Showing papers on "Negative impedance converter published in 1997"

Super capacitor battery clone

Abstract: An aircraft electrical supply bus supplementing arrangement in which electrical energy is stored in a large capacitor and energy flow between the capacitor and the bus is controlled by a bi-directional electrical converter circuit of the switched inductance type. The varying terminal voltage of the energy storing capacitor, a super capacitor, is coupled to the relatively fixed voltage of the aircraft supply bus by way of the voltage changing capability of the converter circuit switched inductance. Current flow levels in this inductance are controlled with a negative feedback regulator circuit. Energy storage efficiency in the converter is enhanced with respect to weight and physical size of the capacitor element by ability of the converter circuit to accept a widely varying input voltage while generating a relatively constant output voltage. Suppression of electrical transients and improved regulation of voltage on the aircraft energy supply bus especially at distal and bus impedance-isolated locations are achieved.

Method and apparatus for matching a variable load impedance with an RF power generator impedance

Abstract: A method and apparatus for matching the variable impedance of a load with the fixed impedance of a radio frequency (RF) power generator to provide maximum power transfer. The impedance matching network further allows an RF power generator to vary the frequency of the voltage applied to a load, e.g., a plasma chamber as may be utilized in semi-conductor or flat panel plasma display manufacturing processes. The impedance matching network further utilizes fixed solid state components to adjust the impedance of the attached load to provide maximum power transfer between the generator and the load. A parallel switched capacitor network is controlled by an electrical switching means such as PIN diodes to turn fixed capacitors on or off. A means for varying the frequency of the applied voltage is used to match the impedance of the load with the impedance of the RF power generator within milliseconds.

Hyperchaotic oscillator with gyrators

Abstract: A fourth-order hyperchaotic oscillator is described. It contains a negative impedance converter, two gyrators, two capacitors and a diode. The dynamics of the oscillator is shown to be characterised by two positive Lyapunov exponents. The performance of the circuit is investigated by means of numerical integration of appropriate differential equations, hardware experiments and PSPICE simulations.

Frequency dependence of the complex impedances and dielectric behaviour of some Mg-Zn ferrites

Abstract: Complex impedances of some magnesium-zinc ferrites, MgxZn1-xFe2O4 (x=04, 05, 06 and 07), in the frequency range of 1 mHz-10 MHz were measured at 300 K The complex-plane impedance spectrum from each sample indicates that the capacitive and the resistive properties of the materials are mainly attributed to the processes that associated with the bulk (grain) and the grain boundary A low-frequency dispersion (LFD) and a negative capacitance regions are also observed at low frequencies A small series resistance of about the same value for all samples is also observed The bulk and the grain boundary components are analysed by assuming a two-layer leaky capacitor The simulated complex impedances using the Cole-Cole expression are in agreement with the measured values The dielectric properties of the materials are attributed to the interfacial polarization and LFD at low frequencies and the orientational polarization at high frequencies These properties result in the dielectric loss which composed of a Debye-like loss peak at high frequency end and a strong LFD below 1 Hz Both regions exhibit universality with regard to the power-law relation between the dielectric loss (e″r or χ″) and frequency as given by e″r∝ωn-1, where n=014 and n=002, respectively The exponent is marginally negative, n=−003, in the region of negative capacitance below 3–4 mHz The variations of the above properties and the characteristic parameters for different compositions of the Mg-Zn ferrites are discussed

Unusual capacitance behavior of quantum well infrared photodetectors

Abstract: We report experimental and simulation results of capacitance of quantum well infrared photodetectors (QWIPs). We found that the QWIP capacitance displays unusual behavior as a function of voltage and frequency, deviating far from the constant geometric capacitance value. At high voltages, capacitance starts with a negative value at low frequencies, increases above zero with frequency, and eventually decays to the geometric capacitance value. The magnitude of negative capacitance exceeds the geometric capacitance by more than two orders of magnitude. Negative capacitance arises when the transient current in response to a voltage step is nonmonotonic with time. Simulation shows that this effect is due to nonequilibrium transient electron injection from the emitter resulting from the properties of the injection barrier and inertia of the QW recharging processes.

Analysis and design of a fixed-frequency LCL-type series-resonant converter with capacitive output filter

Abstract: A fixed-frequency modified (LCL-type) series-resonant converter which uses a capacitive output filter is analysed using the Fourier series approach. Based on the analysis a simple design procedure is given. Detailed SPICE simulation results are presented for the designed converter to evaluate its performance for varying input supply voltage and for load variation. Experimental results obtained from a MOSFET based 500 W, 115 V output converter are presented to verify the analysis. The converter operates in lagging power factor mode for a very wide variation in the load and the supply voltage and is suitable for high voltage output applications.

Fast and noise-insensitive load status detection

Abstract: Method and apparatus for detecting whether load coils are attached to a telephone line. A stimulus waveform having multiple frequency components is applied to the line. The current and voltage at the near end of the line are coherently sampled and transformed to the frequency domain. The frequency spectra are used to compute auto and cross power spectra of the current and voltage. These power spectra are then used to compute the impedance on the line as well as a coherence function that indicates the extent to which the computed impedance was influenced by noise. If the coherence values indicate that the computed impedance is sufficiently reliable, load coils are detected by finding peaks in the magnitude of the impedance function or sign changes in the phase of the impedance function. Calibration, offset adjustments and ensemble smoothing are used to increase the accuracy of the results. The computation is fast because computing the spectra avoids the needs for individual measurements at multiple frequencies. The computation is accurate because it is not sensitive to noise.

Control architecture for interleaved converters

Abstract: A control system for an converter circuit using two interleaved boost circuits is described which uses a single PWM controller to control the switches in both of the interleaved boost circuits. A voltage feedback control circuit monitors the output voltage of the converter circuit and sends that information to the PWM controller. A current sensing circuit is provided that senses the current in each of the boost converters. The current sensed in the current sensing circuit is converted to a voltage and used in conjunction with the voltage information from voltage feedback control circuit by the single PWM controller to regulate both of the boost converter switches. By regulating the boost converter switches, the single PWM controller is able to ensure proper synchronization and current sharing while tightly regulating the output voltage and improving the input power factor of the converter circuit.

Re-lift circuit: a new DC-DC step-up (BOOST) converter

Abstract: A re-lift circuit, which is a new DC-DC step-up (boost) converter, is proposed. This converter performs positive to positive DC-DC voltage increasing conversion with high output voltage.

IGBT negative gate capacitance and related instability effects

Abstract: For high collector voltages, Insulated Gate Bipolar Transistors (IGBTs) exhibit a negative gate capacitance. In this condition, a p-channel inversion layer is formed on the N-base surface. The positive charges in the p-channel induce negative charges in the MOS gate electrode. This results in a negative gate capacitance. As a consequence of this negative capacitance, IGBT operation is inherently unstable, leading to current redistribution between cells or even chips.

Method for controlling the impedance of a driver circuit

Abstract: A method for controlling the impedance of drivers controls the output impedance of drivers by coupling the drivers to a impedance control circuit. Accordingly, a desired driver output impedance can advantageously be established and maintained over a wide range of variations in operating conditions and manufacturing processes. Thereby shortening the signal settling time and increasing the attainable signaling frequency.

Fully switched, class-B, high speed current amplifier driver

Abstract: A current amplifier driver capable of driving both 10 Base-T signalling and 100 Base signalling in a Local Area Network (LAN) includes one constant current source. A voltage controlled switch is contained in each of four vertical segment of an H-bridge circuit. Two voltage signals are applied to the switches to control the direction of current from a constant current source across a load. When one of the voltage signals is high, the other is low and two switches of the four switches turn on. The current amplifier driver sinks the constant current in a first direction, such that a voltage drop across the output nodes is positive. When the other voltage signal is high the switches that were on turn off, and the other two switches turn on to sink the constant current across the load in the opposite direction, such that a voltage drop across the output nodes is negative. When both voltage signals are low, all four switches turn off, and the output voltage is zero. In this manner, a differential signal is generated across a resistive load.

Watt-hour meter with digital per-phase power factor compensation

Abstract: A watt-hour meter employs a power factor compensation technique that inserts a delay into the digitized current or voltage sample stream. An exemplary embodiment of the present invention includes an electronic watt-hour meter comprising a voltage sensor, a current sensor, a conversion circuit, and a processing circuit: The voltage sensor generates a voltage measurement signal responsive to a voltage provided to a load. Similarly, the current sensor generates a current measurement signal responsive to a current provided to a load. The conversion circuit further comprises: a first converter connected to the voltage sensor for generating sampled voltage data stream based on said voltage measurement signal; a second converter connected to the current sensor for generating a sampled current data stream based on said current measurement signal, and a phase correction circuit. The phase correction circuit is connected to one of the first and second converters and inserts a delay into one of the sampled voltage data stream or the sampled current data stream. The processing circuit is operably connected to the first and second converters, and receives information indicative of the sampled voltage data stream and sampled current data stream subject to any delay inserted by the phase correction circuit. The processing circuit then generates power consumption data from the sampled voltage data and sampled current data.

Interpolation circuit for digital-to-analog converter

Abstract: A voltage interpolation circuit for a digital-to-analog converter comprises a differential amplifier with composite input devices, each of which is composed of multiple active subtransistors. Interpolation is effected between a first voltage and a second voltage by selectively connecting the gates of the active subtransistors in one of the composite devices to either the first voltage or the second voltage. Each active subtransistor operates in conjunction with a voltage-controlled degeneration subtransistor to form a functional subtransistor pair. Using the nonlinear conductance characteristic of MOS devices operated in the triode region, the transconductance of each functional subtransistor pair is modulated in such a way as to be made relatively insensitive to changes in effective gate-to-source voltage V GS ', so that the interpolation circuit produces equally sized interpolated voltage steps at an analog output.

Resonance type power converter unit, lighting apparatus for illumination using the same and method for control of the converter unit and lighting apparatus

Abstract: A resonance type power converter unit has, in an inverter circuit in which voltage driven type semiconductor devices each having the function not to prevent a backward current are connected in series, the respective voltage driven devices are associated with capacitors which are charged or discharged with currents flowing through the devices and voltage detectors for detecting voltages of the capacitors, and drive circuits for turning on and off the voltage driven devices in accordance with outputs of the voltage detectors. With the resonance type power converter unit, stable resonance operation synchronous with a high-frequency load current can be warranted.

Low cost battery sensing technique

Abstract: A low cost load sensing technique that is suitable for use in sensing batteries in a battery charging circuit is disclosed. The circuit is adapted to be utilized in conjunction with a power supply which may include a primary converter and a voltage feedback circuit. A transformer with a dual secondary winding is connected between the primary converter and the output terminals of the charging circuit. When no load or battery is present, a first feedback loop is utilized with both of the secondary transformer windings in series, which supplies a constant output voltage at the output terminals. When a load is present, a second feedback loop is utilized which includes one of the secondary windings to provide the voltage of the output terminals. A capacitor is connected in parallel with the other secondary winding. When a load is present, a step increase in voltage occurs across the capacitor due to the fact that the both secondary windings are in phase when a load is present. The voltage across the capacitor is used to drive an indicating circuit which provides an indication of a battery when the voltage across the capacitor exceeds a predetermined value. The indicating circuit may include a voltage divider and a Zener diode, configured to drive a transistor. The configuration of the indicating circuit as well as the feedback loops enable the circuit to detect a load, such as a battery, over a relatively wide dynamic range.

LLAMPÜDKEÑ: A high-current, low-impedance pulser employing an auxiliary exponential transmission line

Abstract: The design and constructional aspects of a novel pulse power generator for use in dense plasma research presently under construction are presented. The generator consists of two Marx capacitor banks, each of 0.25 μF, 480 kV, and 28.8 kJ. Each Marx generator drives a water transmission line, in which the live electrode is the central conductor. The transmission lines consist of a constant impedance section followed by a multielectrode gas line gap followed by an exponential taper to the load section. The novel feature is the use of an auxiliary exponential line coupled at the load. This line controls both the voltage and the effective impedance at the load section. In addition, by leaving this line circuit open, energy not coupled to the plasma in the initial high-impedance phase may be reflected back and deposited into the discharge, increasing the peak current by 50%. Circuit simulations using a real-time-varying load impedance show that the current pulse rises in an approximately linear way to a maximum of 1.2 MA at 250 ns. The current falls to zero in the following 250 ns. The current waveform may be flattened simply by disconnecting the auxiliary line, giving a rectangular pulse of 350 ns with a maximum value of 950 kA. The overall impedance of the entire system may be adjusted by varying the separation between the conductors. The equivalent source impedance at the load is 0.8 Q. This low value is by virtue of the auxiliary line, which limits the voltage at the load section and reduces the insulator constraints. We present simulations of the generator under real load conditions. The model also is checked against analytical solutions of exponential line behavior and against other published models of pulse power generators.

Electronic circuit breaker

Abstract: A monolithic electronic circuit breaker having an input terminal, an output terminal, and a controllable impedance connected between the input and output terminals. A current sensor generates a current magnitude signal indicative of the current flowing between the input and output terminals. In one embodiment, an over-current circuit generates an over-current signal when the current magnitude signal exceeds a threshold. In response to at least a first occurrence of the over-current signal, a control circuit controls the controllable impedance so as to reduce current through the controllable impedance for a period of time, and then automatically increase current through the controllable impedance. Further, in response to an N th (N>1) occurrence of the over-current signal, the control circuit controls the controllable impedance so as to reduce current through the controllable impedance and does not thereafter automatically increase current through the controllable impedance. In another embodiment, an over-current and control circuit controls the controllable impedance so as to reduce current through the controllable impedance when the current magnitude signal exceeds a threshold. A first time period after current through the controllable impedance is reduced, the over-current and control circuit automatically increases current through the controllable impedance by gradually reducing the impedance of the controllable impedance over a second time period. Thus, the impedance at the output terminal slowly transitions from a high impedance state to a low impedance state.

High efficiency bimodal power converter and method of operation thereof

Abstract: A bimodal power converter, having an input couplable to a voltage source, provides a charging current to at least one of first and second serially-coupled output energy storage devices. The bimodal converter includes power switching circuitry, coupled to the input, for controlling the charging current conducted through the power converter and a mode selection circuit. The mode selection circuit includes a voltage sensing circuit for sensing an input voltage at the input of the power converter and a mode switching circuit, coupled to the voltage sensing circuit, for selecting an alternative one of a first and second mode of operation. In the first mode of operation, the charging current concurrently flows through both of the first and second output energy storage devices when the input voltage exceeds a threshold voltage. In the second mode of operation, the charging current alternates flowing through the first and second output energy storage devices when the input voltage is less than the threshold voltage. The mode selection circuit thereby decreases losses associated with components of the power converter. Concurrently, a duty cycle of the power switching circuitry reduces to decrease conduction losses associated with the power converter.

A zero voltage switching forward converter topology

Abstract: A zero voltage switching forward converter topology is presented in this paper. The topology employs an auxiliary circuit. Only a few small rating components and devices are added. The merits of the proposed topology include: lossless switching independent of the input and load conditions, simple control and power circuitry, and ability to operate in either voltage or current mode control. A steady state analysis is presented and the design procedure is illustrated. A 100 W 300 kHz prototype zero voltage switching forward converter is built which shows an efficiency improvement of approximately 5% as compared to a conventional hard switching forward converter.

Regulated resonant converter

Abstract: There is disclosed a parallel loaded series resonant converter 300 suitable for supplying DC to a three axis gradient amplifier in an MRI system. In conventional resonant circuits, output voltage is regulated by controlling the switching frequency of an H-bridge or half bridge switching arrangement and the resonant circuit ( 334, 335 ) is under more stress at no load than at full load. The voltage across the resonant capacitor ( 334 ) is a function of the switching frequency, the load and the voltage applied across the resonant circuit (V A -V B ). In the present invention, the peak current at no load is reduced to lower than the peak current at full load by controlling the voltage applied to the resonant circuit (V A -V B ) rather than controlling the switching frequency.

Reproducible analogue circuit for chaotic synchronisation

Abstract: A highly reproducible analogue oscillator has been designed for chaotic synchronisation and secure communication. The oscillator contains a negative impedance converter, an LC resonance loop, an RC phase shift circuit, and a comparator chip used as a nonlinear device.

Phase-shift power supply

Abstract: Power supply apparatus according to the present invention may comprise a direct current source and a phase-shift converter circuit connected to the direct current source A rectifier is connected to the output of the phase-shift converter circuit and rectifies a modulated output signal produced by the phase-shift converter circuit An average current sensor connected to the rectifier senses the time average current in the rectifier and produces an average current feedback signal A control device connected to the average current sensor and to the phase-shift converter circuit is responsive to the average current feedback signal and operates the phase-shift converter circuit in accordance with the average current feedback signal

Varactor controlled fixed frequency VHF DC-DC converter

Abstract: A DC to DC converter including a resonant switching circuit (13, 51 , 115, 151, 125, 153); an impedance matching circuit (53) responsive to the resonant switching circuit; a rectifier circuit (55) responsive to the impedance matching circuit; an output filter circuit (57) responsive to rectifier circuit for providing a filtered DC to DC converter voltage output; and a varactor diode circuit (27, 29, 31, 61) responsive to the filtered DC to DC converter voltage output for controlling the impedance matching circuit such that the filtered DC to DC converter output voltage is substantially constant.

Voltage-to-current converter

Abstract: A voltage-to-current converter for converting an input voltage signal into an output current signal, while providing a filtering function. The input voltage signal is converted to an intermediate current signal by an input resistance and an equivalent resistance provided by, for example, an inverting amplifier and a transistor. A current mirror having a dominant pole converts the intermediate current signal to the output voltage signal, and provides low pass filtering. The converter avoids the use of linear capacitors, and can be easily implemented in a CMOS device.

The effects of flow impedance on the current - voltage characteristics of liquid-metal ion sources

Abstract: By incorporating the flow impedance into the space-charge model of Mair, the current - voltage curves of high impedance liquid-metal ion sources can be fitted to this modified model for an assumed liquid film thickness that decreases with voltage and/or for assumed values of the change in cone half-angle. The new model strongly suggests that what limits the current in high-impedance sources (and eventually in all sources) is a decrease in film thickness with voltage. Coupled to this effect is a self-shaping of the liquid emitter; the higher the flow impedance of an ion source the more pronounced is this self-shaping.

Waveform shaping circuit for function circuit and high order delta sigma modulator

Abstract: A waveform shaping circuit for use in a function circuit is provided which minimizes interference with a feedback circuit of the function circuit and a load. The waveform shaping circuit disposed in the function circuit includes a voltage transfer unit and a voltage-to-current converter unit. The voltage transfer unit transfers a voltage at an output terminal of an operational amplifier to the converter unit in an electrically isolated condition. The converter unit has a predetermined threshold for the magnitude of the voltage at the output terminal. The converter unit supplies an inverting input terminal of the operational amplifier with a current having a magnitude depending on a relationship in magnitude between the voltage at the output terminal and the predetermined threshold. In one embodiment of the invention the waveform shaping circuit is used to prevent the onset of instability in a high order delta sigma modulator.

Semiconductor power converter

Abstract: PROBLEM TO BE SOLVED: To reduce inductance and control an overshooting voltage by utilizing a conductor of the simplified structure. SOLUTION: This semiconductor power converter comprises a group of capacitors connected in parallel, and a converter and an inverter respectively including a plurality of switching elements. The positive conductor connecting (connecting conductor) portions 21a1 to 21a3 of the divided converter and the positive conductor connecting (connecting conductor) portions 21b1 to 21b3 of the divided inverter are formed to the positive side conductor 21 connected to the capacitor. Moreover, the negative conductor connecting (connecting conductor) portions 22a1 to 22a2 of the divided converter and the negative conductor connecting (connecting conductor) portions 22b1 to 22b2 of the divided inverter are formed to the negative side conductor 22 connected to the capacitor. In addition, the positive side conductor 21 and negative side conductor 22, positive conductor of converter and negative conductor of converter (not illustrated), and positive conductor of inverter and negative conductor of inverter (not illustrated) are respectively laminated via an insulation plate 20.

Apparatus and method for generating a current with a positive temperature coefficient

Abstract: The invention provides for a bias current generator (10) which includes a first circuit component (MP2) having a first voltage developed across a pair of terminals thereof, the first voltage decreasing as an operating temperature of the first circuit component increases. The bias current generator further includes a second circuit component (Q2) having a second voltage developed across a pair of terminals thereof, the second voltage decreasing as an operating temperature of the second circuit component increases. In addition, the bias current generator (10) includes an impedance element (R2) connected to the first circuit component (MP2) and the second component (Q2), the impedance element (R2) having (i) an impedance which increases as an operating temperature of the impedance element increases, and (ii) a first current flowing therethrough, wherein a decrease in the first voltage causes a corresponding increase in the first current, and a decrease in the second voltage causes a corresponding increase in the first current. Moreover, the bias current generator (10) includes a mirroring circuit (MP3, MP4) for generating a second current which mirrors the first current flowing through the impedance element (R2). A method for generating a bias current that counteracts the effects temperature has upon electron and hole mobility is also disclosed.

Method and apparatus for estimating residual capacity of storage battery

Abstract: PROBLEM TO BE SOLVED: To accurately estimate the residual capacity of a storage battery, even when charging and discharging are repeated in a condition in which there is no standard of the residual capacity of the battery in a hybrid electric vehicle or the like. SOLUTION: To digitally process the charging and discharging voltage and current of a load 1 such as a motor and a storage battery, the voltage and current are converted into digital signals with an A/D converter 5 and an A/D converter 6 respectively and subsequently converted into a compound spectrum with a frequency converter (FFT) 7 for voltage and another frequency converter (FFT) 8 for current. From these complex spectra of the voltage and current so obtained with the storage battery in use, impedance is calculated with an impedance calculating part 9 to obtain a radius (rj), a characteristic amount of impedance, from the storage battery in operation. This radius (rj) is compared with the radius (rj) which has been obtained beforehand and stored in a battery residual capacity calculating part 10, so that the residual capacity of the storage battery is estimated from the interrelation.