A 13.56 MHz Low-Power, Single-Stage CMOS Voltage-Boosting Rectifier for Wirelessly Powered Biomedical Implants

Abstract

In this paper, a low-power, single-stage, active rectifier based on a new charge-pump circuit is presented to be used in biomedical implants. The proposed circuit not only rectifies the AC input voltage to a DC voltage but also amplifies the DC output voltage to a higher level. Low-loss MOS switches are used in the structure of the designed circuit to provide high power conversion efficiency. In addition, by using two comparators, the reverse leakage current is somehow eliminated, resulting in a higher increase in the power efficiency. By tying the source and bulk terminals of the utilized transistors, the body effect problem has been solved, and by connecting the p-substrate to the ground, which is the lowest voltage in the circuit, the latch-up phenomenon is eliminated without any extra circuit. The proposed rectifier is implemented and post-layout simulated in a 0.18 µm standard CMOS technology. According to the simulation results, 1.205 V output DC voltage is achieved from an AC input signal with the peak-to-peak amplitude of 1 V at the operating frequency of 13.56 MHz with a 3 kΩ load resistance. The total active area of the designed circuit is 0.167 mm2 with a maximum power conversion efficiency of 98.2%, output power in the range of 0.5–1.5 mW, and voltage conversion ratio of 120%.