A low-loss rectifier unit for inductive-powering of biomedical implants

Biomedical implants have been developed in the recent years with a focus for continuous and real-time monitoring of physiological parameters. Battery-less operation of the implanted unit requires energy harvesting from an inductive link or from the neighboring environment. For efficient conversion of harvested energy to a usable DC level, a rectifier block is employed. However conventional CMOS full bridge rectifier incurs a significant amount of power loss and lowers the overall efficiency of the powering system. In this work a cross-coupled MOSFET based LC oscillator structure has been presented as a modified rectifier circuit. Cross-coupled structure minimizes the loss of the MOS switches and LC tank circuit boosts up the output DC level. The rectifier unit has been designed and simulated using 0.5-μm standard CMOS process. For simulation purposes, different biomedical frequency bands are used to validate the effectiveness of the proposed circuit. Simulation results show that the proposed rectifier circuit can achieve 75% PCE compared to the conventional full bridge CMOS rectifier of only 3% PCE.