Showing papers on "Voltage published in 1998"

A low-voltage, low quiescent current, low drop-out regulator

Abstract: The demand for low-voltage, low drop-out (LDO) regulators is increasing because of the growing demand for portable electronics, i.e., cellular phones, pagers, laptops, etc. LDO's are used coherently with dc-dc converters as well as standalone parts. In power supply systems, they are typically cascaded onto switching regulators to suppress noise and provide a low noise output. The need for low voltage is innate to portable low power devices and corroborated by lower breakdown voltages resulting from reductions in feature size. Low quiescent current in a battery-operated system is an intrinsic performance parameter because it partially determines battery life. This paper discusses some techniques that enable the practical realizations of low quiescent current LDO's at low voltages and in existing technologies. The proposed circuit exploits the frequency response dependence on load-current to minimize quiescent current flow. Moreover, the output current capabilities of MOS power transistors are enhanced and drop-out voltages are decreased for a given device size. Other applications, like dc-dc converters, can also reap the benefits of these enhanced MOS devices. An LDO prototype incorporating the aforementioned techniques was fabricated. The circuit was operable down to input voltages of 1 V with a zero-load quiescent current flow of 23 /spl mu/A. Moreover, the regulator provided 18 and 50 mA of output current at input voltages of 1 and 1.2 V, respectively.

A high-performance generalized discontinuous PWM algorithm

Abstract: In this paper, a generalized discontinuous pulsewidth modulation (GDPWM) method with superior high modulation operating range performance characteristics is developed. An algorithm which employs the conventional space-vector PWM method in the low modulation range, and the GDPWM method in the high modulation range, is established. As a result, the current waveform quality, switching losses, voltage linearity range, and the overmodulation region performance of a PWM voltage-source inverter (PWM-VSI) drive are optimized online, as opposed to conventional modulators with fixed characteristics. Due to its compactness, simplicity and superior performance, the algorithm is suitable for most high-performance PWM-VSI drive applications. This paper provides detailed performance analysis of the method and compares it to the other methods. The experimental results verify the superiority of this algorithm to the conventional PWM methods.

A new generation of high voltage MOSFETs breaks the limit line of silicon

Abstract: For the first time a new device concept for high voltage power devices has been realized in silicon. Our 600 V-COOLMOS/sup TM/ reaches an area specific on-resistance of typically 3.5 /spl Omega//spl middot/mm/sup 2/. Our technology thus offers a shrink factor of 5 versus the actual state of the art in power MOSFETs. The device concept is based on charge compensation in the drift region of the transistor. We increase the doping of the vertical drift region roughly by one order of magnitude and counterbalance this additional charge by the implementation of fine structured columns of the opposite doping type. The blocking voltage of the transistor remains thus unaltered. The charge compensating columns do not contribute to the current conduction during the turn-on state. Nevertheless the drastically increased doping of the drift region allows the above mentioned reduction of the on-resistance.

Multilevel converters for large electric drives

Abstract: Traditional two-level high-frequency pulse width modulation (PWM) inverters for motor drives have several problems associated with their high frequency switching which produces common-mode voltage and high voltage change (dV/dt) rates to the motor windings. Multilevel inverters solve these problems because their devices can switch at a much lower frequency. Two different multilevel topologies are identified for use as a power converter for electric drives: a cascade inverter with separate DC sources; and a back-to-back diode clamped converter. The cascade inverter is a natural fit for large automotive all-electric drives because of the high VA ratings possible and because it uses several levels of DC voltage sources which would be available from batteries or fuel cells. The back-to-back diode clamped converter is ideal where a source of AC voltage is available such as a hybrid electric vehicle. Simulation and experimental results show the superiority of these two power converters over PWM-based drives.

Multilevel converters for single-phase grid connected photovoltaic systems-an overview

Abstract: Multilevel voltage source inverters offer several advantages compared to their conventional counterparts. By synthesising the AC output terminal voltage from several levels of voltages, staircase waveforms can be produced, which approach the sinusoidal waveform with low harmonic distortion, thus reducing filter requirements. The need of several sources on the DC side of the converter makes multilevel technology attractive for photovoltaic applications. This paper provides an overview an different multilevel topologies and investigates their suitability for single-phase grid connected photovoltaic systems. Several transformerless photovoltaic systems incorporating multilevel converters are compared regarding issues such as component count and stress, system power rating and the influence of the photovoltaic array earth capacitance.

SSSC-static synchronous series compensator: theory, modeling, and application

Abstract: This paper describes the theory and the modelling technique of a flexible alternating current transmission systems (FACTS) device, namely, static synchronnous series compensator (SSSC) using an Electromagnetic Transient Program (EMTP) simulation package. The SSSC, a solid-state voltage source inverter coupled with a transformer, is connected in series with a transmission line. An SSSC injects an almost sinusoidal voltage, of variable magnitude, in series with a transmission line. This injected voltage is almost in quadrature with the line current, thereby emulating an inductive or a capacitive reactance in series with the transmission line. The emulated variable reactance, inserted by the injected voltage source, influences the electric power flow in the transmission line.

MOS charge pumps for low-voltage operation

Abstract: New MOS charge pumps utilizing the charge transfer switches (CTSs) to direct charge flow and generate boosted output voltage are described. Using the internal boosted voltage to backward control the CTS of a previous stage yields charge pumps that are suitable for low-voltage operation. Applying dynamic control to the CTSs can eliminate the reverse charge sharing phenomenon and further improve the voltage pumping gain. The limitation imposed by the diode-configured output stage can be mitigated by pumping it with a clock of enhanced voltage amplitude. Using the new circuit techniques, a 1.2-V-to-3.5-V charge pump and a 2-V-to-16-V charge pump are demonstrated.

An interior-point method for nonlinear optimal power flow using voltage rectangular coordinates

Abstract: The paper describes the solution of an optimal power flow (OPF) problem in rectangular form by an interior-point method (IPM) for nonlinear programming. Some OPF variants when formulated in rectangular form have quadratic objective and quadratic constraints. Such quadratic features allow for ease of matrix setup, and inexpensive incorporation of higher-order information in a predictor-corrector procedure that generally improves IPM performance. The mathematical development of the IPM in the paper is based on a general nonlinear programming problem. Issues in implementation to solve the rectangular OPF are discussed. Computational tests apply the IPM to both the rectangular and polar OPF versions. Test results show that both algorithms perform extremely well.

Method and apparatus for an L.E.D. flashlight

Abstract: Improved method and apparatus for hand-held portable illumination. A flashlight and corresponding method are described. The flashlight includes a housing, a plurality of LEDs, and an electrical circuit that selectively applies power from the DC voltage source to the LED units, wherein the flashlight is suitable for handheld portable operation by a user. In one embodiment, the first electrical circuit further includes a control circuit for maintaining a predetermined light output level of the LED units as a charge on a battery varies. In another embodiment, the control circuit maintains an average predetermined light output level of the LED units as the charge on the battery cell varies by changing a pulse width or frequency as the charge on the battery cell varies to maintain a given average light output. Another aspect provides an illumination source that includes a light-emitting diode (LED) housing including one or more LEDs, and a control circuit that selectively applies power from a source of electric power to the LEDs, the control circuit substantially maintaining a light output characteristic of the LEDs as a voltage of the voltage source varies over a range that would otherwise vary the light output characteristic. Still another aspect provides an illumination source including a light-emitting diode (LED) housing including one or more LEDs; and a control circuit that selectively applies power from a source of electric power to the LEDs, thus maintaining or controlling a light output color spectrum of the LEDs.

Capacitive distance sensor

Abstract: A distance sensor has a capacitive element in turn having a first capacitor plate which is positioned facing a second capacitor plate whose distance is to be measured. In the case of fingerprinting, the second capacitor plate is defined directly by the skin surface of the finger being printed. The sensor comprises an inverting amplifier, between the input and output of which the capacitive element is connected to form a negative feedback branch. By supplying an electric charge step to the input of the inverting amplifier, a voltage step directly proportional to the distance being measured is obtained at the output.

Transistor matching in analog CMOS applications

Abstract: This paper gives an overview of MOSFET mismatch effects that form a performance/yield limitation for many designs. After a general description of (mis)matching, a comparison over past and future process generations is presented. The application of the matching model in CAD and analog circuit design is discussed. Mismatch effects gain importance as critical dimensions and CMOS power supply voltages decrease.

Cluster ablation electrode system

Abstract: A multiplicity of high frequency electrodes in a cluster configuration may be inserted into tissue of a patient's body for producing heat ablation of abnormal tissue such as a tumor. The electrodes are connected coherently to the voltage output of a high frequency generator. An enlarged ablation volume is accomplished by the electrode cluster with reduced risk of hemorrhage because of the smaller diameter of the individual electrodes of the cluster. The electrodes terminate in conductive tips, which are cooled by a fluid coolant to further facilitate enlarged ablation volumes. Very large ablation volumes are accomplished by this process and apparatus. Various cluster electrode configurations may be adapted to meet specific clinical requirements.

Variable supply-voltage scheme for low-power high-speed CMOS digital design

Abstract: This paper describes a variable supply-voltage (VS) scheme. From an external supply, the VS scheme automatically generates minimum internal supply voltages by feedback control of a buck converter, a speed detector, and a timing controller so that they meet the demand on its operation frequency. A 32-b RISC core processor is developed in a 0.4-/spl mu/m CMOS technology which optimally controls the internal supple voltages with the VS scheme and the threshold voltages through substrate bias control. Performance in MIPS/W is improved by a factor of more than two compared with its conventional CMOS design.

Circuit layout and method for operating a single- or multiphase current inverter connects an AC voltage output to a primary winding and current and a working resistance to a transformer's secondary winding and current.

Abstract: A circuit layout (10) operates a single- or multiphase current inverter (12) with its AC voltage output connected to a primary winding (15) carrying a primary current (IP). A working resistance can be connected to a secondary winding (60,62) in a transformer carrying a secondary current (IS), including a regulating circuit (78) and a triggering unit (40) for triggering pulse in power semiconductors (T1-T4) in the current converter.

Reliability projection for ultra-thin oxides at low voltage

Abstract: The rate of defect generation by electrical stress in silicon dioxide has been measured as a function of gate voltage down to 2 V on a variety of MOSFETs with thickness in the range 1.4-5 nm. The critical defect density necessary for destructive breakdown has also been measured in this thickness range. These quantities are used to predict time to breakdown for ultra thin oxides at low voltages. The properties of the breakdown distribution, which becomes broader as the oxide thickness is reduced, are used to provide reliability projections for the total gate area on a chip. It is predicted that oxide reliability may limit oxide scaling to about 2.6 nm (CV extrapolated thickness) or 2.2 nm (QM thickness) for a 1 V supply voltage at room temperature and that the current SIA roadmap will be unattainable for reliability reasons by sometime early next century.

Anti-islanding method and apparatus for distributed power generation

Abstract: The invention in the simplest form is a method and apparatus for reliably protecting against island situations with one or multiple power sources connected to an electric distribution grid. The method and apparatus detects variations in the voltage and frequency of the grid. An observed change in grid voltage causes a change in output power that is sufficient to cause an even larger change in grid voltage when the utility AC power source is disconnected. An observed change in grid frequency causes a change in phase or reactive output power that is sufficient to cause an even larger change in grid frequency. If several shifts in voltage or frequency happen in the same direction, the response to the change is increased in an accelerating manner.

Lithium ion batteries : fundamentals and performance

Abstract: Rechargeable batteries with high energy density are in demand as energy sources for various purposes, such as handies, zero emission electric vehicles, or load levelling in electric power. Lithium batteries are the most promising to fulfill such needs because of their intrinsic discharge voltage with relatively light weight. This volume is an overview of the challenges facing the further development of lithium-ion batteries from the standpoint of both materials science and technology.

Identification of conductivity imperfections of small diameter by boundary measurements. Continuous dependence and computational reconstruction

Abstract: We derive an asymptotic formula for the steady-state voltage potential in the presence of a finite number of diametrically small inhomogeneities with conductivity different from the background conductivity. We use this formula to establish continuous dependence estimates and to design an effective computational identification procedure.

Pull-in study of an electrostatic torsion microactuator

Abstract: Pull-in study of an electrostatic microactuator is essential for making the electrostatic actuation more effective. In this paper, pull-in analysis is presented for an electrostatic torsion microactuator. The torsion microactuator can be used as a microtorsion mirror. A polynomial algebraic equation for the pull-in voltage and pull-in angle of a torsion microactuator is derived. Two types of microactuators fabricated using bulk micromachining are presented. Measurements done on the fabricated microactuators are reported, showing deviations within 1% error from the calculations.

Universal ballast control circuit

Abstract: A universal ballast control circuit allows a universal ballast to accommodate a gas discharge lamp within a relatively wide wattage range using a low-speed microcontroller. The control circuit drives the ballast to start, run and dim a particular lamp type by providing a control voltage signal to a conventional inverter MOSFET driver to effect dynamic and selective changes in the duty cycle and the frequency of the inverter signal. In one aspect of the invention, the control circuit comprises a generator for generating a periodic analog voltage signal, a source for producing a DC voltage signal, a controller which includes a low-speed microcontroller for varying the frequency of the periodic analog voltage signal and the magnitude of the DC voltage signal, and a comparator for comparing the periodic analog voltage signal and the DC voltage signal to produce a control voltage signal. In another aspect of the invention, the control circuit comprises a generator for generating a periodic analog voltage signal, a controller for controlling the shape of the periodic analog voltage signal, and a comparator for comparing waveforms of the periodic analog voltage signal with the waveforms of two DC threshold voltages to generate a control signal. The present invention allows for the control circuit to be powered by a power supply signal either derived from an inverter half-bridge MOSFET driver, extracted from a boost inductor of the boost converter or generated by an appropriately configured dedicated miniature switch mode power supply. Finally, control circuit can be utilized to drive PFC circuity in a feedback configuration to regulate the level of boost converter output voltage signal.

The linearized CREATE-L plasma response model for the control of current, position and shape in tokamaks

Abstract: CREATE-L, a simple and reliable linearized plasma response model for the control of the plasma current, position and shape in tokamaks, is presented. The basic assumption made is that the plasma behaviour is described using three degrees of freedom, related to the total plasma current, internal inductance and poloidal beta. The state variables are the coil and plasma currents; the inputs are the applied voltages, whereas poloidal beta and internal inductance play the role of disturbances. The outputs are field and flux values and some basic plasma parameters. The model is tested against non-linear codes and validated via comparison with experimental results.

Coordinate input device and display-integrated type coordinate input device capable of directly detecting electrostatic coupling capacitance with high accuracy

Abstract: In a coordinate detection period, a first electrode drive circuit sequentially selects source electrodes Sn of the TFT LCD panel to connect the same to an x-signal current amplifying circuit, and to apply an AC voltage to the non-selected electrodes. The x-signal current amplifying circuit detects a detection current flowing through the selected electrode, the magnitude of which corresponds to a distance to a finger (or a conductor pen), to obtain an x-coordinate detection voltage. A second electrode drive circuit and a y-signal current amplifying circuit operate in similar fashion to obtain a y-coordinate detection voltage. A coordinate detection circuit then obtains the x- and y-coordinate values of the designated position based on the x-coordinate detection voltage and the y-coordinate detection voltage, thus enabling pointing by a codeless pen and a finger.

Photovoltaic measurement of the built-in potential in organic light emitting diodes and photodiodes

Abstract: We measure the voltage at which the current under illumination in poly[2-methoxy, 5-(2-ethylhexoxy)-1,4-phenylene vinylene] based light emitting diodes is equal to the dark current. At low temperatures, this voltage, which we term the “compensation” voltage, is found to be equal to the built-in potential, as measured with electroabsorption on the same diode. Diffusion of thermally injected charges at room temperature, however, shifts the compensation voltage to lower values. A model explaining this behavior is developed and its implications for the operation of organic light emitting diodes and photovoltaic cells are briefly discussed.

Printer-built-in image-sensing apparatus using strobe-light means and electric-consumption control method thereof

Abstract: A printer-built-in image-sensing apparatus comprising a camera which performs image sensing with film exposure, and a printer which prints an image sensed by the camera. After a shutter button has been pressed and image sensing with strobe light emission has been performed, if printing is instructed by pressing of a print button, electric charge of a capacitor of a strobe circuit is made after the completion of print operation. Otherwise, the charging of the capacitor is started immediately after the image sensing. In this case, even if printing is instructed during the electric charge, printing is started after completion of the electric charge. Thus, electric consumption upon print operation can be reduced and fluctuation of voltage can be suppressed.

Heterojunction field effect transistor

Abstract: A heterojunction field effect transistor realizing a high performance by a significant decrease. in source resistance while maintaining a sufficiently high gate resistivity to voltage is provided. Sequentially stacked on a c-face sapphire substrate via a buffer layer are an undoped GaN layer, undoped Al 0 .3 Ga 07 N layer, undoped GaN channel layer, undoped Al 0 .15 Ga 0 .85 N spacer layer, n-type Al 0 .15 Ga 0 .85 N electron supply layer, graded undoped Al z Ga 1-z N barrier layer and n-type Al 0 .06 Ga 0 .94 N contact layer, and a gate electrode, source electrode and drain electrode are formed on the n-type Al 0 .06 Ga 0 .94 N contact layer to form a AlGaN/GaN HEMT. The Al composition z in the graded undoped Al z Ga 1-z N barrier layer continuously decreases from 0.15 to 0.06, for example, from the n-type Al 0 .15 Ga 0 .85 N electron supply layer toward the n-type Al 0 .06 Ga 0 .94 N contact layer. An n ++ -type GaN contact layer may be formed on the n-type Al 0 .06 Ga 0 .94 N contact layer in the region for the source electrode and the drain electrode, and the source electrode and the drain may be formed on it.

Equalizer system and method for series connected energy storing devices

Abstract: An apparatus and method for regulating the charge voltage of a number of electrochemical cells connected in series are disclosed. Equalization circuitry is provided to control the amount of charge current supplied to individual electrochemical cells included within the series string of electrochemical cells without interrupting the flow of charge current through the series string. The equalization circuitry balances the potential of each of the electrochemical cells to within a predetermined voltage setpoint tolerance during charging, and, if necessary, prior to initiating charging. Equalization of cell potentials may be effected toward the end of a charge cycle or throughout the charge cycle. Overcharge protection is also provided for each of the electrochemical cells coupled to the series connection. During a discharge mode of operation in accordance with one embodiment, the equalization circuitry is substantially non-conductive with respect to the flow of discharge current from the series string of electrochemical cells. In accordance with another embodiment, equalization of the series string of cells is effected during a discharge cycle.

Field effect-controllable semiconductor component

Abstract: Disclosed is a new planar technology IGBT, wherein minority charge carrier density on the cathode side of the IGBT is increased by introducing a shielding zone (13) which is arranged around a base zone (5), thereby leading to reduced conducting-state voltage (VCESat). As a result of the drift field arising from the concentration gradient between the shielding zone (13) and the base zone (6), the inner zone (2) no longer acts as a drain for the minority charge carriers. In order to prevent a reduction in the IGBT breakdown voltage by introducing the shielding zone (13), an unconnected, floating, high-conductivity area is provided in the inner zone, wherein the lower edge (16) of said area is located further inside the inner zone(2) than the upper edge (14) of the shielding zone (13). The unconnected floating area provides a different type of conduction from the shielding zone and the inner zone (2).

Circuit protection device

Abstract: A transient voltage surge suppression system incorporating a current protection device comprised of a voltage sensitive and a thermal sensitive device. The voltage sensitive device has a predetermined voltage rating and increases in temperature as voltage applied thereto exceeds its voltage rating. The thermal sensitive device is responsive to heating of the voltage sensitive device to break an electrical current path if an overvoltage condition sensed by the voltage sensitive device exceeds the voltage rating of the voltage sensitive device.

Lighting circuit for discharge lamp

Abstract: A lighting circuit supplies an input voltage from a battery to a discharge lamp after the input voltage has been sent via a DC power supply section to a DC-AC converter. This lighting circuit comprises a lighting detector for detecting if the discharge lamp is lighted, an input-voltage monitor circuit for detecting the input voltage to the DC power supply section and checking if the input voltage lies within an allowable range, and a stable power supply circuit and a switch section for supplying power to the discharge lamp or inhibiting the power supply thereto in accordance with a signal from the input-voltage monitor circuit. The input-voltage monitor circuit performs variable control on a reference value to be compared with the input voltage, in accordance with a signal from the lighting detector.

Battery state of charge detector with rapid charging capability and method

Abstract: A battery state of charge (SOC) detector for rapid charging and method each provide an efficient means for formatting, charging, and recharging batteries of various types and ratings. The detector determines the SOC of a battery to be charged and then selects an optimal charging signal profile based on the SOC determination. During the charging process, the detector can continuously monitor battery SOC in order to select appropriate waveforms for the charging signal. The charging signal is a pulse width and amplitude modulated current, voltage or power waveform with the amplitude and pulse width of each charging pulse being selected based upon the detected battery SOC. Predetermined battery parameters, such as equivalent circuit capacitance and resistance, electrochemical overcharge, maximum battery temperature, and maximum battery internal pressure, among others, also can be compared with monitored values during the battery charging process to control the charging signal in order to avoid battery damage. The charging process is continued until detected battery SOC reaches 100% or until charging logic indicates that the charging process should be stopped.