Principle Of Charge Balance Research Articles

Suppressing the P2‐O2 phase transition and Na+/vacancy ordering in Na0.67Ni0.33Mn0.67O2 by a delicate multicomponent modulation strategy

AbstractP2‐type Na0.67Ni0.33Mn0.67O2 is a promising cathode for sodium‐ion batteries with features of high specific capacity and air resistance, whereas its cycling stability and rate performance are dissatisfactory suffering from the disastrous P2‐O2 phase transition and Na+/vacancy ordering during sodium‐ion de/intercalation, which makes it an obstruction for future practical applications. Herein, a delicate multicomponent modulation strategy is proposed to tackle these two issues simultaneously, in which Li+ and Ti4+ are introduced to replace the Ni2+ and Mn4+, respectively, whereas the Na+ content is also designed according to the principle of charge balance. Consequently, the designed cathode (Na0.72Ni0.28Li0.05Mn0.57Ti0.10O2) can deliver an enchanting cycling stability of 80% at 1 C after 200 cycles along with a considerable rate performance of 82.7 mAh g−1 at 5 C. In situ X‐ray diffraction measurement demonstrates the destructive P2‐O2 phase transition is suppressed and converted into a P2‐Z phase transition with superior reversibility as well as smooth charge/discharge curves with better Na+/vacancy disordering. In addition, the full cell matched with hard carbon anode delivers an excellent energy density of 263.4 Wh kg−1 at 37.3 W kg−1, exhibiting great practicality. Our work presents a mean to rationally design the component of layered oxide cathode and achieve fabulous performance for sodium ion batteries.

Optimal impurity distribution model and experimental verification of variation of lateral doping termination

Based on the charge balance principle, an optimal impurity distribution variation of lateral doping termination (OID-VLD) and its ion-injection mask design method are proposed and verified. The comparative simulations and experiments show that OID-VLD can achieve better blocking ability and reliability than the traditional VLD (T-VLD). Vertical double diffusion MOSFET (VDMOS) with OID-VLD achieved breakdown voltage (BV) of 1684 V and passed the 168 hours 100 °C–110 °C–120 °C–125 °C high-temperature reverse bias (HTRB) test, while VDMOS with T-VLD obtained BV of 1636 V and failed in the 20 hours 120 °C HTRB test.

Tailoring the oxidation state of metallic TiO through Ti3+/Ti2+ regulation for photocatalytic conversion of CO2 to C2H6

The regulation and stabilization of the oxidation state to promote the conversion of CO2 to C2 fuel still faces many challenges. Based on the principle of charge balance, we creatively propose a co-doping strategy to adjust the surface oxidation state distribution of metallic catalysts. A TiO-based photocatalyst co-doped with Zn and N was synthesized by ammonia assisted one-step calcination method, named ZN-TC. XPS characterization shows that Zn and N adjust the valence states of adjacent Ti elements respectively, so that the surface of TiO maintains a relatively stable Ti3+/Ti2+ ratio. Under visible light irradiation, the material can catalyze CO2 into CO (324.11 μmol·g−1·h−1) and C2H6 (10.27 μmol·g−1·h−1) in the liquid phase. The selectivity of C2H6 reached 14.45%. When irradiated with near-infrared light, ZN-TC shows 100% CO selectivity because the photon energy is not enough to support the catalytic hydrogenation of CO2. Theoretical calculations and experiments proved that Zn and N elements mainly act on the B-1 band to regulate the Ti valence state. In-situ DRIFTS and in-situ Raman tests confirmed the function of oxidation state adjustment to promote the C-C coupling on the catalyst surface to produce ethoxy groups, which ultimately led to the production of C2H6.

Thermodynamic characteristics and mineral dissolution model of the H2O-CO2-CaCO3-Albite-SiO2 system in sedimentary basins

Diagenesis controls the formation, evolution, and distribution of deep-buried sandstone reservoirs in sedimentary basins. The essence of diagenesis is the transformation of substances between different phases (solid, gas and liquid phases) and the migration of materials transported by formation water. Fluids transport in deep-buried formations in sedimentary basins is generally slow, which lead the reaction system is in a near-equilibrium-to-equilibrium state. In this context, thermodynamics can be employed to calculate the solubility and characterize the occurrences of various minerals in different states, which can help reveal the genetic mechanism of secondary pores in the deep-buried rocks of sedimentary basins. In this study, we investigate the types and contents of particles in the aqueous solutions in the H2O-CO2-CaCO3-Albite-SiO2 system under different temperature and pressure conditions. Specifically, the Gibbs free energy of formation of minerals and gases are calculated based on the constant-pressure specific heat model; the apparent standard molal Gibbs free energy of different ions in fluids are computed using the HKF model; the equilibrium constants of different reactions are calculated according to the Gibbs function; the contents of different types of particles are computed based on the charge balance principle in the aqueous solution. The results show that the contents of various particles in the aqueous solution are mainly controlled by temperature and CO2 partial pressure, while they are rarely impacted by the total pressure. Different ions are demonstrated to have different responses to temperature changes. Specifically, types of Ca- and C-containing particles in the aqueous solution are closely related to temperature, while those of Al- and Si-rich particles are rarely changed as temperature varies. The CO2-rich fluid migration environment that results from hydrocarbon generation can be regarded as an open system for the dissolution of calcite, while it is a closed-to-semi-closed system for the dissolution of quartz and feldspar. The content of secondary pores is demonstrated to be determined by the solubility of various particles in the aqueous solution as well as the rate and duration of fluid migration, while the distribution patterns and ranges of secondary pores are controlled by responses of various particles in the solution to temperature and pressure changes.

ANTIGONE: A Programmable Energy-Efficient Current Digitizer for an ISFET Wearable Sweat Sensing System.

This article describes the design and the characterization of the ANTIGONE (ANalog To dIGital cONvErter) ASIC (Application Specific Integrated Circuit) built in AMS 0.35 m technology for low dc-current sensing. This energy-efficient ASIC was specifically designed to interface with multiple Ion-Sensitive Field-Effect Transistors (ISFETs) and detect biomarkers like pH, , and in human sweat. The ISFET-ASIC system can allow real-time noninvasive and continuous health monitoring. The ANTIGONE ASIC architecture is based on the current-to-frequency converter through the charge balancing principle. The same front-end can digitize multiple currents produced by four sweat ISFET sensors in time multiplexing. The front-end demonstrates good linearity over a dynamic range that spans from 1 pA up to 500 nA. The consumed energy per conversion is less than 1 J. The chip is programmable and works in eight different modes of operation. The system uses a standard Serial Peripheral Interface (SPI) to configure, control and read the digitally converted sensor data. The chip is controlled by a portable device over Bluetooth Low Energy (BLE) through a Microcontroller Unit (MCU). The sweat sensing system is part of a bigger wearable platform that exploits the convergence of multiparameter biosensors and environmental sensors for personalized and preventive healthcare.

A Constant Current Digital Control Method for Primary-Side Regulation Active-Clamp Flyback Converter

Constant current controlled flyback converter is widely used in low power applications for its simple structure and low cost. In order to further improve the output power and the efficiency, active-clamp flyback converter with soft-switching technique is always used. To avoid the nonlinearity and temperature drift of opto-coupler in the feedback circuit, a constant current digital control method is proposed for a primary-side regulation active-clamp (PSRAC) flyback converter in this article. Soft-switching technique is realized in discontinuous conduction modulation mode with a modified active-clamp technique. To compensate the nonlinearity of the secondary diode current with primary-side regulation, a new output current estimation algorithm is put forward based on the charge balance principle. The output current is predicted from primary current and the auxiliary winding voltage, and constant output current control is realized with primary peak current control method. The cost is low as only one low speed digital-to-analog converter, three comparators and a digital controller are required. The proposed control scheme was verified by a field-programmable gate array controlled 5.4-10.8 V/1.80 A PSRAC flyback converter. The output current accuracy is within in 1.2% in different input and output condition and the peak efficiency is improved by 3.6% after active-clamp technique is used.

Binary reaction behaviors of red mud based cementitious material：Hydration characteristics and Na+ utilization

Bayer red mud (RM) occupies a large amount of land, which excessive Na+ seriously damages groundwater resources. In this research, a RM based cementitious material (RMC) composed of RM and ordinary Portland cement (OPC) was developed. It is interesting to find that a binary reaction consisting of cement hydration and geopolymer reaction in RMC. The mechanical and Na+ consolidation rate of RMC were improved by the synergistic effect of binary reaction. The results indicated that the compressive strength of RMC is the highest and reaches 32.5R OPC when the mass ratio of CaO/(SiO2+Al2O3) is 1.37, and the Na+ leaching concentration is environmentally acceptable. The 7 days compressive strength of RM-based cementitious material No.2 (RMC2) can reach 93.80% of that of 28 days. As the predominant hydration products, cement hydration product (Ca5(SiO4)2(OH)2) and geopolymer (CaAl2Si2O8·2H2O and Na3Al3Si3O12·2H2O) were principally responsible for the strength development of RMC2 at 7 days. The optimal densification microstructure and [SiO4] polymerization structure was presented in RMC2. The supreme Na+ consolidation rate was 99.23% in RMC2 due to the cooperation of physical fixation and [Si(Al)O4] charge balance principle. This paper provides a fresh theoretical guidance for the utilization of RM and its Na+ in building materials.

Toward a Structural Model for the Aluminum Tellurite Glass System

Neutron diffraction, 27Al MAS NMR, and 27Al Double Quantum MAS NMR results are presented and analyzed to determine the local environments of the cations in a series of aluminum tellurite glasses. Total scattering results show that, within a maximum Te–O distance of 2.36 Å, tellurium exhibits a mix of [TeO3E] and [TeO4E] environments (E = electron lone-pair), with a linear reduction in the average tellurium–oxygen coordination number as Al2O3 is added to the glass. This is accompanied by a linear decrease in the average aluminum–oxygen coordination number as [AlO4] units form at the expense of [AlO6] units, while the fraction of [AlO5] units remains roughly constant. A consideration of the bonding requirements of the five structural units in the glass, [TeO3E], [TeO4E], [AlO4], [AlO5], and [AlO6], has allowed a direct quantitative relationship between tellurium–oxygen and aluminum–oxygen coordination numbers to be derived for the first time, and this has been successfully extended to the boron tellurite system. Double Quantum 27Al MAS NMR indicates that, in contrast to previous reports, the shortest Al...Al separations are significantly smaller (∼3.2 Å) than expected for a uniform distribution and there is a preference for [AlO6]–[AlO6] and [AlO4]–[AlO4] corner sharing polyhedra. These associations support a new structural model which successfully applies the principle of charge balance to describe the interaction of tellurium and aluminum and identifies and explains the clustering of [AlOn] polyhedra in the glass and their preferred associations. [AlO6] and [TeO4E] units dominate the network in TeO2-rich glasses and [AlO4]− units form to stabilize the [TeO3E]+ units as alumina is added to the glass.

Super Field Plate Technique That Can Provide Charge Balance Effect for Lateral Power Devices Without Occupying Drift Region

The super junction has been the most important concept for the design of power devices. However, there are still two problems when the conventional super-junction techniques are applied on lateral power devices: a large portion of the drift region is occupied by a p-type region, and the super junction techniques are not suitable for the gallium nitride-based high electron mobility transistor (GaN-HEMT). To solve the problems, a super field plate (SuFP) technique is proposed as a charge balance principle. Our analyses proved that the SuFP can provide a charge balance effect for a lateral double diffused MOS (LDMOS) without occupying the drift region. As a result, the LDMOS with SuFP has a better performance than the LDMOS with other charge balance realization techniques. Moreover, as a kind of field plate, the SuFP is also suitable for GaN-HEMT. Thereby, the proposed SuFP technique overcomes the two problems in conventional super-junction techniques and is significant for lateral power devices.

The Current Sharing Strategy of Three-Phase Series Capacitor Boost Converter Based on Charge-Balance Method

This article proposed a current sharing strategy for three-phase series capacitor boost converter for continuous conduction mode operation. The phase current can be automatically balanced based on the charge-balance principle, without any additional sensors or devices. And a uniform output voltage expression in full duty ratio range can be obtained. The mechanism of unbalanced current is disclosed. A current sharing strategy is proposed by adjusting the duty ratio in adjacent phase. The selection of capacitor and inductor is discussed via the analysis of topological operation and current deviation. The related characteristics are presented, including uniform output expression, continuous duty ratio operation, insensitivity to inductor parameters, loos analysis, and device stress. Experimental results on 100-W prototype are provided to confirm the feasibility of the proposed strategy.

Precipitation transformation of rare earth sulfate into chloride with p-dodecylphenoxy carboxylic acids

Methods for transforming rare earth (RE) sulfate into chloride mainly include extraction process with organophosphonic mono-acids or aliphatic acids and precipitation process with ammonium bicarbonate (NH4HCO3). In this paper, alkylphenoxy carboxylic acids(HAs) of p-dodecylphenoxy acetic acid (HA-I), p-dodecylphenoxypropanoic acid (HA-II) and p-dodecylphenoxybutyric acid (HA-III), which were liquid at room temperature were synthesized and characterized. The precipitation mechanisms of RE elements with the HAs were investigated and the HA/RE molar ratios of the solid complexes were determined as 3:1 by equi-molar series method which accord with the principle of charge balance. Applicability of HAs for the transformation of RE sulfate from concentrated sulfuric acid roasted RE concentrate into chloride via precipitation method was discussed. 100% HA-II was selected as the liquid organic precipitant without dilution of volatile solvent soracceleration of phase separation by phase-modifiers. The RE sulfate solution can be precipitated by HA-II after neutralization with liquid NaOH and stripped with concentrated HCl at room temperature. High concentration of RE chloride of 218.1 g/L with low residue of sulfate radical of 0.536 g/L was obtained. The residual organic precipitant in the raffinate solution was tested to be lower than 8 mg/L at 25 °C and the chemical oxygen demand (COD) in wastewater was less than 50 mg/L.

An Auxiliary-Parallel-Inductor-Based Sequence Switching Control to Improve the Load Transient Response of Buck Converters

In this paper, a sequence switching control (SSC) scheme based on an auxiliary parallel inductor is proposed to improve the transient performance of buck converters. The proposed SSC scheme introduces a small controlled inductor in parallel with the output inductor, so as to increase the inductor-current slew rate when it is activated during a load transient. Furthermore, an “ n + 1” sequence switching strategy is proposed to control the auxiliary parallel inductor. The proposed scheme divides the transient event into n + 1 periods. In the former n periods, the same small output voltage deviations are designed, while in the last period, a smaller deviation is done for a smooth transition from the transient to the steady state. The switching sequence is derived applying the capacitor–charge balance principle for each of n + 1 periods. For a given buck converter in the experiment, the settling time and the output voltage deviation of the proposed SSC scheme enhance more than 50% and 67%, respectively, over those of the time-optimal control for a 3-A load step.

A high sensitivity low-power capacitive front-end for insulin injection pens

A low-power 14-bits first order incremental Analog-to-Digital Converter (ADC) is presented. Based on the charge balancing principle, this switched-capacitor (SC) circuit integrates the input signal multiple times to reach the targeted resolution, linearity and noise performances. The sensitivities to non-ideal effects usually plaguing analog CMOS SC circuits, such as amplifier finite open-loop gain, offset, noise, parasitic capacitances and charge-injection of the switches are discussed. Their impact on the conversion accuracy and speed are evaluated, and corresponding design constraints are deduced. The ADC is implemented in an Application Specific Integrated Circuit (ASIC) in an AMS0.35 μm process and is aimed for a high accuracy capacitance sensing to monitor the insulin injection in pens for diabetics. A minimum resolution of 0.3 fF, proportional to a third of an injectable insulin unit is targeted. The ADC is made low-power, allowing thus to perform many measurements per day considering its implementation in a lithium battery powered injection pen system of six months' life cycle.

Sensorless predictive current control with a charge balance current estimator for boost converters based on discrete‐time model considering current ripple

The performance of a sensorless predictive current controlled boost converter is usually susceptible to the accuracy of the employed converter and current estimator models. Since the accuracy of conventional current estimator would be degraded due to parasitic parameter variations, a charge balance current estimator (CBCE) is proposed to overcome this issue. Its estimation of peak inductor current is based on the charge balance principle of output capacitor and characteristics of inductor current ripple. Only one parasitic parameter - capacitor equivalent series resistance (ESR) is used in CBCE. Furthermore, the capacitor ESR is also estimated together with output load by a proposed equivalent load estimation scheme which can improve the current estimation accuracy. Besides, to achieve a high dynamic performance digital control, a discrete-time model considering current ripple is developed, in which the ripple is taken into account rather than treats inductor current as a constant in each switching cycle. It can achieve a higher accuracy than conventional averaged model, especially in the high-frequency region. Finally, its effectiveness is verified by simulation and experiment results.

Simulation design of high Baliga's figure of merit normally-off P[sbnd]GaN gate AlGaN/GaN heterostructure field effect transistors with junction field plates

In this paper, we conducted a numerical analysis on novel Normally-off PGaN gate AlGaN/GaN heterostructure field effect transistors with junction field plates (JFP-HFET). The breakdown voltage (BV) was significantly improved with the introduction of the junction field plate (JFP), which can make a rectangular distribution of the electric field in the GaN channel between the gate and the drain. The highest BV of 1340 V of JFP-HFET could be achieved with the gate to the drain distance Lgd = 6 μm, the length of the P-type region of the JFP Lp = 5.8 μm, the thickness of the JFP Tj = 500 nm, the doping concentration of P-type region of the JFP Np = 1 × 1017 cm−3, and the Al fraction of the AlGaN JFP xAl = 0.25. The optimum parameters of the JFP-HFET were achieved by considering both the principle of charge balance and the practical fabrication of the III-V devices. The highest Baliga's figure of merit (BFOM) 1.2 GW/cm2 was obtained under the conditions of Lgd = 6 μm, Lp = 5.8 μm, Tj = 100 nm, Np = 6 × 1017 cm−3, and xAl = 0.3. CV, turn-on and turn-off processes revealed that the JFP-HFET showed better switching characteristics than that of the HFET with metal field plate.

Digital Sensorless Current Mode Control Based on Charge Balance Principle and Dual Current Error Compensation for DC–DC Converters in DCM

For discontinuous conduction mode (DCM) dc–dc converters with digital sensorless current mode (DSCM) control, an observed current error occurs, owing to a low-accuracy current observer. Moreover, a reference current error occurs due to a low-accuracy current controller or a finite dc gain of current loop. Conventionally, the observed current is compensated to increase current regulation accuracy, whereas the reference current error is neglected. However, for charge balance principle (CBP)-based DSCM (CBP-DSCM) control, this paper proves that the reference current should be compensated in a same quantity to that of observed current. Otherwise, single or unequal compensation leads to output voltage steady-state error. For this reason, a dual current error compensation strategy for CBP-DSCM control is proposed. It compensates the errors in a same quantity through a current error observer, which considers parasitics and calculates the current errors without approximation. To verify the proposed strategy, small-signal models with parasitics for both the converter and the controller are constructed by differential functions of key variables. Furthermore, converter stability is analyzed at typical operation condition, while the stability at various operation conditions is verified through robustness analysis. Finally, simulations and experimental results verify the analysis and the improved transient response of the converter.

A Rational Strategy To Construct a Neutral Boron Imidazolate Framework with Encapsulated Small-Size Au–Pd Nanoparticles for Catalysis

A series of 3D neutral boron imidazolate frameworks (BIFs) with octahedral metal centers were synthesized based on the charge-balancing principle. Au-Pd nanoparticles (NPs) with a mean size of 2.12 nm were then successfully obtained and encapsulated in these BIF structures through the simultaneous reduction of Au(3+)/Pd(3+) ions by B-H bonds of tridentate boron ligands. The very small sizes of these Au-Pd NPs are attributed to the pore confinement effect of BIFs. This work not only brings new methodology for the construction of neutral BIFs but also suggests a new strategy for loading smaller-sized bimetallic NPs into BIFs.

Enhancement of On-Resistance Characteristics Using Charge Balance Analysis Modulation in a Trench Filling Super Junction MOSFET

In Super Junction (SJ) MOSFETs, charge balance is the most important issue of the SJ fabrication process. In order to achieve the best electrical characteristics, such as breakdown voltage and on-resistance, the N-type and P-type drift regions must be fully depleted when the drain bias approaches the breakdown voltage, which is known as the charge balance condition. In conventional charge balance analysis, based on multi-epi process SJ MOSFETs, analytical model has only N, P pillar width and doping concentration parameter. But applying a conventional charge balance principle to trench filling process, easier than Multi-epi process, is impossible due to the missing of the trench angle parameter. To achieve much more superior characteristics of on-resistance in trench filling SJ MOFET, the appropriate trench angle is necessary. So in this paper, modulated charge balance analysis is proposed, in which a trench angle parameter is added. The proposed method is validated using the TCAD simulation tool.

A New Digital Control Algorithm for Dual-Transistor Forward Converter

In this paper, a new digital control algorithm is presented to improve the dynamic performance of the dual-transistor forward converter (DTFC) during a transient event. The algorithm uses a linear control scheme under the stable-state condition and the charge balance control scheme under the transient condition. Based on the principle of capacitor charge balance, the proposed algorithm predicts the switch over time to achieve optimal transient response for a DTFC, thus the minimal voltage derivation and recovery time are achieved when the load current has a step change. Compared with a conventional voltage mode controller, the proposed algorithm provides a much better dynamic performance. Furthermore, simulation and experiment results demonstrate the effectiveness of the algorithm.

Calculation of steady‐state solution of parallel‐connected buck converters with active current sharing and its parameter sensitivity

AbstractIn this paper, the effect of active current‐sharing control on the steady‐state operation of parallel‐connected buck converters is investigated. The system under study consists of N voltage‐mode‐controlled buck converters connected in parallel. Three kinds of active current‐sharing schemes are considered, namely, master–slave scheme with automatic master, master–slave scheme with dedicated master, and democratic scheme. Using the principle of charge balance, the mechanism of the operating point drift arising from active current sharing is examined. A general formulation of the steady‐state solution under active current sharing is derived. Moreover, detailed parameter sensitivity analysis is performed to evaluate the effect of parameters' variation on the operating point. The results from sensitivity analysis can be used to categorize parameters for facilitating practical design. Computer simulations are presented to verify the analytical results. Copyright © 2010 John Wiley & Sons, Ltd.