Pulse Width Modulation Signal Research Articles

Thermal Rectification of Integrated Microheaters for Microring Resonators in Silicon Photonics Platform

Heating elements are used to tune the optical properties of silicon photonic devices, to stabilize operating temperatures, and to compensate for fabrication variations. In this paper, we characterize the transient thermal response and develop models for silicon photonic devices equipped with such heating mechanisms. To demonstrate the usefulness and practicality of the proposed models, we investigate pulse width modulation (PWM) drive scheme for microheaters and experimentally demonstrate its use in stabilizing microring resonators by digital driving signals (two-level voltage). Requirements on the drive frequency and duty cycle of the PWM signal to minimize optical power penalties owing to the undesired thermal ripples are discussed based on the accurately modeled thermal frequency response of the heater-ring system. It is shown that smaller duty cycles require higher drive frequencies and the maximum optical ripple for a microring resonator occurs at 65% duty cycle.

Closed-loop volume flow control algorithm for fast switching pneumatic valves with PWM signal

In this paper, a closed-loop volume flow PWM control algorithm of fast switching pneumatic solenoid valves is studied on the basis of experimental results of fluid flow valve characteristics. Dynamic nonlinear behavior of fast switching valves is analyzed using state-of-the-art mass flow sensors. Minimal Pulse Width Modulation (PWM) pulse width and nonlinear flow characteristics depending on pulse width and pressure difference are observed. Based on experimental data, different approaches to mathematically describe correlation of volume flow, pressure difference and pulse width are given. Bilinear interpolation is found out to have the best correlation and is used to develop a closed-loop control algorithm. The algorithm was tested with controlling of Pneumatic Artificial Muscle (PAM) contraction/position with two fast switching valves and minimal PLC / microcontroller requirements were determined.

Neutral point potential balance algorithm for three‐level NPC inverter based on SHEPWM

In order to obtain the capability of neutral point potential balancing with low switching frequency, a novel balance control algorithm for neutral-point-clamped (NPC) three-level inverter based on Selective harmonic elimination pulse-width modulation (SHEPWM) are proposed. On the basis of the switch sequences and voltage vector action angle corresponding to the three-phase SHEPWM waveform at different modulation index, the three kinds of redundant vector adjustment schemes are designed. Then, load current and neutral point potential feedback to the controller, and the three-phase pulse-width modulation signal adjusted directly by the hysteresis controller to realise neutral point potential balance. Experimental results show that different redundant vector adjustment schemes have different neutral point potential balancing speed and average switching frequency, but do not affect the harmonic elimination ability of the line voltage.

Power Controllable LED System with Increased Energy Efficiency Using Multi-Sensors for Plant Cultivation

In this paper, a power-controllable light emitting diode (LED) control system is proposed for plant cultivation. The proposed LED system measures environmental data, such as the distance between the plant and LED system using an infrared sensor and the ambient illuminance based on an illuminance sensor. Then, it converts the illuminance to the photosynthetic photon flux density (PPFD) for plant cultivation. It analyzes the relationship between the data and LED PPFD, and generates an optimal pulse width modulation (PWM) signal. Therefore, it controls the LED PPFD dynamically. The proposed LED system is also implemented in hardware, which consists of red and blue LED arrays with suitable wavelengths and a micro-controller. In the experimental results, the proposed LED system preserved the target PPFD regardless of the change of the distance and ambient PPFD. Additionally, the proposed LED system maximally reduced the power consumption of a conventional system by up to 68%.

Multi-Level Read/Write Signaling Using Pulse Width Modulation for High Density Perpendicular Magnetic Recording

In this letter, we propose a novel read/write (R/W) signal processing method by 3-ary amplitude shift keying for high density perpendicular magnetic recording. We also provide a 3B2T modulation to generate 3-ary signal, which will be converted to a pulse width modulation (PWM) signal, and then recorded on magnetic media. The PWM signal can be simply demodulated to derive the 3-ary signal through a low-pass filter at readback side. The demodulated signal in the presence of intersymbol interference is detected by the Viterbi algorithm as partial response signal. Nonbinary low-density parity-check codes over GF(8) are applied as error correcting codes in our evaluation. Our simulation result shows the proposed R/W method has +4% more user bit density gain than conventional binary recording.

A Soft-Switching Bridgeless AC–DC Power Factor Correction Converter

A new soft-switching, bridgeless power factor correction (PFC) boost converter is proposed for power supply and battery charging applications. The converter operates in both pulse width modulation (PWM) mode and resonant mode each switching cycle, and utilizes standard average current mode control. The converter is bridgeless, therefore eliminating the need for a front-end diode bridge rectifier. It operates in continuous conduction mode and achieves zero voltage switching (ZVS) for all switches. The proposed converter also reduces the turn-off losses of the PWM switches, therefore nearly eliminating switching losses. The output diodes operate with controlled di/dt turn-off, which reduces reverse–recovery losses. The PWM switches of the proposed converter can be driven with the same PWM signal, enabling simplified control. The detailed operation of the proposed converter is presented, including the conditions for ZVS operation and a stress analysis for the circuit components. Experimental results are presented for a 650-W prototype at 150-kHz switching frequency, universal ac input, and 400-V dc output. The proposed converter shows about 1% better efficiency and lower device temperatures at full load and 100-V ac input (maximum loss operating point) compared with the conventional hard switched PFC boost converter.

A Two-Level Sensorless MPPT Strategy Using SRF-PLL on a PMSG Wind Energy Conversion System

In this paper, a two-level sensorless Maximum Power Point Tracking (MPPT) strategy is presented for a variable speed Wind Energy Conversion System (WECS). The proposed system is composed of a wind turbine, a direct-drive Permanent Magnet Synchronous Generator (PMSG) and a three phase controlled rectifier connected to a DC load. The realised generator output power maximization analysis justifies the use of the Field Oriented Control (FOC) giving the six Pulse Width Modulation (PWM) signals to the active rectifier. The generator rotor speed and position required by the FOC and the sensorless MPPT are estimated using a Synchronous Reference Frame Phase Locked Loop (SRF-PLL). The MPPT strategy used consists of two levels, the first level is a power regulation loop and the second level is an extremum seeking bloc generating the coefficient gathering the turbine characteristics. Experimental results validated on a hardware test setup using a DSP digital board (dSPACE 1104) are presented. Figures illustrating the estimated speed and angle confirm that the SRF-PLL is able to give an estimated speed and angle which closely follow the real ones. Also, the power at the DC load and the power at the generator output indicate that the MPPT gives optimum extracted power. Finally, other results show the effectiveness of the adopted approach in real time applications.

A SiC CMOS Digitally Controlled PWM Generator for High-Temperature Applications

This paper describes a silicon carbide pulse width modulation (PWM) signal generator in the 1.2 μm HiTSiC CMOS process developed by Raytheon Systems Ltd. The design features a 6-b binary input, which allows for setting a system's duty cycle. The results presented in this paper utilize a field programmable gate array board in the test setup to dynamically set the duty cycle by controlling each bit. A control current is also available to give the user added flexibility for tuning the duty cycle. Experimental results show the duty cycle range of the PWM generator to be between 4.7% and 95.2% at 400 °C. Sustained operation of the circuit is demonstrated over a period of 50 h at 300 °C. Finally, the PWM generator is evaluated in the operation of a boost converter.

A Switched-Coupling-Capacitor Equalizer for Series-Connected Battery Strings

Due to the low cost, small size, and easy control, the switched-capacitor (SC) equalizer is promising among all types of active cell balancing methods. However, the balancing speed is generally slow and the balancing efficiency is seriously low when the SC equalizer is applied into a long battery string. Therefore, an automatic switched-coupling-capacitor equalizer (SCCE) is proposed, which can realize the any-cells-to-any-cells equalization for a battery string. Only two switches and one capacitor are required for each battery cell. All mosfet s are controlled by one pair of complementary pulse width modulation signals, and energy can be automatically and directly delivered from any higher voltage cells to any lower voltage ones without the need of cell monitoring circuits, leading to a high balancing efficiency and speed independent of the cell number and the initial cell voltages. Contrary to the conventional equalizers using additional components for the equalization among modules, the proposed equalizer shares a single converter for the equalization among cells and modules, resulting in smaller size and lower cost. A prototype for four lithium battery cells is implemented, and an experimental comparison between the proposed SCCE and the conventional SC equalizer is presented. Experimental results show the proposed topology exhibits a substantially improved balancing performance, and the measured peak efficiency is 92.7%.

A Modularization Method for Battery Equalizers Using Multiwinding Transformers

This paper proposes a modularized global architecture using multi-winding transformers for battery cell balancing. The global balancing for a series-connected battery string is achieved based on forward conversion in each battery module and based on flyback conversion among modules. The demagnetization of the multiwinding transformers is also simultaneously achieved by the flyback conversion among modules without the need of additional demagnetizing circuits. Moreover, all MOSFET switches are driven by two complementary pulse width modulation signals without the requirement of cell voltage sensors, and energy can be automatically and simultaneously delivered from any high voltage cells to any low voltage cells. Compared with existing equalizers requiring additional balancing circuits for battery modules, the proposed modularized equalizer shares one circuit for the balancing among cells and modules. The balancing performance of the proposed equalizer is perfectly verified through experimental results, and the maximum balancing efficiency is up to 91.3%. In summary, the proposed modularized equalizer has the advantages of easier modularization, simpler control, higher efficiency, smaller size, and lower cost, ensuring the battery system higher reliability and easier implementation.

A zero-voltage-switched three-phase interleaved buck converter

ABSTRACTThis paper proposes a three-phase interleaved buck converter which is composed of three identical paralleled buck converters. The proposed solution has three shunt inductors connected between each other of three basic buck conversion units. With the help of the shunt inductors, the MOSFET parasitic capacitances will resonate to achieve zero-voltage-switching. Furthermore, the decreasing rate of the current through the free-wheeling diodes is limited, and therefore, their reverse-recovery losses can be minimised. The active power switches are controlled by interleaved pulse-width modulation signals to reduce the input and output current ripples. Therefore, the filtering capacitances on the input and output sides can be reduced. The power efficiency is measured to be as high as 98% in experiment with a prototype circuit.

Fault tolerant control of electronically coupled distributed energy resources in microgrid systems

This paper proposes a sensor fault tolerant control (FTC) strategy for electronically-coupled distributed energy resource (DER) units in grid-connected microgrid systems. First, a fault dependent dynamical model of the DER unit incorporating sensor faults is proposed. The FTC strategy is then developed using a sliding mode observer (SMO) which has an inherent robustness property. The rational for using a SMO is the need to detect and reconstruct any fault that may occur in output measurements of the system as a result of sensor failure. The fault signals are reconstructed by using a robust approach that encompasses uncertainties in the system, such as frequency variation. This paper also represents the cyber attack as an unknown sensor fault, and consequently the DER current sensor measurements manipulated by a data integrity attack can be detected and reconstructed. The reconstructed fault signals are then used to modify the faulty sensor measurements, which are fed to the voltage source converter (VSC) controller. This ensures accurate generation of pulse width modulation (PWM) signals and consequently accurate tracking of real and reactive power references. Different case studies are tested on a detailed nonlinear model of the DER system. The impact of faults on the DER performance and the effectiveness of the proposed FTC scheme are evaluated through extensive simulation studies. Experimental verification of the method is provided to further validate the proposed approach.

Ball-disk rotor gyroscope adaptive quick-start technique

Rotating speed is a critical parameter affecting the performance of rotor gyroscopes. Rotor gyroscopes must operate at the rated rotating speed. To shorten the start time of the ball-disk rotor gyroscope, this paper presents a new design of the drive system for a ball-disk rotor gyroscope. The drive system is monitored by a microcontroller. First, the microcontroller generates a sine pulse width modulation signal to drive the permanent magnet rotor. Second, the position of the rotor is detected according to the back electromotive force in the non-energized coil. Third, a piecewise closed-loop control algorithm is implemented to keep the angular acceleration of the rotor within the safe range automatically during the acceleration process and when running at a constant speed. This control algorithm can avoid rotor stalling due to loss of steps. Experimental result shows that with the help of adaptive quick-start technique, the start time of the device can be shortened by up to 36.6%.

A Four-Switch Single-Stage Single-Phase Buck–Boost Inverter

This paper proposes a single-phase, single-stage buck–boost inverter for photovoltaic (PV) systems. The presented topology has one common terminal in input and output ports which eliminates common mode leakage current problem in the grid-connected PV applications. Although it uses four switches, its operation is bimodal and only two switches receive high-frequency pulse width modulation signals in each mode. Its principle of operation is described in detail with the help of equivalent circuits. Its dynamic model is presented, based on which a bimodal controller is designed. Experimental results, in stand-alone and grid-connected mode, obtained with a 300-W laboratory prototype are presented to validate its performance.

Improved and innovated universal DAQ microcontroller unit

Abstract This paper is aimed at the description of hardware design, software equipment and the functionality of the second evolution of the intelligent multipurpose input/output microcontroller converter and control unit designed and assembled by the authors. Preceding stages of the unit development are concisely overviewed first, the deficiencies of which give rise to the primary motivation of this contribution. Then separate hardware parts of the novel unit are described in detail including electronic schematic diagrams. The device firmware and software capabilities are introduced as well. The advantages of the unit are highlighted compared to older versions. Its functionality, performance and efficiency are then verified by a laboratory control-related dynamic responses measurement example. In the contrary to previous evolutions, a more compact hardware design, increased A/D and D/A converter resolutions, added USB communication capability, better and more accurate analog circuits with more advanced operation amplifiers, the use of OLED instead of LCD display, the pulse-width modulated signal generated by the microcontroller unit itself can be considered among the most important improvements. Moreover, the direct use of the serial link may reduce noise significantly and makes the device more universal.

EFFECT OF PULSE WIDTH MODULATION ON DC MOTOR SPEED

Pulse width modulation (PWM) is used to generate pulses with variable duty cycle rate. The rapid rising and falling edges of PWM signal minimises the switching transition time and the associated switching losses. This paper presents a DC motor speed controller system using PWM technique. The PWM duty cycle is used to vary the speed of the motor by controlling the motor terminal voltage.The motor voltage and revolutions per minutes (RPM) obtained at different duty cycle rates. As the duty cycle increases, more voltage is applied to the motor. This contributes to the stronger magnetic flux inside the armature windings and the increasethe RPM. The characteristics and performance of the DC motor speed control system was investigated. In this paper, a PIC microcontroller and a DC-DC buck converter are employed in the DC motor speed controller system circuit. The microcontroller provides flexibility to the circuit by incorporating two push button switches in order to increase and to decrease the duty cycle rate. The characteristics and performance of the motor speed controller system using microcontroller was examined at different duty cycle rate ranging from 19% to 99%.

Pulse width modulation as energy-saving strategy of shape memory alloy based smart soft composite actuator

This paper presents electrical power consumption decreased in actuating a shape memory alloy (SMA) based smart soft composite (SSC) actuator using pulse width modulation (PWM). A DC current input generator and a PWM signal generator were designed to apply inputs to SSCs. Experiments were carried out on two types of SSC: one conventional, using a single SMA wire, and the other using multiple wires. The blocking force was measured to analyze the performance of the SSC. The experiments demonstrated that the PWM signal was able to reduce the actuation energy while showing the same performance as an analog current input. These results suggest that a PWM signal could be an alternative candidate for the input paradigm for SSCs to reduce energy consumption, expanding the uses of SSC actuators in robotic applications.

Fast switch fault diagnosis for PWM DC–DC low power converters

In this paper, a fast switching fault diagnostic scheme is proposed for low‐power pulse width modulation (PWM) DC–DC converters operating in different conduction modes. The outstanding feature of the proposed scheme is that no additional sensing circuits are needed. This is achieved by using the differential of output ripple voltage and the switch gate driver signal for diagnosis. Since the output voltage has to be normally measured for control purposes and the PWM signals are known to the controller, no additional sensors are needed in the proposed scheme. Moreover, based on the real‐time output voltage measurement and switch gate driver signal, the characteristics of switch open‐ and short‐circuit faults can be rapidly extracted, specifically, in less than one switching cycle. Besides, the fault detection scheme can be implemented by a low‐cost logical hardware circuit, which can be integrated into the control unit. The fault diagnosis principle, design considerations, and implementation of the detection scheme are discussed in this paper. Experimental results show that the fault detection system can detect the switching fault in four‐tenths of the switching period. Besides, the proposed method can be used in the applications where the output voltage ripple rate is more than 4%, which covers most situations. © 2017 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Design and dynamic analysis of a piezoelectric linear stage for pipetting liquid samples

Piezoelectric actuators have been widely used in positioning stages because of their compact size, stepping controllability, and holding force. This study proposes a piezoelectric-driven stage composed of a bi-electrode piezoelectric slab, capacitive position sensor, and capillary filling detector for filling liquid samples into nanopipettes using capillary flow. This automatic sample-filling device is suitable for transmission electron microscopy image-based quantitative analysis of aqueous products with added nanoparticles. The step length of the actuator is adjusted by a pulse width modulation signal that depends on the stage position; the actuator stops moving once the capillary filling has been detected. A novel dynamic model of the piezoelectric-driven stage based on collision interactions between the piezoelectric actuator and the sliding clipper is presented. Unknown model parameters are derived from the steady state solution of the equivalent steady phase angle. The output force of the piezoelectric actuator is formulated using the impulse and momentum principle. Considering the applied forces and related velocity between the sliding clipper and the piezoelectric slab, the stage dynamic response is confirmed with the experimental results. Moreover, the model can be used to explain the in-phase slanted trajectories of piezoelectric slab to drive sliders, but not elliptical trajectories. The maximum velocity and minimum step length of the piezoelectric-driven stage are 130 mm s−1 and 1 μm respectively.

Zero Voltage Vector Sampling Method for PMSM Three-Phase Current Reconstruction Using Single Current Sensor

For the purpose of reducing cost and volume, techniques of reconstructing three-phase currents through a single current sensor have been reported for permanent magnet synchronous motor vector control system. In existing studies, the reconstruction precision is largely affected by the dead zones in space vector PWM plane, which requires additional efforts to compensate the dead zones either by modifying pulse width modulation (PWM) modulation strategy or by phase-shifting of PWM signal. In this paper, a novel zero voltage vector sampling method (ZVVSM) is proposed, which can move the current reconstruction dead zones in low modulation region and sector boundary regions toward the outline of the space vector hexagon without modifying PWM signal. By arranging the single current sensor at a novel position, the proposed method is able to sample current in two zero voltage vectors (ZVV). ZVVSM avoids the complicated algorithms as well as the increase of the switching times, so that it is beneficial to the PMSM drive performance. The proposed method is validated by both simulation and experiments.