Large Signal Transient Analysis Research Articles

Impedance measurement front-end based on signal four-phase detection

Internet of Things (IoT), a new direction in information and communication systems, has a significant impact on the development of novel electronics devices. Further progress in the field of IoT devices is conditioned by the development of sensor devices, and in particular, analog front-ends and signal converters for IoT sensors. High sensitivity and wide range applications of IoT sensors can be achieved by methods of impedance spectroscopy. Compared with other methods of physical research, impedance spectroscopy and based on it IoT sensor devices provide ease of implementation, high energy efficiency, good resolution and selectivity. In this paper, we present results of the development and model study of the impedance measuring transducer using the four-phase signal integration method. The implementation of impedance spectroscopy assumes a transition from frequency plots to plots on the complex plane, called as Nyquist plots. The data obtained in this paper are based on the SPICE (Simulation Program with Integrated Circuit Emphasis) model studding methodology, which compares small signal Alternative Current Analysis with large signal Transient Analysis. During the Alternative Current Analysis, Nyquist impedance plot are obtained in the idealized case, and during the Transient Analysis the active ReZ value and reactive ImZ impedance components are calculated for the actual parameters of the measuring transducers and the form of the activating signals. We have proposed a new solution of the impedance measuring transducer based on the four-phase signal commutation and integration method. This method consists in the formation of four informative signals, namely, the voltages $V_{Q1}$, $V_{Q2}$, $V_{Q3}$ та $V_{Q4}$, each of which corresponds to the integration results in the corresponding four phases of the activation signal. In these phases, or time t, the sign functions $A_{Q1}(t)$, $A_{Q2}(t)$, $A_{Q3}(t)$, $A_{Q4}(t)$ of synchronous detections are used: $A_{Q1}(t)=1$ at $t=[0...\pi/2]$; $A_{Q2}(t)=1$ at $t=[\pi/2...\pi]$; $A_{Q3}(t)=1$ at $t=[\pi...3\pi/2]$; $A_{Q4}(t)=1$ at $t=[3\pi/2...2\pi]$. In other time these sign functions are equal 0. Output signals of the impedance measuring transducer, namely, voltages of active $V_{RE}$ and the reactive $V_{IM}$ components are formed by adding and subtracting the numerical values of the above four voltages: $V_{RE}=V_{Q1}+V_{Q2}-V_{Q3}-V_{Q4}$; $V_{IM}=V_{Q1}-V_{Q2}-V_{Q3}+V_{Q4}$. The main units of the impedance measuring analog front-end are a synchronous quadrature detector and an integrator or filter. In comparison to traditional two-phase detection, four-phase detection we have proposed allows avoiding intermediate signal transducing, which provides a significant simplification of impedance measuring transducing. This simplification is achieved by directly integrating the instantaneous value of the $I_{Z}(t)$ current. Important dependences of the measuring transducer output voltages with four-phase integration on the operational amplifiers bandwidth are obtained. Results presented in the article are important for developing a new generation of microelectronic IoT sensor devices based on impedance spectroscopy methods. Main areas of application of such sensor devices are materials science, biochemistry, instrumentation, avionics, ecology, etc.

Technique of increasing the impedance measuring transducers accuracy at inharmoniousness signals

Introduction. Nowadays, one of the most relevant classes of sensor electronics for the Internet of Things is based on the methods of impedance spectroscopy. In general, the informative signals of impedance spectroscopy, namely, an active component or resistance which forms the real part and a reactive component or reactance which forms the imaginary part of complex impedance of the investigated two-terminal network, are formed by specialized analog front-end or measuring transducers. The defining requirements for measuring converters of sensor devices of the Internet Things are their versatility, minimal power consumption, the ability to work at low supply voltages, stability of operation with changing external factors and so on. In this paper, the problem of improving the accuracy of electrical impedance measuring transducers is considered, taking into account the non-harmonic of the driving signals. SPICE model and research technique. The implementation of impedance spectroscopy assumes a transition from frequency plots to plots on the complex plane, called as Nyquist plots. In a number of modern versions of circuit simulation programs the method of impedance analysis is already provided with the use of mathematical functions of Real (Re) and Imagine (Im) components of the signal. Using these functions, it is possible to calculate the corresponding values of the active (Re Z) and the reactive (Im Z) impedance of the object under investigation. As a result of his usage a Nyquist plot is plotted. However, this approach is not universal, and in particular, imposes significant restrictions taking into account the parameters of real signals, namely, their amplitude, shape, non-harmonics, etc. The results obtained in this paper are based on the new SPICE (Simulation Program with Integrated Circuit Emphasis) model studding methodology, which compares small signal Alternative Current Analysis with large signal Transient Analysis. During the Alternative Current Analysis, Nyquist impedance plot are obtained in the idealized case, and during the Transient Analysis the active Re Z value and reactive Im Z impedance components are calculated for the actual parameters of the measuring transducers and the form of the activating signals. The implementation of the above mentioned methodology involves the use of synchronous quadrature detection of the output signals of the measuring circuit. Analysis and correction of results. In accordance with the task of increasing the impedance measuring transducers accuracy at inharmoniousness signals we consider the method of calculating the coefficients KRE and KIM, allowing correcting the measurement results of the active Re Z and the reactive Im Z impedance components. A few analysis and correction results are presented. The obtained regularities can be widely used in correcting the results of impedance spectroscopy upon activation by pulse signals for the vast majority of research options. Conclusion. A new approach is proposed, according to which three arrays of informative signals of active Re Z and reactive Im Z impedance are formed and compared. The first M(AC) array is obtained using small signal Alternative Current Analysis, which corresponds to an idealized version of the measurement transformation and is subsequently used as a reference. The next two arrays M(H1) and M(HN) are obtained by the method of large signal Transient Analysis using the results of integrating the quadrature detector output voltages of the impedance transducer. The array M(H1) is formed when the input source triggers a harmonic oscillation (the first H1 harmonic), and the M(HN) array when activated by a functionally controlled source synthesizes a non-harmonic signal in the form of harmonics HN. The increase in the accuracy of the measurement conversion is provided by coefficients $K_{RE}$ and $K_{IM}$, which allow the correction of the measurement results of the active and reactive components of the impedance. A method for calculating such coefficients and examples of their use are presented.

Large-signal transient analysis of forward converter with active-clamp reset

The forward converter with the active-clamp reset offers many advantages over the forward converters with other transformer-reset methods. However, during the line and load transients, the maximum magnetizing current of the transformer and the peak voltage of the primary switch are strongly affected by the active-clamp circuit dynamics. As a result, the design of a forward converter with the active-clamp reset cannot be optimized based only on its DC characteristics. Due to the nonlinearity of the circuit, it is very difficult to derive the closed-form equations for the transient response of the active-clamp circuit. In this paper, an average-state-trajectory approach is proposed to analyze the transient behavior so that the trends of the maximum magnetizing current of the transformer and the peak voltage of the primary switch can be easily predicted under worst-case conditions and parameter variations.

Large-signal transient analysis of a soft-switching, two-switch AC-to-DC converter

The paper presents large signal transient analysis of a two-switch, soft-switching, single-stage AC-to-DC converter using it discrete time domain analysis approach. Analysis is used to predict the behaviour of the converter for step changes in load and supply voltages. Theoretical results are verified by PSPICE simulation and experimental results.

PSPICE simulation of three-phase inverters by means of switching functions

Static power converters can be analyzed by means of widely available circuit simulation software packages such as PSPICE. However, they are usually modeled as a set of real switches, which results in long execution times and possible convergence problems in the case of complex circuits. This paper proposes macromodels to simulate three-phase power converters on such packages. The proposed macromodels are based on converter switching functions rather than actual circuit configuration, and they are suited for steady state and large signal transient analysis at system level. In this approach, voltage source inverters (VSI), current source inverters (CSI), and controlled rectifiers (CR) are simulated as multiport networks avoiding the physical nonlinear micromodels of the power switches. Computer memory and the run-times required for the simulation are thereby minimized. Complete examples of VSI, CSI and CR, with different PWM techniques, are given with specific reference to the PSPICE software to illustrate the effectiveness of the proposed models.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Spontaneous oscillations in gallium arsenide field effect transistors

We present results of experiments and numerical simulations designed to reveal the presence of spontaneous oscillations arising from negative differential mobility effects in gallium arsenide field effect transistors. The measurements include d.c. and pulsed current/voltage vs temperature characterization, sampling scope measurements, spectral analysis to 40 GHz and observation of light emission. The simulation is a time dependent large signal transient analysis arising from a fully two-dimensional solution of the self-consistent potential and charge within the device.

Large-signal transient analysis and effects of lateral charge spreading in television camera tubes

The transient response of television camera tubes to changing levels of illumination is examined. When the entire transient occurs within the exponential retarding potential region of the electron beam <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I-V</tex> characteristic and photoconductive lag can be neglected, exact analytical expressions describing the rise and decay of video signal levels are established. The author present separate solutions to the problem based on the assumptions of electron beam scanning and charging by a hypothetical defocused beam (uniform charging case). The results support arguments in favor of target current biasing to minimize lag and turn-on time. We also show the effects of scanning as opposed to continuous dwelling by a flood beam. The decay transient is shown to be universial in the sense that it is independent of the initial signal strength and depends only on physical tube parameters. The validity of the expression describing signal decay is confirmed experimentally for a silicon diode array vidicon and a return beam silicon diode array vidicon. The effect on the resolution of target surface conductivity in conjunction with a finite electron beam impedance is treated for a steady-state per pattern and isolated circular spot illumination. In particular, the strong dependance of resolution, as limited by a conducting target surface, on operating current level is described. Lateral target leakage is shown to offer little advantage in decreasing lag.