Negative impedance converter

About: Negative impedance converter is a(n) research topic. Over the lifetime, 5801 publication(s) have been published within this topic receiving 87636 citation(s).

A comparison of half-bridge resonant converter topologies

Abstract: The half-bridge series-resonant, parallel-resonant, and combination series-parallel resonant converters are compared for use in low-output-voltage power supply applications. It is shown that the combination series-parallel converter, which takes on the desirable characteristics of the pure series and the pure parallel converter, avoids the main disadvantages of each of them. Analyses and breadboard results show that the combination converter can run over a large input voltage range and a large load range (no load to full load) while maintaining excellent efficiency. A useful analysis technique based on classical AC complex analysis is introduced. >

Use of Negative Capacitance to Provide Voltage Amplification for Low Power Nanoscale Devices

Abstract: It is well-known that conventional field effect transistors (FETs) require a change in the channel potential of at least 60 mV at 300 K to effect a change in the current by a factor of 10, and this minimum subthreshold slope S puts a fundamental lower limit on the operating voltage and hence the power dissipation in standard FET-based switches. Here, we suggest that by replacing the standard insulator with a ferroelectric insulator of the right thickness it should be possible to implement a step-up voltage transformer that will amplify the gate voltage thus leading to values of S lower than 60 mV/decade and enabling low voltage/low power operation. The voltage transformer action can be understood intuitively as the result of an effective negative capacitance provided by the ferroelectric capacitor that arises from an internal positive feedback that in principle could be obtained from other microscopic mechanisms as well. Unlike other proposals to reduce S, this involves no change in the basic physics of the FET and thus does not affect its current drive or impose other restrictions.

Automatic bipolar control for an electrosurgical generator

Abstract: An automatic circuit measures electrosurgical generator output and controls in accord with impedance between activated movable bipolar electrodes able to contact tissue. Voltage monitor in parallel and current monitor in series with the electrodes measure instantaneous variations and generate proportional signals. First and second calculators receive the signals and find respectively, by dividing the voltage by current, short circuit impedances and impedances other than short circuit impedances between the electrodes. First and second comparators receive the respective outputs from the first and second calculators and assess them against respective first and second references providing signs of short conditions and assessments of changes in impedance between the electrodes. A logic analyzer receives the signs and assessments and evaluates them to permit the instantaneous starting, operating or stopping of the electrosurgical generator. The electrodes include an instrument and a set of cables with a preselected combined impedance so the maximum instantaneous impedance between the electrodes is less than the preselected combined impedance. The second reference is user adjustable. Switches, associated with each of the voltage monitor and the current monitor, choose the gain applied to the proportional signals respectively therefrom. First and second calculator gain changers receive the signals for setting the range across which those respective signals are used. Methods have steps of monitoring voltage and current, generating signals, dividing the voltage signal by current signal to find short circuit impedance between the electrodes and the instantaneous changes in impedance for other than the short circuit impedance, assessing those findings against references and permitting the starting, operating, or stopping of the electrosurgical generator.

Impedance Modeling and Analysis of Grid-Connected Voltage-Source Converters

Abstract: This paper presents small-signal impedance modeling of grid-connected three-phase converters for wind and solar system stability analysis. In the proposed approach, a converter is modeled by a positive-sequence and a negative-sequence impedance directly in the phase domain. It is further demonstrated that the two sequence subsystems are decoupled under most conditions and can be studied independently from each other. The proposed models are verified by experimental measurements and their applications are demonstrated in a system testbed.

A Bidirectional DC–DC Converter for an Energy Storage System With Galvanic Isolation

Abstract: This paper addresses a bidirectional dc-dc converter suitable for an energy storage system with an additional function of galvanic isolation. An energy storage device such as an electric double layer capacitor is directly connected to a dc side of the dc-dc converter without any chopper circuit. Nevertheless, the dc-dc converter can continue operating when the voltage across the energy storage device drops along with its discharge. Theoretical calculation and experimental measurement reveal that power loss and peak current impose limitations on a permissible dc-voltage range. This information may be useful in design of the dc-dc converter. Experimental results verify proper charging and discharging operation obtained from a 200-V, 2.6-kJ laboratory model of the energy storage system. Moreover, the dc-dc converter can charge the capacitor bank from zero to the rated voltage without any external precharging circuit.