A Battery-less Energy Harvesting Front-end for Powering Multiple IoT Nodes

Advancements in sensor technology and wireless connectivity have led to significant growth  in Internet-of-Things (IoT) systems, requiring autonomous, self-sustained operation with a prolonged  lifetime. Powering them solely with batteries is not a sustainable solution due to their limited lifespan  and need for periodic replacement, which is challenging for remote deployments. Additionally,  batteries contain toxic materials that are harmful to the environment. Therefore, harvesting energy  from environmental sources (e.g., solar, heat, vibration) becomes essential to power them up.

In this work, we developed a battery-less photovoltaic (PV) energy harvesting front-end for  powering multiple Internet-of-things (IoT) nodes. In the first stage, a fast and accurate time-to-voltage  converter-based maximum power point tracking (MPPT) controller is proposed along with a built-in  over-voltage protection and cold-start operation. 

Next, we explored a scalable non-inverting buck-boost derived single inductor multiple outputs  (SIMO) converter suitable for powering multiple IoT nodes. To improve the overall efficiency with a  low-quiescent power, we propose a constant charge transfer scheme in the non-inverting buck-boost  power stage. The constant inductor current peak exhibits an inherent soft-start feature, and the  discontinuous conduction mode (DCM) of operation prevents the cross-regulation. The internal  priority sequencing logic of the proposed controller ensures a reliable power-up sequencing during  start-up. 

Next, an alternative buck-derived SIMO converter stage is proposed to achieve a fast transient  response for powering the command-directed IoT nodes. The multiple outputs are sequentially charged  and regulated afterwards by the proposed state-driven priority sequencing and the delay-adjusted fixed  window (DAFW) hysteretic controller to keep the output transient ripple low. To make a better trade

off between light load efficiency and fast transient response at the high load, the proposed converter  has two distinct command-directed modes, namely constant current-peak sequential DCM (CCPS DCM) at low load conditions and constant current-peak sequential DCM-CCM (CCPS-DCM-CCM)  at high load conditions. Additionally, the CCPS-DCM-CCM operation ensures zero cross-regulation  and fast transient response using a low-profile inductor.  Lastly, a complete battery-less PV energy harvesting front-end is developed for powering the  self-sustained IoT nodes, featuring self-start operation even at low PV harvester voltage, efficiently  scavenging power from the harvester, powering three regulated outputs, and storing excess energy in  a super-capacitor with integrated over-voltage protection. The entire system is integrated into a single  chip implemented in 180-nm CMOS technology.

Fig. 1: (a) Architecture of the overall battery-less energy harvesting front-end, (b) Chip micro photograph of the IC, and (c) component placement on the PCB.

Contributors: Dr. Aditi Chakraborty (Ex-PhD Scholar), and Dr. Ashis Maity (Supervisor), Electrical Engineering, IIT Kharagpur

Broad Field of Work: Power Management Integrated Circuits, Energy Harvesting

Journals:

    1. Chakraborty and A. Maity, “A Time-to-Voltage Converter-based MPPT With 440 μs Online  Tracking Time, 99.7% Tracking Efficiency for a Battery-less Harvesting Front-end With Cold startup and Over-voltage Protection,” IEEE Transactions on Circuits and Systems I: Regular  Papers, vol. 71, no. 10, pp. 4499-4511, Oct. 2024, doi: 10.1109/TCSI.2024.3435533. 
    2. A. Chakraborty, A. K. Jha, A. Deo, A. Maity and A. Patra, “A Scalable Single-Inductor  Multiple-Output DC-DC Converter With Constant Charge-Transfer and Power-up Sequencing  for IoT Applications,” IEEE Transactions on Circuits and Systems I: Regular Papers, vol. 71,  no. 6, pp. 2964-2975, June 2024, doi: 10.1109/TCSI.2024.3349404. 
    3. A. Chakraborty and A. Maity, “A Fast SIMO Converter for Command-Directed IoT Nodes  With State-Driven Priority Sequencing and Delay-Adjusted Fixed Window Hysteretic Control  Using Constant Current-Peak Sequential DCM-CCM Operation,” in IEEE Journal of Solid State Circuits, vol. 60, no. 1, pp. 286-297, Jan. 2025, doi: 10.1109/JSSC.2024.3406565. 
    4. A. Chakraborty and A. Maity, “A Battery-less Energy Harvesting Front-end for Powering  Multiple IoT Nodes Using Single Solar Cell: a System-level Perspective,” IEEE Transactions  on Power Electronics, vol. 40, no. 9, pp. 14072-14083, Sept. 2025, doi:  10.1109/TPEL.2025.3567569.

Conference:

    1. A. Chakraborty and A. Maity, “Minimizing Quiescent Power in a Dynamically Biased  Comparator and its Application in Relaxation Oscillator,” 2023 18th Conference on Ph.D  Research in Microelectronics and Electronics (PRIME), Valencia, Spain, 2023, pp. 33-36, doi:  10.1109/PRIME58259.2023.10161905. 

Group Website: https://facweb.iitkgp.ac.in/~ashismaity/ISDG.html

Keywords: Photovoltaic Energy Harvesting, Maximum Power Point Tracking (MPPT), Single Inductor Multiple-Outputs (SIMO) Converter, Battery-Less System, Hysteretic Control.

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