Pulse Width Modulation Waveform Research Articles

Enhancing the Precision of Proportional Electromagnetic Actuators used in Automatic Processes Control

In this study, an electromagnetic actuator is presented, that features precise proportional action and wide displacement capabilities. This actuator operates in two distinct modes. In the proportional mode, the actuator positions its mobile equipment within a 0 to 14 mm range, governed by the balance between electromagnetic force and spring elastic force. By employing the pulse width modulation (PWM) principle, the electronic control section finely tunes the duty cycle factor and the coil current, thus achieving precise displacement control. The displacement control was further enhanced through the integration of a magnetic sensor that correlates movement with the Hall Voltage. This additional feature augments the actuator's precision by providing real-time feedback on the position of the mobile equipment, thereby refining the overall control mechanism. In the modulated mode, the actuator's oscillation frequency spans from 1Hz to 10 Hz, requiring control from the arbitrary signal generator. The PWM waveform controller DRV101 and the related electronic circuits are powered by two stabilized encapsulated continuous voltage sources that are compact enough to fit inside the actuator housing. The final power stage was represented by two power IGBT transistors that are powered by an external continuous voltage source. Experiments were also realized for heat management and to measure the plunger force at different distances between 0 and 14 mm. These analyses aim to optimize performance across both operational modes, advancing the efficiency and reliability of precision control systems in automated processes.

Applications of power electronics technology: Advanced inverters

An inverter is a crucial component of renewable energy systems, converting direct current from solar panels and wind turbines into alternating current for use in homes and businesses. Inverters have a wide range of applications in power electronics technology, including electric vehicles, industrial equipment, and microgrid. Maximizing the efficiency of inverters is a hot research topic in the electronic and electrical fields. Engineers and researchers are interested in understanding the structure and parameters of inverters to optimize their performance. This article explores the basic inverter topology, presenting three circuit structures and their pulse-width modulation waveform modulation method. It also introduces a new type of inverter and explains its working state. The article concludes by examining potential future developments and research directions for inverters. As the world seeks to transition to cleaner energy sources, inverters will continue to play a vital role in making renewable energy systems more efficient and cost-effective.

A statistical analysis of a fuel injection rate waveform by the bosch method according to a piezoelectric injector driving pattern

To drive a diesel piezo injector, the charge and discharge of the current supplied to the piezo stack in the injector are controlled as a pair. The charge and discharge currents expand and contract the piezo stack, respectively. The expansion of the piezo stack causes an increase in the hydraulic pressure that presses the top of the injector needle, which results in the fuel injection. In contrast, the contraction of the piezo stack stops the fuel injection. The charge and discharge currents are controlled by a peak and hold method. The hold current is controlled by PWM (pulse width modulation) control of the driving power supplied to the injector. The duty ratios of the PWM signal used for the hold current control are 10%, 30%, and 100%. The injector driving voltage was 140V. A variety of charge and discharge current waveforms were generated by combining the duty ratio control of the PWM waveform with the driving power source. To measure the time-resolved injected mass under various current waveform conditions, the Bosch method was used in this study. An uncertainty analysis was performed on the Bosch injection rate waveform when it was measured 40 times for each fuel injection condition.

Comparison of Different Circuit Topology for Generation of PWM Signal with High Power for Electroporation

Electroporation refers to a microbiological method which involves application of electric field to cells for ameliorating the cell membranes permeability, allowing electrode arrays, drugs and chemicals to be inserted into the cells. This process requires HV pulses or signals for creating pores within the cell membrane. As these signals are less effective, nowadays, Pulse Width Modulation (PWM) signals are extensively employed for electroporation. These signals can be exploited for constructing coveted output voltage in power amplifiers and are found to be useful for regulating power devices. Therefore, generation of top quality PWM signals is essential for achieving superior electroporation performance. Different PWM methods are available and circuit topologies employed for generating these waveforms are also different. This paper thus provides an exploratory study of distinct circuit topologies exploited for generating PWM waveforms. The review paper also provides the significance of PWM signals for electroporation. It reviews the existing circuit topologies exploited for PWM signal generation and other related studies. It also presents a circuit for PWM waveform generation. The paper then provides the substantial future directions pertaining to the study. This review article mainly educates the reader regarding existing circuit topologies for PWM signal generation, their characteristics and improvements required for developing better topologies satisfying the requisites of modern applications.

P‐9: LTPO TFTs Based PWM Pixel Circuit for AM‐Micro‐LED Display with Falling‐time <10μs

A pulse‐width‐modulation (PWM) pixel circuit for Micro‐LED display based on low‐temperature poly‐silicon and oxide (LTPO) thin‐film transistor (TFT) is proposed. The PWM falling‐time is reduced to 10 μs, which is only 1/10 of conventional PWM pixel schematics, thanks to the high gain dynamic CMOS inverter for converting data voltage to PWM waveforms and an independent diode‐connected compensation structure for generating constant driving current. The maximum error of PWM conversion and driving current of Micro‐LED is less than 1%, despite VTH shift of oxide TFT ±2 V or VTH variation of LTPS TFT ±1 V. Furthermore, high display resolution above 270 PPI is obtained as the pixel layout reduced to 94 μm×94 μm due to the simplified pixel structure.

Equalization of camera-based channel to mitigate uncertain sampling for optical camera communications.

The asynchronous nature of optical camera communication makes uncertain sampling a fundamental and inevitable problem that degrades data transmission performance. Based on a parametric model describing the exposure effect of the camera-based channel as the source of uncertain sampling, a simple channel equalization method and implementation are proposed in this paper to mitigate the uncertain sampling by exploiting the space-time relationship of the transmitted spatial delayed pulse width modulation waveform on multiple light sources. In addition, the rate of equalization error caused by under-sampling and over-exposure is analyzed for different duty cycles and exposure times. Numerical simulation and experiment results demonstrate the availability and reliability in mitigating uncertain sampling by the proposed channel equalization.

An Analysis of Minor Hysteresis Loops Behavior under PWM Voltage - Electromagnetic Device at No-Load and Loaded Conditions

This paper addresses the influence of the primary and secondary resistances on the behavior of minor hysteresis loops when the electromagnetic device is fed by three-level PWM (pulse width modulation) voltage. To study the device transferring energy to a load, the experimental approaches are different of traditional procedures to material characterization, where problems inherent to the process are added. Analytical, FEM and experimental analysis are performed on a toroidal transformer equipped with a flux sensing coil. The leakage fluxes related to the primary and secondary currents are shown to cause errors in the measurement of the core magnetization current. A solution to mitigate this problem is employed, consisting in twisting and winding together primary and secondary conductors. Experimental methodologies for obtaining the value of the iron losses when the device is transferring energy to a load are also performed. The study shown showed that supply voltage with three-level PWM waveform causes minor hysteresis loops and the greater the resistance value of the excitation winding, the larger the areas of the minor hysteresis loops. On the other hand, by increasing the energy transferring to a load the minor loops areas tend to decrease.

Space-Charge Accumulation and Its Impact on High-Voltage Power Module Partial Discharge Under DC and PWM Waves: Testing and Modeling

Emerging applications of compact high-voltage SiC modules pose strong challenges in the module package insulation design. Such SiC module insulations are subjected to both high-voltage dc and pulsewidth modulation (PWM) excitations between different terminals during different switching intervals. High <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dV/dt</i> strongly interferes with partial discharge (PD) testing as it is hard to distinguish PD pulses and PWM excitation-induced interferences. This article covers both the testing and modeling of PD phenomena in the high-voltage power modules. A high <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dV/dt</i> PD testing platform is proposed, which involves a super-high-frequency (SHF) (SHF >3 GHz) down-mixing PD detection receiver and a high-voltage scalable square wave generator. The proposed method captures SHF PD signatures and determines PD inception voltage (PDIV) for packaging insulation. Using this platform, this article provides a group of PDIV comparisons of packaging insulation under dc and PWM waveforms and discloses discrepancies in these PDIV results with respect to their excitations. Based on these PD testing results, the article further provides a model using the space-charge accumulation to explain the PD difference under dc and PWM waveforms. Both simulation and sample testing results are included in this article to support this hypothesis. With this new model, the article includes an updated insulation design procedure for the high-voltage power modules.

Control of Power Converters With Hybrid Affine Models and Pulse-Width Modulated Inputs

In this paper, hybrid dynamical systems theory is applied to the analysis and control of switched converters with Pulse-Width Modulated (PWM) inputs. The system is described by a state-space model with continuous flows and discrete jumps, without averaged equations. The modulation effects are captured in full without using time-dependent signals, by enlarging the state vector to include the PWM waveform generation process. Furthermore, the sample-and-hold mechanism associated with the sampling frequency is also taken into account with this approach. A control law is proposed based on a Lyapunov function candidate. Furthermore, convergence sets and the steady state jitter, inherent to PWM-based controllers, are analyzed estimating limit sets for the augmented state. Consequently, output chattering can be bounded. By using hybrid dynamical system theory, the control designer gains a deeper understanding of the effect of modulation in the closed-loop dynamics, avoiding the problems associated with the use averaged models. Experimental results validate the proposed method.

Enhanced Fault-Tolerant Model Predictive Current Control for a Five-Phase PM Motor With Continued Modulation

To deal with the single-phase open-circuited fault, an enhanced fault-tolerant model predictive current control with continued modulation is proposed in this article. This method includes reconstructing the postfault vector distribution and adopting a multistep vector selection method. In the reconstruction procedure, the transition vectors are generating to realize standard pulsewidth modulation waveforms. Then, the unreachable area can be filled by creating new synthetic vectors. Finally, the vectors with oversized amplitudes are optimized by using null vectors. In order to cover the full modulation area, a multistep vector selection method is used to determine the phase angle and amplitude of the optimal vector. The phase angle can be determined by defining two cost functions and adopting duty cycle modulation technology. The amplitude of the optimal vector can be optimized by utilizing the duty cycle modulation technology again. The oscillation, due to the back electromotive force, is compensated in each step. A thorough experimental evaluation has been conducted to confirm the effectiveness and superiority of the proposed fault-tolerant method.

Partly isolated three‐port DC–DC converter based on impedance network

This study proposed a novel partly isolated three port converter (PITPC) based on a quasi-Z source converter for photovoltaic applications. Compared with the conventional quasi-Z source converter, the proposed DC–DC converter has dual input sources and uses the switched capacitors and coupled inductor techniques, helping the converter to gain a high voltage. To achieve the power flow control, the proposed converter uses only three power switches with low voltage stress and it is developed for hybridising photovoltaic panels, rechargeable batteries and isolated loads. For this purpose, the proposed PITPC can be easily reconfigured into dual-input single-output, single-input dual-output and single-input single-output modes; so it can even operate when the photovoltaic panel fails to provide energy to the load. Moreover, the study thoroughly discusses various converter operating modes and provides explanations and necessary relationships for circuit operations. The study also explains the control strategy as well as the pulse width modulation waveforms for the proposed converter. Simulation results from MATLAB/Simulink examine the proposed topology performance. The experimental results confirm the advantages claimed for the proposed converter; the results also show a well-distributed efficiency curve and a peak of 96.3%.

Comprehensive Spectral Analysis of PWM Waveforms With Compensated DC-Link Oscillations

In the available literature, including reference books on the topic, the spectral analysis of voltage waveforms obtained through the use of pulse width modulation (PWM) relies on the assumption of an ideally flat voltage across the dc-link of a considered switching structure. Nevertheless, certain converter families (e.g., modular multilevel converter, characterized by the presence of distributed and floating dc-links), feature low-frequency oscillations of dc voltage within their switching stages. On these terms, the flat dc-link assumption cannot be considered valid from both theoretical and practical viewpoints. In case carrier-based modulation is employed, unless properly compensated through the modulation signal adjustments, the above mentioned voltage oscillations cause undesirable distortion of the converter currents. However, the very same adjustments of modulation signals introduce additional challenges in the spectral analysis of the voltage across the ac terminals of an observed switching stage. This article provides the ac terminals voltage analysis of a single half-bridge experiencing dc-link oscillations, which are compensated through the modulation signal generation process. PWM with the conventional triangular carrier is considered, while all the results are presented in a generalized form, making them easily extendable to cascaded structures. All of the presented results were experimentally validated.

A New Perspective on Constraints in the Optimization of PWM Waveform Synthesis in Inverters

The mathematical formulation of pulse width modulation waveform optimization typically involves defining an optimality criterion and constraints on the switching times and other pulse width modulation parameters. In this brief, new results are presented in relation to two constraints. One constraint ensures the strict sequential ordering of switching times. The second constraint ensures that the average value of the pulse width modulation waveform over each segment matches the average of the sine wave to be generated over the corresponding segment. The significance of this latter constraint is explored and a number of new optimal pulse width modulation waveforms are defined based on the enforcement of this constraint. Numerical results of the performance of the optimal pulse width modulation waveforms are presented and compared with respect to indicators which are significant in inverters, such as magnitude of the fundamental frequency component, harmonic content and shortest switching interval of the pulse width modulation waveforms.

A Practical Inductor Loss Testing Scheme and Device With High Frequency Pulsewidth Modulation Excitations

Voltages across magnetic components of power converters are generally pulsewidth modulation (PWM) waveforms, whereas the parameters of present magnetic core loss models are often tested under sinusoidal excitation by most magnetic material manufacturers. This leads to a significant difference with a PWM excitation and then impacts the testing accuracy of inductor losses. A testing device, based on dc law, has been designed to generate different kinds of PWM waveforms, and a corresponding testing scheme is proposed to accurately measure total inductor losses of different inductances with high frequency PWM excitations. Finally, experiments have been conducted to verify the effectiveness and correctness of the proposed scheme. The results show that the proposed testing scheme can accurately test the total inductor loss. Moreover, the proposed loss model of the testing device is in exact agreement with the actual device's loss with the fitting error within 1%, ensuring the accuracy of the proposed testing scheme.

Multi-rise time PWM: A way to reduce PD exposure in motor windings

Decreasing the rise time of pulse width modulated waveforms (PWM) has been observed to reduce the life length of high voltage motors. To solve this problem, the advantages of employing multilevel PWM waveforms with adjustable rise times operating above partial discharge inception are discussed in this paper. Examples of how the voltage supply circuits can be designed to enable investigation of this well as measured results are presented. To elucidate this approach, it is investigated what influence the choice of inverter levels has on the partial discharge (PD) characteristics within motor winding material applying adjustable rise times. The test objects were fed from either three- or four level inverter voltage waveforms to resemble realistic stress conditions as in field application. Presented experimental results show that the total peak and summed PD magnitude (exposure) drops considerably when applying a longer rise time at the critical voltage flanks and is shown to reduce the wear of the winding insulation material, showing the consistency between PD pattern and wear. It is further suggested that the presence of PDs can be eliminated by adjusting the rise times at the most critical voltage flanks and thus enhance the life of the machine winding. The presented principles can be implemented for various PWM pattern.

A linear programming approach for designing multilevel PWM waveforms

This paper considers the problem of designing a multilevel pulse width modulated (PWM) waveform with a prescribed harmonic content. Multilevel PWM design plays a major role in many diverse engineering disciplines. In power electronics, multilevel PWM design corresponds to determining the inverter switching times and levels for selective harmonic elimination and harmonic compensation. In mechatronics, the same design corresponds to shaping input signals to damp residual vibrations in flexible structures. More generally, in many applications, the aim of PWM design is to minimise the total harmonic distortion while adhering to a prescribed harmonic content. The solution approach presented in this paper is based on linear programming with the objective of minimising the total harmonic distortion. This objective is achieved within an arbitrarily small bound of the optimal solution of the related convex optimisation problem. In addition, the linear programming formulation makes the design of such switching waveforms computationally tractable and efficient. Simulations and experiments are provided for corroboration.

Dual PWM Control for High Step-Down DC-DC Converters

The conventional step-down dc–dc converters under the single pulsewidth modulation (PWM) control scheme may not provide enough step-down voltage conversion capabilities with considering the minimum on -time and the switching frequency of the power switch. In order to overcome this difficulty, a dual PWM control scheme for designing the high step-down dc–dc converter is proposed in this article. Both high-frequency and low-frequency PWM waveform generators are utilized in synthesizing the dual PWM control of buck converters. The resulting PWM waveform will lead to various switching cycles, and five operating modes of the buck converter, which can be defined accordingly. The operation principle of the proposed converter and its small-signal switched model are presented in detail. One salient feature of the proposed design is that if the duty cycle of the high-frequency PWM is exactly equal to that of the low-frequency PWM, by exploring the volt–second balance condition, the voltage gain can be expressed as the quadratic formula of the duty cycle of the PWM signal when power switches are operated under the continuous conduction mode. Thus, a high step-down conversion ratio and significant reductions of the inductor current ripple can be ensured simultaneously. Since no modifications of the conventional circuit topology are made, the proposed scheme is very cost-effective. Simulation studies and hardware prototype circuit implementations are conducted to validate the proposed design with satisfactory performance.

EMI mitigation in switching power converters combining closed‐loop gate drive and chaotic frequency modulation technique

All switching power converters are characterised by inevitable switching actions with relevant interference emissions. The voltage and current transients of power metal oxide semiconductor field effect transistor (MOSFET)/insulated-gate bipolar transistor are the main sources in switching power converters for both conducted and radiated emissions. In this study, a promising electromagnetic interference (EMI) mitigation method combining the closed-loop gate drive method and the chaotic switching frequency modulation technique is demonstrated for switching power converters. A chaotic pulse-width modulation waveform with Gaussian S-shape switching transients was proposed to achieve remarkable reduced EMI generation at all frequencies. Spectral characteristics of this new switching waveform were investigated by the power spectral density to verify the feasibility of reduced EMI generation. A closed-loop gate controller was presented to shape the switching transients of power MOSFET into the proposed switching waveform. Circuit tests were carried out in both simulations and experiments. The results validated that the proposed method could achieve remarkable EMI mitigation in switching power converters.

Phase flicker optimisation in digital liquid crystal on silicon devices.

Phase flickers in the digital liquid crystal on silicon (LCOS) devices employing the pulse width modulation (PWM) driving scheme have a detrimental effect on optical performances, especially in the non-display applications. This paper investigated the relationship between the PWM waveform and the corresponding phase flicker in digital LCOS devices. It has been identified that the magnitude of the phase flicker depends on the pulse patterns in the driving waveform as well as the dynamic response of the liquid crystal molecules at different tilting angles. A simple but generic method has been developed based on these findings, which is able to accurately predict the temporal phase response of the liquid crystal to any PWM waveforms. This method is further used for rapid identifications of low-flicker PWM waveforms, without the need for increasing the complexity of the driving circuitry. The peak-to-peak phase flicker in the LCOS device under our investigation has been reduced by >80% from ∼0.16pi to ∼0.03pi when operating at 30°C.

A Practical Approach for Core Loss Estimation of a High-Current Gapped Inductor in PWM Converters With a User-Friendly Loss Map

Core loss estimation of filter inductors is increasingly important for modeling and optimizing high-frequency, high-efficiency, and high-density pulsewidth modulation (PWM) power electronic converters. However, data provided by inductor core manufacturers are insufficient for core loss estimation in PWM converters, particularly in the case of customized gapped inductors. This paper presents a whole process of characterizing and estimating the core loss of a customized high-current gapped inductor for PWM converters. To excite the inductor for the B–H loop measurement, a test circuit formed by a half-bridge structure is proposed, which has the ability to compensate the asymmetric rectangular voltage on the inductor caused by the device voltage drops. To overcome the other challenges raised by a high excitation current, a refined discontinuous test procedure, triple pulse test, is proposed to reduce the requirements of the high-current test setup (thermal stress, current–time stress for current probes, capacity of dc sources, etc.). For practical purposes, a user-friendly loss map approach is proposed involving only time-domain and electrical variables to replace magnetic variables to enable the straightforward loss mapping process and core loss calculations. Presented experimental results show consistency between the estimated inductor loss and measured values. Overall, the proposed testing approach can be easily implemented on the user's side to develop a loss map of a given inductor. The established core loss map enables the users to accurately and rapidly estimate the core loss of a tested inductor for given PWM waveforms.