Showing papers on "Output impedance published in 2000"

Electrical energy storage device

Abstract: An electricity storage device and a portable electric-powered tool. The device comprises at least a battery; at least a super capacitor, which has lower internal impedance, when fully charged, than that of the battery and connects the battery in parallel; and an output end for supplying the electricity. The super capacitor is the major power supply for the pulse current output; the battery is used for generating electricity to the super capacitor and is the secondary power supply for the pulse current output. The connection of the battery and the super capacitor does not need any converters or current-limiting resistors.

Automatic activation of electrosurgical generator bipolar output

Abstract: An automatic circuit that controls a surgical instrument having a pair of bipolar electrodes. The circuit comprises means for measuring the current between the pair of electrodes, an impedance detection circuit in electrical communication with the current measuring means, a comparator in electrical communication with the impedance detection circuit and a controller electrically connected to the comparator. The impedance detection circuit calculates the impedance between the electrodes based on the measured current and generates a first signal indicative of the calculated impedance. The comparator processes the first signal and generates an activation signal if the calculated impedance falls within a predetermined range of impedance values and generates a deactivation signal if the calculated impedance exceeds a deactivation threshold. The controller receives the activation and deactivation signals and transmits a first control signal to a radiofrequency energy output stage to activate the electrodes in response to the activation signal and transmits a second control signal to the radiofrequency output stage to deactivate the electrodes in response to the deactivation signal.

Synthetic impedance for implementation of piezoelectric shunt-damping circuits

Abstract: Piezoelectric transducer (PZT) patches may be attached to structures to reduce vibration. The PZT patches essentially convert vibrational mechanical energy to electrical energy. The electrical energy can be dissipated via an electrical impedance. The authors introduce a method of implementing any arbitrary impedance, using a digital signal processor. The ‘synthetic impedance’ is demonstrated on a resonant simply supported beam.

Transformerless 3 phase power inverter

Abstract: The invention in the simplest form is an improved transformerless 3 phase power inverter topology and control method for power distribution systems. This 3 phase power inverter system provides the necessary output voltage and current waveform regulation, harmonic distortion rejection, very low output impedance, and ultra low DC offset of the output AC power, even when exposed to a high magnitude of the non-linear, single phase, or the unbalanced loading.

Automatic input impedance balancing for electrocardiogram (ECG) sensing applications

Abstract: A voltage sensing system includes input impedance balancing for electrocardiogram (ECG) sensing or other applications, providing immunity to common-mode noise signals while capable of use with two electrodes. Signals are received at first and second electrodes having associated impedances. An impedance circuit includes a feedback controller that adjusts an effective impedance associated with the second electrode based on a difference signal, a common mode signal, a phase-shifted (e.g., quadrature common mode) signal, and an impedance associated with the first electrode. As a result, signals associated with each electrode undergo a similar degree of gain/attenuation and/or phase-shift. This reduces common mode noise and enhances the signal-to-noise characteristics of a desired ECG or other output signal, without requiring the use of more than two electrodes.

A comparison of modified Howland circuits as current generators with current mirror type circuits

Abstract: Multi-frequency electrical impedance tomography (EIT) systems require stable voltage controlled current generators that will work over a wide frequency range and with a large variation in load impedance. In this paper we compare the performance of two commonly used designs: the first is a modified Howland circuit whilst the second is based on a current mirror. The output current and the output impedance of both circuits were determined through PSPICE simulation and through measurement. Both circuits were stable over the frequency ranges 1 kHz to 1 MHz. The maximum variation of output current with frequency for the modified Howland circuit was 2.0% and for the circuit based on a current mirror 1.6%. The output impedance for both circuits was greater than 100 kohms for frequencies up to 100 kHz. However, neither circuit achieved this output impedance at 1 MHz. Comparing the results from the two circuits suggests that there is little to choose between them in terms of a practical implementation.

Measurement of noise source impedance of off-line converters

Abstract: The insertion loss method is proposed to measure the noise source impedance of off-line power supplies. The information obtained through the proposed method enables the prediction of EMI filter performance and the design of a suitable filter for a switch mode power supply.

Impedance control system for a center tapped termination bus

Abstract: A method and apparatus for an impedance control system for a center tapped termination bus. One method of the present invention comprises comparing an output potential of a buffer with a pair of reference potentials. The output impedance of the buffer is adjusted to cause the buffer output voltage swing to match the reference potentials.

Current-Mode High Output Impedance Sinusoidal Oscillator Configuration Employing Single FTFN

Abstract: In this study, a general current-mode high output impedance sinusoidal oscillator configuration is proposed. The proposed oscillator configuration uses a single four terminal floating nullor (FTFN), two capacitors and five resistors. The oscillator configuration exhibits high output impedance which makes easy to drive loads without using any buffering devices and provide non-interactive control of oscillation condition and oscillation frequency. The proposed topology also yields single frequency oscillators with reduced number of passive components. All of the proposed oscillators permit good frequency stability and exhibit low active and passive sensitivities. Theoretical analysis is verified with experimental results.

A novel parametric-effect MEMS amplifier

Abstract: This paper presents the theory and measurements of a mechanical parametric-effect amplifier with a 200-kHz input signal and a 1.84-MHz output signal. The device used is a MEMS time-varying capacitor which is composed of an array of low-stress metallized silicon-nitride diaphragms, and is pumped by a large-signal voltage at 1.64 MHz. This induces a large change in the capacitance, and results in parametric amplification of an input signal at 200 kHz. The parametric amplifier capacitance is 500 pF, resulting in an output impedance of 140 /spl Omega/. A higher impedance can also be achieved with a lower capacitance. To our knowledge, this device is the first-ever MEMS mechanical up-converter parametric-effect amplifier developed with an up-conversion ratio of 9:1. The measurements agree very well with theory, including the effect the series resistance and the and of the MEMS time-varying capacitor. The application areas are in amplifiers which operate at very high temperatures (200/spl deg/C-600/spl deg/C), under high particle bombardment (nuclear applications), in non-semiconductor-based amplification, and in low-noise systems, since parametric amplifiers do not suffer from thermal, shot, or 1/f noise problems.

Three-dimensional stability analysis of DC power electronics based systems

Abstract: Power electronics based power distribution systems are becoming increasingly common, particularly in marine and aerospace applications. Stability analysis of this class of systems is crucial due to the potential for negative impedance instability. Existing techniques of stability analysis introduce artificial conservativeness, are sensitive to component grouping, and at the same time do not explicitly address uncertainties and variations in operating point. Recently, a new stability criterion which reduces artificial conservativeness and is also insensitive to component grouping has been set forth along with a means of readily establishing design specifications from an arbitrary stability criterion which specifically includes a provision to incorporate uncertainty, parameter variation, and nonlinearities. Therein, the method is used to develop a load admittance constraint based on a generalized source impedance. In this paper, that work is further explained and the converse problem, that of generating a constraint on the source impedance from the load admittance, is also illustrated.

Methods for dual-gated transistors

Abstract: A circuit and method for an improved inverter is provided. The present invention capitalizes on a switched source impedance to prevent subthreshold leakage current at standby in low voltage CMOS circuits. The switched source impedance is provided by dual-gated transistors. The dual gates of the transistors are biased to modify the threshold voltage of the transistors (V t ). This design provides fast switching capability for low power battery operated CMOS circuits and systems. The devices can be used in a variety of applications, digital and analog, wherever a more compact structure with low power consumption and fast response time is needed.

Current sensing and current sharing

Abstract: An interleaved small-inductance buck voltage regulator (VRM) converter with the novel current sensing and sharing technology significantly improves transient response with size minimization. Specifically, two or more buck VRM modules are interleaved or connected in parallel. The resultant current waveform has a fast transient response but with reduced ripples since the ripples in the individual modules mathematically cancel one another. The result is a smooth output current waveform having spikes within an acceptable tolerance limits when for example the load increases due to a connected processor changing from “sleep” to “active” mode. A novel current sensing and sharing scheme between the individual VRMs is implemented using an RC network in each module to detect inductor current for that module. Good current sharing result can be easily achieved. Unlike peak current mode control and average current mode control, with this technology, the converter still has low output impedance and fast transient response. As a result, the VRM can be very cost-effective, high power density, high efficiency and have good transient performance.

Controller arrangement for boost converter systems sourced from solar photovoltaic arrays or other maximum power sources

Abstract: Conventional power converter systems, such as boost converters, derive their input from sources that may be considered to have negligible output impedances. As such, the use of quite simple conventional control algorithms suffice to give acceptable performance. When the output impedance of the source to such a converter is no longer negligible, and moreover if the source has a markedly nonlinear output impedance, the simple conventional algorithms will no longer be adequate to satisfy the control requirements of the converter. The effect of driving such a converter from a type of source, for example a photovoltaic array which has a point of maximum power delivery within the operating range is discussed, as is the impact that the use of such a source has upon the control requirements of the converter. A novel control arrangement, which includes a complete embedded maximum power tracker, is then presented together with results validating the proposed controller.

Non-contact tag

Abstract: PROBLEM TO BE SOLVED: To provide a non-contact tag capable of easily realizing an impedance matching circuit, maximizing power transmittable from an antenna part to an IC even when supply power is small and performing long distance communication by constituting the impedance matching circuit for matching the impedance of the antenna part and the impedance of the IC by using a capacitor and/or a coil. SOLUTION: This non-contact tag is provided with the antenna part for transmitting and receiving data, the IC for processing the data and the impedance matching circuit for matching the impedances of the antenna part and the IC and is provided with the functions of storing reception data and transmitting storage data. The impedance matching circuit is constituted of the capacitor and/or the coil.

RF amplifier having switched load impedance for back-off power efficiency

Abstract: Efficiency of an RF/microwave power amplifier is increased at a back-off power level by increasing the load resistance of the amplifier at the reduced output power level as compared to load impedance at a higher power level including full operating power. The different load impedances can be realized with two amplification units in parallel each having different load impedances. Alternatively, a single amplification path can be provided with an output impedance matching network which is selectively bypassed for increased impedance load during back-off power operation. In another embodiment, the output impedance matching network can include a shunt inductance which is selectively switched into the network to increase impedance for back-off power operation.

Refined multiload method for measuring acoustical source characteristics of an intake or exhaust system

Abstract: The one-port source characteristics in a duct system, viz., source impedance and strength, can be determined by using the four-load method. In this paper, to avoid the instability problem of the conventional four-load method, a new formulation for the multiload method has been proposed, which employs an error function based on the linear, time-invariant source model. It is shown that the method is less sensitive to input errors compared to the previous methods. For a 10% input error, the proposed method yields a relative error in the source resistance that is about 1/100 times smaller than for the conventional method. The effectiveness of the present method is demonstrated by two test examples, a loudspeaker and a blower, each operating in a duct. It is observed that the conventional and least-squares methods result in large errors, whereas the present method yields far better agreement with the actual source parameters, as measured by the direct method. The present method is then used to obtain the source parameters on the exhaust side of an operating internal combustion engine. The radiated sound spectrum from the exhaust opening is predicted by using the measured source parameters and the calculated result agrees very well with the measured one.

Segemented D/A converter with enhanced dynamic range

Abstract: A digital-to-analog converter having series-connected transistors forming high impedance current sources for respective segmented resistor strings. A series transistor forming a current sink for one resistor string presents a high output impedance by utilizing a negative feedback amplifier. The effects of a headroom resistor and an offset resistor in one resistor string are negated by configuring an output amplifier with appropriate gain resistors. A highly accurate D/A conversion can be achieved by utilizing all resistors of the main and sub-resistor strings with the same value.

Power system impedance measurement using a power electronic converter

Abstract: This paper describes a method for on-line measurement of power system impedance to source. The method employs a power electronic circuit to inject a small current disturbance onto the energised power network, and the measurements of the disturbance current and resultant voltage transient are used to identify impedance. Simulation results demonstrate the effectiveness of the technique for identification of the impedance of transmission lines and linear loads. An alternative data processing technique is introduced in order to address the measurement problems associated with nonlinear loads. This technique is also illustrated using simulation.

Method and system for power line impedance detection and automatic impedance matching

Abstract: A system and method for the automatic detection and matching of power line impedance which makes use of level detection and source impedance circuits in electronic communication with the existing circuitry of a power line communication devices are disclosed. This invention uses modified power line communication device circuitry to sense the impedance of the power line and to correct its impedance to match the impedance of the power line. By automatically sensing and adjusting the source impedance of the power line jack this invention maximizes power transfer to and from the power line, reduces radiated power as well as the power line reflection coefficient.

Method for estimating remaining capacity of secondary battery

Abstract: PROBLEM TO BE SOLVED: To accurately estimate a remaining capacity of a secondary battery using simple calculations. SOLUTION: There are set a step of obtaining a temperature T (S301), a step of obtaining a time averaged value Iav of a current (S302), a step of obtaining a time average value Vav of a voltage (S303), a step of obtaining an internal impedance Z, based on the temperature T (S304), a step of calculating an open-circuit voltage OCV (S305) and a step of estimating the battery remaining capacity from the open-circuit voltage OCV (S306). The open-circuit voltage OCV is calculated with the use of the current time averaged value Iav, the voltage time average value Vav and the internal impedance Z. The battery remaining capacity SOC is determined, on the basis of the open circuit voltage OCV and the temperature T. A value, obtained by correcting the voltage time average value Vav by the product of the current time average value Iav and the internal impedance Z, is calculated as the open-circuit voltage OCV. COPYRIGHT: (C)2002,JPO

System impedance measurement for use with active filter control

Abstract: This paper describes a method for on-line measurement of power system impedance to source. The method employs a power electronic circuit to inject a small current disturbance onto the energised power network, and the measurements of the disturbance current and resultant voltage transient are used to identity impedance. Simulation results demonstrate the effectiveness of the technique for identification of the impedance of transmission lines and linear loads. An alternative data processing technique is introduced in order to address the measurement problems associated with nonlinear loads. This technique is also illustrated using simulation.

High-speed high-precision min/max circuits in CMOS technology

Abstract: New voltage-mode min/max circuits are introduced that have a simple architecture. Unlike conventional winner-take-all or source follower based schemes, the proposed circuits are characterised by reduced voltage swing at all internal nodes and by a very low output impedance, which enables them to provide high-speed and high-precision operation. Their complexity grows linearly with the number of inputs. The characterisation of a test chip prototype has provided experimental verification of these features.

An Accurate Fault Location Algorithm For Double-Circuit Transmissisn Systems

Abstract: This paper describes an accurate fault locatio11 algorithm based on sequence current distribution facbrs for

Method of hot switching a plasma tuner

Abstract: The present hot switching method and impedance matching circuit extends the tuning range of matching circuits to include increased power levels. The hot switching method and circuit includes coupling a controlled impedance network between an RF generator output and a plasma chamber input for matching impedances. The controlled impedance network includes an RF switch for switching a predetermined impedance. A device performance characteristic of the RF switch is determined. RF power is applied from the RF generator through the controlled impedance network to the plasma chamber. A signal characteristic of the impedance match is measured. The RF switch is controlled based upon the measured signal characteristic such that the impedance match is driven towards a predetermined matching range. The RF switch is switched any speed based upon the device performance characteristic.

An accurate fault location algorithm for double-circuit transmission systems

Abstract: This paper describes an accurate fault location algorithm based on sequence current distribution meters for a double-circuit transmission system. The proposed method uses the voltage and current collected at only the local end of a single-circuit. This method is virtually independent of the fault resistance and the mutual coupling effect caused by the zero-sequence current of the adjacent parallel circuit and insensitive to the variation of source impedance. The fault distance is determined by solving the forth-order KVL (Kirchhoff's voltage law) based distance equation. The zero-sequence current of adjacent circuit is estimated by using a zero-sequence current distribution factor and the zero-sequence current of the self-circuit. Thousands of fault simulations by EMTP have proved the accuracy and effectiveness of the proposed algorithm.

High-speed output driver with an impedance adjustment scheme

Abstract: A dynamic impedance adjustment circuit that reduces overshoot and undershoot noise while achieving fast slew rates. The dynamic impedance adjustment circuit has an output driver for selectively driving or drawing current providing source or sink current. The dynamic impedance adjustment circuit also has an a variable impedance output driver for selectively providing a dynamic current (source or sink) for a predetermined time after transitions from a logic low level to a logic high level or from a logic high level to a low logic level in the input signal. An impedance adjustment control circuit is coupled to the variable impedance output driver for automatically detecting the transitions in the input signal and for changing the impedance of the variable impedance output driver based on the input signal, enable signal, and the output node.

Programmable impedance control output circuit and programmable impedance control method thereof in semiconductor device

Abstract: The invention relates to an impedance control output circuit of a semiconductor device and a method relevant thereto to prevent or minimize various problems caused by a transmission error by automatically resetting the impedance mismatch resulting from variances of supply voltage, temperature, other operational conditions. The impedance control output circuit of the semiconductor device comprises: an impedance detection, comparison and adjustment part for performing a normal operation and an automatic reset operation by comparing array reference voltage with pad voltage of a pad connected to an external resistance to obtain the pad voltage tracking the array reference voltage and by comparing the array reference voltage with the reference voltage predetermined by a resistant voltage divider for resetting the level of the array reference voltage to obtain the array reference voltage tracking the constant reference voltage; and a driving and data outputting part for driving impedance of a data output terminal of the semiconductor device in response to results of the normal and automatic reset operation to thereby output the internal data.

Impedance Spectroscopy by Voltage‐Step Chronoamperometry Using the Laplace Transform Method in a Lithium‐Ion Battery

Abstract: Impedance spectroscopy by voltage-step chronoamperometry (VSCA) using the Laplace transform method is proposed. With this method an impedance Bode diagram for a very wide range of frequencies can be obtained by only one measurement of the current response to an applied voltage step change. Further, by applying staircase voltage-step chronoamperometry (SVSCA), each impedance diagram at each voltage step can be obtained, and it is easy to examine the change in the impedance of batteries due to discharging or charging. The VSCA method has been applied to a lithium-ion battery. It has been demonstrated that an impedance diagram for a wide range of frequencies between 1 mHz and several kilohertz can be obtained by only one VSCA and that the results obtained by this method agree with the results from applied sine-wave measurements in a battery at equilibrium. The impedance change at every 50 mV between 2.8 and 4.2 V due to discharging or charging is measured by applying SVSCA in a lithium-ion battery, and the results are discussed. The battery impedance is realized to increase due to discharging, and the impedance may be affected by the previous treatment applied to the battery.