Showing papers on "Negative impedance converter published in 2003"

A broadband controller for shunt piezoelectric damping of structural vibration

Abstract: In this paper a broadband active shunt technique for controlling vibration in piezoelectric laminated structures is proposed. The effect of the negative capacitance controller is studied theoretically and then validated experimentally on a piezoelectric laminated simply supported plate. The 'negative capacitance controller' is similar in nature to passive shunt damping techniques, as a single piezoelectric transducer is used to dampen multiple modes. While achieving comparable performance to that of the passive shunt schemes, the negative capacitance controller has a number of advantages. It is simpler to implement, less sensitive to environmental variations and can be considered as a broadband vibration absorber.

Methods and circuits for programmable automatic burst mode control using average output current

Abstract: The present invention comprises a user-programmable control circuit for use in a power converter to automatically transition the converter into BURST mode when load current demand is low. The control circuit senses load current demand by monitoring the output current of the converter, and generating a signal representative of the monitored output current. The control circuit may automatically transition the converter into BURST mode when the signal indicative of the average monitored output current decreases below a user-programmable threshold. BURST mode may increase overall converter efficiency by turning OFF a plurality of electronic components, and maintaining the converter's output voltage at a regulated level by energy stored in an output capacitor.

Optimization arrangement for direct electrical energy converters

Abstract: An arrangement is provided for supplying electrical energy to a load from a direct electrical energy converter that optimizes converter power generation efficiency. The arrangement for optimizing converter power generation efficiency includes an impedance transformation circuit coupled between the energy converter and load for regulating current delivered by the energy converter so as to maximize power delivered to the load.

Small-signal model of PWM converters for discontinuous conduction mode and its application for boost converter

Abstract: A small-signal circuit model for pulsewidth-modulated DC-DC converters operated in discontinuous conduction mode is presented. The model is composed of controlled current sources, an independent voltage source and resistances. The principle of energy conservation approach is used to take into account parasitic resistances of the transistor and diode and the diode threshold voltage. The proposed model is suitable for small-signal, frequency-domain representation of the converters. This model is used to derive the expressions for a boost converter control-to-output transfer function, input-to-output voltage transfer function, input impedance and the output impedance. Bode plots are also given for these transfer functions. The predicted and experimental results were in excellent agreement.

Fast start-up low-voltage bandgap voltage reference circuit

Abstract: A fast start-up low-voltage bandgap voltage reference circuit is disclosed. The bandgap voltage reference circuit includes: a first current generator, which is implemented by a self-bias unit and a current mirror for generating a first reference current with positive temperature coefficient; a second current generator, which is connected to a point with negative temperature coefficient in the first current generator to generate a second reference current with negative temperature coefficient; and a resistor for converting the first reference current and the second reference current into a low-voltage bandgap voltage independent of temperature. Because the bandgap voltage reference circuit of the invention uses the resistor to convert the first reference current and the second reference current into voltage, the circuit can provide low-voltage bandgap voltage.

A scalable multiphase buck converter with average current share bus

Abstract: The paper presents a scalable multiphase synchronous buck converter which meets the tight requirements of the next generation microprocessors. Flexibility in the number of phases (1-16 phases) accommodates requirements of various applications. The converter can be easily expanded or paralleled with other voltage regulator modules (VRM) through an average current share bus. The distributed control IC architecture allows for local phase current signal processing, which minimizes induced noise and facilitates layout while reducing the gate driver to power stage impedance. The experimental results are given to show the advantages of the converter.

Impedance source power converter

Abstract: An impedance source power converter includes a power source, a main converter circuit and an impedance network. The main converter circuit is coupled to a load and the impedance network couples the power source to the main converter circuit. The impedance network is configured such that the main converter circuit is adapted to perform both buck conversion and boost conversion.

Microprocessor-based hand-held electrical-testing system and method

Abstract: The present invention provides methods and systems for testing voltage drops in positive and negative legs of an electrical system and for determining maximal current capacity of the electrical system based on the measured voltage drops. This is accomplished by connecting load leads of a testing unit at a starter or alternator of the electrical system, and connecting voltage leads of the testing unit at a battery of the electrical system. A load of known resistance is applied and a voltage at the load is measured. Voltage drops at the positive and negative legs of the electrical system are determined, based at least in part on the voltage at the load. A maximum current capacity of the electrical system is calculated based on the determined voltage drops.

Apparatus and method for performing impedance measurements

Abstract: An impedance module for calculating the impedance of a body part creates stimulus currents for injection into the body part and receives resulting voltages generated by the body part The impedance module includes a current generator for generating the stimulus currents, the stimulus currents including a current signal and a complementary current signal thereby forming a differential current signal. The impedance module also includes voltage processing circuitry for pre-processing the received voltages and amplifying the received voltages to generate a measured voltage signal; processing circuitry for creating a current control voltage signal for controlling parameters related to the stimulus currents, and for calculating an impedance value based on the stimulus current and the measured voltage signal, and interface circuitry for interconnecting the components of the impedance module.

N-point-converter circuit

Abstract: An n-point-converter circuit with two series-connected power converter valves, each having (n−1) turn-off semiconductor switches, is disclosed. The converter circuit has a voltage intermediate circuit with (n−1) electrically series-connected capacitors. The voltage intermediate circuit is connected in parallel to DC-side terminals of the series-connected power converter valves. At least one AC-side terminal can be connected to one or more of the n potentials of the voltage intermediate circuit by means of (n−2) cross arms, each of which includes at least (n−3) turn-off semiconductor switches. The multipoint converter is easy to implement, has an improved output voltage quality, and possesses an emergency running feature.

Method and apparatus for power management

Abstract: A system in accordance with the invention includes a power converter for converting a thermally generated voltage where the power converter includes a low-voltage direct current to direct current voltage converter (DC-DC converter) and a high-efficiency DC-DC converter coupled with the low-voltage DC-DC converter. The system also includes a charge storage circuit coupled with the low-voltage DC-DC converter and the high-efficiency DC-DC converter for storing converted electrical energy and a programmable controller circuit. The programmable controller circuit is coupled with the high-efficiency DC-DC converter, the low-voltage DC-DC converter, and the charge storage circuit such that the controller circuit substantially controls operation of the system when the voltage potential of the converted electrical energy stored by the charge storage circuit is greater than a brown out voltage of the controller.

Short-circuit impedance measurement

Abstract: Methods for estimating the short-circuit impedance in the power grid are investigated for various voltage levels and situations. The short-circuit impedance is measured, preferably from naturally occurring load changes in the grid, and it is shown that such a measurement system faces different kinds of problems at different locations in the grid. This means that the best measurement methodology changes depending on the location in the grid. Three typical examples with different measurement problems at 400 kV, 132 kV and 400 V voltage level are discussed.

Method and apparatus to match output impedance of combined outphasing power amplifiers

Abstract: Briefly, an apparatus having a first capacitor-inductor-capacitor impedance converter operably coupled to a second capacitor-inductor-capacitor impedance converter. The first and second capacitor-inductor-capacitor impedance converter may combine a first and second signals of first and second outphasing power amplifiers and may provide a matched output impedance to a desired load.

Single-ended-to-differential converter with common-mode voltage control

Abstract: Provided is a circuit to perform single-ended to differential conversion while providing common-mode voltage control. The circuit includes a converter to convert a single-ended signal to a differential signal and a stabilizing circuit adapted to receive the differential signal. The stabilizing circuit includes a sensor configured to sense a common-mode voltage level of the differential signal and a comparator having an output port coupled to the converter. The comparator is configured to compare the differential signal common-mode voltage level with a reference signal common-mode voltage level and produce an adjusting signal based upon the comparison. The adjusting signal is applied to the converter via the output port and is operative to adjust a subsequent common-mode voltage level of the differential signal.

Switching DC-DC converter with the output voltage changing inversely to any change in the converter inductor current

Abstract: In a DC-DC converter, a technique for sensing current supplied to a load and establishing an output voltage that conforms to a predetermined load line. The current carried by an inductor is sensed and used to control the duty cycle of the voltage applied to the inductor, thereby controlling the output voltage. A current sensing circuit includes a feedback network. A pole attributable to the feedback network cancels a zero attributable to the inductor so that a control voltage is developed that varies substantially linearly with the load current.

Multiple-phase DC-DC converter topology

Abstract: A multiple-phase DC—DC converter adds at least one additional phase to an N-phase DC—DC converter to improve the converter's response to changes in load. In one embodiment, an additional phase operates at a switching frequency greater than that of the N phases, to generate a current which is added to the N phase currents to improve the converter's response to changes in load. In another embodiment, an additional phase is configured to improve the converter's response to a load release. Here, the additional phase is kept off during load increase and steady-state conditions. However, when a load release occurs, the additional phase is turned on and acts to extract current from the converter's output terminal while the N phase currents slowly fall, to reduce the magnitude of output voltage overshoot that occurs on load release.

Multiple-mode structural vibration control using negative capacitive shunt damping

Abstract: This paper deals with a novel shunt circuit, which is capable of suppressing multimode vibration amplitudes by using a pair of piezoceramic patches. In order to describe the characteristic behaviors of a piezoelectric damper connected with a series and a parallel resistor-negative capacitor branch circuit, the stiffness ratio and loss factor with respect to the non-dimensional frequency are considered. The mechanism of the shunt damper is also described by considering a shunt voltage constrained by shunt impedance. To obtain a guideline model of the piezo/beam system with a negative capacitive shunting, the governing equations of motion are derived through the Hamilton’ s principle and a piezo sensor equation as well as a shunt-damping matrix is developed. The theoretical analysis shows that the piezo/beam system combined with a series and a parallel resistor-negative capacitor branch circuit developed in this study can significantly reduce the multiple-mode vibration amplitudes over the whole structural frequency range.

Indirect current control of a single-phase voltage-sourced boost-type bridge converter operated in the rectifier mode

Abstract: An H-bridge transistorized converter intended for front-end power conversion at a high power-factor and a constant desired output voltage has been analyzed. The state-space model of the H-bridge converter controlled by the bipolar pulse width modulated (PWM) technique is described and the expressions for the equilibrium points of operation of the state variables corresponding to the circuit parameters have been derived. The converter is intended for use as a voltage source feeding an inverter. Hence the requirement of maintaining a desired DC voltage at its output becomes necessary. Transient behavior of two control strategies have been tested to examine their performance in stabilising the converter at the desired operating state. Comparison of the two feedback strategies has been done by simulation studies and the one that was found superior has been experimentally implemented. The experimental implementation of the controller for the converter operation in the rectifier mode is also described. The experimental results obtained are presented and compared with simulation results to validate the controller's performance under transient conditions.

Multi-mode vibration damping device and method using negative capacitance shunt circuits

Abstract: A novel multi-mode vibration damper is invented by using a pair of piezoelectric patches connected with negative capacitance shunt circuit units. A piezoelectric material connected with a series resistor-negative capacitor branch circuit is capable of suppressing the vibration and/or noise amplitudes in the low frequency range. The other piezoelectric material connected with a parallel resistor-negative capacitor circuit is for suppressing the vibration and/or noise amplitudes in the high frequency range. By combining two negative capacitance shunt circuit units, a multi-mode vibration damper is capable of suppressing the whole structure modes simultaneously. In order to describe the characteristic behaviors of a multi-mode vibration damper, the stiffness ratio and loss factor with respect to the non-dimensional frequency are considered. The mechanism of a shunt damper is also described as considering a shunt voltage generated by the shunt impedance. The example results show that the multi-mode vibration damper reduces the vibration amplitudes of the vibrating system significantly across a broadband frequency range.

ZCS-ZVS bi-directional phase-shifted DC-DC converter with extended load range

Abstract: The work described is based on a bidirectional phase-shifted DC-DC converter that conventionally suffers from the restricted load range and nonlinear control of the output voltage. The concepts developed are used to extend the load range of the converter by applying both zero current switching (ZCS) and zero voltage switching (ZVS). In addition, the control to output voltage characteristics of the converter is improved to be more linear over the large load range.

System and method to establish an adjustable on-chip impedance

Abstract: A method to establish an adjustable on-chip impedance within a predetermined range that involves establishing a reference current for the adjustable on-chip impedance and applying this reference current to the adjustable on-chip impedance. A voltage produced by applying the reference current to the adjustable on-chip impedance is sensed and compared with the comparator or other similar processor to a reference voltage. This comparison allows the adjustable on-chip impedance to be tuned when the comparison of the sense voltage and the reference voltage is unfavorable. Tuning the impedance results in an impedance value within a predetermined range that accounts for variances of both the reference current and reference voltage.

Modeling negative capacitance effect in organic polymers

Abstract: We have developed an extension of the Drude model for oscillators to determine capacitance in organic polymers. The extension covers the effect of time delay caused by dispersion in the carrier transport. This was done using a complex mobility parameter. Negative capacitance effect could be observed in simulation at low frequencies provided that model parameters are appropriately chosen. In matching the simulation results to a set of data reported [Phys. Rev. B. 63 (2001) 125328] we have computed very reasonable values of the transport parameters in regimes where either positive capacitance or negative capacitance is dominant. Negative capacitance effect was attributed to charge trapping in a dispersive media when the carrier mobility had a negative imaginary component. Qualitative agreement was achieved to first order between simulation and observation provided that a mild frequency dependence exists in the carrier mobility. We believe our model is a better approach to extract transport parameters from capacitance–frequency curves when detailed conduction processes could not be easily identified such as in an environment of disordered complex molecules.

Peak current sharing in a multi-phase buck converter power system

Abstract: A plurality of constant ON-time buck converters are coupled to a common load. The output of each buck converter is coupled to a common load via a series sense resistor. The regulated output voltage across the common load is compared to a reference voltage to generate a start signal. The start signal is alternately coupled to the controller on each buck converter. The ON-time of a master buck converter is terminated when a ramp signal generated from the regulator input voltage exceeds the reference voltage. All other slave converters have an ON-time pulse started by the start signal and stopped by comparing a sense voltage corresponding to their output current during their ON-time pulse to the peak current in the master converter during its ON-time. A counting circuit with an output corresponding to each of the plurality of buck converters is used to select which buck converter receives the start signal.

Semiconductor device with programmable impedance control circuit

Abstract: An output impedance control circuit of a semiconductor device. A first transistor is connected to a pad and a level controller controls a gate voltage of the first transistor in response to a voltage of the pad and a reference voltage. A MOS array is connected between the pad and a power supply voltage and supplies current to the pad in response to an impedance control code. A first control circuit generates the impedance control code in response to whether a voltage of the pad is converging to the reference voltage. A second control circuit controls a pull-up impedance of the output buffer circuit in response to the first impedance control code when a voltage of the pad is converging to the reference voltage.

Feed-forward method for improving a transient response for a DC—DC power conversion and DC—DC voltage converter utilizing the same

Abstract: In a method for a DC-DC power conversion performed by a switching mode buck voltage converter, the power conversion is split into two or more stages, and a feed-forward signal is generated by one of the stages and sent to another stage prior thereto. The feed-forward signal is generated by responding to a load current transient, such as output voltage drop, ON-duty increment or decrement occurred in the PWM control loop, error amp output swinging, and any other detectable signals in response to load current transient of the voltage converter. As a result, the performance of the DC-DC voltage converter is improved due to the prior stage modulated early in time, and both lower ripple current and peak current in steady state operations and fast response to load current transient conditions could be simultaneously obtained.

Device for turning on light and illumination apparatus

Abstract: A device for turning on light allowing the brightness of an inverter-type illumination apparatus to be adjusted without having to install an additional oscillation circuit. The device comprises an active converter which generates a DC voltage from the commercial AC voltage and an inverter which switches the generated DC voltage, includes a capacitor connected in parallel with a discharge tube to be lighted, and supplies a high-frequency current to the discharge tube via a resonance circuit whose resonance frequency is determined according to the equivalent impedance of the discharge tube. The active converter has a triac adjusting the DC voltage, and switching elements of the inverter perform self-oscillation under control of the phase of the resonance current flowing through the resonance circuit.

Power management system for a floor care appliance

Abstract: A floor care appliance is provided with an improved power management system for controlling the total amount of current provided to at feast a first and a second load device of an appliance. The power management system is comprised of a microprocessor, an alternating current voltage source, a voltage regulating circuit, a clamping circuit, at least two load devices, and a MOC and a triac for each of the at least two load devices. The clamping circuit outputs a fixed voltage of 5.7 volts during the positive portion of the ac cycle and a fixed voltage of -0.7 volts during the negative portion of the ac cycle. The fixed voltages are input to a microprocessor which utilizes these inputs to control the average voltage and the amount of time the current is turned on to each of the at least first and second load devices. A current sensing circuit is used to monitor the current to one of the at least two load devices to provide feedback to the microprocessor so that the microprocessor can adjust the average voltage and current to the at least two load devices so that the total current consumed does not exceed a pre-determined level.

Method and circuit for producing control signal for impedance matching

Abstract: A method for producing a stable control signal for impedance matching is provided which is capable of suppressing variation in impedance matching data by adding a shift voltage to a voltage to be compared. A comparator compares the voltage to be compared with a reference voltage and an up-down counter performs a counting operation according to a result from the comparison. A code converting circuit converts a count value output from the up-down counter to a thermometer code used for changing an impedance of an impedance varying circuit. A change in the impedance is made in a manner that, even when the voltage to be compared gets closest to the reference voltage, a shift voltage for the comparator to make an exact comparison is fed to the voltage to be compared. An averaging circuit averages a count value and the code converting circuit converts a resulting average value to the thermometer code.

DC-DC converter, duty-ratio setting circuit and electric appliance using them

Abstract: A DC—DC converter in which no operational instability occurs and ranges of input and output voltages are wide, an electric appliance using such DC—DC converter, and a duty-ratio setting circuit in which no operational instability occurs and ranges of input and output voltages of a converter circuit can be widen in controlling the converter circuit are provided. A DC—DC converter 10 has a converter circuit 110 , an output voltage detection circuit 120 and a duty-ratio setting circuit 20 . An error amplifier circuit 21 compares Vref 1 with Vd to output a control voltage Vfb. A pulse-width modulator circuit 25 compares a triangular-wave voltage Vct with the control voltage Vfb to output a first pulse signal PWO. A second-pulse generator circuit 26 outputs a second pulse signal PSO having a predetermined on-duty ratio. A selector circuit 27 selects the first pulse signal PWO or the second pulse signal PSO according to the control voltage Vfb to output the selected signal to a transistor M 1 as a rectangular-wave signal PS.

High resolution bio-impedance device

Abstract: A method and apparatus for the non-invasive measurement of cardiac function. A signal is applied between a pair of electrodes on a patient. The signal delivers a constant alternating current at multiple simultaneous frequencies. A second pair of electrodes measures a voltage signal. The impedance at each frequency is obtained by demodulating the current signal and the voltage signal using techniques such as Fast Fourier Transform (FFT). The FFT gives a phase and amplitude which is converted to an impedance value. The impedance values are fitted to a theoretical frequency dependent impedance locus and the locus is extrapolated to obtain a value at zero frequency. The steps are repeated to obtain a time-varying plot of impedance and measures of cardiac function are calculated from the time-varying plot.