Nicolas Degrenne

Self-powered ultra-low power DC-DC converter for RF energy harvesting

In this paper, an autonomous low voltage and ultra-low power DC-DC converter is presented. This novel topology is inspired from the classical Armstrong oscillator structure. In addition to be self-powered and autonomous, this converter is suitable for high-impedance sources. Theoretical and simulation-based optimizations are used in order to design the converter. A fabricated prototype is tested. It harvests RF energy from a low power rectenna (rectifying antenna). High output voltage and good performances are achieved in the range of 4μW to 1mW of input power.

Self-starting DC:DC boost converter for low-power and low-voltage microbial electric generators

This paper describes and evaluates an original boost converter able to harvest energy from low-power and low-voltage power sources. Design and sizing are made according to specifications issued from the stringent characteristics of microbial electric generators such as microbial fuel cells and microbial desalination cells. The harvested power is 10mW under input voltage Vin=0.3V (33mA input current). The design of the converter is adapted from a classical boost topology. It includes a self-oscillating circuit for autonomous operation, and a simple analog maximum power point regulation. Measurements of the conceived discrete realization enable evaluation of the circuit. Best global efficiency of 74% is achieved under realistic harvesting conditions.

Autonomous ultra-low power DC/DC converter for Microbial Fuel Cells

In this paper, an ultra-low voltage and power DC/DC converter is presented. This converter harvests energy from a Microbial Fuel Cell (MFC) in order to feed another circuit such as an autonomous wireless sensor. The MFC behaves as a voltage generator of 475mV open-circuit voltage with a 600Ω serial internal impedance. The maximum delivered power is therefore around 100μW. The DC/DC converter provides output voltage in the range 2–7.5V and performs impedance matching with source. The converter achieves when associated with the MFC, 60% peak efficiency. Furthermore, this DC/DC converter is self-operating without the need for external power source of start-up assistance.

A 140 mV Self-Starting 10 mW DC/DC Converter for Powering Low-Power Electronic Devices from Low-Voltage Microbial Fuel Cells

This paper presents an original self-starting DC/DC converter for low-power and low-voltage applications such as energy harvesting from microbial fuel cells to supply low-power electronic devices. Design is performed according to specifications issued from the stringent characteristics of microbial fuel cells. The harvested power reaches 10 mW under 0.3 V input voltage for the ten 1.3-liter experimental microbial fuel cells connected in parallel. The converter is adapted from a boost topology. It includes a self-oscillating sub-circuit for autonomous operation and a simple analog input-voltage control to harvest maximum energy from the source. The paper presents experimental results from a discrete and low-cost prototype. A global efficiency of more than 73% is achieved for 0.3 V input-voltage and under realistic harvesting conditions for the MFCs and the converter prototype.

Voltage Reversal in Unbalanced Rectenna Association

Rectifying antenna (rectenna) associations can be advantageously used to harvest electromagnetic energy from different directions. When the rectennas are associated in series, their output voltages are added, and the electrical dc energy is more easily exploitable. This letter shows that if a rectenna receives significantly less energy than the others (i.e., unbalanced association), its voltage polarity may reverse. Simulation and experimental results show that when an unbalanced association is operated at maximum power point, voltage reversal can result in a total decrease in efficiency of up to 26%. Possible solutions to reduce these detrimental consequences are also discussed.

Ultra-Low Power, Low Voltage, Self-Powered Resonant DC-DC Converter for Energy Harvesting

This article presents a resonant DC-DC converter suitable for ultra-low power and low voltage sources. This original topology allows a self-starting and a self-operation under harsh conditions of input voltage and power without any additional start-up assistance. A global theoretical modeling of the converter which includes start-up and steady-state phases is presented and a methodology for optimal design is detailed. It is based on the combination of both theoretical calculations and circuit simulations. Experimental tests based on discrete prototypes are carried out in order to demonstrate the good operation of the converter. Experimental tests have been achieved using an RF energy harvesting source. Ultra-low power and low voltage conditions as low as 3 μW and 100 mV respectively can be achieved as demonstrated by the experimental measurements. The input low voltage is stepped-up to a conventional level of some volts, what allows to power autonomously and solely low power circuits from energy harvesting sources.

Progress in Microbial Fuel Cells Energy Production

Microbial fuel cells (MFCs) harness the natural metabolisms of microbes to produce electrical power from almost any kind of organic matter. In addition to the low power densities (about 1mW for a 1-liter reactor), MFCs are presently built with expensive membrane and electrodes. The payback time of MFCs is therefore very long (evaluated to 25000 years for our lab prototype). Progresses in designing low-cost MFCs are necessary before conceiving large scale energy production.

Association of Flyback Converters to Harvest Energy from Multiple Hydraulically Connected Biofuel Cells

Biofuel cells use catalysts (chemical, enzymatic or microbial) to convert chemical energy from organic substrates into electrical energy. This paper investigates energy harvesting from several low-power biofuel cells to power a load under several volts. As biofuel cells can share the same fuel source, an isolation is required to aggregate energy towards high voltages (compared to a cell voltage). The proposed converter is based on the well known fly back topology. The efficiency of the fly back converter is about 60 % for an input power of 10 mW. The PCB area is 29 cm2 compared to around 74 cm2 for a previously built boost converter. The topology of the fly back converter includes a control circuit which allows a regulation of the input voltage to keep it around the maximum power point (MPP at around 0.3 V). This control circuit is powered internally through an auxiliary sub-circuit.