Ali Muhtaroglu

Fully Self-Powered Electromagnetic Energy Harvesting System With Highly Efficient Dual Rail Output

This paper presents a vibration-based energy harvesting system composed of a compact electromagnetic (EM) power generator and highly efficient full-wave interface electronics in a system-on-package. The system harvests energy from ambient vibrations, and delivers a smooth and reliable dual rail DC supply to power up a practical load. The energy harvester module is an in-house double-coil EM transducer which generates AC voltage in response to low frequency ambient vibrations. Voltage regulation is achieved by the interface electronics at the core of the system, which is designed to rectify the input AC voltage with peak amplitude ranging from several hundred mVs to several Volts, with maximum efficiency. The interface electronics contains an active rectifier with high conversion efficiency (>;80%) for a wide range of load currents (0-42 μA). A passive network, built from low threshold-voltage chip diodes and capacitors, generates a dual supply voltage from one of the coils to power up the active rectifier. The autonomous system of 16 cm3 volume (comparable to the size of a C-Type battery), delivers 54 μW to a 37-μA load through a dual rail 1.46 V DC voltage with total system efficiency of 81%, when subjected to low frequency (8 Hz) external vibrations. The maximum overall system power density has been validated to be 6.06 μW/cm3, three times what was previously reported for a batteryless vibration driven system.

AC IO loopback design for high speed /spl mu/processor IO test

This work presents the next generation AC IO loopback design for two Intel processor architectures. Both designs detect I/O defects with 20 ps resolution and 50 ps jitter for up to 800 MHz bus speed. Even though the implementations differ in some aspects to accommodate two different bus architectures, the same prudent considerations for high speed operation, minimum test inaccuracy, and low implementation costs apply to both.

A Fully Integrated and Battery-Free Interface for Low-Voltage Electromagnetic Energy Harvesters

This paper presents a fully integrated and battery-free 90 nm interface circuit for ac/dc conversion and step up of low-voltage ac signals generated by electromagnetic (EM) energy harvesters. The circuit is composed of two stages: The rectifier in the first stage utilizes an improved ac/dc doubler structure with active diodes internally powered by a passive ac/dc doubler and custom-designed comparators to minimize the voltage drops. With this, the efficiency is enhanced to 67% while providing 0.61 V to 40 μA load. The second stage is a dc/dc converter utilizing a low-voltage charge pump with an on-chip ring oscillator for further voltage step up. The rectifier stage is functional down to 125 mV input peak voltage, and the full interface circuit can maintain more than 1 V dc at 1 MΩ load for input peak voltages higher than 0.4 V. The circuit delivers 2.48 V to a 4.4 MΩ load, when interfaced to an in-house EM harvester, operating under 10 Hz, 0.5 g vibration.

A vibration-based electromagnetic energy harvester system with highly efficient interface electronics

This paper presents a vibration-based electromagnetic (EM) energy harvester system utilizing novel and highly efficient interface electronics. The energy harvesting module up-converts the environmental low frequency vibrations for increased AC power output. The interface circuit employs a boot-strap technique to reduce the threshold voltage of the rectifiers further increasing the power conversion efficiency of the overall system. The complete system, composed of an energy harvester module, and a compact 0.35 µm CMOS IC, was fully validated. It is capable of powering a 1.5V, 15µA load with 65% conversion efficiency, and 5% ripple, at an external vibration frequency of 10Hz. The recorded efficiency is the highest achieved value for vibration-based EM energy harvesters with passive rectification to the best of our knowledge.

Hybrid thermoelectric conversion for enhanced efficiency in mobile platforms

Hybrid thermoelectric conversion (HTC) has been used as a means to improve the efficiency of high performance mobile computing systems. HTC utilizes the thermal margin in the cooling solution, when the electronic component is not fully active, to integrate a thermoelectric (TE) module into the heat dissipation path for energy scavenging. When the component is driven to its junction temperature limit through a heavy workload, the same TE module is switched to refrigeration mode to provide additional cooling headroom for improved performance. A set of semi-realistic system usage assumptions and parameters has been utilized for the evaluation of HTC in system environments. Results from finite-element analysis (FEA) simulation of the topology and full TE characterization are presented. Common TE models are then used to build an iterative system solver to estimate up to 10% system efficiency benefit from HTC integration using characterized off-the-shelf TE components.

An interface circuit prototype for a vibration-based electromagnetic energy harvester

This paper describes the interface electronics for a vibration based Electromagnetic (EM) energy harvester, which works on the mechanical frequency-up-conversion principle. The interface electronics is used to step up and rectify the harvested AC signal of the energy harvester through a two-stage charge-pump circuit. Output voltage of 4.5 V with 2.5% ripple has been demonstrated at a load current of 5μA. The maximum power efficiency is 35% with an output voltage and current range of 2–2.5V and 15–20 μA respectively. Furthermore, a synchronous rectifier was powered by the energy harvester to verify usage under active loading conditions.

Feasibility analysis and proof of concept for thermoelectric energy harvesting in mobile computers

Thermoelectric (TE) energy harvesting in compact microelectronic systems necessitates detailed upfront analysis to ensure unacceptable performance degradation is avoided. TE integration into a notebook computer is empirically investigated in this work for energy harvesting. A detailed finite element model was constructed first for thermal simulations. The model outputs were then correlated with the thermal validation results of the selected system. In parallel, a commercial TE micro-module was empirically characterized to quantify maximum power generation opportunity from the combined system and component data set. Next, suitable “warm spots” were identified within the mobile computer model to extract TE power with minimum or no notable impact to system performance, as measured by simulated thermal changes in the system. The prediction was validated by integrating a TE micro-module to the mobile system under test. Measured TE power generation density in the vicinity of the heat pipe was 1.26 mW/cm3 using ...

Hybrid energy harvesting from keyboard

This paper presents a hybrid energy harvester which combines piezoelectric (PZT) and electromagnetic (EM) transduction mechanisms to scavenge vibration energy from a keyboard. The system comprises of improvements to the dome structure presented in previous studies, in which only PZT transduction mechanism was used to harvest 16.95 μW of experimentally verified power. An in-house modeling and simulation tool is first introduced in this work to evaluate the integration of EM transduction into the PZT system. The tool combines analytical mechanical equations and FEM results for magnetic fields for the optimization of the electromagnetically generated power. Two designs of different cost are then compared. It is concluded that the design utilizing the frequency-up-conversion technique at an incrementally higher cost is superior due to significantly higher contribution to the generated power compared to the alternative implementation without frequency-up-conversion. Modeling and simulations show an additional 2.81 μW power can be generated through EM integration to the previous PZT based keyboard energy harvester system.

I/O self-leakage test

This work presents the implementation of the self-leakage test, a new approach for unconnected I/O leakage testing. It provides a path for leakage current through the on-chip leakers and uses the voltage drop at the pad to detect a pass/fail condition. A detailed methodology for defining the self-leakage test specifications has been developed. Preliminary silicon data shows that self-leakage test methodology provide a viable method for high-volume monitoring of I/O leakage at minimal on-die DFT (design-for-test) overhead.

An electromagnetic energy harvester for low frequency and low-g vibrations with a modified frequency up conversion method

This paper presents a MEMS-based electromagnetic (EM) energy harvester for low frequency and low acceleration vibrations. The harvester is an improved version of [1], which operates with the frequency up conversion (FupC) principle. The former structure was composed of a low-frequency diaphragm carrying a magnet and 16 high-frequency cantilevers with coils. In this work, the phase difference between the coil outputs, leading to voltage cancellation in serial connection, has been eliminated by using a single coil placed on a diaphragm. Furthermore, the placement and the volume of the magnetic film have been modified for better magnetic coupling. The RMS values of the generated voltage and delivered power to an equivalent resistive load have been measured as 6.94 mV and 1.2 nW, respectively with 10 Hz, 3 mm peak to peak vibrations (0.6 g acceleration). About 32-fold increase in the peak power output has been demonstrated with the presented energy harvester with respect to the previous work.