Low Startup Voltage Research Articles

Start-up process of ion optics in ion thrusters

In this study, a particle-in-cell model of ion optics was established to simulate the changing trend of an ion beam shape over time during an ion optic start-up. This model was established to study the effect of ion beam shape change on the accel grid during ion optical start-up and to discuss the start-up strategy of ion optics. The results show that the ions at the edge of the beam have a radial velocity component toward the centerline of the ion optics owing to the electric field; this causes the ion beam to shrink gradually toward the centerline over time. Furthermore, the accel grid can be prevented from being bombarded by ions by design at the operating voltage. However, the grid may still be bombarded by ions during the low-voltage start-up process, thereby affecting its life. Thus, the ion dynamics must be considered during the start-up process.

Self-Operating Flyback Converter for Boosting Ultra-Low Voltage of Thermoelectric Power Generator for IoT Applications

This article presents a novel self-operating flyback converter to boost the ultra-low voltage produced by thermoelectric power generator (TEG). The proposed converter uses dual transformer, one for low-voltage startup and other to extract power from TEG. The use of separate transformer provides high-voltage transfer ratio, reduces high series resistance loss, and brings down the input impedance of circuit. The copper wire wounds ferrite toroid core transformer provides very low series resistance and negligible core loss, which improves the circuit efficiency. This boost converter operates with an input voltage range of 22–300 mV and provides maximum output power of 0.073 – 147 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${\rm{mW}}$</tex-math></inline-formula> correspondingly. The peak efficiency of 68% with output power of 1.32 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${\rm{mW}}$</tex-math></inline-formula> (voltage ∼1.83 V) is achieved at an input voltage of 50 mV. For regulated output voltage, a feedback loop is used to keep output voltage constant during sudden voltage rise of TEG. The proposed circuit uses discrete components, ferrite toroid core, and PCB, which has lower cost than available energy harvester module, which uses energy harvesting ICs, discrete components, and tiny transformer. The lower startup voltage, higher output power, and voltage with high conversion efficiency of this boost converter maximize the applications potential of the TEG as a portable power source for Internet of Things (IoT) devices.

Low-Voltage DC-DC Converter for IoT and On-Chip Energy Harvester Applications

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.

Starter for Voltage Boost Converter to Harvest Thermoelectric Energy for Body-Worn Sensors

This paper examines the suitability of selected configurations of ultra-low voltage (ULV) oscillators as starters for a voltage boost converter to harvest energy from a thermoelectric generator (TEG). Important properties of particularly promising configurations, suitable for on-chip implementation are compared. On this basis, an improved oscillator with a low startup voltage and a high output voltage swing is proposed. The applicability of n-channel native MOS transistors with negative or near-zero threshold voltage in ULV oscillators is analyzed. The results demonstrate that a near-zero threshold voltage transistor operating in the weak inversion region is most advantageous for the considered application. The obtained results were used as a reference for design of a boost converter starter intended for integration in 180-nm CMOS X-FAB technology. In the selected technology, the most suitable transistor available with a negative threshold voltage was used. Despite using a transistor with a negative threshold voltage, a low startup voltage of 29 mV, a power consumption of 70 µW, and power conversion efficiency of about 1.5% were achieved. A great advantage of the proposed starter is that it eliminates a multistage charge pump necessary to obtain a voltage of sufficient value to supply the boost converter control circuit.

An Asynchronous AC-DC Boost Converter With Event-Driven Voltage Regulator and 94% Efficiency for Low-Frequency Electromagnetic Energy Harvesting

This brief presents an asynchronous AC-DC boost converter with a high power conversion efficiency (PCE) and a low start-up voltage. The converter consists of a self-powered rectifier with unbalanced comparator, followed by a hysteresis DC-DC boost converter with an `event-driven' regulation loop, enabling boost conversion and output regulation without the need for a system clock, leading to significant reduction of the driving power loss and thus improvement of the PCE. The converter can be started up from an input AC voltage with 500 mV amplitude, achieving a maximum PCE up to 94% with reduced chip-to-chip variation as low as 4%, delivering 103 μW output power. The chip has been fabricated in 180 nm standard CMOS process with a 0.11 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> core area, targeting on the low-frequency electromagnetic (EM) energy harvesting.

A parallel auto-adaptive topology for integrated energy harvesting system

This work presents a new topology for a thermal and RF energy harvesting system for integrated circuits. The system improves two circuit parameters: low start-up voltage and high-efficiency energy extraction. The high efficiency is achieved with a new parallel auto-adaptive DC-DC converter with a charge-pump based design to collect thermal energy. The low start-up voltage is possible with the assistance of a Radio-Frequency harvester circuit, resulting in a new hybrid energy harvesting architecture. The circuit was designed and fabricated with a CMOS 180 nm process, using an active area of 954 μm × 341 μm. The measurement results show an 87% peak efficiency with a maximum regulated output voltage of 2 V. The minimum operating input voltage is 250 mV without the start-up circuit and 30 mV with the RF start-up circuit at 33 KHz of switching frequency.

Design of a Boost DC–DC Converter With 82-mV Startup Voltage and Fully Built-in Startup Circuits for Harvesting Thermoelectric Energy

In this letter, a boost dc–dc converter with fully built-in startup circuits has been proposed as a thermoelectric energy harvester. The proposed chip was fabricated using a 0.18- $\mu \text{m}$ 1P6M mixed-signal standard CMOS process. Neither post-fabrication trimming nor additional external components are needed to startup the converter. Moreover, a new type of low-leakage logic gates is proposed for lowering the minimal startup voltage, and several low-voltage startup circuits are also proposed. According to the measured results, the minimal startup voltage is only 82 mV, and the input voltage range is 60–460 mV. The measured maximal input power is 2.7 mW, the measured quiescent power with 200-mV input voltage is 8.2 $\mu \text{W}$ , and the measured peak efficiency is 78.55%.

A 7.5-mV-Input Boost Converter for Thermal Energy Harvesting With 11-mV Self-Startup

A DC-DC boost converter for ultra-low-voltage thermal energy harvesting is presented herein. The focus of this brief is to provide both self-startup and efficient conversion at ultra-low input voltages. The converter startup is achieved through the use of a cold starter based on an ultra-low-voltage oscillator and a charge pump. The inductive boost converter architecture uses two low-side switches in order to independently optimize the low-voltage startup and the steady-state conversion efficiency. The model of the developed converter allows optimization of the boost switches as a function of the TEG internal resistance and input voltage. A zero current switching circuit with accurate detection for low input voltages is designed and implemented. The prototype fabricated in 130 nm standard CMOS technology achieves startup for an input voltage of 11 mV and, once started, the system can perform the boost operation for input voltages as low as 7.3 mV, delivering 50% of end-to-end efficiency at 10.5 mV and peak end-to-end efficiency of 85% at 140 mV.

Harvesting thermoelectric energy from railway track

This study aims to develop a prototype for harvesting thermoelectric energy from railway track. By capturing the existing thermal energy in railway tracks, this technology helps power rail-side sensors in off-grid and remote areas without depleting natural resources. In low latitudes such as southern China, the temperature of railway tracks can reach 57 °C due to solar radiation. However, at a relatively shallow depth (200 mm), the substratum below the track foundation (e.g., soils) has a lower temperature (i.e., 15 °C–26 °C). This temperature difference can be used to generate electricity through a thermoelectric generator (TEG). The proposed approach captures thermal energy from the railway track and transfers the energy to the TEG prototype beneath the bottom of rails. Evaluation of the prototype is conducted by finite volume analysis, field test, and laboratory experiment. The results indicate that the TEG prototype can produce 5.8 mW–316.8 mW of power across a resistant load at thermal gradient from 8 °C to 29.2 °C. A DC-DC buck-booster circuit with lithium battery management is developed to charge the batteries by the harvested thermal energy. The system operates at a low startup voltage of 0.9 V and its conversion efficiency is larger than 60%.

An ultra-low power, low voltage DC-DC converter circuit for energy harvesting applications

In this paper a compact, fully-integrated voltage multiplier with a low start-up voltage is presented for energy harvesting applications. Two voltage doublers are cascaded with the overall conversion ratio of 2 and 4. The voltage multiplier has a 2-phase clock signal with a wide range of operating frequency from 1 kHz to 1 MHz. Cascading and positive feedback with cross-coupled gates have been used to increase the efficiency and conversion ratio of the converter. The DC-DC converter has an efficiency of more than 70% when operating from a 0.34 V input voltage and generating 1.28 V output voltage. The proposed voltage multiplier has a power consumption of 36 nW to 1.24 μW for input voltage range of 280–450 mV in 0.18 μm CMOS technology.

A 12 mV Input, 90.8% Peak Efficiency CRM Boost Converter With a Sub-Threshold Startup Voltage for TEG Energy Harvesting

This paper proposed a high efficiency boost converter targeting thermoelectric generator energy harvesting. The proposed converter adopts the critical conduction mode rather than the discontinuous mode to reduce the conduction loss, which can improve the peak efficiency at high input power. To reduce the minimum input voltage, an adaptive on-resistance switch, which can automatically change the high side and low side on-resistance according to the input voltage, is used. To maximize the output power, a maximum power point tracking circuit is designed to track the internal source resistance. Radio frequency (RF) kick-up and low voltage startup are used to improve the cold start voltage. The proposed converter is implemented in a 0.18- $\mu \text{m}$ standard CMOS process, which occupies a chip area of about 0.48 mm2. Measurement results show that the peak efficiency of the converter can be up to 90.8% and 60% at 180 and 20 mV of the open-circuit voltage, respectively. Owing to the cold startup circuit, the proposed converter can start successfully with 260-mV open-circuit voltage or −16-dBm RF input. Moreover, the open-circuit voltage can be further lowered to 12 mV with 1.5- $\mu \text{W}$ output power after startup.

Self-start-up fully integrated DC-DC step-up converter using body biasing technique for energy harvesting applications

An ultra-low power, self-start-up switched-capacitor Two Branch Charge Pump (TBCP) circuit for low power, low voltage, and battery-less implantable applications is proposed. In order to make feasible the low voltage operation, the proposed charge pump along with Non-Overlapped Clock generator (NOC) are designed working in sub-threshold region by using body biasing technique. A four-stage TBCP circuit is implemented with both NMOS and PMOS transistors to provide a direct load flow. This leads to a significant drop in reverse charge sharing and switching loss and accordingly improves pumping efficiency. A post-layout simulation of designed four-stage TBCP has been performed by using an auxiliary body biasing technique. Consequently, a low start-up voltage of 300 mV with a pumping efficiency of 95% for 1 pF load capacitance is achieved. The output voltage can rise up-to 1.88 V within 40 μs with 0.2% output voltage ripple in case of using 400 mV power supply. The designed circuit is implemented by 180-nm standard CMOS technology with an effective chip area of 130.5 μm × 141.8 μm while the whole circuit consumes just 3.2 μW.

A CMOS MF energy harvesting and data demodulator receiver for wide area low duty cycle applications with 250\xa0mV start-up voltage

A low voltage start-up energy harvesting medium frequency receiver is presented, for use as the power and synchronisation part of a remote sensor node in a wide area industrial or agricultural application. The use of embedded low bandwidth network synchronisation data permits very low operational duty cycle without the need for real time clocks or wake up receivers at each node with their associated continuous power drain. The receiver consists of a rectifier, a power management unit and a phase-shift keying demodulator. The rectifier is optimised for low start-up and operating voltage rather than power efficiency. With standard MOS thresholds the rectifier can cold start with only 250 mV peak antenna input, and useful battery charging is delivered with 330 mV peak input. The QPSK demodulator consumes 1.27 μW with a supply voltage of 630 mV at a data rate of 1.6 kbps with 1 MHz carrier frequency. The IC is implemented in a standard threshold 0.18 μm CMOS technology, occupies 0.54 mm2 and can deliver 10.3 μW at 3 V to an external battery or capacitor.

Overview of recent experimental results from the Aditya tokamak

Several experiments, related to controlled thermonuclear fusion research and highly relevant for large size tokamaks, including ITER, have been carried out in ADITYA, an ohmically heated circular limiter tokamak. Repeatable plasma discharges of a maximum plasma current of ~160 kA and discharge duration beyond ~250 ms with a plasma current flattop duration of ~140 ms have been obtained for the first time in ADITYA. The reproducibility of the discharge reproducibility has been improved considerably with lithium wall conditioning, and improved plasma discharges are obtained by precisely controlling the position of the plasma. In these discharges, chord-averaged electron density ~3.0–4.0 × 1019 m−3 using multiple hydrogen gas puffs, with a temperature of the order of ~500–700 eV, have been achieved. Novel experiments related to disruption control are carried out and disruptions, induced by hydrogen gas puffing, are successfully mitigated using the biased electrode and ion cyclotron resonance pulse techniques. Runaway electrons are successfully mitigated by applying a short local vertical field (LVF) pulse. A thorough disruption database has been generated by identifying the different categories of disruption. Detailed analysis of several hundred disrupted discharges showed that the current quench time is inversely proportional to the q edge. Apart from this, for volt–sec recovery during the plasma formation phase, low loop voltage start-up and current ramp-up experiments have been carried out using electron cyclotron resonance heating (ECRH). Successful recovery of volt–sec leads to the achievement of longer plasma discharge durations. In addition, the neon gas puff assisted radiative improved confinement mode has also been achieved in ADITYA. All of the above mentioned experiments will be discussed in this paper.

Efficient ECH-assisted plasma start-up using trapped particle configuration in the versatile experiment spherical torus

An efficient and robust ECH (electron cyclotron heating)-assisted plasma start-up scheme with a low loop voltage and low volt-second consumption utilizing the trapped particle configuration (TPC) has been developed in the versatile experiment spherical torus (VEST). The TPC is a mirror-like magnetic field configuration providing a vertical magnetic field in the same direction as the equilibrium field. It significantly enhances ECH pre-ionization with enhanced particle confinement due to its mirror effect, and intrinsically provides an equilibrium field with a stable decay index enabling prompt plasma current initiation. Consequently, the formation of TPC before the onset of the loop voltage allows the plasma to start up with a lower loop voltage and lower volt-second consumption as well as a wider operation range in terms of ECH pre-ionization power and H2 filling pressure. The TPC can improve the widely-used field null configuration significantly for more efficient start-up when ECH pre-ionization is used. This can then be utilized in superconducting tokamaks requiring a low loop voltage start-up, such as ITER, or in spherical tori with limited volt-seconds. The TPC can be particularly useful in superconducting tokamaks with a limited current slew-rate of superconducting PF coils, as it can save volt-second consumption before plasma current initiation by providing prompt initiation with an intrinsic stable equilibrium field.

A Single-Chip Solar Energy Harvesting IC Using Integrated Photodiodes for Biomedical Implant Applications.

In this paper, an ultra-compact single-chip solar energy harvesting IC using on-chip solar cell for biomedical implant applications is presented. By employing an on-chip charge pump with parallel connected photodiodes, a 3.5 × efficiency improvement can be achieved when compared with the conventional stacked photodiode approach to boost the harvested voltage while preserving a single-chip solution. A photodiode-assisted dual startup circuit (PDSC) is also proposed to improve the area efficiency and increase the startup speed by 77%. By employing an auxiliary charge pump (AQP) using zero threshold voltage (ZVT) devices in parallel with the main charge pump, a low startup voltage of 0.25 V is obtained while minimizing the reversion loss. A 4 Vin gate drive voltage is utilized to reduce the conduction loss. Systematic charge pump and solar cell area optimization is also introduced to improve the energy harvesting efficiency. The proposed system is implemented in a standard 0.18- [Formula: see text] CMOS technology and occupies an active area of 1.54 [Formula: see text]. Measurement results show that the on-chip charge pump can achieve a maximum efficiency of 67%. With an incident power of 1.22 [Formula: see text] from a halogen light source, the proposed energy harvesting IC can deliver an output power of 1.65 [Formula: see text] at 64% charge pump efficiency. The chip prototype is also verified using in-vitro experiment.

Low start‐up voltage dc–dc converter with negative voltage control for thermoelectric energy harvesting

This Letter presents a low start-up voltage dc–dc converter for low-power thermoelectric systems which uses a native n-type MOS transistor as the start-up switch. The start-up voltage of the proposed converter is 300 mV and the converter does not need batteries to start up. The negative voltage control is proposed to reduce the leakage current caused by native n-type transistor and increase the efficiency. The proposed converter was designed using standard 0.18 µm CMOS process with chip size of 0.388 mm2. The peak efficiency is 63% at load current of 1.5 mA. The proposed converter provides output voltage >1 V at maximum load current of 3.2 mA.

Design of Transformer-Based Boost Converter for High Internal Resistance Energy Harvesting Sources With 21 mV Self-Startup Voltage and 74% Power Efficiency

Thin-film thermoelectric generators (TEG) or graphene-based microbial fuel cells (MFC) are emerging energy harvesting sources with promising power density and sustainability. Nevertheless, conventional transformer-based boost converters commonly used to achieve autonomous low voltage startup encounter low efficiency and potential startup problems with these novel power sources due to their high internal resistance. In this paper, an improved design of transformer-based boost converter addressing these issues is demonstrated with prototype chip fabricated using a standard 0.13 μm CMOS process. The self-start oscillation does not rely on the conventional LC resonant principle, but instead is dependent on the MOS transistor's active-over-leakage current ratio and the mutual coupling between the two identical transformer coils. Circuit design techniques to regulate output voltage and to track system's maximum power point (MPP) of this boost converter are presented. Measurement results confirmed that the proposed circuit works with either low threshold voltage or native MOS transistors. It needs minimum self-startup voltage of 21 mV (at 5.8 μW input power) and minimum startup power of 1.3 μW (at 35 mV input voltage) respectively. The maximum output power is 2 mW and peak power conversion efficiency is 74% at a regulated output voltage of 1 V.

A Load-Modulated Rectifier for RF Micropower Harvesting With Start-Up Strategies

In this paper, we introduce a new load-modulated two-branch rectifier, designed to dynamically cooperate with an ultra-low power management unit (PMU), interposed between the rectenna and application circuits. The design targets batteryless RF energy harvesting applications with typical input power ranging from ~ 10 to ~ 100 μW. Energy is stored in a low leakage capacitor. In order to allow activation in discharged states, the PMU implements a low-voltage start-up stage, whose current consumption is specifically optimized for biasing the rectifier accordingly. When a sufficient voltage is reached, the PMU activates a more efficient boost converter stage with maximum power point tracking capabilities and micro-power consumption. Such two circuits are designed to provide two very different loading conditions to the rectifier. A joint design of the nonlinear rectifier paths and of the two PMU subsystems based on two specific optimizations of the matching networks is proposed, along with a circuit solution for automatically switching between the start-up stage and the boost converter. In order to validate the concept, a microstrip prototype operating at 900 MHz with a discrete components PMU is characterized, although the proposed idea is fully technology independent. With respect to a conventional rectifier, the proposed design allows the system to operate with significantly lower input power, while preserving efficiency during steady-state power conversion.

Optimization of ECR-breakdown and plasma discharge formation on T-10 tokamak, using X-mode second harmonic of ECR.

In order to obtain breakdown and suitable plasma parameters for low-voltage OH start-up, high level of EC-power was injected into T-10 tokamak. Input HF-power was varied in the range of 0.15-1.0 MW. Two HF-launcher systems with different output beams allowed to inject EC-waves with maximum power density 0.25 MW/cm 2 and 0.01 MW/cm 2 . Dependence of breakdown time delay on HF-power was obtained. It was shown, that optimal plasma parameters were achieved in presence of plasma equilibrium currents I=3 kA (input HF-power=1.0 MW). Electron temperature Te=100÷150 eV and electron density ne=5•10 12 cm -3 was measured in these discharges. These parameters remained constant during full HF-pulse-length.