Rectifier Design for Highly Loaded Inductive Wireless Power Transfer Systems for Biomedical Applications

Power transfer efficiency (PTE) and harmonics are crucial performance parameters of the resonant rectifier design for low/medium coupling inductive wireless power transfer (WPT) systems used in wireless biomedical implants. The performance of a resonant rectifier degrades under higher loading and lower coupling conditions as the voltage available to the rectifier at the output of the receiver coil becomes low. As the diode turn-on impedance increases, diodes turn on incompletely, leading to non-linearities that reduce rectifier efficiency and output voltage. This work proposes a new rectifier design to increase efficiency and reduce harmonics by decreasing the diode turn-on impedance compared to traditional rectifier designs, such as resonant Half Wave Rectifier (HWR). The proposed rectifier design offers individual paths for RF and rectification signals, which reduces the non-linear loading on the receiver coil and improves diode turn-on performance. Measurement and SPICE simulation results show efficiency enhancement of 50% and reduction of harmonics by 6 dB for the proposed rectifier compared to HWR.