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 μm 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 μm 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.