A 6.78-MHz Soft-Switching Push-Pull Amplifier Achieving 60.9-%-Efficiency Wireless Power Transfer for Medical Implant Applications

In this study, a highly efficient 6.78-MHz power amplifier (PA) is proposed for power and data transfer in implantable medical systems. Based on a soft-switching push-pull topology, the amplifier maintains high power transfer efficiency (PTE) over a wide range of resistive load without requiring compensation networks. Moreover, the PTE degradation caused by increased distance has been significantly mitigated. A programmable bus voltage enables linear control of the PA’s output power which is preferable for closed-loop power control applications. The proposed power transfer system achieves a remarkable PTE of 60.9 % at 6.78 MHz, with an output power programmable between 20 mW and 130 mW. Additionally, 100-kbps on-off keying (OOK) modulation is demonstrated to establish the forward data link of the wireless system.