Abstract
The power saving issue and clean energy harvesting for wireless and cost-affordable electronics (e.g., IoT applications, sensor nodes or medical implants), have recently become attractive research topics. With this in mind, the paper addresses one of the most important parts of the energy conversion system chain – the power management unit. The core of such a unit will be formed by an inductorless, low-voltage DC-DC converter based on the cross-coupled dynamic-threshold charge pump topology. The charge pump utilizes a power-efficient ON/OFF regulation feedback loop, specially designed for strict low-voltage start-up conditions by a driver booster. Taken together, they serve as the masters to control the charge pump output (up to 600 mV), depending on the voltage value produced by a renewable energy source available in the environment. The low-power feature is also ensured by a careful design of the hysteresis-based bulk-driven comparator and fully integrated switched-capacitor voltage divider, omitting the static power consumption. The presented converter can also employ the on-chip RF-based energy harvester for use in a wireless power transfer system.
Highlights
In the field of analog integrated circuits (ICs) design, such methods include the gm /ID design methodology and the so-called bulk-driven approach. Such methods of IC design for ultra low-voltage applications form the core of the research presented in this paper, where the bulk-driven design approach has been implemented in the design of several subcircuits in order to improve the total Energy harvesters (EHs) performance focused on low-voltage conditions
In order to demonstrate the suitability of the developed DC-DC converter in the application example as a PMU in an RF-based energy harvesting system (RF-EH), we demonstrated its functionality in conjunction with a fully integrated wireless power transfer (WPT)
The measurements with the transmitter input power between 10 dBm and 20 dBm were performed with the maximum reported DC output power of around 60 μW and the maximum DC output voltage of more than 0.5 V under various load conditions. These results prove the overall functionality of the implemented WPT system, as well as its suitability for use in conjunction with the developed DC-DC converter described in the previous section
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. According to the state-of-the art, the RF-EH systems dominantly employ inductive DC-DC converters These are more attractive compared to the capacitive counterparts (charge pumps) due to the higher power conversion efficiency (PCE) and suitability for low-voltage start-up [10]. In the field of analog IC design, such methods include the gm /ID design methodology and the so-called bulk-driven approach Such methods of IC design for ultra low-voltage applications form the core of the research presented in this paper, where the bulk-driven design approach has been implemented in the design of several subcircuits (e.g., a charge pump core, a boosted driver, comparator and a voltage divider) in order to improve the total EH performance focused on low-voltage conditions. Comparison of the results achieved in this research with other works is addressed in Section 5, where a short discussion and conclusions can be found
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