Showing papers on "Voltage published in 2000"

A comprehensive study of neutral-point voltage balancing problem in three-level neutral-point-clamped voltage source PWM inverters

Abstract: This paper explores the fundamental limitations of the neutral-point voltage balancing problem for different loading conditions of three-level voltage source inverters. A new model in the DQ coordinate frame utilizing current switching functions is developed as a means to investigate theoretical limitations and to offer a more intuitive insight into the problem. The low-frequency ripple of the neutral point caused by certain loading conditions is reported and quantified.

The Voltage Sensor in Voltage-Dependent Ion Channels

Abstract: In voltage-dependent Na, K, or Ca channels, the probability of opening is modified by the membrane potential. This is achieved through a voltage sensor that detects the voltage and transfers its energy to the pore to control its gate. We present here the theoretical basis of the energy coupling between the electric field and the voltage, which allows the interpretation of the gating charge that moves in one channel. Movement of the gating charge constitutes the gating current. The properties are described, along with macroscopic data and gating current noise analysis, in relation to the operation of the voltage sensor and the opening of the channel. Structural details of the voltage sensor operation were resolved initially by locating the residues that make up the voltage sensor using mutagenesis experiments and determining the number of charges per channel. The changes in conformation are then analyzed based on the differential exposure of cysteine or histidine-substituted residues. Site-directed fluorescence labeling is then analyzed as another powerful indicator of conformational changes that allows time and voltage correlation of local changes seen by the fluorophores with the global change seen by the electrophysiology of gating currents and ionic currents. Finally, we describe the novel results on lanthanide-based resonance energy transfer that show small distance changes between residues in the channel molecule. All of the electrophysiological and the structural information are finally summarized in a physical model of a voltage-dependent channel in which a change in membrane potential causes rotation of the S4 segment that changes the exposure of the basic residues from an internally connected aqueous crevice at hyperpolarized potentials to an externally connected aqueous crevice at depolarized potentials.

Nonvolatile semiconductor memory device

Abstract: PURPOSE: A nonvolatile semiconductor memory device is provided to reduce current consumed at a sense amplifier when amplifying a small signal induced to a bit line by that a cell capacitor and a bit line capacitor hold an electric charge in common by precharging a bit line in a semiconductor device using a ferroelectric capacitor to a half of the level of a power voltage and increase amplifying function by decreasing the coupling effect by a gate capacitance of a sense amplifier CONSTITUTION: The memory device includes a sense amplifier(S1), a memory cell(M1), a plate driver(F1), a reference voltage generating portion(R1), a half power voltage generating device and a precharging circuit(P1) The sense amplifier senses a difference of a voltage between a bit line(BL) and a bit line bar(BLB) and amplifies the difference The memory cell, in which a switching transistor and a ferroelectric capacitor are in series connected, stores a data The plate driver is connected to the ferroelectric capacitor and drives a plate line applying a voltage to the ferroelectric capacitor The reference voltage generating portion generates a reference voltage necessary for sensing and amplifying The half power voltage generating device, to which a level of a power voltage is inputted, outputs a level of a half power voltage The precharging circuit supplies the half power voltage inputted from the half power voltage generating device to the bit line and bit line bar in response to a signal for controlling a bit line

Virtual flux based direct power control of three-phase PWM rectifiers

Abstract: In this paper, direct power control (DPC) of three-phase pulsewidth-modulated rectifiers without line voltage sensors is presented. The new system is based on virtual flux (VF) estimation. Theoretical principles of this method are discussed. The steady-state and dynamic behavior of VF-DPC are presented that illustrate the operation and performance of the proposed system compared to a conventional DPC method. Both strategies are also investigated under unbalance and predistorted grid. It is shown that the VF-DPC exhibits several advantages, particularly providing sinusoidal line current when the supply voltage is not ideal. Test results show the excellent performance of the proposed system.

Battery pack including input and output waveform modification capability

Abstract: A battery pack includes a plurality of electrochemical cells and a control circuit. The battery pack provides power to a tool in the form of a pulse width modulated waveform. The plurality of electrochemical cells provide a total output voltage. The control circuit is coupled to the plurality of electrochemical cells and receives a trigger signal from the tool. In response to the trigger signal, the control circuit determines whether a pulse width of the pulse width modulated waveform requires adjustment. Additionally, the control circuit can be configured to receive an indication of the total output voltage. In this case, the control circuit determines whether the pulse width of the pulse width modulated wavefrom requires adjustment based on the level of the total output voltage.

Small signal stability for parallel connected inverters in stand-alone AC supply systems

Abstract: This paper presents a small-signal analysis for parallel-connected inverters in stand-alone AC supply systems. The control technique of the inverters is based on frequency and voltage droops, which depends on the local variable measurements and does not need control interconnections. Simulation and experimental results show that the system is well represented by the small-signal model. Some root locus plots for the system are provided, which make the stability studies and design easier.

Pumping liquids using asymmetric electrode arrays

Abstract: Following a general symmetry argument, I suggest using locally asymmetric electric geometries to pump liquid in channels or drive droplets on surfaces. This strategy, which requires no global gradient in the pumping direction, should be of interest for microfluidic devices and micro-electro-mechanical systems. A practical realization consists in using polar periodic arrays of electrodes addressed by an ac voltage difference. A simple electro-osmotic model provides an estimate of the pumping velocities achievable.

Fluid flow induced by nonuniform ac electric fields in electrolytes on microelectrodes. II. A linear double-layer analysis

Abstract: Frequency-dependent fluid flow in electrolytes on microelectrodes subjected to ac voltages has recently been reported. The fluid flow is predominant at frequencies of the order of the relaxation frequency of the electrode-electrolyte system. The mechanism responsible for this motion has been termed ac electro-osmosis: a continuous flow driven by the interaction of the oscillating electric field and the charge at the diffuse double layer on the electrodes. This paper develops the basis of a theoretical approach to this problem using a linear double layer analysis. The theoretical results are compared with the experiments, and a good correlation is found.

Enhanced semi-passive damping using continuous switching of a piezoelectric device on an inductor

Abstract: The SSD technique proposed here addresses the problem of resonance damping on a mechanical structure. SSD stands for Synchronized Switch Damping. Apart from active techniques, passive ones consist in connecting a piezoelectric insert attached to the structure to a passive electric network in which the energy generated by the piezoelectric inserts is degraded. In the semi passive approach, the piezoelectric inserts are continuously switched from open circuit to short circuit synchronously to the structure motion. Due to this switching mechanism, a phase shift appears between the piezoelectric strain and the resulting voltage, thus creating energy dissipation. For the new technique proposed here, instead of discharging the piezoelectric inserts during a brief short circuit, they are connected on a small inductor, allowing the inversion of the voltage and then released to open circuit. In this case the voltage amplitude is optimized and is 90 degrees out of phase with the motion then enhancing the damping mechanism. The technique is applicable at any frequency without the need for a large tuned inductor, especially for low frequency applications. There is no need for external power supply unless for the low power circuitry of the switch device. The implementation of the switch drive with a very cheap micro-controller is described. Experimental results measured on cantilever beams made with different materials are proposed. Damping ability ranges from 6 dB on a very viscoelastic epoxy beam to nearly 20 dB on a steel beam. Harmonic excitation and transient results are both proposed and compared. Finally, an electromechanical model is proposed, giving an interpretation of the damping mechanism. Theoretical predictions are in good agreement with the experiments.

Selection and stability issues associated with a navy shipboard DC zonal electric distribution system

Abstract: The US Navy is currently investigating the implementation of a DC zonal electric distribution system (DC ZEDS) for the next generation of surface combatant. In replacing the current AC radial distribution system, significant gains can be realized in terms of survivability, weight, manning and cost. DC ZEDS is predicated on having starboard and port DC buses feeding electrical zones delineated by watertight bulkhead compartments. The main bus DC voltage is stepped down within the zone and then converted to three-phase AC and lower voltage DC by additional power converters. Due to the large interconnection of tightly-regulated power converters in a stiffly-connected system, negative input impedance effects create the possibility of unwanted resonances. In this paper, the authors describe the rationale for the DC zonal system, characterize the stability issues, and discuss fault detection and load shedding problems.

Pumping of water with ac electric fields applied to asymmetric pairs of microelectrodes.

Abstract: Bulk fluid flow induced by an ac electric potential with a peak voltage below the ionization potential of water is described. The potential is applied to an ionic solution with a planar array of electrodes arranged in pairs so that one edge of a large electrode is close to an opposing narrow electrode. During half the cycle, the double layer on the surface of the electrodes charges as current flows between the electrodes. The electrodes charge in a nonuniform manner producing a gradient in potential parallel to the surface of the electrodes. This gradient drives the ions in the double layer across the surface of the electrode and this in turn drags the fluid across the electrode surface. The anisotropic nature of the pairs of electrodes is used to produce a net flow of fluid. The flow produced is approximately uniform at a distance from the electrodes that is greater than the periodicity of the electrode array. The potential and frequency dependence of this flow is reported and compared to a simple model. This method of producing fluid flow differs from electrical and thermal traveling-wave techniques as only a low voltage is required and the electrode construction is much simpler.

The Field Stop IGBT (FS IGBT). A new power device concept with a great improvement potential

Abstract: By a vertical shrink of the NPT IGBT to a structure with a thin n/sup -/ base and a low doped field stop layer a new IGBT can be realized with drastically reduced overall losses. Especially the combination of the field stop concept with a trench transistor cell results in the almost ideal carrier concentration for a device with minimum on state voltage and lowest switching losses.

Effects of pulsed electric fields on cell membranes in real food systems

Abstract: High frequency current and voltage measurements were used to determine passive electrical properties, such as the polarization effect at intact membrane interfaces and field-induced electropermeability changes in the cellular materials during direct current pulses. The time sequence of the electropermeabilization at the level of the cell membrane showed a similarity to the breakdown phenomena observed in cell systems (potato, apple and fish tissues, as well as plant cell suspension cultures) when a single pulse with critical or supercritical field amplitude is applied. A slight membrane breakdown phenomenon occurred in the first few microseconds after the initiation of the pulse at a critical electric field strength of 150–200 V/cm. Significant membrane breakdown was observed when the field strength of the electric pulses applied directly on the cell systems was in the range of 400–800 V/cm. At various field intensities, the electrical potential across a cell membrane reached a critical value of approximately 0.7–2.2 V. The initiation of conductive channels across the membrane occurred within nanoseconds during the charging process of the membrane, whereas the formation of a high-conductance membrane due to pore expansion took place within a few microseconds. The application of a single pulse, even with supercritical field amplitude, does not necessarily cause an irreversible membrane rupture. The insulating properties of the cell membrane can be completely recovered within several seconds after the termination of the pulse. The biological and engineering aspects of the membrane permeabilization are discussed in this paper. These data are utilized as the basis for the design and optimization of high-intensity pulsed electric field applications in the areas of food science and biotechnology.

Ultrahigh strain response of field-actuated elastomeric polymers

Abstract: Extremely large strains were achieved with elastomeric polymer films that are subject to high electric fields. The films were coated on both sides with complaint electrode material. When voltage was applied, the film compressed in thickness and expanded in area. The strain response is dominated by the electrostatic forces produced by the charges on the compliant electrodes. Actuated strains up to 117% were demonstrated with silicone elastomers, and up to 215% with acrylic elastomers. A key to achieving these large strains is to introduce a high prestrain to the film. Specific energy densities were much greater than those of other field-actuated materials. Because the response is electrostatic in nature, the actuation mechanism is predicted to be fast. Response speeds in excess of 2000 Hz have ben demonstrated in silicones. Acrylic response speeds are more than an order of magnitude slower, although the reason for this difference is not yet known. Measurement of material viscoelastic and electrical properties predicts that high efficiencies (> 80%) may be achieved with efficient driver circuits. A variety of actuators, including electrooptical devices, diaphragm pumps, and muscle like linear actuators, have been demonstrated with these materials, suggesting that this technology is well suited to small-scale electromechanical devices and robots.

Controlled electroporation and mass transfer across cell membranes

Abstract: Electroporation is performed in a controlled manner in either individual or multiple biological cells or biological tissue by monitoring the electrical impedance, defined herein as the ratio of current to voltage in the electroporation cell. The impedance detects the onset of electroporation in the biological cell(s), and this information is used to control the intensity and duration of the voltage to assure that electroporation has occurred without destroying the cell(s). This is applicable to electroporation in general. In addition, a particular method and apparatus are disclosed in which electroporation and/or mass transfer across a cell membrane are accomplished by securing a cell across an opening in a barrier between two chambers such that the cell closes the opening. The barrier is either electrically insulating, impermeable to the solute, or both, depending on whether pore formation, diffusive transport of the solute across the membrane, or both are sought. Electroporation is achieved by applying a voltage between the two chambers, and diffusive transport is achieved either by a difference in solute concentration between the liquids surrounding the cell and the cell interior or by a differential in concentration between the two chambers themselves. Electric current and diffusive transport are restricted to a flow path that passes through the opening.

Method and apparatus for charging a battery

Abstract: An apparatus for charging a battery includes a first electrical connection adapted to connect to a positive terminal of the battery and a second electrical connector adapted to connect to a negative terminal of the battery. An electrical charging source couples to the first and second electrical connectors to charge the battery. Voltage measurement circuitry couples to the first and second electrical connectors and responsively provides a voltage output related to voltage across the battery. Current measurement circuitry also couples to the first and second electrical connectors and responsively provides a current output related to electrical current through the battery. State of charge measurement circuitry responsively provides a state of charge output as a function of the voltage output and the current output.

High voltage vertical conduction superjunction semiconductor device

Abstract: A high voltage vertical conduction semiconductor device has a plurality of deep trenches or holes in a lightly doped body of one conductivity type. A diffusion of the other conductivity type is formed in the trench walls to a depth and a concentration which matches that of the body so that, under reverse blocking, both regions fully deplete. The elongated trench or hole is filled with a dielectric which may be a composite of nitride and oxide layers having a lateral dimension change matched to that of the silicon. The filler may also be a highly resistive SIPOS which permits leakage current flow from source to drain to ensure a uniform electric field distribution along the length of the trench during blocking.

Fast power grid simulation

Abstract: The decrease in feature size and added chip functionality in large sub-micron integrated circuits demand larger grids for power distribution. Since power grids are performance limiting factors [1, 2, 3], then their analysis is important in order to (1) predict the performance and (2) improve the performance if necessary. Thus, there is a clear need for new efficient, in terms of both execution time and memory, techniques for power grid analysis.This paper discusses the modeling of power grids and proposes a new PDE-like multigrid method for the simulation of power grids. The proposed method is very efficient and suitable for both DC and transient simulation of power grids.

Discharge lamp lighting device

Abstract: PROBLEM TO BE SOLVED: To allow a circuit for lighting a fluorescent lamp to inhibit source voltage fluctuation and fluctuation of light rays caused by fluctuation of ambient temperature. SOLUTION: A power detecting part 5 detects via a resistance R1 a voltage signal proportional to a current in a fluorescent lamp and detects via voltage dividing resistances R3, R4 a voltage signal proportional to the voltage of the fluorescent lamp, and the instantaneous values of the two voltage signals at every moment are multiplied via a multiplying circuit U41, with this multiplication output smoothed via a low-pass filter U42 to detect the average power value S5 of the fluorescent lamp. Next, a control circuit 4 compares the average power value S5 with a reference voltage value Vref via an error amplifier U2, and controls the drive circuit U3 of an inverter circuit 3 via a voltage controlled oscillator U1 so that the difference therebetween becomes zero, thereby varying the switching frequencies of switching elements T1, T2.

A distributed monitoring and protection system for a distributed power network

Abstract: A distributed monitoring and protection system for a distributed power network. The system includes a plurality of high-speed measuring units (MUs), wherein each MU is coupled to a power line to measure values of electrical parameters of the power line. Electrical parameters, such as current, voltage, power and frequency are measured by the MUs. The MUs communicate with a control unit (CU) over a high-speed communications network. The CU includes a processor executing algorithms for evaluating the measured parameters to determine the status of the power network and the MUs. The processor also executes fault detection and isolation by comparing the measured values against predetermined threshold values. When a fault is detected by the CU, protective action, such as tripping of a circuit breaker, may be initiated by the CU directly or by transmitting the tripping command over the high speed data network to a local MU. The local MU may then trip the circuit breaker. The availability at the CU of concurrent measurements from the plurality of MUs enables improved coordination and sequencing of protective actions.

Josephson voltage standards

Abstract: This paper reviews the development and use of Josephson voltage standards over the last 30 years, including classical dc standards, programmable standards based on binary weighted arrays, pulse-driven delta–sigma standards for ac wave-form synthesis, and single-flux-quantum voltage multipliers.

Method and apparatus for electronically evaluating the internal temperature of an electrochemical cell or battery

Abstract: A testing device applies time-varying electrical excitation to a cell or battery (20) and senses the resulting time-varying electrical response. Computation circuitry (50) within the device uses voltage and current signals derived from the excitation and response signals as inputs and computes values of elements of an equivalent circuit representation of the cell or battery (20). The internal temperature of the cell or battery (20) is calculated from the value of the time constant of a particular parallel G-C subcircuit of the equivalent circuit. The battery's (20) internal temperature is then either displayed to the user, used to apply appropriate temperature corrections to other computed quantities, used to detect thermal runaway, and/or used to control an external process such as charging of the battery (20).

Optimization of VDD and VTH for low-power and high speed applications

Abstract: Closed-form formulas are presented for optimum supply voltage (VDD) and threshold voltage (VTH) that minimize power dissipation when technology parameters and required speed are given. The formulas take into account short-channel effects and the variation of VTH and temperature. Using typical device parameters, it is shown that a simple guideline to optimize the power consumption is to set the ratio of maximum leakage power to total power about 30%. Extending the analysis, the future VLSI design trend is discussed. The optimum VDD coincides with the SIA roadmap and the optimum VTH for logic blocks at the highest temperature and at the lowest process variation corner is in the range of 0V~0.1V over generations.

High-efficiency multiple-output DC-DC conversion for low-voltage systems

Abstract: This versatile power converter controller provides dual outputs at a fixed switching frequency and can regulate either output voltage or target system delay (using an external L-C filter). In the voltage regulation mode, the output voltage is monitored with an analog-digital (A/D) converter, and the feedback compensation network is implemented digitally. The generation of the pulsewidth modulation (PWM) signal is done with a hybrid delay line/counter approach, which saves power and area relative to previous implementations. Power devices are included on chip to create the two independently regulated output PWM signals. The key features of this design are its low-power dissipation, reconfigurability, use of either delay or voltage feedback, and multiple outputs.

A thyristor controlled series compensator model for the power flow solution of practical power networks

Abstract: A new and comprehensive load flow model for the thyristor controlled series compensator (TCSC) is presented in this paper. In this model the state variable is the TCSC's firing angle, which is combined with the nodal voltage magnitudes and angles of the entire network in a single frame-of-reference for a unified iterative solution through a Newton-Raphson method. Unlike TCSC models available in the open literature, this model takes account of the loop current that exists in the TCSC under both partial and full conduction operating modes. Also, the model takes proper care of the resonant points exhibited by the TCSC fundamental frequency impedance. The Newton-Raphson algorithm exhibits quadratic or near-quadratic convergence characteristics, regardless of the size of the network and the number of TCSC devices.

A high force low area MEMS thermal actuator

Abstract: This paper presents a new type of MEMS (micro-electromechanical systems) actuator consisting of an array of in-plane micro-fabricated thermal buckle-beam actuators. The technology used in MEMS actuators is typically magnetic, electrostatic or thermal. Magnetic actuators may require special materials in the fabrication process while electrostatic actuators typically require high voltages, large chip areas and produce very low forces. Thermal actuators have seen some use in MEMS applications, the most popular being the pseudo-bimorph that relies on differential expansion of a cold and hot arm to cause it to bend in-plane (parallel to the substrate). These thermal actuators typically generate on the order of a few micro-Newtons each but can be combined for larger forces by linking with small tendons. A disadvantage of this type of actuator is that it moves in an are where most desired movements are linear. Also, when combined in an array, the linking tendons consume much of the energy in bending them. Also, arrays of these can still occupy a fairly large chip area. The electro-thermal actuator described here resembles a chevron where an array of buckle-beams are packed close together and link two common anchored arms with a movable third arm. Arrays can be made within a single released micromachined layer and generate many mN of force. Additional actuators can be arrayed with no coupling penalty and occupy much less area that an equivalent pseudo-bimorph actuator. Preliminary tests indicate that a 450/spl times/120 /spl mu/m array consumes 240 mW of power, deflection up to 14 /spl mu/m and can produce many milli-Newtons. A chip of actuator geometry variations and different applications has been fabricated and tested.

System and method for determining battery state-of-health

Abstract: A system and method for accurate and in real time determination of factors relating to the state of health of a storage battery. The system measures the values of battery temperature, voltage and current flow into and out of the battery. This data is multiplexed into a computer and the battery's internal resistance (IR), polarization resistance (PR), state of charge (SOC) and its cold cranking amp (CCA) capability are computed and displayed. The presence of shorted and mismatched cells also can be determined and displayed. The state of health of the battery is related to these displayed measured values and calculated factors which are made known to the user of the battery.

Multi-phase and multi-module power supplies with balanced current between phases and modules

Abstract: A multi-phase power supply utilizes a current sensor including a sensor inductor winding connected in parallel with a filter inductor winding at the output of each phase for sensing the phase currents and balancing the current by adjusting the duty cycle of each phase through feedback control. In addition, in a multi-module power supply configuration, current between power supply modules is balanced through use of the same current sensor and current sharing technique. Each phase of the power supply includes at least one input power source and a current sensor. The sensor inductor winding and the filter inductor winding have the same number of turns and are wound about a magnetic core also present at each phase. A differential amplifier at each phase senses and amplifies any voltage difference between the outputs of the sensor inductor winding and the corresponding filter inductor winding. A current-sharing bus is formed between each of the phases, carrying the summed and averaged outputs from all the differential amplifiers. A feedback correction circuit at each phase utilizes the voltage on the current-sharing bus as a reference to control a pulse width modulator in adjusting the duty cycle of the corresponding phase, thereby balancing the load current among the phases. In a multi-module, multi-phase power supply, the current-sharing bus and a voltage-sharing bus are extended between each module and the phases of each module to achieve the same current balancing between all phases and modules.

Design of a contactless battery charger for cellular phone

Abstract: In this paper, the design of a contactless charger for a 3.3 W lithium-ion battery of a cellular phone is presented. In this charger, the primary core of the transformer is in the charger unit and the secondary core is in the telephone. The gap (3 mm) between them is the thickness of the two plastic cases. The transformer core design for the maximum coupling coefficient and the maximum magnetizing inductance with the size constraint on the secondary side is presented. A half-bridge series resonant converter is used to compensate the leakage inductance and to achieve ZVS operation. Voltage gain, current gain analysis, and design procedure are presented. For the battery charging control, an infrared LED is used and its performance is verified from the hardware experiments.

Hybrid electric vehicle

Abstract: A hybrid electric propulsion system for powering a vehicle using a natural fuel engine and an electric motor. The hybrid electric vehicle is comprised of a drive train; an electric motor for driving the drive train; an auxiliary power unit (APU); an electric energy storage system electrically coupled to the electric motor; and wherein the auxiliary power unit and the electric energy storage system provide energy for powering the vehicle. An electric bus is directly connected to both the auxiliary power unit and the electric energy source and the voltage across the electric bus is substantially the same as the voltage across the electric energy source so that a change in voltage of the electric bus results in the same change to the voltage across the electric energy source. A power management controller is programmed to control output power of the power unit to maintain the energy storage system between a predetermined high voltage set-point and a predetermined low voltage set-point.