An Adaptive Impedance Matching System With Fast Optimization Control Algorithm for Wireless Power Transfer via Magnetic Coupling Resonance

For a magnetic coupling resonant wireless power transfer (MCR-WPT) system, the most challenging design issue is to maintain the reasonable transfer efficiency and the output power, especially over varying transmitting distances. To address this issue, this study proposes an adaptive impedance matching (AIM) system with a fast optimization control algorithm for the MCR-WPT system. By dynamically monitoring system input impedance variations at a given frequency, the matching system can be automatically activated. The matching precision is enabled by combining an amplitude-phase measurement circuit, a Pi-type impedance matching (IM) network, and the local optimization algorithm. Experimental comparisons show a significant improvement in the transfer efficiency. The maximum improvement is over 32.6%. The results also show that the local optimization algorithm helps the MCR-WPT system to effectively overcome the efficiency challenges caused by parasitic parameters, resulting in a maximum improvement of 19.8%. The stability of the output power is also significantly improved, with a 27.8% reduction in oscillation amplitude compared to the scenario without the local optimization algorithm, and a 60.0% reduction compared to the scenario without the IM network. The output power range (1.55 -2.21 W) could meet the power requirements of most implantable medical devices. Moreover, this system adopts a control algorithm of tracking the theoretically optimal matching solution through Microcontroller Unit (MCU) computation, leading to a notable enhancement in matching accuracy.