Free-Positioning Wireless Power Transfer to Multiple Devices Using a Planar Transmitting Coil and Switchable Impedance Matching Networks

Kim, Jin-Wook; Kim, Do-Hyeon; Park, Youngjin

doi:10.1109/tmtt.2016.2608802

Cited by 79 publications

(40 citation statements)

References 23 publications

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“…Consider the input impedance of asymmetric WPT system at frequencies of (18). Substitute (18) into the expression of Zin (22), then the imaginary part of Zin Im(Zin) can be obtained in Figure 14 using parameters for the case ω1 < ω2. In Figure 14, Im(Zin) is close to zero at the frequency corresponding to the maximum output power when k is relatively low; however, as the value of k becomes larger, Im(Zin) are not close to zero at all splitting frequencies, which means that the solutions to Im(Zin) = 0 is not suitable to assess the peak output power in the asymmetric case: Furthermore, when k < k s is met the frequency corresponding to the maximum output power becomes gradually close to the resonant frequency of the transmitter f 1 as shown in Figure 12; this is also consistent with the values of f max in Table 2.…”

Section: The Case Where ω1 ≠ ω2mentioning

confidence: 99%

“…In order to simplify the analysis, the operating frequency is fixed to 145 kHz, which is the same as the resonant frequency of the receiver. According to (22), the input impedance of the asymmetric WPT system is inductive. For a fixed-frequency WPT system the frequency splitting phenomenon causes a drastic variation of output power.…”

Section: Prototype Descriptionmentioning

confidence: 99%

“…The common structure in a multi-load WPT system is to transfer power from one large transmitter to several small receivers. The corresponding asymmetric coil structure has been optimized in [22], but the transmission characteristics of the asymmetric system have not been analyzed clearly. A large transmitting coil is designed to transfer power to several small receiving coils in [23], but the influence of the coupling coefficient on the system characteristics was not discussed.…”

Section: Introductionmentioning

confidence: 99%

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Influence of Asymmetric Coil Parameters on the Output Power Characteristics of Wireless Power Transfer Systems and Their Applications

2019

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Nowadays, it is a trend to update electronic products by replacing the traditional wire charging with emerging wireless charging. However, other features of the products must generally be left unchanged, which limits the options in receiving coil design. As a result, asymmetric coil designs should be adopted in wireless charging systems. In this paper, a wireless power transfer system with asymmetric transmitting and receiving coils is modelled using circuit theory. The output power of the asymmetric system is analyzed, and the conditions of the maximum power splitting phenomenon are addressed in detail. Cases for different resonant frequency conditions are elaborated. The splitting frequencies and critical coupling coefficient are obtained, which are different and more complicated compared with the symmetric counterparts. Asymmetric coil designs can be adopted based on the proposed method, so that adequate and efficient output power transfer can be realized. Finally, the asymmetric coils design is utilized in an experimental prototype in order to contactlessly charge a portable power tool lithium-ion battery pack with 18 V DC and 56 W output through 220 V AC input, without altering its original configuration, and the correctness of proposed analysis can thus be verified.

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Section: The Case Where ω1 ≠ ω2mentioning

confidence: 99%

Section: Prototype Descriptionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Influence of Asymmetric Coil Parameters on the Output Power Characteristics of Wireless Power Transfer Systems and Their Applications

2019

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“…Therefore, it is important to eliminate frequency detuning by using a certain control strategy. Many methods to deal with this problem are reported in previous works, including frequency tracking [7-9], impedance matching (IM) [10,11] and compensation capacitor tuning [12][13][14]. In [8], a phase-locked-loop (PLL) controller is applied to the primary side.…”

mentioning

confidence: 99%

“…IM control is a method that adds an adaptive impedance matching network between the inverters and the primary resonant network or the rectifier and secondary resonant network. The scheme of adaptive IM network consists of a capacitor-switch matrix [10,11]. The method tracks the maximal S-parameters.…”

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confidence: 99%

Dual-Side Independent Switched Capacitor Control for Wireless Power Transfer with Coplanar Coils

et al. 2018

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The transfer coils of traditional Magnetic Coupling Resonant Wireless Power Transfer (MCR-WPT) systems are generally arranged coaxially. Coplanar coils can be an alternative scheme that can save more space in some applications, such as mobile phone wireless charging. However, the inductances of coplanar coils are sensitive to foreign objects, which leads to a reduction in transfer efficiency and output power. A MCR-WPT system with coplanar coils and its control strategy are proposed in this paper. First, the characteristic of the mutual inductance and the magnetic field distribution between the coplanar coils are analyzed. A formula to calculate mutual inductance between the coplanar coils is proposed in this part. Secondly, the effect of inductance offset and frequency detuning on transfer efficiency and output power are analyzed. Then, the control strategy to eliminate frequency detuning is proposed. The proposed method implements switched capacitor to take place of constant compensation capacitor. The equivalent capacitance of switched capacitor is adjusted when the frequency detuning occurred. Thus, the inherent frequency of the resonant tank tracks the source frequency all the time. Since the switched capacitor of each side is controlled based on the quantity of their own, the control process is independent and does not require wireless communication. The complexity and the cost of the system are reduced. At the end of the article, the veracity of mutual inductance formula and the effectiveness of the proposed control strategy are verified by experiments. The experimental coils are placed in in an environment full of interference. The inductances of the coils are reduced from 224 µH to about 214 µH. The transfer efficiency and output power of MCR-WPT system with closed-loop control are higher than the one without control. At a distance of 5 cm from edge to edge, the transfer efficiency is 76.37% under the proposed control and 72.21% under no control. The output power is 285.66 W under the proposed control and 271.37 W under no control.field distribution are different from the coaxial ones. There are some works that have analyzed the mutual inductance of coils with lateral misalignment [5] or with angular azimuth misalignment [6]. However, there is no research on the MCR-WPT system with coplanar coils. This kind of coils arrangement has been neglected before.Inductances of coils are very sensitive to external interferences. For instance, ferrite cores are used frequently in the design of coils to improve the mutual inductance. However, ferrite cores can change the distribution of the magnetic field [7]. Thus, the inductances of coils will vary significantly with misalignment. Metal objects outside coils can also cause the instability of inductances. Meanwhile, the capacitances of compensation capacitors in the MCR-WPT system may be affected by temperature, frequency, bias voltage, etc. Therefore, the inherent frequency of the resonant tanks consisting of an inductor and compensation capacitor is changed accor...

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Control Scheme for Multiple‐pickupWPTSystem

2022

Wireless Power Transfer: Principles and Applications

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Free-Positioning Wireless Power Transfer to Multiple Devices Using a Planar Transmitting Coil and Switchable Impedance Matching Networks

Cited by 79 publications

References 23 publications

Influence of Asymmetric Coil Parameters on the Output Power Characteristics of Wireless Power Transfer Systems and Their Applications

Influence of Asymmetric Coil Parameters on the Output Power Characteristics of Wireless Power Transfer Systems and Their Applications

Dual-Side Independent Switched Capacitor Control for Wireless Power Transfer with Coplanar Coils

Control Scheme for Multiple‐pickupWPTSystem

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