Large-signal Behavior Research Articles

Large-signal stability analysis of solar array power system

A large-signal stability analysis of the solar array regulator system is performed to facilitate the design and analysis of a low-earth-orbit (LEO) satellite power system. The effective load characteristics of various control methods in the solar array regulator system, such as the constant power load, variable power load, constant voltage load, constant current load, and constant resistive load, are classified to analyze the large-signal stability. Then, using the state plane analysis technique, the large-signal behavior of the solar array system is portrayed and the stability of various equilibrium points is analyzed. Thus, this approach can be contributed to organize the optimal controller structure of the system by representing the relationship between the control method of the solar array regulator and the large-signal stability. For the verification of the proposed large-signal analysis, a solar array regulator system that consists of two 100 W parallel module buck converters has been built and tested using a real 200 W solar array.

Large-Signal Modeling and Steady-State Analysis of a 1.5-kW Three-Phase/Switch/Level (Vienna) Rectifier With Experimental Validation

In this paper, a large-signal modeling technique has been developed for a three-phase, three-level Vienna rectifier operating in continuous conduction mode. The considered circuit is a fifth-order system with time-varying variables on the ac side. This model is first established in the direct abc reference frame using the state space averaging technique, then modified through an abc/dqo transform and adequate duty cycle alteration to avoid time-dependency. The system stability in a closed loop, using a multiloop PI-based control scheme, is proved by the convergence of the phase plane trajectories to the nominal point for any initial condition. These curves are drawn as ac line peak currents as a function of total output dc voltage. The different relationships governing the system inputs/outputs are verified not only for the nominal operating point, but also for a wide operation range. The accuracy of the proposed model is verified on a 1.5-kW experimental prototype controlled by the DS-1104 board of dSPACE. The converter large signal behavior is experimentally analyzed using output time domain responses toward different input variations. Significantly high accordance between the experimental results and the theoretical model, implemented with SIMULINK/Matlab, is verified.

Pulse input Class-C power amplifier response of SiC MESFET using physical transistor structure in TCAD

The switching behavior of a previously fabricated and tested SiC transistor is studied in Class-C amplifier in TCAD simulation. The transistor is simulated for pulse input signals in Class-C power amplifier. The simulated gain (dB), power density (W/mm) and power added efficiency (PAE%) at 500 MHz, 1, 2 and 3 GHz was studied using computational TCAD load pull simulation technique. A Maximum PAE of 77.8% at 500 MHz with 45.4 dB power gain and power density of 2.43 W/mm is achieved. This technique allows the prediction of switching response of the device for switching amplifier Classes (Class-C–F) before undertaking an expensive and time consuming device fabrication. The beauty of this technique is that, we need no matching and other lumped element networks for studying the large signal behavior of RF and microwave transistors.

Analytical extraction of small and large signal models for FinFET varactors

In this work we report on the small and large signal behaviour of advanced nMOS varactors fabricated in FinFET technology. This is the first paper showing large signal network analyzer (LSNA) measurements performed on FinFET varactors. These nonlinear measurements are modeled with a lookup table based model that is constructed using an accurate multi-bias small signal equivalent circuit. The validity of the extracted small and large signal models is verified through the very good agreement between measurements and simulations.

High-Order Switching Surface in Boundary Control of Inverters

A high-order switching surface for boundary control of inverters is presented in this paper. The concept is based on using the natural response of the power stage to formulate a logarithmic function to approximate the ideal switching surface. With the proposed control method, the inverter exhibits better dynamic responses than the ones with the first-order or recently proposed second-order switching surfaces. It will also be shown that the first- order and second-order switching surfaces are the low-order approximations of high-order switching surface. As the high-order switching surface is close to the ideal switching surface, its high trajectory velocity along the switching surface makes the inverter state trajectory move toward the steady-state operating point in two switching actions under large-signal disturbances. The effects of the parametric variations on the output voltage and the large- signal characteristics of the inverter will be discussed. The proposed control method has been successfully applied to a 300-W, 110-V, 60-Hz, single-phase full-bridge inverter. The steady-state and large-signal dynamic behaviors of the inverter supplying to resistive, nonlinear inductive, and full-wave rectifier loads will be given.

EFFECTS OF CIRCUIT ELEMENTS AND HARMONIC OSCILLATION POWER ON FUNDAMENTAL PM NOISE POWER OF FET OSCILLATOR

Analytical expressions for the PM noise in FET oscillators are derived in terms of the FET equivalent circuit elements and the passive circuitry. Efficient methods to reduce the PM noise in fundamental and in harmonic modes are suggested and implemented. The effects of the different FET equivalent circuit parameters on large-signal, small-signal, and noise behavior of FET oscillators are investigated. Finally, the effects of harmonic signal on the output noise power and on the phase noise at both fundamental and harmonic frequencies are determined.

Multitone large-signal analysis of superconducting transition-edge sensors for astronomy

A simple transition-edge sensor (TES) is governed by two coupled, nonlinear equations, which when solved give the behavior of the device given the initial conditions. The two equations describe the full electrical and thermal characteristics of the device and the way in which the device interacts with the external electrical and thermal circuits. To date these coupled nonlinear equations have been solved analytically in the small-signal limit, by linearizing the equations about some operating point. The resulting coupled linear equations contain a wealth of interesting physics, and form the principal tool by which all detectors are currently designed and modeled. In this article we describe a numerical technique for solving the coupled nonlinear equations rigorously, without any assumptions about the magnitudes of the various signals and parameters that determine the behavior of a device. The technique is based on a harmonic balance algorithm that searches, in the frequency domain, for voltage, current, and temperature wave forms that are consistent with the solid-state physics of the device. Indeed, both the small and large signal limits can be simulated, and the full harmonic content of the system retrieved. In this article, we will outline the principal features of the algorithm, and show various results such as I−V curves, saturation when signal power is modulated, impedance response when the bias current is modulated and signal power kept constant, and pulsed signal power analysis that shows the dynamics of a device. Numerous extensions of this fundamental technique are now possible including multitone nonharmonic analysis, large-signal impedance calculation, modeling of complicated thermal circuits, noise models, and frequency-domain multiplexing. We believe that our algorithm will become the principle technique for analyzing the large-signal behavior of all TES detectors and on that basis we are developing computer aided design software.

Permittivity and loss tangent of unpoled LaSr-doped PZT under compressive loading

Piezoelectric ceramics are commonly applied under a compressive pre-stress in order to avoid failure under tensile stresses. This is the case for piezoelectric actuators, for instance. Under such stress states, the piezoelectric large signal behaviour is strongly affected [1–4]. More recent results on various ferroelectric materials and single crystals are reported by Viehland [5]. But also small signal parameters are influenced by compressive pre-stresses [6, 7]. In order to reveal the effect of material composition, measurements were performed for systematically changed Zr/Ti ratios, resulting in materials located on both sides of the morphotropic phase boundary (MPB). In this communication the effects of compressive load on the dielectric properties of LaSr doped soft PZT ceramics are investigated. Lanthanum is a typical donor dopant in PZT. The La ion occupies the Pb (A) site in the ABO3 perovskite structure. The charge compensation occurs by formation of lead vacancies resulting in soft ferroelectric behaviour. Sr also substitutes for the Pb. The isovalent Sr doping reduces the Curie temperature Tc and enhances dielectric properties [8]. Measurements of the relative dielectric permittivity e and dielectric loss tand parallel and perpendicular to a compressive loading were performed for three PZT ceramics in the unpoled state and analysed as effects resulting from domain switching and lattice deformation. Three compositions of 1 mol% La-2 mol% Sr-doped morphotropic PZT with Zr/Ti ratios of 53/47, 54/46 and 55/45, respectively, were prepared by the mixed-oxide route. The powders were prepressed by uniaxial die pressing at low pressure and, after that, isostatically pressed at 400 MPa and sintered in closed alumina crucibles at 1225 C in an oxygen atmosphere [9]. From the sintered specimens, bars with dimensions of 20 · 4.5 · 4.5 mm were fabricated by sawing and grinding. These samples were equipped with sputtering Au electrodes on two opposite 4.5 · 20 mm surfaces. X-ray diffraction patterns showed after sintering phase assemblage of both tetragonal and rhombohedral perovskite. Volume fractions of these phases were estimated from integral peak intensity ratios of {200} and {111} reflections. The tetragonal volume fraction of the PZT 53/ 47 is about 65% and of the PZT 54/46 about 37%. The PZT 55/45 is a predominantly rhombohedral phase material with a tetragonal volume fraction of about 16% [10]. For the dielectric measurements a sinusoidal voltage of 1 V amplitude and a frequency of f = 1 kHz was used [7]. The measurements were carried out with an LCR meter (HP-4263A). Compressive loads were applied to the 4.5 · 20 mm surfaces (Fig. 1a). For the dielectric measurements in compression direction, the specimens (1) with electrodes (2) were put on a steel block (3) and loaded by a second steel block (4). Their cross sections were identical with those of the test specimens. This yields a nearly homogeneous z-stress in the test piece with rz 1⁄4 rz (PZT) ffi rz (steel). Superimposed xand y-stress components are very small and proportional to the difference in Poisson ratios, rx, ry / rz (mPZT mSteel), mSteel ffi 0.3, mPZT ffi 0.35 0.5. This ensures maximum xand y-stresses <10% T. Fett (&) H. Kungl M. J. Hoffmann Institut fur Keramik im Maschinenbau, Universitat Karlsruhe, Karlsruhe, Germany e-mail: theo.fett@ikm.uni-karlsruhe.de

PEM fuel cell model representing steady-state, small-signal and large-signal characteristics

Fuel cell applications become increasingly attractive. Therefore, comprehensive models, simulation software and analysis tools are required to characterize fuel cell behavior. This paper introduces a model capable of representing the static and dynamic (dynastatic) behavior of PEM fuel cells. The model approximates the theoretical current–voltage description with an equivalent electric circuit. The parameter values of the model are found by analyzing small-signal measurement results from electrochemical impedance spectroscopy, together with the steady-state electric characteristic and large-signal behavior from step-response measurements. Because the modeling approach is completely based on measurements on the fuel cell electric output terminals, electrochemical aspects like temperature dependency, charge double layer and adsorption effects are implicitly covered.

On-Chip Multi-Channel Monitoring for Analog Circuit Diagnosis in Systems-on-Chip Integration

A highly multi-channel on-chip signal monitor and off-chip waveform acquisition processor established analog circuit diagnosis against environmental disturbances in SoC. An array of 53 distributed probes followed by a single shared waveform acquisition kernel is embedded in a 0.18-μm CMOS experimental on-chip test bench. In combination with the off-chip processor materialized in FPGA and a host PC, fully automated on-chip waveform monitoring achieves high-throughput data acquisition of 300ms per sample point with adaptive 10-bit timing and voltage resolutions at a minimum LSB of 100ps and 400μV, respectively. Analog signals of interest in a 1.5-bit conversion stage of a pipeline ADC were evaluated in terms of their response to substrate noises that globally existed in a chip. On-chip diagnosis derives in-depth findings relating to dynamic, large-signal, and sensitive behaviors of analog circuits in a real SoC environment, far beyond simulations with inevitably limited capacity.

Induction-heating voltage inverter with hybrid LLC resonant load, the D-Q model

Simulation of the closed-loop, large-signal behavior of resonant converters is a challenge due to high-frequency variation of the state variables, which makes the State Space A veraging method useless. In this paper the d-q modeling technique is proposed and applied in case of a voltage inverter with LLC resonant load. The d-q model is embedded in a closed-loop inverter model with voltage and frequency control.

Simplified Analytical Model and High Power Characteristics of InGaP/GaAs HBTs at X-Band

Simplified large-signal analysis and high power characterization of InGaP/GaAs heterojunction bipolar transistors (HBTs) at X-band are reported. The simplified analytical model suggested in this work allows a first order prediction of the power performance trends as functions of device physical parameters. The solution to nonlinear equations governing the large signal behavior of the transistor is found by an iterative approach. The impact of different large signal parameters on the power performance of HBTs has been analyzed. Under class B operation, a 10-finger 2times20mum2 HBT at VCE= 10V achieves a maximum output power of 1.08W (5.4W/mm) with power-added efficiency of 44%

A Constant-&lt;formula formulatype="inline"&gt;&lt;tex&gt;$g_{m}$&lt;/tex&gt; &lt;/formula&gt; Constant-Slew-Rate Rail-to-Rail Input Stage With Static Feedback and Dynamic Current Steering for VLSI Cell Libraries

A constant-g <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</sub> input stage featuring both constant small signal and large signal behaviors over the entire input common-mode range is proposed in this brief. A novel static feedback loop is employed to minimize the N and P transconductance mismatch due to process and temperature variations. The output currents of the N and P differential pairs are dynamically steered to keep a constant g <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m </sub> and a constant slew rate. The overall technique is independent of the operation regions of input transistors, and does not rely on the quadratic characteristics of input MOS transistors. A prototype chip was designed for a 0.35-mum CMOS technology with 3-V power supply. The experimental results demonstrate that a constant-g <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</sub> (plusmn3% variations) and a constant slew rate over the entire input common-mode range have been achieved

Behavioral modeling of power amplifiers for wireless applications

In this paper, an improved empirical behavioral model for radio-frequency power amplifiers (RF-PAs) is presented. The model was implemented in a commercial nonlinear microwave simulator. It belongs to the category of bandpass PA models, which exhibits memory effects due to the low frequency dependence of bias and temperature. Additionally, it facilitates accurate and efficient system level simulations of RF-PA large-signal behaviors such as self-bias, AM-AM, AM-PM, gain expansion effects, and intermodulation distortion (IMD) sweet-spots. The model was validated using measurement data obtained from a commercial CDMA PA at 1.88 GHz. © 2007 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2007.

Composition influences on the electrical and electromechanical properties of lead zirconate titanate thin films

The influences of the Zr content on the structural, electrical, and electromechanical properties of Pb[Zr(x),Ti(1−x)]O3 [PZT(x∕1−x)] thin films are investigated in detail. Additionally to measuring all major characteristics of the samples, the electromechanical large-signal behavior is modeled. Raising the Zr content increases the unit cell size and forces the preferred phase to become rhombohedral above the morphotropic phase boundary (MPB). The increased unit cell size changes the switching behavior and increases the intrinsic behavior of the unit cells. The intrinsic behavior is reduced by the phase change, which also introduces non-180° domain wall motion, improving the large-signal strain. Additionally, the domain configuration in saturation is more stable further away from the MPB. Finally, the most suitable materials will be selected for different applications.

Hysteresis and delta modulation control of converters using sensorless current mode

Sensorless current mode (SCM) is a control formulation for dc–dc converters that results in voltage-source characteristics, excellent open-loop tracking, and near-ideal source rejection. Hysteresis and delta modulation are well-known, easy-to-construct large-signal methods for switched systems. Combining either large-signal method with SCM creates a controller that is simpler and more robust than a pulse-width modulation (PWM) based controller. The small-signal advantages of PWM-based SCM are retained and expanded to include converter response to large-signal disturbances. These approaches can be used with any converter topology over a broad range of operating conditions. In the present work, hysteresis and delta modulation SCM controllers are derived and simulated. Extensive experimental results demonstrate the large-signal behavior of both control schemes.

A Compact Digitally Controlled Fuel Cell/Battery Hybrid Power Source

A compact digitally controlled fuel cell/battery hybrid power source is presented in this paper. The hybrid power source composed of fuel cells and batteries provides a much higher peak power than each component alone while preserving high energy density, which is important and desirable for many modern electronic devices, through an appropriately controlled dc/dc power converter that handles the power flow shared by the fuel cell and the battery. Rather than being controlled to serve only as a voltage or current regulator, the power converter is regulated to balance the power flow to satisfy the load requirements while ensuring the various limitations of electrochemical components such as battery overcharge, fuel cell current limit (FCCL), etc. Digital technology is applied in the control of power electronics due to many advantages over analog technology such as programmability, less susceptibility to environmental variations, and low parts count. The user can set the FCCL, battery current limit, and battery voltage limit in the digital controller. A control algorithm that is suitable for regulating the multiple variables in the hybrid system is described by using a state-machine-based model; the issues about embedded control implementation are addressed; and the large-signal behavior of the hybrid system is analyzed on a voltage-current plane. The hybrid power source is then tested through simulation and validated on real hardware. This paper also discusses some important issues of the hybrid power source, such as operation under complex load profiles, power enhancement, and optimization of the hybrid system. The design presented here can not only be scaled to larger or smaller power capacities for a variety of applications but also be used for many other hybrid power sources

Surface Effects of Piezoelectric 1-3 Ceramic-Polymer Composites

The surface deformation of piezoelectric 1-3 composites was modelled with the finite element method (FEM). Nonlinear and linear FEM calculations were used for the study of the large and small signal behaviour, respectively. The role of the volume content and the aspect ratio of the rods was investigated. The influence of these parameters on the results of different measurement methods was discussed. The theoretical results were compared with experimental data of PZT ceramic-polymer composites.

Resistorless floating immittance function simulators employing current controlled conveyors and a grounded capacitor

In this paper, new floating immittance function simulators employing second-generation current controlled conveyors are proposed. The first four of the presented circuits employ only a single grounded capacitor as passive component and can realize either a negative or a positive floating inductor or capacitor. The last two of the proposed circuits do not employ passive components and can realize either negative or positive floating resistances. All of the proposed circuits do not require passive element matching. As an application, a third-order butterworth filter is realized using the proposed positive floating inductance simulator. SPICE simulation results and large signal behavior of the filter are included.

Experimental investigation of domain switching criterion for soft lead zirconate titanate piezoceramics under coaxial proportional electromechanical loading

In this experimental work, “soft” lead zirconate titanate specimens in an initially unpoled state were subjected to combined electromechanical loading, in which a compressive stress and a parallel, proportional electric field were applied simultaneously. By changing the ratio of stress to the electric field between tests, a series of nonlinear polarization and strain responses were obtained. An attempt has been made to explain the experimental findings by simultaneously taking into account the contributions of dielectric response, elastic deformation, piezoeffects, and irreversible domain switching. Initial domain switching surfaces in the biaxial stress and electric field space were determined based on an offset method. Several switching conditions existing in the literature were summarized and compared with the experimental data obtained in this work. Such an investigation may serve to calibrate and validate existing constitutive models concerning the large-signal nonlinear behavior of piezoceramics.