Low-voltage Energy Harvesting Research Articles

Fully-integrated switched-capacitor voltage boost converter with digital maximum power point tracking for low-voltage energy harvesting

This paper proposes a fully-integrated switched-capacitor voltage boost converter with a digital maximum power point tracking (MPPT) control circuit for low-voltage and low-power energy harvesting. The proposed digital MPPT control circuit converts the analog voltage information of a PV cell into digital values and extracts the maximum power regardless of the harvester conditions and load current. Measurement results demonstrated that our proposed circuit can track the maximum power point of a PV cell successfully. The maximum voltage conversion ratio of our circuit was 5.6. The proposed power management system generated a 2.58 V output voltage from a 0.46 V input voltage. The maximum power conversion efficiency was 63.6%.

An ultralow voltage circuit for energy harvesting with 3.3 mW capacity

This brief describes an astable multivibrator aimed to low voltage energy harvesting using inductive coupling and bipolar junction transistors. The topology needs a bias voltage at the bases, and we propose a circuit called starting block to generate this voltage from the supply. A proof-of-concept circuit with discrete devices was able to work with a voltage as low as 50 mV and deliver 3.3 mW from a 100 mV supply. To the authors’ knowledge, it is the energy harvesting circuit with highest power capacity. It has the additional advantage of using conventional devices, in contrast with other approaches that use special devices like junction field effect transistors and native metal–oxide-semiconductor field effect transistors (MOSFETs). The circuit also needs a smaller transformer when compared to its version using conventional MOSFETs.

A 42 mV startup ring oscillator using gain-enhanced self-bias inverters for extremely low voltage energy harvesting

This paper presents a ring oscillator (ROSC) capable of operating at an extremely low supply voltage. The proposed ROSC consists of gain-enhanced self-bias inverters. The voltage gain of the proposed inverter is improved by controlling the body bias voltages. Measurements of a prototype chip demonstrated that our proposed ROSC can operate at an extremely low supply voltage of 42 mV.

Review of Power Conversion and Energy Management for Low-Power, Low-Voltage Energy Harvesting Powered Wireless Sensors

In this paper, state-of-the-art power electronics and energy management solutions utilized in low-power (less than 5 mW), low-voltage (less than 3 V) energy harvesting powered wireless sensors for Internet of things related applications are detailed. All aspects of an energy harvesting powered sensor system are examined, including the challenges of low-power energy harvesting sources, energy management circuits including power converters and energy storage elements, as well as the impact of wireless sensor pulsed power profiles. In particular, this paper focuses on existing voltage step-up energy management techniques, including the issues of cold-start and maximum power point tracking, as well as energy storage which is necessary for wireless sensor operation. Both academic and commercially available energy harvesting powered systems are examined to provide a comprehensive analysis of existing solutions. Issues that are limiting the current system performance are identified to help define future developments needed to enable efficient and effective energy harvesting powered wireless sensor operation.

Demonstrating the Scope of a Switched Supercapacitor Circuit for Energy Harvesting Powered Wireless Sensor Loads

This paper describes the design of a high-efficiency energy management system for low-power, low-voltage energy harvesting powered wireless sensor systems. With typical voltages of less than 1 V and power levels lower than 1 mW, there are significant challenges when applying energy harvesting sources to supply pulsed power levels of up to 120 mW at voltage levels of 1.8–4 V as required by wireless sensor loads. The proposed approach integrates energy storage elements within a voltage step-up circuit to produce a new high-efficiency energy management circuit that converts the energy produced by a low-power, low-voltage source into a series of high power pulses. An optimized switched supercapacitor energy buffer circuit including a self-powered control circuit is proposed. Efficiencies of up to 91% are shown for an indoor solar cell source with a power level of 0.5 mW, supplying an equivalent wireless sensor with pulsed power levels of 10–120 mW. This is significantly higher than 83% achieved for the dc–dc stage of the existing best solution under the same source conditions, but requires an additional conversion step to provide high power pulses.

A LabVIEW-based Real-Time GUI for Switched Controlled Energy Harvesting Circuit for Low Voltage Application

ABSTRACT This paper develops a universal Real-Time Graphical User Interface for the first time for low-voltage energy Harvesting. The proposed GUI is built in LabVIEW with NIUSB 621 DAQ that synchronized the data to perform real-time analysis through the use of power electronics. A hybrid Vertical Axis Wind Turbine adapted to a 200 W Permanent Magnet Synchronous Generator is used for incorporating the supercapacitor-based battery charging energy harvesting system. The GUI displays the real-time energy harvesting output readings both graphically and digitally along with wind speed and angular velocity of the turbine. The model is built in such a way so that it could be used as a universal GUI for both wind and solar energy harvesting with minimal adjustment.

A new multi-mode multi-input–multi-output (MIMO) converter in an efficient low-voltage energy harvesting system for a gas sensor

This paper presents a new multi-mode multi-input–multi-output (MIMO) converter with a battery for operating an energy harvesting (EH) system for gas sensors. In this EH system, the MIMO converter has a single DC–DC structure with multiple inputs and outputs. The converter is designed and tuned to harvest ambient light energy from a photovoltaic module, and it then provides regulated power at biases of 3.3 and 5 V to charge the battery and/or to drive a gas sensor. The battery serves as a load to be charged by the MIMO or as a power source when the ambient light energy is insufficient to drive the gas sensor. For regulating the DC–DC converter, maximum power point tracking is implemented for each power path from inputs and outputs. The proposed MIMO converter has the least number of switches among existing converters. Experimental results reveal that the MIMO converter exhibits a high efficiency of 89.73% for a large power throughput of 0.9 W for a gas sensor.

The Design of Operational Amplifier for Low Voltage and Low Current Sound Energy Harvesting System

The objective of this paper is to design a combination of an operational amplifier (op-amp) with a rectifier used in an alternate current (ac) to direct current (dc) power conversion. The op-amp was designed to specifically work at low voltage and low current for a sound energy harvesting system. The goal of the op-amp design with adjustable gain was to control output voltage based on the objectives of the experiment conducted. The op-amp was designed for minimum power dissipation performance, with the means of increasing the output current when receiving a large amount of load. The harvesting circuits which designed further improved the power output efficiency by shortening the fully charged time needed by a supercapacitor bank. It can fulfil the long-time power demands for low power device. Typically, a small amount of energy sources were converted to electricity and stored in the supercapacitor bank, which was built by 10 pieces of capacitors with 0.22 F each, arranged in parallel connection. The highest capacitance was chosen based on the characteristic that have the longest discharging time to support the applications of a supercapacitor bank. Testing results show that the op-amp can boost the low input ac voltage (∼3.89 V) to high output dc voltage (5.0 V) with output current of 30 mA and stored the electrical energy in a big supercapacitor bank having a total of 2.2 F, effectively. The measured results agree well with the calculated results.

Non‐isolated multiple‐input boost converter for energy harvesting

In this Letter, a new dual/multiple-input non-isolated boost converter is proposed. It provides a positive boosted output voltage without any additional transformer. It is suitable to interface sources of different current–voltage characteristics to a common load, with a simple topology and a low part count. The topology and the behaviour are similar to the single-input boost converter; hence, the control strategy can be accomplished easily. It can be used in low-voltage energy harvesting applications to collect energy from multiple sources. Simulations and experimental results are presented to demonstrate the effectiveness of the proposed topology.

An inductor-based converter with EMI reduction for low-voltage thermoelectric energy harvesting

ABSTRACTThis paper presents a self-powered inductor-based converter which harvests thermoelectric energy and boosts extremely low voltage to a typical voltage level for supplying body sensor nodes. Electromagnetic interference (EMI) of the converter is reduced by spreading spectrum of fundamental frequency and harmonics via pseudo-random modulation, which is obtained via combining the linear feedback shift register and digitally controlled oscillator. Besides, the methods, namely extracting energy near MPP and reducing the power dissipation, are employed to improve the power efficiency. The presented inductor-based converter is designed and verified in CSMC CMOS 0.18-µm 1P6M process. The results reveal that it achieves the high efficiency and EMI reduction at the same time.

Fully-Integrated High-Conversion-Ratio Dual-Output Voltage Boost Converter With MPPT for Low-Voltage Energy Harvesting

This paper proposes a fully-integrated high-conversion-ratio dual-output voltage boost converter (VBC) with maximum power point tracking (MPPT) circuits for low-voltage energy harvesting. The VBC consists of two voltage generators that generate $V_{\mathrm { OUT1}}$ and $V_{\mathrm { OUT2}}$ . $V_{\mathrm { OUT1}}$ and $V_{\mathrm { OUT2}}$ are three and nine times higher than the harvester’s output $V_{\mathrm { IN}}$ , respectively. $V_{\mathrm { OUT1}}$ is used as a supply voltage for on-chip application circuits while $V_{\mathrm { OUT2}}$ is used as the charging voltage for a Li-ion secondary battery. The VBC achieves a high voltage conversion ratio (max. $\times \,\,9$ ) and a high power conversion efficiency. The MPPT circuits control the operating frequencies of the CPs to extract maximum power at each output. The measurement results demonstrated that the circuit converted a 0.59 V input to a 1.41 V output with 75.8% efficiency when the output powers of $V_{\mathrm { OUT1}}$ and $V_{\mathrm { OUT2}}$ were 396 and $0~\mu \text {W}$ , respectively, and a 0.62 V input to a 4.54 V output with 49.1% efficiency when the output powers were 0 and $114~\mu \text {W}$ , respectively.

A Review of DC/DC Converters for Ultra Low Voltage Energy Harvesting

A Review of DC/DC Converters for Ultra Low Voltage Energy Harvesting

A Highly Efficient Switched-Capacitor Voltage Boost Converter with Nano-Watt MPPT Controller for Low-Voltage Energy Harvesting

A Highly Efficient Switched-Capacitor Voltage Boost Converter with Nano-Watt MPPT Controller for Low-Voltage Energy Harvesting

A Wide Conversion Ratio, Extended Input 3.5-μA Boost Regulator With 82% Efficiency for Low-Voltage Energy Harvesting

An inductive boost regulator is presented that can harvest energy over a wide input voltage range. The wide input range is enabled by a current-based analog oscillator capable of providing very high duty cycle. The analog control circuits are designed to operate at subthreshold voltage to enable low voltage all electronic autonomous startup. A test chip designed in 130-nm CMOS demonstrates energy harvesting from as low as 12-mV input while biased by an external 1-V battery and autonomous (without using any additional device or battery) startup above 305 mV at output. The design typically consumes 3.5-μA standby current, achieves peak efficiency of 82%, and can regulate output from 0.66 to 3.3 V. The booster is coupled with a thermoelectric generator and the integrated system delivers output power of 6 μW at ~2 °C temperature difference to a maximum of 12 mW at ~50 °C temperature difference.

Low Voltage Energy Harvesting by an Efficient AC-DC Step-Up Converter

In this paper, a direct ac-to-dc power converter is proposed for efficient energy harvesting from the low voltage inertial micro generators. The conventional power converters use diode bridge rectifiers and condition the micro generator outputs in two stages. Hence, they are inefficient and may not be a feasible option for very low voltage micro generators. Moreover, they are not conducive for optimum energy harvesting. The proposed converter avoids the use of bridge rectifiers, and directly converts the ac input to the required dc output. This converter uses a boost converter and a buck-boost converter to process the positive and negative half cycles of the ac input voltage, respectively. Furthermore, using this converter, maximum energy harvesting can be implemented effectively. Analysis of the converter is carried out. Based on the analysis, two schemes are proposed to control the converter. Design guidelines are presented for selecting the converter component and control parameters. A self-starting circuit is proposed for independent operation of the converter. Simulation results are presented to validate the proposed converter topology and control scheme.

Low-power low-voltage AC–DC converters for electromagnetic energy harvesting with efficient indirect feedback scheme

In this study, two single-stage AC-DC converters for low-voltage electromagnetic energy harvesting are presented. The converters are designed to boost very low AC voltage (hundreds of millivolts) to a high DC voltage (3.3 V DC). The successful operation of such systems depends on proper development of control and driver circuits. The converters also need to be designed in proper accordance with the associated microgenerator. Detailed discussion on the design and selection of critical components of the converter is also presented. Low-power driver circuits are used to enable a self-sustaining system. Unlike DC-DC converters, direct AC-DC converters generally do not have a common ground. Such a structure makes implementation of feedback and control difficult. A novel indirect feedback strategy is proposed to solve this problem. The idea is to obtain the output voltage information referenced to the system ground. The feedback circuit is very simple to implement and consumes very low power. An auxiliary supply has also been designed to provide power to the gate drivers. It is shown that the indirect feedback strategy also works for load variations. Both simulation and experimental results with a suitable microgenerator are presented to verify the self-sustainable efficient operation of the harvesting systems.

Design and Implementation of a Direct AC–DC Boost Converter for Low-Voltage Energy Harvesting

In this paper, a direct ac-dc power electronic converter topology is proposed for efficient and optimum energy harvesting from low-voltage microgenerators. The converter utilizes the bidirectional current-conduction capability of MOSFETs to avoid the use of a front-end bridge rectifier. It is operated in discontinuous conduction mode and offers a resistive load to the microgenerator. Detailed analysis and modeling of the converter is presented. In such low-power applications, the power consumption of gate drive and control circuits should be minimal. In this paper, they are specifically designed to consume very low power. A suitable startup circuit and auxiliary dc supply circuit is proposed for the implementation of the converter. A low-voltage microgenerator is used to verify the performance and operation of the converter and the gate drive circuits.