Modified Coupler With Reduced Misalignment Issues for Wireless Power Transfer System

Misalignment conditions are often present in wireless power transfer (WPT) systems which significantly affects the performance (output voltage, output power and system efficiency) due to reduction in mutual inductance. This article presents a modified transmitter coil (TX) structure assisted by misalignment detection circuit (MDC) to improve the mutual inductance profile under lateral misalignment conditions. Here, the modified TX coil structure is evolved by embedding tertiary coils with the square coil. Series connection of tertiary coils with main square coil enhances the WPT performance under misalignment conditions. As compared to other structures, the proposed TX-coil structure under misalignment scenarios shifts the magnetic field distribution in the direction of misalignment, minimizes the leakage flux and improves the coefficient of coupling. The modified TX coil structure is effective in mitigating the fluctuations in output power and voltage within 5% tolerance up to 60 mm against lateral misalignment (i.e., 30% of coil size). To demonstrate the working of formulated TX coil and MDC, a laboratory prototype with 36 V input to 48 V output is developed. The system achieves 105 Watt output power with nominal efficiency of 86% under 100 mm air-gap (half the coil size). It maintains the same efficiency, output power and output voltage with 5% tolerance up to 60 mm misalignment (120 mm range).