results show that 35 W can be easily transferred using a set of 12 mm2 capacitive surfaces and 32 V source.

A Capacitively Coupled Contactless Matrix Charging Platform With Soft Switched Transformer Control

Capacitively coupled power transfer (CCPT) technology has been proposed and investigated recently as an alternative contactless power transfer method. A CCPT system has the advantage of being able to transfer power across metal barriers with low standing power losses, so it is potentially good for charging consumer electronics such as mobile phones, laptops, lamps, etc. However, a big challenge in designing a CCPT charging platform is the output voltage of a CCPT power supply varies greatly with the positioning and alignment of the pickup on a charging pad due to the change in power flow. This paper proposes a CCPT charging platform with a matrix charging pad and a dynamically soft switched transformer to control the power flow and regulate the output voltage under variable coupling conditions. The proposed charging platform is verified by simulation and experimental results.

Comparative Study of CCPT Systems With Two Different Inductor Tuning Positions

Capacitively coupled power transfer (CCPT) technology has been proposed and investigated as an alternative to inductive power transfer solution in certain low-power applications with the advantages of being able to transfer power across metal barriers and having low standing power losses. A series inductor is often used to compensate a CCPT system for the reactance introduced by the capacitive coupling, and there is a preconception that the tuning inductor can be placed either before or after the capacitive coupling without affecting the system performance. This paper develops a simple circuit model to enable the performance differences of placing such a tuning inductor on the primary and secondary sides of the circuit to be compared. The output voltage transfer function, voltage across the tuning inductor, displacement power factor, and total harmonic distortion are evaluated, and it is found that due to the existence of cross capacitive coupling there are significant differences in each of these performance indices when coupling variations are considered. The output voltage can be boosted, the misalignment tolerance can be improved, and the total harmonic distortion can be reduced when the tuning inductor is placed on the primary side of the circuit. The theoretical analysis is verified by experimental results.

Effect of series tuning inductor position on power transfer capability of CCPT system

Capacitively coupled power transfer (CCPT) technology offers an alternative contactless power transfer solution with the advantages of being able to transfer power across metal barriers and having low power losses in metal surrounding circumstances. In a series tuned CCPT system, a designer may tend to believe that the position of the tuning inductor in the circuit makes no difference. It has been found in this reported research that the output power capability exhibits clear difference under misaligned conditions when the same tuning inductor is placed at the primary and secondary side of the circuit owing to the existence of the cross-coupling between the metal plates. Both theoretical and experiment results show that placing the tuning inductor at the primary side of a CCPT system can significantly increase its output power under a misaligned condition.