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This tutorial brief presents a concise overview of integrated switched-capacitor (SC) DC-DC converter topologies for miniaturized energy harvesting (EH) IoT systems aiming for extended power dynamic range (PDR) and enhanced power conversion efficiency (PCE). This tutorial initiates by delving into the intricate SC conversion methodologies tailored for energy harvesting (EH) applications, including i) fine-grained conversion ratio (CR) tuning, ii) multiphase soft charging, and iii) clock frequency and amplitude scaling. Next, mathematical analysis is conducted along with an established model to correlate the prevailing dominant loss and its impact on the PCE and the PDR, aiming to provide designers with a guideline for different design parameter choices for the triode/subthreshold domain.

This article presents a fully integrated tri-band RF energy harvesting system (RFEH) in 65-nm CMOS technology. The system is designed to harvest ambient RF energies at 900 MHz, 1.9 GHz, and 2.4 GHz through a tri-band impedance matching network (IMN), cross-coupled differential-drive (CCDD) rectifier, and an output voltage monitoring circuit to limit the rectified output voltage to 3.3 V. The system achieves a power conversion efficiency (PCE) of over 30 % across all three frequency bands with a peak of 42.8 %. Furthermore, the system exhibits a peak sensitivity of -20 dBm at an output DC voltage of 1 $V$ output.

This brief presents a cross-coupled CMOS rectifier for ambient RF energy harvesting, which utilizes an advanced topology amalgamation technique to significantly improve the rectifier’s power conversion efficiency (PCE) and power dynamic range (PDR), also known as the high-PCE range. Our novel technique involves adaptively self-biasing the rectifying PMOS in the last stage of the proposed rectifier, which deactivates the cross-coupled counterpart and enables the subsequent diode-based rectifier circuitry to operate efficiently during high-power operation and extends the high-PCE range by mitigating the leakage current. Fabricated in a 65-nm CMOS process, our proposed rectifier scores a wide PDR of 21 dB at 900 MHz and 15 dB at 1.8 GHz with a peak PCE of 79.77% and 51.3%, respectively, under a 100- $\text{k}\Omega $ load. Moreover, we perform a Monte Carlo simulation to showcase the impact of transistor variations. Our proposed rectifier, which offers the widest PDR compared to recently-reported designs operating at a similar frequency, is highly adaptable to the varying RF environment, enabling efficient and reliable energy harvesting for Internet of Things devices.

This brief reports a dual-topology CMOS rectifier with an extended power dynamic range (PDR) for radio frequency (RF)-based hybrid energy harvesting (RF-HEH) systems. By leveraging both the cross-coupled differential drive (CCDD) and the Dickson topologies with high forward conduction and low reverse leakage, we obtain an extension of the rectifier’s PDR by adaptively disabling the CCDD counterpart and enabling the Dickson counterpart to dominate the rectifier’s performance during high-power operation. Apart from that, we formulate a rectifier-performance index (RPI), which accounts for the power conversion efficiency (PCE), the PDR, the sensitivity, and the load resistance of the rectifier to provide an adequate performance benchmark with the state-of-the-art rectifiers. Fabricated in a 130-nm CMOS, the proposed dual-topology rectifier measures a wide PDR of 19.5 dB with a peak PCE of 78.4% for a 100- $\text{k}\Omega $ load operating at 900 MHz. Besides, our prototype records the highest RPI of 19.2 compared to the recent arts operating at GSM900.