A Hybrid Load Matching Method for WPT Systems to Maintain High Efficiency Over Wide Load Range

Abstract

The efficiency of a wireless power transfer (WPT) system is highly dependent on the load resistance. However, the load resistance, such as the battery, is not constant during the charging process. Therefore, a crucial challenge for a WPT system is to keep high efficiency over wide load range. In this work, a hybrid load matching method for WPT systems is proposed to achieve high efficiency. The basic principle of this system is to use a hybrid load matching method, i.e., adding an <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${L}$ </tex-math></inline-formula> – <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${C}$ </tex-math></inline-formula> resonant matching network and choosing the rectifier operation modes (full-/half-bridge), to convert the load to an optimal range. Then, the system efficiency can be kept at the top regions of the efficiency curves. Finally, a prototype is built to validate the performance of the WPT system with the proposed approach. The experimental results show that the optimal load of the WPT system can be transformed from 30 to 60, 120, and 240 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Omega $ </tex-math></inline-formula> , and the efficiency of the proposed system can be maintained above 89% from 10 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Omega $ </tex-math></inline-formula> (527.8 W) to 600 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Omega $ </tex-math></inline-formula> (8.64 W).