Self-oscillating Circuit Research Articles

Modeling of self-oscillating flexible circuits based on liquid crystal elastomers

Modeling of self-oscillating flexible circuits based on liquid crystal elastomers

Программно-аппаратные методы подавления электроакустической обратной связи в радиоэлектронных системах аудиомониторинга

The purpose of the article is to analyze software and hardware methods of suppression of electroacoustic feedback in radioelectronic systems of audio monitoring and television production. The work shows a numerical analysis of signal methods for compensating positive feedback of radio acoustics, as well as an architectural DSP solution for constructing a notch equalization ruler with auto-tracking multitonal sound suppression based on an ADAU1701 audio processor. Methods: algorithms of digital signal processing, theory of stability of sound-amplifying and sound-picking radio systems, methods of signal radio acoustics, theory and methods of analysis of self-oscillating circuits, vector theory of the sound field. Results: the causes of electroacoustic feedback have been identified; an adaptive algorithm for suppressing electroacoustic feedback has been proposed and investigated; an experiment with the use of an electroacoustic feedback auto-suppression submodule has been analyzed.

МОДЕЛЬ АВТОКОЛЕБАТЕЛЬНОЙ ЦЕПИ ДЛЯ ТЕСТИРОВАНИЯ МЕТОДОВ ЧИСЛЕННОГО АНАЛИЗА ПЕРЕХОДНЫХ ПРОЦЕССОВ В SPICE-СИМУЛЯТОРАХ

At present time the problem of developing methods for numerical analysis of RF circuits in thetime domain remains actual because the known Gear and trapezoidal methods used in SPICE simulatorshave a number of significant disadvantages. To evaluate the effectiveness of new numerical methods,special test problems are needed to determine the accuracy of methods in various operating modes.Numerical analysis of self-oscillating circuits in the time domain offers the most difficulties for circuitsimulation programs (SPICE-simulators) since models of self-oscillating circuits can be both oscillatoryand stiff simultaneously. The aim of this work is to create the model of a self-oscillating circuit that allowsto quantify the accuracy of numerical methods. In accordance with the aim, the following problemsare solved: the features of the numerical analysis of classical self-oscillators in SPICE-simulators areinvestigated; the generalized mathematical model of self-oscillating circuits is described; the universalcircuit model of self-oscillating circuits for SPICE-simulators is presented; the quantitative accuracyassessment of numerical methods of transient analysis in SPICE-simulators was carried out. The modelproposed in this paper makes it possible to determine the relative errors of numerical methods in theharmonic oscillations mode, in the relaxation oscillations mode, as well as in the «mixed» mode, whenthe circuit response contains both exponential components with different rates of change and quasiharmoniccomponents. The obtained results confirm the high accuracy of the trapezoidal method in themode of harmonic oscillations, and the Gear method in the mode of relaxation oscillations. The relativeerrors in determining the amplitude of oscillation using these methods for the corresponding operatingmodes do not exceed 3%. At the same time, in the «mixed» mode, the relative errors in determining theamplitude of oscillation for both methods can reach 100%, that confirms the need to use additionaloptions or special methods of numerical analysis in SPICE-simulators.

A Control Actuation Concept for Self-Oscillating Resonant Converters

This article presents a concept of controller actuation mechanism for self-oscillating resonant converters (SORCs). Simplicity, robustness, and cost-effectiveness are among the main features of this type of converter. Described as a self-oscillating system with an intrinsic positive-type feedback switching network, also known as the self-oscillating command circuit (SOCC), it performs its own gate drive with self-sustained frequency, designed around an equilibrium point. Designers often disregard this converter as an explicit solution for closed-loop applications, especially those that require extra layers of control, due to its inherent inability to operate under pulse frequency modulation without extra circuitry. Thus, in this article, a robust, efficient, and simple way of controlling the SORC through frequency modulation is proposed. The idea consists of varying the self-oscillating frequency through the equivalent magnetizing inductance of the SOCC, using a mechanism called variable current transformer. Thus, through the injection of a small controllable dc current, it is possible to modulate the frequency of resonant converters. This allows the self-oscillating system to follow a reference current signal, operating in closed-loop over a wide range of input voltage and load variation.

Development of an In-Tank Tuning Fork Resonator for Automated Viscosity/Density Measurements of Drilling Fluids

Maintaining the viscosity and density of drilling fluids within their optimal performance margins is of utmost importance in running a safe and efficient operation when drilling oil and gas wells. Safety and efficiency may be adversely affected by current measurement practices of these two key properties as they still mostly rely on onsite personnel to carry out periodic manual measurements. These laborious measurement protocols limit the quantity and quality of the produced data. Here we describe an automated system for viscosity/density measurements of drilling fluids based on a tuning fork electromechanical resonator. The resonator works as the frequency-defining element of an oscillator circuit, and a digital gain control algorithm is used to control the feedback loop and actuate the device. The self-oscillating circuit allows the measurement to be repeated several times per second, enabling higher measurement precision and real-time monitoring in changing flows. The resonator was integrated into an in-tank system, which performed continuous measurements at the suction tank of the mud circulating system during drilling operations. Measurements in three different wells are presented. The results were in very good agreement with manual measurements reported from standard mud reports and further highlighted opportunities in detecting operational problems from the real-time data streams obtained.

FPGAD efender

Sharing configuration bitstreams rather than netlists is a very desirable feature to protect IP or to share IP without longer CAD tool processing times. Furthermore, an increasing number of systems could hugely benefit from serving multiple users on the same FPGA, for example, for resource pooling in cloud infrastructures. This article researches the threat that a malicious application can impose on an FPGA-based system in a multi-tenancy scenario from a hardware security point of view. In particular, this article evaluates the risk systematically for FPGA power-hammering through short-circuits and self-oscillating circuits, which potentially may cause harm to a system. This risk includes implementing, tuning, and evaluating all FPGA self-oscillators known from the literature but also developing a large number of new power-hammering designs that have not been considered before. Our experiments demonstrate that malicious circuits can be tuned to the point that just 3% of the logic available on an Ultra96 FPGA board can draw the power budget of the entire FPGA board. This fact suggests a waste power potential for datacenter FPGAs in the range of kilowatts. In addition to carefully analyzing FPGA hardware security threats, we present the FPGA virus scanner FPGAD efender , which can detect (possibly) any self-oscillating FPGA circuit, as well as detecting short-circuits, high fanout nets, and a tapping onto signals outside the scope of a module for protecting data center FPGAs, such as Xilinx UltraScale+ devices at the bitstream level.

Исследование динамических пороговых характеристик VO-=SUB=-2-=/SUB=--переключателя в осцилляторном контуре

This paper investigates the dependence of the dynamic threshold characteristics of a VO2-switch on the oscillation frequency of a self-oscillating circuit. A transitional oscillation regime related to the self-heating of the substrate is discovered. Proposed analytical formulas allow consider these regularities and having practical significance in designing oscillator neural networks based on VO2-switches.

Self-sustained oscillation in a memristor circuit

In this paper, we consider dynamical behavior of a comparatively simple self-oscillating circuit only with an inductor, a capacitor and a memristor, but this circuit can produce a self-sustained oscillation. By applying the point transformation method and the multiple-scale method, we carefully analyze dynamics of this circuit and find there exists a periodic solution. In our study, the two cases for the flux–charge relation of a memristor, i.e., continuous piecewise-linear function and discontinuous function, are considered. By using the above two approaches, we analytically obtain the approximated period and amplitude of the periodic solution. Some numerical examples also verify the correctness of theoretical analysis.

Tubular Fluorescent Lamps Detection Based on the Self-Oscillating Electronic Ballast

In this paper, the detection of T5 tubular fluorescent lamps (FLs) is carried out with a self-oscillating electronic ballast. The developed topology identifies and operates different lamps with their rated powers. A single-ended primary-inductor converter (SEPIC) is used for power factor correction (PFC), with a half-bridge inverter to supply the lamps. The lamps detection is realized by means of an analog electronic circuit. The command of the switches of the PFC and inverter stages is accomplished by the self-oscillating circuit. Experimental results, as well as an analysis of the data referring to compliance with the technical standard NBR 14418 are presented in relation to preheating of the T5 FLs electrodes.

A Low-Power, Wireless, Capacitive Sensing Frontend Based on a Self-Oscillating Inductive Link

Wireless sensing systems are becoming popular in a range of applications, particularly in the case of biomedical circuits and food monitoring systems. A typical wireless sensing system, however, may require considerable complexity to perform the necessary analog to digital conversion and subsequent wireless transmission. Alternatively, in the case of inductive link based systems, large, manually operated impedance analyzers are required. Based on a detailed analysis of the link impedance, this paper proposes a simple method for wireless capacitive sensing through an inductive link that uses a self-oscillator and a frequency counter. The method enables changes in capacitance to be sensed and wirelessly transmitted simultaneously. In order to test the effectiveness of the method, a self-oscillating circuit was designed and fabricated in $0.18~\mu \text{m}$ CMOS, and combined with an on-chip humidity sensing capacitor. The system was tested in a humidity chamber across a range of 20–90%rh. Measured results from the system demonstrate that capacitive changes as small as 28 fF, translating to <2%rh, can be resolved, with a power consumption of 1.44 mW.

Design Approach for a Self-Oscillating Resonant Converter Operating in High Frequency for LED Applications

In this paper, a design approach for the self-oscillating command circuit (SOCC) as a driver for a resonant converter operating in high frequency for LED applications is proposed. This proposal, conceived from the proposed methodologies, contemplates the influence of the Cascode gallium nitride (GaN) FET input and output capacitances, making it relevant to higher switching frequencies, where such parasitic elements lead to increased errors. In conjunction with higher efficiency levels, series resonant inverters like the zero-voltage switching half-bridge are known to have potentially reduced size on its reactive components when operated at higher frequencies, resulting in smaller and lighter systems. Combined to the ‘simplicity and low cost of the SOCC, these advantages translate into a simple and cost-effective high-power-density application. The self-oscillating resonant converter (SORC) accurate design is based upon the describing function method as a linearization tool and the extended Nyquist stability criterion that evaluates whether or not the system can oscillate around given predicted frequency. Practical input capacitance measurement data for different silicon MOSFETs and a Cascode GaN FET are compared and considered in order to obtain a high-frequency design approach for an SORC. Simulation and experimental results for an SORC with Cascode GaN FET operating at 1 MHz for a 10-W LED are shown based on the design procedure described.

Introducing Self-Oscillating Technique for a Soft-Switched LED Driver

In this paper, a self-oscillating soft-switched converter for light-emitting-diode (LED) driver application is presented. In the proposed converter, the self-oscillation conditions are provided with a low number of additional components, and this converter provides a zero-current switching (ZCS) condition for instant switch turn- OFF . This converter does not need additional output current feedback because the output current changes only 10% when the output voltage changes by 33%. The self-oscillating part of this converter applies three low-power BJT and guarantees a soft-switching condition. The proposed self-oscillating control circuit can be implemented with a low cost since it does not need any IC and power supply for the control circuit. The proposed self-oscillating circuit detects the proper moment to turn the switch OFF under the ZCS condition. In order to justify the validity of theoretical analysis, the results of the implemented prototype for driving an LED string are presented. The measured power factor of the prototype shows that, although the input current of the converter is not sinusoidal, this converter can meet the IEC61000-3-2 standard at an operating power of less than 25 W, in addition to having a simple structure and achieving the robust ZCS condition.

EDLC のための自励発振形電圧平衡化回路の電流特性

In this paper, a voltage equilibrate circuit which applied to the multiple EDLCs (Electric Double-Layer Capacitors) by using self-oscillation circuit is proposed. Additionally, the proposed circuit has the ability of the current control on EDLC. Accordingly, the current characteristics result of simulation and experiment in the proposed circuit are described mainly. A proposed circuit is used self-oscillation technique, and the circuit is supplied voltage form the EDLC therefore the circuit structure is very simple, namely using only 19 electric parts. Generally, when connecting two EDLCs or two batteries with a converter, a large current may flow between the two EDLCs or the battery. However, in the proposed circuit, even if a voltage difference occurs between the EDLCs, it showed that the circuit maintains the zero-current switching mode and does not flows large current if it is the potential difference in the design. In addition, in this paper the range of the voltage that keeps the zero-current switching mode is obtained by the formula, and the calculation expression for obtaining the maximum p-p current value of the circuit is also shown.

Suppression Efficiency of the Correlated-noise and Drift of Self-oscillating Pseudo-differential Eddy Current Displacement Sensor

The suppression efficiency of the correlated noise and drift of self-oscillating front-end circuit in a pseudo-differential eddy-current displacement sensor (ECDS) is investigated using COMSOL and MATLAB. The transfer characteristic of the sensor coil, excited at 200 MHz, is obtained through a FE model in COMSOL. The characteristic is linearized to a second-order fit around a standoff distance to the target (xso) of 55 μm. The nonlinearity of the interface is modelled in MATLAB. It is found that, in order to tolerate 1% drift in the oscillator amplitude, a maximum 2nd harmonic distortion (HD2) of the interface has to be less than −72 dB when the sensor HD2 is −51.5 dB for 5 μm displacement range around xso = 55 μm.

自励式発振回路を有する渦電流形変位センサの発振電圧特性

自励式発振回路を有する渦電流形変位センサの発振電圧特性

Angular rate sensor based on hemispherical resonator gyro: Development and test results

The paper is devoted to the development of angular rate sensor (ARS) based on hemispherical resonator gyro (HRG). Simplified gyro model in the form of two equations for mathematical oscillator is proved to be sufficient. Physical parameters of the metal resonator are compared with the mathematical model to select the equations’ coefficients and to introduce the additional terms describing external perturbations in the right side of equation. The obtained gyro mathematical model can be used to synthesize the sensor controller with the preset parameters. Three-axis angular rate sensor assembly is manufactured and calibrated using the generating filter in self-oscillation circuit.

Noise performance of frequency modulation Kelvin force microscopy

Noise performance of a phase-locked loop (PLL) based frequency modulation Kelvin force microscope (FM-KFM) is assessed. Noise propagation is modeled step by step throughout the setup using both exact closed loop noise gains and an approximation known as “noise gain” from operational amplifier (OpAmp) design that offers the advantage of decoupling the noise performance study from considerations of stability and ideal loop response. The bandwidth can be chosen depending on how much noise is acceptable and it is shown that stability is not an issue up to a limit that will be discussed. With thermal and detector noise as the only sources, both approaches yield PLL frequency noise expressions equal to the theoretical value for self-oscillating circuits and in agreement with measurement, demonstrating that the PLL components neither modify nor contribute noise. Kelvin output noise is then investigated by modeling the surrounding bias feedback loop. A design rule is proposed that allows choosing the AC modulation frequency for optimized sharing of the PLL bandwidth between Kelvin and topography loops. A crossover criterion determines as a function of bandwidth, temperature and probe parameters whether thermal or detector noise is the dominating noise source. Probe merit factors for both cases are then established, suggesting how to tackle noise performance by probe design. Typical merit factors of common probe types are compared. This comprehensive study is an encouraging step toward a more integral performance assessment and a remedy against focusing on single aspects and optimizing around randomly chosen key values.

A New System for Acoustoelectronic Gas Sensors Analysis

Typical approach to the surface acoustic waves sensors response analysis is based on the use of self-oscillating circuits with surface acoustic wave device working inside positive feedback loop of an ampli er. Such kind of parametric measurement allows to track the center frequency of the sensor changes in particular. The method is widely used mainly due to their relative simplicity. Unfortunately, it has many disadvantages like frequency (phase) instability, sensitivity to unwanted factors, surface acoustic wave substrate mass-load limit etc. A new system to the analysis of surface acoustic wave gas sensors response as well as an exemplary measurement results are described in the paper. The presented system make the rst step to the more complex conception realization.

Analysis of self‐oscillating switched‐mode circuit for low‐voltage energy harvesting

The operation of a self-oscillating switched-mode circuit topology for low-voltage thermal energy harvesting is analysed and experimental efficiency results are presented. Circuit self-start-up function as well as high-efficiency power transfer are obtained by using only one transformer without additional inductors. It is shown that even without using a maximum power point tracking (MPPT) tracking circuit, it is possible to achieve efficiencies up to 65% over a relatively broad input voltage range which can be optimised by properly varying the transformer turns ratio n.

용량형 마이크로 공진기의 주파수 응답 보상 기법

This paper presents frequency response compensation technique, and a self-oscillation circuit for capacitive microresonator with the compensation technique using programmable capacitor array, to compensate for the frequency response distorted by parasitic capacitances, and to obtain stable oscillation condition. The parasitic capacitances between the actuation input port and capacitive output port distort the frequency response of the microresonator. The distorted non-ideal frequency response can be compensated using two programmable capacitor arrays, which are connected between anti-phased actuation input port and capacitive output port. The simulation model includes the whole microresonator system, which consists of mechanical structure, transimpedance amplifier with automatic gain control, actuation driver and compensation circuit. The compensation operation and oscillation output of the system is verified with the simulation results.