Interface Circuit Research Articles

Optimization of Suzuki Stack Circuit to Reduce Power Dissipation

Superconductor–semiconductor hybrid circuits can combine the benefits of the high-speed and low-power operation of single-flux quantum circuits and high integration densities of CMOS technology such as memory. The Suzuki stack, a type of Josephson latching driver/amplifier, is a widely used interface circuit in Josephson–CMOS hybrid memories. Due to the limited cooling power at cryogenic temperatures, the power dissipation is becoming an important concern, especially in large-scale systems. An optimization technique to significantly reduce the power dissipation of Suzuki stack circuits is proposed in this article. The proposed design can reduce the power dissipation by 30–70% while causing a voltage drop of 2–9% in the output voltage depending on the circuit parameter configuration. The tradeoffs between the power dissipation and output voltage characteristics are discussed. The proposed design can operate correctly within at least <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\pm$</tex-math></inline-formula> 20% of process parameter variations as demonstrated with extensive simulations.

A Neonatal Intravenous Monitor Prototype

An intravenous (IV) infusion monitoring system prototype H2neO has been developed for low drip rates (25–400 drops/hr) using a macrodrip infusion set (gtt/drop factor of 20 drops/ml), corresponding to low IV infusion rates (1–20 mL/hr). We demonstrate H2neO as an accurate, low-cost, gravity-based solution that can be used in low-resourced settings for neonates. H2neO uses an infrared emitter, detector, interface circuit, and signal processor implemented on an Arduino-based microcontroller to detect drops in a standard macrodrip infusion system. The infrared signal was preprocessed using a median filter to establish the baseline (no drop) condition and an 8.5% threshold to determine the initial presence of a drop in the IV drip chamber. Using signal preprocessing alone, the monitoring system underestimated the drip rate and flow rate by a maximum error of 1.33% and overestimated it with a maximum error of 0.91%. Using a <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">k</i> -means approach to classify drops into “normal” and “noisy” clusters and then considering drip rates estimated from only the “normal” cluster, underestimation errors improved at all infusion rates tested while overestimation errors improved at half of the infusion rates tested. The average detection error over 1–20 mL/h infusion rates was +/- 0.5% compared to +/- 1% for commercially available monitors and +1.8% for recent results reported in the literature. This approach, based on both signal preprocessing and analyzing the shape of each drop, is promising for implementation on a standalone, microcontroller-based drip-based IV infusion monitoring system for neonates and other populations, including adults.

New Insights for Parasitic Effects of Label-Free Biosensors Based on Capacitive Micromachined Ultrasonic Transducers

Capacitive micromachined ultrasonic transducers (CMUTs) are regarded as an attractive candidate in bio-applications such as imaging and molecule monitoring. However, the previous researches on biochemical sensing are mostly air-coupled application based on a CMUTs array because cell-to-cell mutual radiation and large motional loss in liquid environment are able to produce nonignorable noise. For a CMUTs cell, its characteristics (e.g., electrical, mechanical, and acoustic) are susceptible to parasitic effects owning to the physically capacitive dielectric dispersion, motional damping, and connection loss. Neglecting the parasitic effects on multidomain characteristics of CMUTs leads to significant robustness errors. Furthermore, finite element method (FEM) is not sufficient enough to model such parasitic effects when considering an integrated circuit interface and the evaluation of system responses. This article highlights a lumped element model (LEM) to analyze the behaviors of a label-free biosensor based on a single CMUTs cell directly operating in liquid. We successfully explore the performance of the biosensor with different types of parasitic effects in transient and frequency domains through LEM and FEM. The parasitic effects on mass loading of sensing layer and biomolecule such as deoxyribonucleic acid (DNA) and Immunoglobulin G (IgG) probes are predicted by LEM based on their surface mass densities. The proposed approach is capable of analyzing the variation’s margin of CMUTs-based biosensors to improve robustness for parasitic extraction in liquid.

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.

Toward a Gas Sensor Interface Circuit—A Review

With the development of science and technology, gas sensors have gradually expanded to many vertical fields. However, each application requires different technical requirements for gas sensors, such as low cost, small size, high sensitivity, high precision, and low power consumption. To create gas sensors that meet the performance requirements, researchers worldwide are working on solutions in fields such as sensitive materials, sensor arrays, and interface circuits. However, there are bottlenecks in the research of interface circuits, which limits the volume, power consumption, and intelligent design development of gas sensors. Therefore, this article reviews various types of gas sensors and interface circuits implemented with different technologies, analyzes their research significance in various areas, and provides ideas for future gas sensor research directions.

A Fully Integrated Low-Cost HF Multistandard RFID Reader SoC and Module for IoT Applications

The deployment and application of large-scale Internet of Things require a large number of 13.56-MHz radio-frequency identification (RFID) reader chips with lower cost. The existing RFID reader module needs to integrate multiple chips, such as microcontroller and high-frequency (HF) RFID reader IC on a single printed circuit board (PCB), which has the bottleneck of cost, power consumption, stability, and reliability. In order to adapt to the development trend of high integration, miniaturization, and low-power consumption of RFID reader, this article proposes a fully integrated low-cost RFID reader System-on-a-Chip (SoC), which integrates RF transceiver and analog circuit, baseband protocol processing, microcontroller, memory, and interface circuit into a single chip. The proposed reader IC supports communication protocols, such as ISO/IEC 14443 Type A and Type B, ISO/IEC 15693, and ISO/IEC 7816. The reader can communicate with contact and contactless IC cards. The modulation depth of the transmitter circuit ranges from 1% to 100%, and the maximum transmitting current is 126 mA. The receiver circuit is composed of I/Q clock generation, switched capacitor sampling circuit, variable gain amplifier (VGA) with filter, comparator, and pulse shaping circuit, which has good anti-noise performance. This 13.56-MHz RFID reader SoC is fabricated in a 180-nm CMOS process and is housed in a 64-pin QFP package. The total area is 8.75 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , including 1.47 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> for analog and RF circuits.

A Mode-Matched DRG Realized by Monolithic Integrated Interface Circuit Design

This article proposes a novel design method for the mode-matched disk resonator gyroscope (DRG) realized by the monolithic integrated interface circuit. The mode-mismatched dynamics model of DRG is simplified by introducing the analysis method of “slow” dynamics, the effect of mode mismatching is quantified, and the automatic mode-matched interface circuit is designed based on the analysis of the simplified model. The force-rebalance loop is designed based on a self-clock circuit that releases the chip from the dependence on external clocks, avoids the design of multipliers, analog-to-digital converters (ADCs), and digital-to-analog converters (DACs), and improves the integration of the chip. The highly integrated automatic mode-matching loop is realized by the designing of a quadrature loop and stiffness tuning loop on the basics of the mode-matching theory. The design method is applied to develop a monolithic integrated interface chip of DRG with an area of 4.2 mm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times4.3$ </tex-math></inline-formula> mm and power consumption of 90 mW. The DRG integrated circuit achieves the bias instability (BI) of 0.38°/h and the angle random walk (ARW) of 0.0354°/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\surd \text{h}$ </tex-math></inline-formula> within a full scale of ±300°/s, which provides a highly integrated circuit design scheme for DRG’s extensive application.

Design of BLDCM servo controller based on TMS320F28377D

To meet the application requirements of high-precision and fast-response thrust vector control from a solid rocket motor, a digital and integrated servo controller for four brushless direct current motors was designed and implemented. The controller hardware system proposed in this paper includes control circuit module and drive circuit module. The former mainly includes power conversion circuit, DSP system circuit, A/D circuit, SPI communication interface circuit, and SCI communication interface circuit. The later mainly includes three-phase full-bridge six-arm drive circuit and optocoupler isolation circuit. The three closed-loop control strategies of position, speed and current based on PID control algorithm are adopted, and the mathematical model of the motor is established in Matlab/Simulink for verification. The structure composition and working principle of the servo controller are briefly introduced, and the hardware design scheme, software workflow and control strategy are described in detail. Experimental results show that the response speed and control accuracy of the proposed controller meet the technical requirements.

Toward Nonlinear Galloping Energy Harvesting Interfaced With Different Power Extraction Circuits

While there has been a surge of study on nonlinear aeroelastic energy harvesting structures for enhanced wind power extraction, there is a gap in the literature on the integration of advanced power conditioning circuits with these mechanically sophisticated nonlinear structures. This article presents an investigation on the influence of different voltage processing interface circuits on the power generation performance in nonlinear galloping energy harvesting. Cubic hardening, cubic softening, and bistable configurations are studied. Their mechanical and electrical responses associated with the simple ac, standard dc, and synchronous charge extraction (SCE) circuits analyzed and compared. Results show that with the ac and standard dc circuits, the bistable and cubic hardening configurations are superior to the cubic softening configuration, generating comparably high power outputs with beneficially small displacements. The SCE circuit significantly boosts the power generation of the two monostable (cubic hardening and softening) harvester designs, but degrades the performance of the bistable design by trapping the oscillation within a single potential well over a large wind speed range. The findings form a baseline for future enhancement in the design of nonlinear aeroelastic wind power generators.

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.

Signal processing of capacitive force sensors installed in the foot of an anthropomorphic robot

Introduction: The force-moment sensing of the functional surfaces in robots based on compact capacitive force sensors can significantly improve interaction with the environment and humans. Capacitive force sensors provide high measurement accuracy and speed, but the electromagnetic interference can affect significantly the signal. When processing signals the influence of external noise must be taken into account, which increases the computation time. Purpose: To apply the developed interface circuit for processing signals from capacitive primary force transducers in a real-world robot. Results: Experimental verification of the developed solutions implied simulation of a step of the pedipulator of an anthropomorphic robot with the calculation of the coordinates of the center of pressure exerted on the foot with the four installed capacitive sensors. Software filtering and measuring capabilities of the microcontroller made it possible to achieve a signal-to-noise ratio of approximately 62.24 dB, which allows a closed-loop control system to function correctly. The average time for calculating the coordinates of the center of pressure on the foot with software filtering of the signal on the on-board computer of the robot was from 3.1 to 6.1 ms and meets the requirements for the sensory system of a walking robot. Practical relevance: The interface circuit allows to scale the number of connected primary force transducers, while software processing allows to normalize transducer signals by applying the calculated correction factors. Proposed solutions can be used in different robotic systems for real-time force measurement.

Energy management and nonlinear control strategy of hybrid energy storage system for electric vehicle

The energy management of hybrid energy storage system (HESS) and the nonlinear control strategy of the interface circuit are studied in this paper. In order to realize the reasonable distribution of load power between the battery and the supercapacitor, the energy management strategies (EMS) are used to decompose the load power required for electric vehicles under different driving cycle conditions, aiming at choosing an optimal power allocation strategy. Based on the local modeling, the global mathematical model of two bidirectional DC/DC converters under the HESS with active control topology is established, and the nonlinear control strategies are studied for the interface circuit and then the target controller is designed to realize the EMS. The current inner loop controller based on synergetic control theory is to track the battery current and supercapacitor current. The voltage outer loop controller takes power conservation as the criterion and adds the DC bus voltage PI controller to construct the Lyapunov function, where the connection between the DC bus voltage stability and the supercapacitor reference current is established. The supercapacitor replaces the battery to overcome the fluctuation of the DC bus voltage caused by the sudden change of the load power, maintaining the stability of the entire control system, and at the same time the case that the power allocated by the supercapacitor is consistent with the EMS is ensured. Two typical vehicle driving cycle conditions, IM240 and ECE-15, are selected to test the effectiveness of the current controller and the voltage controller. The experimental platform of a small-capacity HESS is built to conduct experimental verification. The simulation and experimental results show that the nonlinear controllers are feasible and have strong robustness and good adaptability under different driving conditions.

Piezoelectric Energy Harvesting at Circuit Resonance with Active Inductor (CRAI)

Background: Most of the proposed interface circuits use bulky inductors to enhance the key performance parameter i.e., power transfer efficiency. This sets constraints on the design of power conditioning circuitry for constrained IoT applications. Objective: To replace the bulky physical inductor with area optimized components suitable for integrated circuit realization with reduced silicon footprint for constrained applications like Internet-of-Things (IoT). Method: This paper presents the implementation of Circuit Resonance with Active Inductor (CRAI) technique based interface circuit design to deliver the maximum power generated from the Piezoelectric Energy (PEH) source to the load. Results: Compared to the conventional FWBR technique, the proposed CRAI technique improves ≈2X power delivered to the load. Conclusion: The proposed work presents an inductor-less interface circuit for PEH. An active inductor (gyrator) is used to induce ‘IP’ rejection at the PEH circuit resonant frequency to enhance the performance parameters. Since the proposed technique is based on active inductor, it can be easily fabricated in small integrated circuit (IC) packages, allowing integration with state-of-the-art constrained IoT applications. CRAI technique based on the rejection of ‘IP’ at the resonance using active inductor is first reported here. The proposed concept is non-adiabatic, but it could be used for constrained self-powered autonomous IoT applications and it could be of importance in guiding the design of new interface circuits for PEH.

A Self-Powered P-SSHI Array Interface for Piezoelectric Energy Harvesters With Arbitrary Phase Difference

Piezoelectric energy harvester (PEH) arrays are promising in many application scenarios. However, few interface circuits have been developed to manage the multiple ac inputs from PEHs. This article proposes an extensible parallel synchronized switch harvesting on inductor array interface scheme to realize a multiinput conversion from PEH arrays. We develop a split-inductor-capacitor topology that can extract electrical energy from multiple PEHs. The proposed circuit topology effectively handles the inductor access conflict in the cases of PEHs with close, identical, and opposite vibration phases, insensitive to ac input phase changes. For demonstrating the capability of dealing with multiple ac inputs from PEHs and the enhancement effect on power output, we construct and test a self-powered three-channel array circuit with the passive peak detection function. Excited by sinusoidal vibrations, our circuit effectively avoids the energy return and efficiently achieves the power combination of the three PEHs. Compared with the classic full-bridge circuit, the proposed circuit helps increase the power output by 4.8 times. Also, to show the universality of the circuit, the circuit's operation under various excitations istested and analyzed.

Monopolar Fault Reconfiguration of Bipolar Half Bridge Converter for Reliable Load Supply in DC Distribution System

This article proposed the concept of monopolar fault reconfiguration for bipolar dc distribution system realized with Bipolar Half Bridge (BiHB) converter. Monopolar fault reconfiguration oriented from bipolar high voltage direct current (HVdc) transmission grid. For dc distribution, the operation aim is to provide uninterrupted power supply to critical load under monopolar fault. It requires interfacing circuit with fault-tolerant capability as well as control design considering both bipolar and monopolar working mode. The proposed BiHB converter achieves mode switching by reconfiguring the converter switching pattern. Considering both monopolar and bipolar working mode, a bipolar modulation method is proposed for coordinate circuit design. Key influence factors relating to the transient voltage spikes have been identified, including the fault detection delay and the modulation method. Besides, to suppress the voltage spikes caused by monopolar fault, feed-forward compensation is adopted for smooth mode transition. The proposed BiHB converter and control strategy have been comparatively evaluated under fault protection and restoration. Uninterrupted power supply of load has been attained, in validation of the proposed monopolar fault reconfiguration concept.

A multi-channel power input automatic switching system based on power quality analysis

AbstactA Multi-channel power input automatic switching system used for mobile vehicle equipment based on power quality analysis is proposed in this paper. The basic measurement principle of power quality analysis is introduced first, based on this principle, a hardware implementation of the power quality analysis unit is fulfilled, including function diagram, measurement sampling circuit, and communication interface circuit. A communication interface protocol is designed based on CAN bus used for interaction between the multi-channels of power supply input. Based on the power quality analysis unit, the multi-channel power input automatic switching system is proposed driven by the priority of input channel determined by sharing the data of the power quality between the multi-channel power supplies.

Maximum power point tracking for a multi-layered piezoelectric heel charger with a levered mechanism toward impact-based energy harvesting.

The piezoelectric footstep energy harvester does not always work at its maximum power point when the external load is fixed, as the optimal load changes when the walking excitation alters. Thus, the harvesting efficiency is downgraded largely in real-life scenarios compared to in-lab experiments and theoretical or numerical predictions due to the mismatch between the actual load and the optimal load. To address this issue, the concept of Maximum Power Point Tracking (MPPT) is investigated in this paper and the circuit design is implemented for a multi-layered levered piezoelectric footstep energy harvester (heel charger). The proposed event-driven MPPT circuit interface with a customized buck converter aims to maximize the power gained from daily walking using the heel charger to power a fixed load, such as smart insole or shoes. The MPPT circuit design is conceptually simulated and then tested with the heel charger to further validate if it works at its maximum power point when the frequency of the input excitation alters. Results show that the extracted power from the heel charger connected to a fixed resistance load with MPPT implementation is improved up to 300% compared to the one without MPPT implementation in simulation and up to 180% in the experiment when connected to a fixed load. The difference between simulation and experimental results is due to the optimization of using voltage sources as the heel charger and the control signals (pulse width modulation) from the microcontroller in the simulation.

Design of the digital interface circuit system for MEMS gyroscope

In this paper, a digital closed-loop measurement and control system of MEMS vibrating silicon gyro is proposed, which includes the sensitive structure model of gyro and the design of interface circuit. Because of the high sensitivity and precision of the MEMS gyroscope under the condition of modal matching, the measurement and control circuit is established under the condition of modal matching. The system uses automatic gain control (AGC) to control the amplitude of self-excited oscillation of the driving loop, which has the characteristics of simple and quick start. First, the working principle of gyro sensitive structure is introduced and an interface circuit with digital drive and detection mode is designed. Second, a high precision one-bit sigma-Delta ([Formula: see text] analog-to-digital converter (ADC) is designed, and the signal-to-noise ratio (SNR) of the modulator is 102.5 dB at 10 kHz bandwidth. Third, a nonlinear multiplier is used in the driving loop to realize fast self-excited start-up of gyro, and a proportional integral (PI) controller is used in the self-excited loop to realize stable oscillation. Finally, Simulink is used to simulate and verify the sensitive structure model and the measurement and control system. The nonlinearity of the gyroscope is tested by experiment, and the well measurement and control precision of the gyro interface circuit is verified.

Crossing the Boundaries between Analogue and Digital

Given that they do not benefit from CMOS technology scaling, analogue integrated circuits are soon becoming a constraint in terms of the cost and performance of nanoscale integrated systems. This has led to some debate about whether analogue circuits are still useful in the era of digital technology. The usual reaction is that analogue circuitry will always be needed, if not everywhere, then at least in interface circuits that exchange data with physically analogue environments. The fact that matter is made up of discrete atoms and molecules, that basic physical quantities like electromagnetic radiation and electric charge are quantized, and even that information is transmitted as discrete pulses in biological systems all make the physical world less "intrinsically analog" than it first appears. In other words, it appears more and more plausible that the foundation for our regular analogue experiences is a distinct or digital one.

An epidermal electronic system for physiological information acquisition, processing, and storage with an integrated flash memory array.

Epidermal electronic systems that simultaneously provide physiological information acquisition, processing, and storage are in high demand for health care/clinical applications. However, these system-level demonstrations using flexible devices are still challenging because of obstacles in device performance, functional module construction, or integration scale. Here, on the basis of carbon nanotubes, we present an epidermal system that incorporates flexible sensors, sensor interface circuits, and an integrated flash memory array to collect physiological information from the human body surface; amplify weak biosignals by high-performance differential amplifiers (voltage gain of 27 decibels, common-mode rejection ratio of >43 decibels, and gain bandwidth product of >22 kilohertz); and store the processed information in the memory array with performance on par with industrial standards (retention time of 108 seconds, program/erase voltages of ±2 volts, and endurance of 106 cycles). The results shed light on the great application potential of epidermal electronic systems in personalized diagnostic and physiological monitoring.