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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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Proceedings ArticleDOI
01 Nov 2010
TL;DR: In this article, an adaptive voltage regulator is proposed that adjusts its proportional and integral gains as the steady state operating conditions vary, to achieve the design target of a slightly underdamped response at all times.
Abstract: It is important for a bi-directional dual active bridge DC-DC converter to maintain a stable output voltage under input voltage and output load changes, as well as providing a fast transient step response. However, designing a voltage regulator that achieves this performance is challenging, and requires a precise analytical converter model. This paper develops such a model, firstly by analysing the response of the converter to the individual harmonics of the phase shifted square waves that modulate the bridges, and then by combining these responses into a small signal model that accurately describes the dynamic performance of the converter. From this model, an adaptive voltage regulator is then proposed that adjusts its proportional and integral gains as the steady state operating conditions vary, to achieve the design target of a slightly underdamped response at all times. The theoretical analysis is confirmed by matching simulation and experimental results.

43 citations

Patent
Nicolas Marty1
21 Dec 2012
TL;DR: In this article, the authors present a voltage regulation circuit that includes a DC-DC converter and a linear regulator, and a single control loop is configured to generate a single error signal between the output voltage across the load and the first reference voltage.
Abstract: An embodiment of a voltage regulation circuit includes a DC-DC converter configured to control a first current provided from a source to a load via a first output, and a linear regulator configured to control a second current provided from the source to the load via a second output. The voltage regulation circuit further includes a single control loop configured to receive an output voltage across the load and a first reference voltage. The single control loop is further configured to generate a single error signal between the output voltage across the load and the first reference voltage and to control the DC-DC converter and the linear regulator using the single error signal such that when the single error signal is outside of a predetermined range the DC-DC converter provides the first current to the load and the linear regulator provides the second current to the load simultaneously.

43 citations

Journal ArticleDOI
TL;DR: In this article, a wave electromechanical coupling factor is used as a criterion for the design of periodic piezoelectric structures for broadband vibration control, which is based on wave characteristics and does not rely on any modal information.
Abstract: This paper deals with the design of periodic piezoelectric structures for broadband vibration control. By shunting identical negative capacitances to the periodically distributed piezoelectric patches, a wide and continuous band gap is created so as to cover the frequency range of interest. This way the modal density of the structure is reduced and the modal shapes are localized at the boundaries. A large proportion of the energy can then be removed or dissipated by a small number of dampers or energy harvesters integrated within the negative capacitance circuits. A design process is proposed to achieve the wide band gap. The overall amount of piezoelectric materials is constrained in order to keep mass of structures low. The wave electromechanical coupling factor is proposed and used as a criterion. This allows to reach the largest width of the band gap by using a stable value of negative capacitance. The control of multiple high-order modes of a cantilever beam is considered as an example. The vibration reduction performance of the designed piezoelectric structures is presented and the influences of band gap resonance, resistor and the boundary condition are discussed. The proposed approach is fully based on wave characteristics and it does not rely on any modal information. It is therefore promising for applications at mid- and high frequencies where the access to the exact modal information is difficult.

43 citations

Journal ArticleDOI
TL;DR: It is shown that the bulk distribution of ions close to the electrodes differs from the one obtained by means of the linear analysis already for small amplitudes of the applied voltage, and the concept of electrical impedance remains valid.
Abstract: We analyze in which experimental conditions the concept of electrical impedance is useful for an electrolytic cell. The analysis is performed by solving numerically the differential equations governing the phenomenon of the redistribution of the ions in the presence of an external electric field and comparing the results with the ones obtained by solving the linear approximation of these equations. The control parameter in our study is the amplitude of the applied voltage, assumed a simple harmonic function of the time. We show that the bulk distribution of ions close to the electrodes differs from the one obtained by means of the linear analysis already for small amplitudes of the applied voltage. Nevertheless, the concept of electrical impedance remains valid. For larger amplitudes, the current in the circuit is no longer harmonic at the same frequency of the applied voltage. Therefore the concept of electrical impedance is no longer meaningful. The impedance spectroscopy technique is a powerful method for characterizing several electrical properties of me- dia 1. According to this technique, a sample of the material to be characterized is submitted to an external electrical volt- age of amplitude V0 and frequency f = /2 and the elec- trical current in the external circuit, I, is measured. By as- suming that the system is linear, the current I is harmonic as the applied voltage and the amplitude of the current is pro- portional to V0 2,3. In this framework, the electrical imped- ance Z, defined as the applied voltage divided by the current, is independent of the amplitude of the applied voltage. From the analysis of the frequency dependence of Z it is possible to deduce the equivalent dielectric constant and equivalent conductivity 4, or the real and imaginary parts of the com- plex dielectric constant 5, of the sample under consider- ation. These quantities are not molecular properties of the material to be investigated, but depend, usually, on the thick- ness of the sample. The true phenomenological parameters characterizing the medium from the dielectric point of view are then derived by means of a theoretical model 6. The impedance spectroscopy technique is based on the fundamental assumption that the system behaves as a linear system 7. Only in this case the concept of electrical imped- ance can be defined. When the system behaves nonlinearly, even if the applied voltage is harmonic, the electrical current in the circuit contains all the harmonics of higher order. The presence of second- and third-order harmonics is responsible for a deviation from the ellipsoidal shape of the parametric curve representing the current versus the applied voltage. Consequently, the electrical impedance depends on the am- plitude of the applied voltage and on the time. In this case, in our opinion, it is no longer possible to derive the dielectric properties of the medium from the analysis of the electrical impedance only. Our aim is to investigate under which conditions the con- cept of electrical impedance can be useful from an experi- mental point of view. In our analysis we consider the case of an electrolytic cell 8. In this case the fundamental equa- tions describing the redistribution of the ions in the presence of an external electric field are the continuity and drift- diffusion equations for the ions and the Poisson equation for the actual electrical potential 9. These equations are pre- sented in Sec. II in their general form. The case in which the fundamental equations of the problem can be linearized is also discussed and the concept of electrical impedance intro- duced. In Sec. III, we compare the numerical solutions for the bulk densities of the ions and for the electric potential across the sample with the solutions obtained by means of the linearized equations. As expected, the two are in good agreement when the amplitude of the applied voltage is small with respect to the thermal voltage—i.e., of the order of 25 mV for monovalent ions at room temperature. Increasing the amplitude of the applied voltage, the agreement is poorer

43 citations

Patent
17 Apr 2008
TL;DR: In this article, a control method and a controller for a DC-DC converter, such as a synchronous Buck converter, which exploits the principle of capacitor charge balance to allow the converter to recover from a positive and/or negative load current step in the shortest achievable time, with the lowest possible voltage undershoot/overshoot.
Abstract: The invention relates to a control method and a controller for a DC-DC converter, such as a synchronous Buck converter, which exploits the principle of capacitor charge balance to allow the converter to recover from a positive and/or negative load current step in the shortest achievable time, with the lowest possible voltage undershoot/overshoot. The control method may be implemented by either an analog or a digital circuit. The controller may be integrated with existing controller schemes (such as voltage-mode controllers) to provide superior dynamic performance during large-signal transient conditions while providing stable operation during steady state conditions. The invention also relates to a method and a modification of a DC-DC converter topology that comprises connecting a controlled current source between an input terminal and an output terminal of the DC-DC converter; detecting a load current step to a new load current; modifying a duty cycle of the DC-DC converter; and modifying current through a parallel output capacitor of the DC-DC converter by controlling current of the current source. The methods and circuits provided herein are applicable to Buck converters and Buck-derived converters such as forward, push-pull, half-bridge, and full-bridge converters.

43 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202330
2022104
2021120
2020131
2019134
2018155