Ingo Kuehne

A Fully Autonomous Integrated Interface Circuit for Piezoelectric Harvesters

This paper presents a fully autonomous, adaptive pulsed synchronous charge extractor (PSCE) circuit optimized for piezoelectric harvesters (PEHs) which have a wide output voltage range 1.3-20 V. The PSCE chip fabricated in a 0.35 μm CMOS process is supplied exclusively by the buffer capacitor where the harvested energy is stored in. Due to the low power consumption, the chip can handle a minimum PEH output power of 5.7 μW. The system performs a startup from an uncharged buffer capacitor and operates in the adaptive mode at storage buffer voltages from 1.4 V to 5 V. By reducing the series resistance losses, the implementation of an improved switching technique increases the extracted power by up to 20% compared to the formerly presented Synchronous Electric Charge Extraction (SECE) technique and enables the chip efficiency to reach values of up to 85%. Compared to a low-voltage-drop passive full-wave rectifier, the PSCE chip increases the extracted power to 123% when the PEH is driven at resonance and to 206% at off-resonance.

A fully autonomous pulsed synchronous charge extractor for high-voltage piezoelectric harvesters

This paper presents a fully autonomous, self-adjusting pulsed synchronous charge extractor chip optimized for piezoelectric harvesters with an output voltage from 3V to 18V. The chip which has been fabricated in a 0.35 μm CMOS process is supplied exclusively by the buffer capacitor where the harvested energy is stored in. Due to the low power consumption, the chip can handle a minimum piezo output power of 30μW. The system performs a startup from an uncharged buffer capacitor and operates in the adaptive mode at storage buffer voltages from 1.4 V to 5V. The implementation of the improved switching technique increases the chip efficiency by up to 15% compared to the commonly used Synchronous Electric Charge Extraction technique and enables the chip efficiency to reach values of up to 90%.

Design And Analysis Of A Capacitive Vibration-To-Electrical Energy Converter With Built-In Voltage

This paper reports on the design and analysis of a capacitive vibration-to-electrical energy converter. A theoretical design model of a parallel-plate electrostatic spring-mass-system is presented, based on state space equations. The charging of the parallel-plate capacitor takes place by utilizing materials with different work functions for the electrodes. Numerical simulations are performed in order to optimize design parameters targeting a maximum output power. Such a micro-electro-mechanical system (MEMS) based capacitive energy converter is able to provide an output power of 4.28 muW at an external vibration with a frequency of 1 kHz and an amplitude of 1.96 m/s2 (0.2 g). This corresponds to a power density of 79.26 muW/cm 3 based on a typical MEMS die size

Piezoelectric MEMS energy harvesting module based on non-resonant excitation

The paper reports the system design of a piezoelectric energy harvesting module for a tire based wireless sensor node application. Impacts of material propertie, generator design and power management circuitry are considered. In context of a non-resonant generator excitation scheme, dissipative damping mechanisms are investigated. In particular air damping is measured, simulated and modeled. A design procedure is presented to identify a geometry design space for the microgenerator consistent with application specific requirements.

Optimum design of a piezoelectric MEMS generator for fluid-actuated energy harvesting

This paper reports the optimum design, fabrication and characterization of a piezoelectric MEMS generator for fluid-actuated energy harvesting. Depending on the specific load scenario optimum beam shapes of piezoelectric cantilevers are investigated by theoretical estimations and related experiments. A point load at the free-end of a cantilever requires a triangular beam shape. Compared to a classical rectangular shape the electrical area energy density is three times larger. A maximum area energy density value of 35 nJ/mm2 is measured for the triangular beam shapes. A uniform load as occurring for fluid-actuated energy harvesting calls for a triangular-curved beam shape and is also superior to classical geometries.

System modeling of a piezoelectric energy harvesting module for environments with high dynamic forces

This paper reports the design of a piezoelectric energy harvesting module for a tire based wireless sensor node. System considerations comprise the generator design, material impact and the generator interface circuitry. A design procedure is presented, which allows identifying a geometry design space for the piezoelectric microgenerator consistent with given specifications. For the addressed application a large dynamic force range occurs for a given mass. The acceleration is in the range of some ten up to some thousand units of gravitational acceleration. Therefore, a conventional generator cantilever design with a mass in the gram-range is critical. For our design we use a piezoelectric MEMS generator approach without seismic mass. The intrinsic mass of the cantilever is in the microgram region and the resulting acceleration forces are very small. For the energy transfer from the environment to the generator we suggest a non-resonant excitation scheme. Tire related forces during the period of tread shuffle passage are to be used for a pulsed excitation of the generator. Based on analytical modeling the system parameters are calculated for a given generator geometrical design. The results are utilized to identify a design space consistent with given requirements and operation conditions.

A novel MEMS design of a piezoelectric generator for fluid-actuated energy conversion

In this paper a novel MEMS design of a piezoelectric generator for fluid-actuated energy conversion is presented. An exemplary energy scavenging scenarios is introduced. Moreover, the electro-mechanical properties of different piezoelectric thin films (PZT, AlN, ZnO) are introduced and compared to each other. Depending on the specific load scenario optimum piezoelectric cantilever shapes are investigated. A point load at the free-end of a cantilever requires a triangular cantilever shape. Compared to a classical rectangular shape the electrical area energy density is three times larger. A maximum area energy density value of 35 nJ/mm2 is measured for the triangular cantilever shapes. A uniform load as occurring for fluid-actuated energy harvesting calls for a triangular-curved cantilever shape and is also superior to classical geometries.

Digital potentiostat for electrochemical bio sensor chips

A rail-to-rail potentiostat circuit suitable for CMOS based electronic bio sensors is presented. The design approach enables robust operation far a large range of electrochemical conditions. Measurement results prove proper operation of the potentiostatic control circuitry.

MEMS-based piezoelectric energy harvesting modules for distributed automotive tire sensors

This article presents the realization of a new energy self-powered sensor node. The wireless node is supplied by 10 μW of electrical power and is able to send three measured values in intervals of 80s. The power supply is carried out with a MEMS-based piezoelectric vibration converter. A specially developed ASIC for this type of generator takes over the energy management. The wireless connection to a base station is established by a microcontroller predestinated for energy autonomous applications in conjunction with a standard IEEE 802.15.4 RF-frontend. The used Route Under MAC wireless protocol is specifically designed for energy-saving operations. The protocol supports the IPv6/6LoWPAN standard whereby multiple sensor nodes can be integrated in a wired network.

A new approach of a shape-optimized piezoelectric MEMS generator for fluid-actuated energy scavenging

In this paper a new approach of a shape-optimized piezoelectric MEMS generator for fluid-actuated energy scavenging is presented. Different energy scavenging scenarios are introduced. Depending on the specific load scenario optimum piezoelectric cantilever shapes are investigated. A point load at the free-end of a cantilever requires a triangular cantilever shape. Compared to a classical rectangular shape the electrical area energy density is three times larger. A maximum area energy density value of 35 nJ/mm2 is measured for the triangular cantilever shapes. A uniform load as occurring for fluid-actuated energy harvesting calls for a triangular-curved cantilever shape and is also superior to classical geometries.