A Wireless Charging System Applying Phase-Shift and Amplitude Control to Maximize Efficiency and Extractable Power

Abstract

Wireless Power Transfer (WPT) is an emerging technology with an increasing number of potential applications to transfer power from a transmitter to a mobile receiver over a relatively large air gap. However, its widespread application is hampered due to the relatively low efficiency of current WPT systems. This work presents a concept to maximize the efficiency as well as to increase the amount of extractable power of a WPT system operating in non-resonant operation. The proposed method is based on actively modifying the equivalent secondary-side load impedance by controlling the phaseshift of the active rectifier and its output voltage level. The presented hardware prototype represents a complete wireless charging system, including a DC-DC converter which is used to charge a battery at the output of the system. Experimental results are shown for the proposed concept in comparison to a conventional synchronous rectification approach. The presented optimization method clearly outperforms state-ofthe-art solutions in terms of efficiency and extractable power.

Secondary-side-only Control for High Efficiency and Desired Power with Two Converters in Wireless Power Transfer Systems

“…Previous papers dealt with power control on primary side (13) (14) , efficiency control on secondary side (15)- (17) or power and efficiency control by using both sides (18)- (20) . If efficiency control was performed on the secondary side, the power had to be regulated on the primary side and vice versa, as until now it has been impossible to manipulate them both on the same side without using complex phase-shift controls (21) . In particular, primary side voltage regulation is a popular choice for power flow control and may be a necessity in case of particular applications such as medical implants to limit the secondary side heating (13) .…”

“…Previous literature encompassing converter control without communication between sides dealt with secondary side efficiency maximization (21) as well as primary side maximum efficiency tracking (22) and charging time control (23) . In (21) , a complex phase-shift control regulating the imaginary part of the load impedance is devised for non-resonance operation.…”

“…In (21) , a complex phase-shift control regulating the imaginary part of the load impedance is devised for non-resonance operation. The studies in (22) and (23) use a three level voltage waveform c 2017 The Institute of Electrical Engineers of Japan.…”

“…By considering a WPT system with two converters on the secondary side, it is possible to fulfill the requirements for simultaneous power and efficiency control only by manipulating those converter and without commanding the primary side. However, unlike the study in (21) , this is achievable in a much simpler way by using the HAR to control the average power and the DC/DC converter to control the transmission efficiency. This method is based on using two different switching frequencies for the converters and can be applied to any WPT system.…”

A novel DCES based voltage control stragety for critical load supplied by wireless power

“…Wireless power transfer (WPT) is a technology to transfer power from a transmitter to a mobile receiver over a relatively large air gap [1]. It was first proposed by Nikola Tesla in 1890s, and it is regarded as an emerging technology to transfer power nowadays.…”