A High-Efficiency Low-Power Rectifier for Wireless Power Transfer Systems of Deep Micro-Implants

In this article, the so-called bootstrapping rectifier (BSR) proposed by Hashemi et al. is re-analyzed, and a novel high-efficiency low-power rectifier called Opto-Coupled Dynamic Gate-Control (OCDGC) rectifier is presented based on the bootstrapping structure. Circuit analysis of BSR shows that the rectifier design has inherent problems that cause a high forward voltage drop and limit its power conversion efficiency (PCE). The BSR is simulated and fabricated in TSMC 0.18 mu m process, and both simulation and experiment results prove the analysis. Inspired by the idea of bootstrapping structure, the presented OCDGC rectifier utilizes an opto-coupler to control the on-off switching of the active diode to maximize input power and prevent reverse leakage. A feedback loop is also introduced in the rectifier to limit the forward voltage drop. The proposed design is simulated in the TSMC 0.18 mu m process. Simulation results show that, with a 3 MHz input, OCDGC rectifier is able to achieve more than 80% PCE at an input power down to 0.55 mW and achieve a forward voltage drop less than 0.1 V. More than 20% PCE improvement is achieved compared with the PCE of BSR.