Abstract
Magnetic resonance wireless power transfer (WPT) is an emerging technology that may create new applications for wireless power charging. However, the mutual inductance fluctuations resulting from lateral misalignments are the major factors hindering the promotion of this technology. In this paper, a structure of a transmission coil and four cascaded receiving coils for wireless charging systems is proposed to suppress fluctuations in mutual inductance with lateral misalignments. The mathematical model of the proposed structure with lateral misalignments is built based on the equivalent circuit method. The expressions of the output voltage and the efficiency are then derived by solving the system equivalent equations. In addition, a method of compensation capacitance is proposed to suppress the effect of the cross-coupling mutual inductance on the voltage and efficiency. The primary advantage of the proposed structure is that the sum of the mutual inductances between the receiving coils and the transmission coil is nearly constant with lateral misalignments. Therefore, the output voltage and efficiency can also be kept nearly constant by using the proposed structure with lateral misalignments. Simulation and experimental results validating the proposed method are shown.
Highlights
Magnetic resonance wireless power transfer (WPT) systems are widely used in many applications [1]–[3], such as consumer electronics, medical devices, automatic guided vehicles, and battery charging of electric vehicles due to the advantages of high convenience, safety, and reliability [4], [5]
The equivalent load resistor corresponding to the maximum efficiency is not the same as that corresponding to the constant output voltage for a given mutual inductance [11], [12]
When the mutual inductance between the transmission coil and the receiving coil is changed, the minimum DC input current can be tracked by real-time changes to the duty cycle of the DC-DC converter
Summary
Magnetic resonance wireless power transfer (WPT) systems are widely used in many applications [1]–[3], such as consumer electronics, medical devices, automatic guided vehicles, and battery charging of electric vehicles due to the advantages of high convenience, safety, and reliability [4], [5]. PROPOSED STRUCTURE AND MODEL To keep the mutual inductance constant with lateral misalignments, a structure of a transmission coil and four cascaded receiving coils for wireless charging systems is proposed. A. STRUCTURE OF TRANSMISSION COIL AND FOUR CASCADED RECEIVING COILS a structure of a transmission coil and four cascaded receiving coils for wireless charging systems is proposed to address variations in mutual inductance and output voltage with lateral misalignments. Because the output terminal of each full-bridge rectifier is connected in series, the relationship among the currents of the receiving coils can be obtained as follows: I2 = I3 = I4 = I5. According to (19) and (20), the output power and the efficiency can be calculated
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