Topic
Negative impedance converter
About: Negative impedance converter is a research topic. Over the lifetime, 5801 publications have been published within this topic receiving 87636 citations.
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TL;DR: This brief presents a fast energy-efficient level converter capable of converting an input signal from subthreshold voltages up to the nominal supply voltage with robust results from a 130-nm test chip.
Abstract: This brief presents a fast energy-efficient level converter capable of converting an input signal from subthreshold voltages up to the nominal supply voltage. Measured results from a 130-nm test chip show robust conversion from 188 mV to 1.2 V with no intermediate supplies required. A combination of circuit methods makes the converter robust to the large variations in the current characteristics of subthreshold circuits. To support dynamic voltage scaling, the level converter can upconvert an input at any voltage within this range to 1.2 V.
123 citations
TL;DR: Comparing the results from the two circuits suggests that there is little to choose between them in terms of a practical implementation, and both circuits were stable over the frequency ranges 1 kHz to 1 MHz.
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.
122 citations
TL;DR: The proposed converter topology possesses the low switch voltage stress characteristic, which will allow one to choose lower voltage rating MOSFETs to reduce both switching and conduction losses, and the overall efficiency is consequently improved.
Abstract: In this paper, a novel transformerless interleaved high step-down conversion ratio dc-dc converter with low switch voltage stress is proposed. In the proposed converter, two input capacitors are series-charged by the input voltage and parallel-discharged by a new two-phase interleaved buck converter for providing a much higher step-down conversion ratio without adopting an extreme short duty cycle. Based on the capacitive voltage division, the main objectives of the new voltage-divider circuit in the converter are for both storing energy in the blocking capacitors for increasing the step-down conversion ratio and reducing voltage stresses of active switches. As a result, the proposed converter topology possesses the low switch voltage stress characteristic. This will allow one to choose lower voltage rating MOSFETs to reduce both switching and conduction losses, and the overall efficiency is consequently improved. Moreover, due to the charge balance of the blocking capacitor, the converter features automatic uniform current sharing characteristic of the interleaved phases without adding extra circuitry or complex control methods. The operation principles and relevant analysis of the proposed converter are presented in this paper. Finally, a 400-V input voltage, 25-V output voltage, and 400-W output power prototype circuit is implemented in the laboratory to verify the performance.
122 citations
TL;DR: In this article, the authors report negative capacitance at low frequencies in organic semiconductor based diodes and show that it appears only under bipolar injection conditions and account quantitatively for this phenomenon by the recombination current due to electron-hole annihilation.
Abstract: The authors report negative capacitance at low frequencies in organic semiconductor based diodes and show that it appears only under bipolar injection conditions. They account quantitatively for this phenomenon by the recombination current due to electron-hole annihilation. Simple addition of the recombination current to the well established model of space charge limited current in the presence of traps yields excellent fits to the experimentally measured admittance data. The dependence of the extracted characteristic recombination time on the bias voltage is indicative of a recombination process which is mediated by localized traps.
121 citations
TL;DR: A multilevel converter with regeneration capability that uses several power cells connected in series, each working with reduced voltage and with an active front end at the line side, works with very high power factor.
Abstract: This paper presents a multilevel converter with regeneration capability. The converter uses several power cells connected in series, each working with reduced voltage and with an active front end at the line side. This paper presents the following: (1) the control method of each cell; (2) the use of phase-shifting techniques to reduce the current and voltage distortion; and (3) criteria to select the connection of the cells. The converter generates almost sinusoidal currents at the load and at the input and works with very high power factor.
121 citations