Showing papers on "Negative impedance converter published in 2010"

Analysis and Design of High-Frequency Isolated Dual-Bridge Series Resonant DC/DC Converter

Abstract: Bidirectional dual-bridge dc/dc converter with high frequency isolation is gaining more attentions in renewable energy system due to small size and high-power density. In this paper, a dual-bridge series resonant dc/dc converter is analyzed with two simple modified ac equivalent circuit analysis methods for both voltage source load and resistive load. In both methods, only fundamental components of voltages and currents are considered. All the switches may work in either zero-voltage-switching or zero-current-switching for a wide variation of voltage gain, which is important in renewable energy generation. It is also shown in the second method that the load side circuit could be represented with an equivalent impedance. The polarity of cosine value of this equivalent impedance angle reveals the power flow direction. The analysis is verified with computer simulation results. Experimental data based on a 200 W prototype circuit is included for validation purpose.

Novel High Step-Up DC–DC Converter for Fuel Cell Energy Conversion System

Abstract: A novel high step-up dc-dc converter for fuel cell energy conversion is presented in this paper. The proposed converter utilizes a multiwinding coupled inductor and a voltage doubler to achieve high step-up voltage gain. The voltage on the active switch is clamped, and the energy stored in the leakage inductor is recycled. Therefore, the voltage stress on the active switch is reduced, and the conversion efficiency is improved. Finally, a 750-W laboratory prototype converter supplied by a proton exchange membrane fuel cell power source and an output voltage of 400 V is implemented. The experimental results verify the performances, including high voltage gain, high conversion efficiency, and the effective suppression of the voltage stress on power devices. The proposed high step-up converter can feasibly be used for low-input-voltage fuel cell power conversion applications.

Metal-Ferroelectric-Meta-Oxide-semiconductor field effect transistor with sub-60mV/decade subthreshold swing and internal voltage amplification

Abstract: This work reports the first complete experimental demonstration and investigation of subthreshold swing, SS, smaller than 60 mV/decade, at room temperature, due to internal voltage amplification in FETs with a Metal-Ferroelectric-Metal-Oxide gate stack. The investigated p-type MOS transistor is a dedicated test structure to explore the negative capacitance effect by probing the internal voltage between the P(VDF-TrFE) and SiO 2 dielectric layers of the gate stack. We find that the region of internal surface potential amplification, dψ S /dV g >1, corresponds to an S-shape of the polarization versus ferroelectric voltage (associated with negative capacitance). In Fe-FETs the internal voltage amplification could significantly lower their SS, even without reaching sub-60mV/dec values. SS min as low as 46 to 58 mV/decade and average swings, SS avg , as small as 51 to 59 mV/dec are observed for the first time in a minor loop hysteretic characteristics of Fe-FETs.

Interleaved-Boost Converter With High Voltage Gain

Abstract: This paper presents an interleaved-boost converter, magnetically coupled to a voltage-doubler circuit, which provides a voltage gain far higher than that of the conventional boost topology. Besides, this converter has low-voltage stress across the switches, natural-voltage balancing between output capacitors, low-input current ripple, and magnetic components operating with the double of switching frequency. These features make this converter suitable to applications where a large voltage step-up is demanded, such as grid-connected systems based on battery storage, renewable energies, and uninterruptible power system applications. Operation principle, main equations, theoretical waveforms, control strategy, dynamic modeling, and digital implementation are provided. Experimental results are also presented validating the proposed topology.

Erratum: Analytic Model for the Surface Potential and Drain Current in Negative Capacitance Field-Effect Transistors

Abstract: In 2008, Salahuddin and Datta proposed that a ferroelectric material operating in the negative capacitance (NC) region could act as a step-up converter of the surface potential in a metal-oxide-semiconductor structure, opening a new route for the realization of transistors with steeper subthreshold characteristics (S <; 60mV/dec). In this paper, a comprehensive physics-based surface potential and a drain current model for the NC field-effect transistor are reported. The model is aimed to evaluate the potentiality of such transistors for low-power switching applications. This paper also sheds light on how operation in the NC region can be experimentally detected.

An Energy-Efficient Subthreshold Level Converter in 130-nm CMOS

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.

Broadband, Efficient, Electrically Small Metamaterial-Inspired Antennas Facilitated by Active Near-Field Resonant Parasitic Elements

Abstract: The possibility of using an active internal matching element in several types of metamaterial-inspired, electrically small antennas (ESAs) to overcome their inherent narrow bandwidths is demonstrated. Beginning with the Z antenna, which is frequency tunable through its internal lumped element inductor, a circuit model is developed to determine an internal matching network, i.e., a frequency dependent inductor, which leads to the desired enhanced bandwidth performance. An analytical relation between the resonant frequency and the inductor value is determined via curve fitting of the associated HFSS simulation results. With this inductance-frequency relation defining the inductor values, a broad bandwidth, electrically small Z antenna is established. This internal matching network paradigm is then confirmed by applying it to the electrically small stub and canopy antennas. An electrically small canopy antenna with k? = 0.0467 that has over a 10% bandwidth is finally demonstrated. The potential implementation of the required frequency dependent inductor is also explored with a well-defined active negative impedance converter circuit that reproduces the requisite inductance-frequency relations.

Hybrid Buck–Boost Feedforward and Reduced Average Inductor Current Techniques in Fast Line Transient and High-Efficiency Buck–Boost Converter

Abstract: This paper presents a buck-boost converter with high efficiency and small output ripple to extend the battery life of portable devices. Besides, the hybrid buck-boost feedforward (HBBFF) technique is integrated in this converter to achieve fast line response. The new control topology minimizes the switching and conduction losses at the same time even when four switches are used. Therefore, over a wide input voltage range, the proposed buck-boost converter with minimum switching loss like the buck or boost converter can reduce the conduction loss through the use of the reduced average inductor current (RAIC) technique. Moreover, the HBBFF technique minimizes the voltage variation at the output of error amplifier. Consequently, a fast line transient response can be achieved with small dropout voltage at the output. Especially, the converter can offer good line and load regulations to ensure a regulated output voltage without being affected by the decreasing battery voltage. Experimental results show that the output voltage is regulated over a wide battery lifetime, and the output ripple is minimized during mode transition. The peak efficiency is 97% and the transient dropout voltage can be improved substantially.

Soft-Switching PS-PWM DC–DC Converter for Full-Load Range Applications

Abstract: An improved soft-switching full-bridge phase-shifted pulsewidth modulation converter using insulated-gate bipolar transistors with a special auxiliary transformer is presented in this paper. Zero-voltage switching for leading leg and zero-current switching for lagging leg switches in the converter are achieved for full-load range from no load to short circuit by adding an active energy recovery clamp and auxiliary circuits. The new significant feature of the converter consists in suppression of circulating current also in short-circuit conditions. The proposed converter is very attractive for applications where short circuit and no load are the normal states of the converter operation, e.g., arc welding. The principle of operation is explained and analyzed, and experimental results are presented on a 3-kW 50-kHz laboratory converter model.

A Dynamic LVRT Solution for Doubly Fed Induction Generators

Abstract: Doubly fed induction generators have become the most common type of wind turbine generators. However, this type of generator is susceptible to grid-side low voltage and short circuits due to existence of a power electronics converter on the rotor side. When a short circuit or voltage sag happens on the grid side, the rotor current of the generator tends to rise, which could cause damage to the rotor converter. Design and implementation of a series converter on the stator side is presented in this paper to limit the current rise in the rotor. This system includes an active AC/DC inverter, three series transformers, and a DC-bus capacitor. To lower the rating of the components and make the system viable for practical solutions, an exponential decaying sinusoidal voltage, instead of a pure sinusoidal voltage, is applied by the converter during short circuit.

Two-stage insulated bidirectional DC/DC power converter using a constant duty ratio LLC resonant converter

Abstract: A two-stage insulated bidirectional DC/DC power converter is disclosed. A two-stage insulated bidirectional DC/DC power converter according to an embodiment of the invention has the characteristic of including: an LLC resonant converter operating at a constant duty ratio; a bidirectional converter joined to a front part of the LLC resonant converter and configured to perform a booster converter function of outputting the input voltage at a consistent input voltage for the LLC resonant converter, and a buck converter function of reducing the voltage by way of the LLC resonant converter and then outputting a consistent voltage; and a bidirectional converter control unit configured to control changes in an input voltage of the bidirectional converter and regulate an output voltage of the LLC resonant converter to thereby maintain a consistent input voltage of the LLC resonant converter, such that the LLC resonant converter operates at a constant duty ratio.

Analysis of Passive Boost Power Converter for Three-Phase SR Drive

Abstract: This paper presents a novel passive boost power converter and its analysis for a three-phase switched reluctance (SR) drive. The proposed simple passive circuit adds three diodes and one capacitor to the front end of a conventional asymmetric converter in order to obtain a high negative bias. Based on this passive power network, the terminal voltage of the converter side is at general dc-link voltage level in parallel mode and is up to a double dc-link voltage level in series mode. As a result, it can suppress the negative torque generation from the tail current and improve the output power. Combining a passive circuit with a three-phase asymmetric converter without phase-current overlap, the phase winding obtains the dc-link voltage in the excitation mode and the negative double dc-link voltage in the demagnetization mode. With the phase-current overlap, the dc-link voltage or the double dc-link voltage is dependent on the overlap current. The operation modes of the proposed converter are analyzed with a three-phase SR motor. The selection of the boost capacitor is considered, and a detailed analysis of current-overlap modes is presented. The compared simulation and experiments are done. The results verify the performance of the proposed converter.

Analytic model for the surface potential and drain current in negative capacitance field-effect transistors

Abstract: In 2008, Salahuddin and Datta proposed that a ferroelectric material operating in the negative capacitance region could act as a step-up converter of the surface potential in a MOS structure, opening a new route for the realization of transistors with steeper subthreshold characteristics (S<60 mV/decade). In this letter, a comprehensive physics-based surface potential and drain current model for the negative capacitance field-effect transistor is reported. The model is aimed to evaluate the potentiality of such transistors for low-power switching applications. Moreover it provides a model core for memories devices relying on the hysteretic behavior of the ferroelectric gate insulator.

An Improved Current-Fed ZVS Isolated Boost Converter for Fuel Cell Applications

Abstract: This paper proposes an improved current-fed zero-voltage switching isolated boost converter suitable for fuel cell applications. Preserving the inherent advantages of the current-fed converter which include smaller input current ripple, lower diode voltage rating, and lower transformer turns ratio, the proposed converter does not require any clamping and start-up circuits unlike the conventional current-fed converters. The voltage ratings of the primary switches and secondary diodes of the proposed converter are significantly reduced. Some alternative schemes of the proposed converter without the voltage-second unbalance are presented. These characteristics of the proposed converter lead to a high overall efficiency over wider load range. Experimental results on a 1 kW prototype are provided to validate the proposed concept.

Circuit arrangement including a multi-level converter

Abstract: In accordance with an embodiment, a circuit includes voltage supply terminals configured to provide an AC output voltage, at least two converter units, and a control circuit. Each converter unit includes input terminals configured to be connected to an electrical charge storage unit, output terminals, and a switch arrangement connected between the input and output terminals. The switch arrangement is configured to receive a control signal, and provide an output voltage having a duty-cycle dependent on the control signal. The control circuit is configured to provide a set of parameter sets that are dependent on a desired output voltage waveform, define a duty-cycle, and generate the control signals for the at least two converter units such that one parameter set is selected from the set of parameter sets is assigned to one converter unit, and the assignment of parameter sets to the converter stages varies over time.

Enhanced Self-Lift Cûk Converter for Negative-to-Positive Voltage Conversion

Abstract: This letter introduces a new step-up dc-dc converter that provides a negative-to-positive voltage-conversion path for the negative dc-voltage source. Compared with the classical Cuk and buck-boost converters, the proposed converter increases the voltage boost ability significantly using the switched capacitor and self-lift techniques. It is featured with single power switch operation, common ground, transformerless structure, and clear energy delivery process; therefore, the relative simple structure is beneficial to potential industrial applications in future. A detailed theoretical analysis for the continuous and discontinuous conduction modes is given, and the main general aspects for circuit design are derived. A preliminary system modeling based on the flow graph is also presented for reference. Both simulation and experimental results are provided to validate the analysis results.

Distributed Impedance Network (Z-Network) DC–DC Converter

Abstract: This paper presents a novel dc-dc converter incorporating a distributed impedance-source network (Z-source network, or Z-network) to achieve the buck (step-down) and boost (step-up) function of a transformer-isolated dc-dc converter. In this paper, the distributed impedance source network composed of an array of inductors and capacitors is coupled between power source and main switching devices. The great and unique feature about the distributed impedance source network dc-dc converter is that unlike the traditional V-source or I-source converters, it can be open- and short-circuited without damaging switching devices. Therefore, the desired buck and boost function can be achieved. Moreover, converter reliability can be greatly improved. A dc-dc converter using this proposed concept is built and tested. Its performances are verified with experimental results.

Power converter with compensation circuit for adjusting output current provided to a constant load

Abstract: A power converter for constant loads includes an energy transfer element, a switch, a controller, and a compensation circuit. The energy transfer element is coupled to receive a rectified voltage having a non-blocked portion and a blocked portion, where an amount of the blocked portion corresponds to a phase angle. The controller is coupled to control switching of the switch to regulate an output current of the power converter in response to a plurality of signals. The plurality of signals includes a peak input voltage signal and a feedback signal, where the peak input voltage signal is representative of a peak input voltage of the power converter and the feedback signal is representative of the output voltage of the power converter. The compensation circuit is coupled to adjust at least one of the plurality of signals in response to the phase angle exceeding a phase angle threshold.

Voltage source converter in high voltage applications: Multilevel versus two-level converters

Abstract: This paper presents a comparison between two-level and multilevel converters for medium-voltage applications. The comparison focuses on issues such as waveform quality, voltage and current stresses on the switching devices, switching frequency per device, and conversion losses (mainly, on-state and switching losses). The modular multilevel converter (M2C) is selected as viable representative of the multilevel family in this study, because it can be extended to a high number of levels and is able to function independent of operating condition. (5 pages)

Adaptive dynamic control of a bi-directional DC-DC converter

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.

Bidirectional energy converter

Abstract: The invention provides a bidirectional converter that operates under an AC generation mode or a charge mode. The bidirectional converter may be a single component or circuit, which may include a DC-DC conversion stage using a unique "Smith 2 Stage conversion" technique and a DC-AC conversion stage or AC-DC conversion stage using a switchable filter depending on the mode. During the charge mode, the converter may be able to control the voltage and current of the DC output using a software algorithm, to match the battery being charged, or the DC receiver. This may enable the converter to control the nature of the DC output so it can be adapted to any energy storage technology. The controllable output voltage and synchronizable frequency may allow the converter to be used in series combinations to achieve a variety of high voltage outputs from simpler building blocks.

Systems and methods of primary-side sensing and regulation for flyback power converter with high stability

Abstract: System and method for regulating an output voltage of a power conversion system. The system includes an error amplifier coupled to a capacitor. The error amplifier is configured to receive a reference voltage, a first voltage, and an adjustment current and to generate a compensation voltage with the capacitor. The first voltage is associated with a feedback voltage. Additionally, the system includes a current generator configured to receive the compensation voltage and generate the adjustment current and a first current, and a signal generator configured to receive the first current and a second current. The signal generator is further configured to receive a sensing voltage and to generate a modulation signal. Moreover, the system includes the gate driver directly or indirectly coupled to the signal generator and configured to generate a drive signal based on at least information associated with the modulation signal.

Battery charger and method for collecting maximum power from energy harvester circuit

Abstract: An energy harvesting system for transferring energy from an energy harvester ( 2 ) having an output impedance (Z i ) to a DC-DC converter ( 10 ) includes a maximum power point tracking (MPPT) circuit ( 12 ) including a replica impedance (Z R ) which is a multiple (N) of the output impedance. The MPPT circuit applies a voltage across the replica impedance that is equal to an output voltage (V in ) of the harvester to generate a feedback current (I ZR ) which is equal to an input current (I in ) received from the harvester, divided by the multiple (N), to provide maximum power point tracking between the harvester and the converter.

High step-up converter based on charge pump and boost converter

Abstract: In this paper, a novel step-up converter is presented, where the charge pump concept, combined with the traditional boost converter structure, is utilized. Although two inductors are used in such a converter, the difference in value between the two inductors does not degrade the performance of this converter. Besides, the behavior of this converter is similar to the traditional boost converter, and hence control of this converter can be realized easily. In this paper, the basic operating principles of the proposed converter are presented along with some experimental results to demonstrate the effectiveness of this converter.

Operation of a three level converter

Abstract: A method of operating a three level converter (20) includes controlling the output voltage of the converter when a DC link voltage of the three level converter (20) is lower than one-half of a rated DC link voltage of the converter (20) by, for each leg of the converter (112), alternately connecting an output terminal of the leg to the positive terminal or the negative terminal of the DC link (46). When the DC link voltage is at least one-half of the rated DC link voltage, the method includes controlling the output voltage of the converter (20) by, for each leg (112), selectively connecting the output terminal of the converter to the positive terminal, the negative terminal, or a mid-point of the DC link (46).

An area efficient fully monolithic hybrid voltage regulator

Abstract: A hybrid voltage regulator module for an on-chip DC-DC voltage converter is proposed in this paper. The circuit is appropriate for point-of-load voltage regulation due to an ultra area efficient architecture. The proposed voltage regulator is a hybrid combination of a switching DC-DC voltage converter and a low-dropout regulator exploiting active circuitry rather than bulky passive devices within the filter structure. The proposed circuit can supply over 100 mA current while generating 0.9 volts from a 1.2 input voltage, exhibiting a high current efficiency of greater than 99%. The on-chip area is 0.026 mm2 which is 500 times smaller than a monolithic buck converter and four times smaller than an LDO. The proposed regulator provides a means for distributing multiple local power supplies across an integrated circuit while providing high current efficiency.

Analysis and Design of a Soft-Switched PWM Sepic DC-DC Converter

Abstract: This paper proposes a new soft-switched Sepic converter. It has low switching losses and low conduction losses due to its auxiliary communicated circuit and synchronous rectifier operation, respectively. Because of its positive and buck/boost-like DC voltage transfer function (M=D/(1-D)), the proposed converter is desirable for use in distributed power systems. The proposed converter has versions both with and without a transformer. The paper also suggests some design guidelines in terms of the power circuit and the control loop for the proposed converter.

Method for operating an inverter, and inverter

Abstract: In an inverter and a method for operating an inverter, the inverter includes a step-up converter circuit, a dynamic intermediate circuit, and a step-down converter circuit for converting a direct voltage of a direct voltage generator or string into an alternating voltage for supplying a network. The step-up converter circuit increases the direct voltage if the latter is lower than a peak-to-peak maximum of the network voltage, and the step-down converter circuit lowers a dynamic intermediate circuit voltage, as needed, to a lower voltage currently required in the network. The step-up converter circuit dynamically increases the direct voltage to the value currently required in the network and in the process temporarily supplies an approximately sinusoidal voltage curve for the intermediate circuit voltage.

System and method for over-voltage protection in a photovoltaic system

Abstract: A photovoltaic array for use in an electrical power system includes multiple photovoltaic modules and a voltage converter coupled to at least one of the photovoltaic modules. The photovoltaic array also includes an over-voltage protection circuit. The over-voltage protection circuit includes an interface adapted to couple to an output of the voltage converter. The over-voltage protection circuit also includes a spike detector configured to detect a voltage spike in an output voltage of the voltage converter. The over-voltage protection circuit further includes a voltage control module configured to regulate an output voltage slew rate of the voltage converter in response to an over-voltage signal received from the spike detector.