Synchronized Switch Harvesting Research Articles

Active and passive electronic interfaces adapted to a capacitive micromachined ultrasonic transducer (CMUT) used in acoustic energy transfer

Wireless power transfer is a key feature in the field of biomedical engineering. It allows a reduction of the energy storage devices in medical implants. An efficient way to safely transfer energy to medical implants is to convey ultrasounds through the body to a Capacitive Micromachined Ultrasonic Transducer (CMUT). For an application of ultrasonic energy transfer through skin, the present work compares the efficiency of two different electronic architectures to receive energy from an array of CMUT. The well known Synchronous Switch Harvesting on Inductor (SSHI) is compared in simulation to a simple impedance matching. Indeed, for an ultrasonic energy transfer, the high excitation frequency (1–8 MHz) allows the use of an inductor matching the CMUT’s clamped capacitor. The simplicity of an impedance matching circuit, its low volume and its efficiency makes it the best choice for an efficient energy transfer process to the targeted load. The CMUT model used in the simulations is a mason’s model which component values are extracted from the impedance measurement of a real device. In the end, the impedance matching is experimentally tested on this same device and compared to the simulation. A maximum 4,5 mW power is transferred to an optimal load for an input ultrasound pressure of 90 kPa.

Performance of surge-induced synchronized switch harvesting on inductor as an efficient technique under strong electromechanical coupling and low amplitudes of vibration

The process of harvesting energy from ambient sources is key for various applications. This study examined the performance of two representative techniques from the surge-induced synchronized switch harvesting on inductor (S3HI) family under strong electromechanical coupling and compared this performance with that of some established techniques. S3HI techniques exploit the surge voltage to overcome the voltage barrier of diodes for rectifiers and storage capacitor voltages. One of their features, revealed in a previous study on weakly coupled systems, is that they can harvest substantial energy from low-level vibrations. This feature is desirable for certain use cases. This study aimed to clarify whether this feature is applicable even when the coupling is strong. The performance of various established techniques and two representatives from the S3HI group was studied by formulating an approximate analytical solution and performing numerical simulations and experiments. The theoretical results were confirmed to be consistent, and the discrepancy between experimental and theoretical results was minor. These results clearly demonstrate that the techniques from the S3HI family can effectively harvest substantial energy from small-amplitude vibrations, even when the coupling is strong. Moreover, the performance advantage of S3HI methods is even greater when the coupling is strong.

A comparative analysis of parallel SSHI and SEH for bistable vibration energy harvesters

The present work focuses on ambient vibration energy harvesting. Specifically, this article deals with bistable piezoelectric energy harvesters (PEHs) which exhibits a wider bandwidth than linear oscillators. These complex systems require an energy extraction circuit (EEC) to rectify their voltage to supply power to autonomous sensors. This EEC needs to be optimized in order to increase the harvested power and even the bandwidth of PEHs. Because of the complex dynamics of bistable PEHs, there is a lack of simple and physically-insightful models in the literature that would allow the understanding and optimization of the extraction circuit. To address this issue, the present work derives closed-form models of a bistable PEH coupled to a passive and an active synchronous EEC: respectively the standard energy harvesting (SEH) circuit and the parallel synchronized switch harvesting on inductor (P-SSHI) circuit. Experimental measurements conducted on a custom bistable PEH demonstrate the validity of the proposed models with a relative error lower than 15% on the harvested power and the bandwidth. The proposed models allow to easily understand the influence of the P-SSHI circuit on the dynamics of a bistable PEH. Moreover, a comparison of the performance of the SEH and the P-SSHI circuits, valid for any bistable generator, is proposed. The latter shows that under low electromechanical coupling and low acceleration amplitude the P-SSHI circuit leads to multiply the maximum harvested power up to 4.3 compared to the SEH circuit, and the bandwidth by a factor of 2.3.

A Synchronized Switch Harvesting Rectifier With Reusable Storage Capacitors for Piezoelectric Energy Harvesting

Synchronized ac–dc rectifiers are widely used for energy rectification in piezoelectric energy harvesting (PEH), which have to employ a bulky inductor or some dedicated flying capacitors for high energy conversion efficiency. This article proposes a synchronized switch harvesting on shared capacitors (SSHSC) rectifier achieving synchronized voltage flipping without inductors or dedicated flying capacitors for PEH. The proposed SSHSC rectifier employs only three energy-storage capacitors with a specific capacitance ratio (3:3:1). These three capacitors mainly serve as storage capacitors; they can also be reused as flying capacitors for bias-flip operations. Thanks to the capacitor-sharing technique, this SSHSC rectifier takes a small volume and fewer I/O pads compared to prior SSHC rectifiers. This design was fabricated in a 180-nm BCD process, and the measured results show 78% voltage flipping efficiency and 7.58 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times$</tex-math> </inline-formula> power enhancement.

Bias-Voltage-SSHI Interface Circuit for Strong Coupling Piezoelectric Energy Systems

Compared with the standard extraction interface circuit (SEH), the harvested energy and harvested power of synchronized switching harvesting interface circuits (SSHI) and synchronous charge extraction interface circuit (SECE) cannot improve more effectively. This paper proposes a Bias-Voltage-SSHI Interface Circuit (BV-SSHI), consisting of a single peak voltage detection switch and a rectifier, to solve this problem. The proposed BV-SSHI improves the output voltage by biasing the voltage of the piezoelectric energy harvester and obtains similar harvested power as SSHI. Simulation results show that the BV-SSHI can obtain more harvested energy and harvested power than SEH under weak, medium, and strong coupling systems. Results show that the higher harvester's voltage and the larger phase difference cause the electrical restoring force (χV) to significantly weaken the vibration displacement, especially under strong coupling systems. Thus, the gain effect of the SSHI and SECE is weakened. The experimental results of the medium coupling systems show that the BV-SSHI can obtain 247.2% harvested energy and 121.2% maximum harvested power compared with SEH. The BV-SSHI can achieve at least 142.4% harvested energy and 100.3% maximum harvested power compared with what SSHI and SECE can achieve.

A self-powered extensible P–SSHI array interface circuit with thermoelectric energy assistance for piezoelectric energy harvesting

In this paper, a self-powered extensible parallel synchronized switch harvesting on inductor (EP-SSHI) interface is presented. The proposed interface addresses multiple piezoelectric transducers (PZTs) with arbitrary phase differences, while avoiding the conflict of accessing the single inductor simultaneously. In addition, the proposed interface enhances the voltage flipping performance of the PZT by incorporating thermoelectric energy assistance to increase its output power. Measurements demonstrate that the voltage flipping efficiency of the EP-SSHI with thermoelectric energy assistance (EP–SSHI–TEA) was increased to 53.33% with the assistance of 75 mV thermoelectric energy. Experimental results reveal that the proposed interface can effectively harvest energy from multiple PZTs with any phase difference. Compared with the conventional full bridge rectifier, the EP-SSHI achieves 3.63x power improvement and 6.42x load voltage range. Relative to other advanced circuits, the proposed interface strikes a superior balance between high output power and wide output voltage range while maintaining circuit simplicity and extensibility.

A Self-Powered DSSH Circuit with MOSFET Threshold Voltage Management for Piezoelectric Energy Harvesting.

This paper presents a piezoelectric (PE) energy harvesting circuit based on the DSSH (double synchronized switch harvesting) principle. The circuit consisted of a rectifier and a DC-DC circuit, which achieves double synchronized switch operation for the PE transducer in each vibration half-cycle. One of the main challenges of the DSSH scheme was precisely controlling the switch timing in the second loop of the resonant loops. The proposed circuit included a MOS transistor in the second loop to address this challenge. It utilized its threshold voltage to manage the stored energy in the intermediate capacitor per vibration half-cycle to simplify the controller for the DSSH circuit. The circuit can operate under either the DSSH scheme or the ESSH (enhanced synchronized switch harvesting) scheme, depending on the value of the intermediate capacitor. In the DSSH scheme, the following DC-DC circuit reused the rectifier's two diodes for a short period. The prototype circuit was implemented using 16 discrete components. The proposed circuit can be self-powered and started up without a battery. The experimental results showed that the proposed circuit increased the power harvested from the PE transducer compared to the full-bridge (FB) rectifier. With two different intermediate capacitors of 100 nF and 320 nF, the proposed circuit achieved power increases of 3.2 and 2.7 times, respectively. The charging efficiency of the proposed circuit was improved by a factor of 5.1 compared to the typical DSSH circuit.

Multimodal piezoelectric energy harvesting on a thin plate integrated with SSHI circuit: an analytical and experimental study

Multimodal piezoelectric energy harvesting can be achieved by integrating piezo-patch harvesters into plate-like structures available in marine, aerospace, and automotive applications. A synchronized switch harvesting on inductor (SSHI) interface as the harvesting circuit has been well studied for cantilever beams, considering the single vibration mode of the structure. However, integrating a two-dimensional electromechanical structure with a SSHI circuit for multimodal energy harvesting is missing in the literature. This paper evaluates the performance of the SSHI interface integrated with a piezoelectric energy harvester (PEH) on a plate-like host structure. The analytical solution is developed based on an equivalent impedance approach to predict the steady-state electrical response of the harvester as a closed-form solution. The experiments are conducted to validate the analytical solution for the system’s first and second vibration modes. The experimental results reveal that integration of SSHI to a plate-like harvester introduces a multi-switching behavior rather than a standard single-switching behavior. Due to the multimodal vibrational characteristics of the plate, the circuit switch is triggered several times at each half period of the vibration, which increases the energy dissipation of the circuit and thus reduces the output voltage. On the other hand, single switching at each half period of the vibration happens for lower piezoelectric voltage levels. This is the desired behavior of the SSHI circuit where the analytical prediction matches with the experimental data. Finally, the energy harvesting performance of the SSHI circuit is compared against the standard rectifier, showing 183% and 134% power output enhancement for the first and second vibration modes, respectively.

Performances of Multi-Configuration Piezoelectric Connection with AC-DC Converter in Low Frequency Energy Harvesting System

Harvesting energy by capturing vibration from low frequency energy have been explored extensively. In essence, a single piezoelectric transducer or an array of piezoelectric connections are used to convert kinetic energy into electrical energy in order to produce low frequency energy. In this paper, multi-configuration array piezoelectric connections are used to investigate the performances of different converter circuit types in low energy harvesting applications. This research utilized three pieces of circular piezoelectric sensor to test the combinations of array connection. There are four options for the piezoelectric sensor configuration: parallel (P), series (S), parallel-series (PS), and series-parallel (SP) while the full wave bridge rectifier (FWBR), parallel voltage multiplier (PVM), and parallel Synchronized Switch Harvesting on Inductor (P-SSHI) converter circuit are chosen AC-DC converter circuits. The system is assessed using a variety of load configurations, including 10 kΩ and 1 MΩ with a 3 Hz input frequency. In order to produce the highest possible output of collected power, the observation focuses on identifying the ideal combination of array piezoelectric connections with AC-DC converter. The result shows that 3-Parallel (3P) piezoelectric connection obtained a higher power output among the other types of array piezoelectric which was 5.97μW. The FWBR circuit generated the highest output power with 2.42μW for a combination of piezoelectric sensors array of 3P connection with the AC-DC converter.

A Self-Powered Rectifier-Less Series-Synchronized Switch Harvesting on Inductor (S-SSHI) Interface Circuit for Flutter-Based Piezoelectric Energy Harvesters

Energy harvesting from flow-induced vibrations has been a hot spot in recent years. In this study, a flutter-based piezoelectric energy harvester (FPEH) connected with a self-powered rectifier-less S-SSHI interface circuit is working at the limit cycle oscillation (LCO) state to efficiently harvest wind-induced vibration energy. First, an FPEH is designed, and the theoretical model is derived. The dynamic response of the FPEH is tested and measured in a wind tunnel, and results show that flutters start at the wind speed of 7.3 m/s. Meanwhile, the root mean square (RMS) output voltage increases with the increase of the wind speed which is also proved by the numerical simulations and the experiment. A self-powered optimized series synchronized switch harvesting on inductor circuit (SP-OSSHI) is proposed to efficiently harvest the electrical energy according to the output characteristic from flutter. The proposed circuit reduces the number of components and the circuit size by improving the positive and negative peak detection switches, which reduces the internal energy loss and thus improves the energy harvesting efficiency. The energy harvester is verified by the experiment, and a maximum output power of 36 μ W is obtained.

A new multi-piezoelectric input synchronized switch harvesting on inductor circuit

This paper has proposed a multi-piezoelectric input synchronized switch harvesting on inductor (MI-SSHI) circuit. The MI-SSHI circuit is mainly composed of an extreme detector unit and synchronized switch harvesting on inductor (SSHI) units. The extreme detector unit generates real-time control signals. Since the principle of SSHI circuit, each voltage on piezoelectric element can be switched at different instant in a period. In this paper, two piezoelectric element inputs are selected as an example. The experimental result validates that the output power of the MI-SSHI circuit is improved by 11.67%, in comparison to the traditional S-SSHI circuit.

Performance Optimization of SSHC Rectifiers for Piezoelectric Energy Harvesting

In the past decades, inductor-based synchronized switch harvesting on inductor (SSHI) rectifiers have been widely employed in many active rectification systems for piezoelectric energy harvesting. Although SSHI rectifiers achieve high energy extraction performance compared to passive full-bridge rectifier (FBR), the performance greatly depends on the inductor employed. While a larger inductor can achieve higher performance, the system form factor is also increased, which is counter to system miniaturization in many applications. To solve this issue, an efficient synchronized switch harvesting on capacitors (SSHC) rectifier was proposed recently. Instead of using large inductors, the SSHC rectifier employs on-chip or off-chip flying capacitors to achieve comparable or higher performance. In previous studies, the flying capacitors are chosen equal to the inherent capacitance of the piezoelectric transducer (PT) to achieve 1/3 voltage flipping efficiency <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$(\eta _{F})$ </tex-math></inline-formula> for a 1-stage SSHC rectifier and 4/5 flipping efficiency for a 8-stage SSHC rectifier. This brief presents that the flipping efficiency can be further increased to 1/2 for a 1-stage SSHC rectifier if the flying capacitor is chosen to be much larger than <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$C_{P}$ </tex-math></inline-formula> and the 4/5 flipping efficiency can be achieved by employing only 4 flying capacitors.

Self-Powered Synchronized Switching Interface Circuit for Piezoelectric Footstep Energy Harvesting.

Piezoelectric Vibration converters are nowadays gaining importance for supplying low-powered sensor nodes and wearable electronic devices. Energy management interfaces are thereby needed to ensure voltage compatibility between the harvester element and the electric load. To improve power extraction ability, resonant interfaces such as Parallel Synchronized Switch Harvesting on Inductor (P-SSHI) have been proposed. The main challenges for designing this type of energy management circuits are to realise self-powered solutions and increase the energy efficiency and adaptability of the interface for low-power operation modes corresponding to low frequencies and irregular vibration mechanical energy sources. In this work, a novel Self-Powered (SP P-SSHI) energy management circuit is proposed which is able to harvest energy from piezoelectric converters at low frequencies and irregular chock like footstep input excitations. It has a good power extraction ability and is adaptable for different storage capacitors and loads. As a proof of concept, a piezoelectric shoe insole with six integrated parallel piezoelectric sensors (PEts) was designed and implemented to validate the performance of the energy management interface circuit. Under a vibration excitation of 1 Hz corresponding to a (moderate walking speed), the maximum reached efficiency and power of the proposed interface is 83.02% and 3.6 mW respectively for the designed insole, a 10 kΩ resistive load and a 10 μF storage capacitor. The enhanced SP-PSSHI circuit was validated to charge a 10 μF capacitor to 6 V in 3.94 s and a 1 mF capacitor to 3.2 V in 27.64 s. The proposed energy management interface has a cold start-up ability and was also validated to charge a (65 mAh, 3.1 V) maganese dioxide coin cell Lithium battery (ML 2032), demonstrating the ability of the proposed wearable piezoelectric energy harvesting system to provide an autonomous power supply for wearable wireless sensors.

A novel switch control scheme for concise S–SSHI array interface with multiple piezoelectric energy harvesters

Energy harvesting array formed by multiple piezoelectric transducers (PZTs) can concurrently supply power to the load to improve the reliability. However, the switch control scheme adopted by the existing extensible parallel/series synchronized switch harvesting on inductor interfaces use either dual inductors or redundant peak detectors, both increasing the volume of the circuits. Hence, a novel switch control scheme using RC differential circuit (SCS-RCD) to simplify circuits for multiple piezoelectric harvesters is proposed in this article. It is implemented by reducing the number of switches required for the single piezoelectric block and improving the reuse of components. Extensible S–SSHI (ES-SSHI) circuit based on the SCS-RCD scheme with self-powered performance is proposed. Both theoretical simulation and experimental test demonstrate the effectiveness of the proposed SCS-RCD. The maximum harvested power of prototyped ES-SSHI circuit for single PZT is 3.76 times that of SEH circuit. The results show that the proposed scheme is an alternative option for multiple piezoelectric inputs.

Design and analysis of piezoelectric energy harvester for laser pointer

Obtaining energy from human body activities to power electronic equipment has broad application prospects. In this study, a piezoelectric energy harvesting system is designed to harvest energy from human finger rapping. The harvested energy can drive a laser lamp group to operate. The piezoelectric energy harvester uses a piezoelectric cantilever beam with a spring-mass block at the free end to obtain the kinetic energy of the finger operating a laser pen. The structure can produce considerable bending deformation under finger movement. At the same time, a dual-input synchronized switch harvesting on inductor circuit is designed to extract the charge generated by the piezoelectric beam when the spring-mass block at the free end is rapped and store it in the energy storage element. The charge and discharge of the energy storage element are controlled by a DC-DC management circuit. Experimental results show that the average harvesting power of the piezoelectric energy acquisition system is 169 μW, and its power density is 388.5 μW/cm3. When the spring-mass block is rapped for 8 s, the energy generated by the piezoelectric energy harvester lights the laser pen for 0.35 s.

A comprehensive analysis of piezoelectric energy harvesting from bridge vibrations

Piezoelectric energy harvesting from bridge vibrations has the potential to power wireless sensors used for bridge health monitoring. Often, it is necessary to store the harvested energy before it could be used to power the sensor intermittently. However, the behavior of the piezoelectric energy harvester (PEH) with nonlinear interface circuits for energy extraction and storage subject to realistic bridge vibrations has not been fully understood. This work performs a comprehensive analysis on the performance of the PEH subject to the measured railway bridge vibrations and compares the energy stored on a capacitor using four different interface circuits. Firstly, the dynamic characteristics of the railway bridge is analyzed. A cantilevered PEH is then designed and fabricated based on the dynamic characteristics of the bridge. Subsequently, four realistic energy extraction and storage interface circuits, namely, the standard energy harvesting (SEH), synchronized charge extraction (SCE), parallel synchronized switch harvesting on inductor (P-SSHI) and series SSHI (S-SSHI) circuits, are evaluated and compared when the PEH subject to the measured bridge vibrations. The influence of the storage capacitance and the 1st short-circuit natural frequency of the PEH on the stored energy with these four circuits is then discussed. An optimal storage capacitance exists in the systems based on SEH, P-SSHI and S-SSHI circuits. The system based on P-SSHI circuit has the highest efficiency on energy storage. This work provides a technical framework to develop the realistic energy harvesting and storage system for realization of self-powered bridge condition monitoring.

A Multistep Charge Extractions and Voltage Bias-Flip (MCEBF) Interface Circuit for Piezoelectric Energy Harvesting Enhancement

In piezoelectric energy harvesting (PEH), interface circuits using synchronous switch actions, including synchronized charge extraction (CE) and/or bias-flip (BF), can achieve much higher energy harvesting (EH) capability, compared with the standard energy harvesting (SEH) bridge rectifier. In this article, a multistep charge extraction and voltage bias-flip (MCEBF) interface circuit is proposed to further enhance the harvesting capability under weakly coupling conditions. The EH enhancement is realized by reducing the dissipation in CE with multiple CE actions and simultaneously enlarging the extracted energy with a BF action. MCEBF can also generate positive and negative voltage rails via buck-boost topology to supply power for double-rail devices. The optimal control method of MCEBF is theoretically derived. In our experiment, under constant deflection excitation, the best MCEBF case offers 487%, 95%, and 49% more harvested power, compared with SEH, synchronous electric charge extraction (SECE), and parallel synchronized switch harvesting on inductor (P-SSHI) interface circuits, respectively. MCEBF also keeps the benefit of load independence as SECE does under weakly coupling conditions.

Self-Powered Single-Inductor Rectifier-Less SSHI Array Interface With the MPPT Technique for Piezoelectric Energy Harvesting

Piezoelectric energy harvester (PEH) arrays are practical solutions to the low and unreliable power output of a single PEH. However, most PEH circuits are developed for addressing the one-channel ac input from a single PEH. In this article, an extensible rectifier-less synchronized switch harvesting on inductor (ReL-SSHI) array interface with the maximal power point tracking (MPPT) function to manage the multiple ac inputs from the PEH arrays is designed. The ac–dc conversion is performed by the ReL-SSHI topology with passive peak switches featured with self-powered characteristic and fast cold-start. Only one shared inductor is employed, greatly reducing the circuit volume and cost. The MPPT module for each channel is implemented by a simple envelope detector and an ultra-low power hysteresis controller and achieves continuous energy extraction by adapting the fractional normal-operation voltage method. A developed discrete array interface able to handle three PEHs effectively executes the MPPT for each channel with the uphill and downhill response speeds of 2.0 and 7.1 V/s, and a maximal MPPT efficiency of 97.1%. This circuit boosts the power output by 485% compared with that by the traditional full-bridge rectifier, around 33% higher than that from existing synchronous electric charge extraction array interfaces.

Comparison of Four Electrical Interfacing Circuits in Frequency Up-Conversion Piezoelectric Energy Harvesting.

Efficiently scavenging piezoelectric vibration energy is attracting a lot of interest. One important type is the frequency up-conversion (FUC) energy harvester, in which a low-frequency beam (LFB) impacts a high-frequency beam (HFB). In this paper, four interface circuits, standard energy harvesting (SEH), self-powered synchronous electric charge extraction (SP-SECE), self-powered synchronized switch harvesting on inductor (SP-SSHI) and self-powered optimized SECE (SP-OSECE), are compared while rectifying the generated piezoelectric voltage. The efficiencies of the four circuits are firstly tested at constant displacement and further analyzed. Furthermore, the harvested power under FUC is tested for different electromechanical couplings and different load values. The results show that SP-OSECE performs best in the case of a weak coupling or low-load resistance, for which the maximum power can be 43% higher than that of SEH. As the coupling level increases, SP-SSHI becomes the most efficient circuit with a 31% higher maximum power compared to that of SEH. The reasons for the variations in each circuit with different coupling coefficients are also analyzed.

Energy harvesting using integrated piezoelectric transducer in a composite smart structure for self-powered sensor applications

Self-sensing structures are tremendously needed in transport or energy applications. Nevertheless, structures are rarely designed in advance to harvest energy in realistic operational conditions, leading to sensing functions using most of the time batteries. Thus, this paper proposes a complete application of self-powered sensing using an integrated piezoelectric transducer on a representative composite structure, namely a smart composite reduced-model car. Based on an optimized self-powered Synchronized Switch Harvesting on Inductor circuit (SSHI) coupled with a complete electromechanical behavior study, up to 40[Formula: see text] W can be harvested on a resistive load of 3 M[Formula: see text] for a linear velocity of 12.5 km.h−1. This power allows supplying a temperature sensor and its wireless transmitter, whose data can be sent each 60s. Our functionalized car is a first step toward real industrial application cases and demonstrates the ability of the proposed method to enhance the energy harvesting process on an existing weakly coupled structure and use the vibrations as an energy source for relevant embedded microgenerators and associated self-powered sensors.