Digital Pulse Width Modulator Techniques For Dc - Dc Converters

Recent research activities focused on improving the steady-state as well as the dynamic behavior of DC-DC converters for proper system performance, by proposing different design methods and control approaches with growing tendency to using digital implementation over analog practices. Because of the rapid advancement in semiconductors and microprocessor industry, digital control grew in popularity among PWM converters and is taking over analog techniques due to availability of fast speed microprocessors, flexibility and immunity to noise and environmental variations. Furthermore, increased interest in Field Programmable Gate Arrays (FPGA) makes it a convenient design platform for digitally controlled converters. The objective of this research is to propose new digital control schemes, aiming to improve the steady-state and transient responses of a high switching frequency FPGA-based digitally controlled DC-DC converters. The target is to achieve enhanced performance in terms of tight regulation with minimum power consumption and high efficiency at steady-state, as well as shorter settling time with optimal over- and undershoots during transients. The main task is to develop new and innovative digital PWM techniques in order to achieve: 1. Tight regulation at steady-state: by proposing high resolution DPWM architecture, based on Digital Clock Management (DCM) resources available on FPGA boards. The proposed architecture Window-Masked Segmented Digital Clock Manager-FPGA based Digital Pulse Width Modulator Technique, is designed to achieve high resolution operating at high switching frequencies with minimum power consumption. 2. Enhanced dynamic response: by applying a shift to the basic saw-tooth DPWM signal, in order to benefit from the best linearity and simplest architecture offered by the conventional counter-comparator DPWM. This proposed control scheme will help the compensator reach the steady-state value faster. Dynamically Shifted Ramp Digital Control Technique for Improved Transient Response in DC-DC Converters, is projected to enhance the transient response by dynamically controlling the ramp signal of the DPWM unit

A Non-isolated Half Bridge Buck-based Converter For Vrm Application And Small Signal Modeling Of A Non-conventional Two Phase Bu

This dissertation is about treatment of the nonbiodegradable organic content of landfill leachate by chemical oxidation combined with biological treatment. It is divided into three parts. In the first part, ferrate was compared to Fenton\u27s reagent for the purpose of removing non-biodegradable organic compounds from mature leachate. Oxidation conditions (time, pH, and dose) were optimized to yield maximum organic removal using two leachate samples from 20 and 12-year old solid waste cells. Results from this research demonstrated that ferrate and Fenton\u27s reagent had similar optimum pH ranges (3-5), but different organic removal capacities, ranging from 54 to 79 % of initial leachate organic contents. An advantage of ferrate was that it was relatively effective over a wide pH range (Fenton\u27s reagent lost its reactivity outside optimum pH range). Advantages associated with Fenton\u27s reagent include a higher organic removal capacity, production of more oxidized organic compounds (measured as chemical oxygen demand/dissolved organic carbon), and production of more biodegradable byproducts (measured as 5-day biochemical oxygen demand/chemical oxygen demand). Finally, both treatments were found to oxidize larger molecules (\u3e1000 dalton) and produce smaller molecules, as indicated by an increase in smaller molecule contribution to organic carbon. In part two, effects of Fenton\u27s reagent treatment on biodegradability of three landfill leachates collected from a Florida landfill were evaluated using biochemical oxygen demand (BOD), biochemical methane potential (BMP), and tertamethylammonium hydroxide (TMAH) thermochemolysis gas chromatography/mass spectrometry (GC/MS). The hypothesis was that Fenton\u27s reagent will remove refractory compounds that inhibit biodegradation and will produce smaller, more biodegradable organic molecules which will result in an increase in BOD and BMP values. Both BOD and BMP results demonstrated that Fenton\u27s reagent treatment did not convert mature leachate to biodegradable leachate, as indicated by a low BOD5 expressed as C /dissolved organic carbon (DOC) ratio of almost 0.15 in treated samples and a low net methane production / theoretical methane potential (less than 0.15). Ultimate BOD only slightly increased. However the first-order BOD reaction rate increased by more than five fold, suggesting that Fenton\u27s reagent removed refractory and inhibitory compounds. BMP results demonstrated that the ratio of CO2/CH4 produced during anaerobic biodegradation did not increase in treated leachate (compared to untreated), indicating that small biodegradable organic acids produced by oxidation were removed by coagulation promoted by Fenton\u27s reagent. Finally, the TMAH thermochemolysis results showed that several of the refractory and inhibitory compounds were detected fewer times in treated samples and that carboxylic acids did not appear in treated samples. In the third part of this dissertation the application of flushing/Fenton\u27s reagent oxidation to produce sustainable solid waste cells was evaluated. A treatment similar to pump and treat process utilizing Fenton\u27s reagent on-site treated leachate combined with in-situ aeration was proposed. Treated leachate would be recycled to the landfill cell flushes releasable nonbiodegradable carbon from the cell and oxidizes it externally. This technique was demonstrated to have treatment cost and time benefits over other alternatives for producing completely stable solid waste cells such as anaerobic flushing and biological and/or mechanical pretreatment of solid waste (used in the EU)

E-Engineering: from concept to reality

Even before the digital era, the implementation of distance learning in higher education was a reality in many areas. Notwithstanding, the offer of distance higher education courses was not equal in all knowledge areas due to different teaching and learning requirements. The experimental work developed during the learning process in engineering areas is widely recognized as essential for engineering students. However, the remote availableness of this experimental, hands-on, works, typically done in University laboratories designed according to the different teaching subject requirements, was nonexistent. With the advent of remote laboratories, real-time remotely controlled laboratory facilities made possible by the advancements on the Internet network, this limitation disappeared. The concept of e-engineering, a merge between the e-learning concept and the remote laboratories, emerged as a solution to offer distance learning engineering courses without abdicating of the indispensable practical component of any engineering course. Two European projects – the Tempus EOLES project and the ERASMUS+ e-LIVES project – try to bridge the gap between concept and reality by first implementing an accredited higher education engineering course in Electronics and Optics e-Learning for Embedded Systems and then by producing a set of guidelines to help others to be autonomous in the creation of their own eengineering courses.info:eu-repo/semantics/publishedVersio

Non-Isolated Half Bridge Buck Based Converter For Vrm Application

High efficiency and fast transient response are very critical to Voltage Regulator Module (VRM) and they are contradicted to each other. Continuous output voltage drop with increased current and power densities force small duty cycle operation, resulting in lower efficiency and worse transient response. This paper presents a new, transformer based, non-isolated, buck derived, half bridge converter for VRM application. The transformer in the presented topology helps in decreasing the top switch current as well as the bottom switch voltage stresses, it also extends the duty cycle to a favorable range enhancing the efficiency and transient response by optimizing MOSFET selections. The proposed converter is designed, analyzed and the experimental results are presented. © 2007 IEEE

A Dynamic, Linearly-Shifted, Fixed-Slope Digital-Ramp Control Technique For Improved Transient Response In Dc - Dc Converters

A conventional Counter-Comparator Digital Pulse Width Modulator (DPWM) with a fixed slope is dynamically and linearly shifted upwards or downwards by a value proportional to the error signal. The shift is done through applying a positive or negative offset (shift) value depending on the direction of the transient. This control approach aims to improve the transient response and efficiency of an FPGA-based digitally controlled DC-DC converters in terms of shorter settling time with optimal over-and undershoots. The dynamic Ramp Shift design method presented in this work is a linear DC shift control achieving a better dynamics response through reducing the time required by the compensator to reach back to the steady state during a transient condition. Moreover, it utilizes existing system digital controller, and does not require any additional circuitry. This shifting will only occur during transients for the reason that the error (which basically formulates the shift value) is almost zero during steady state, while during transients; the positive or negative value of the error will shift the ramp downwards or upwards. The proposed digital technique is validated by computer simulation. Experimental result of a prototype on a Xilinix FPGA platform verifies the concept

Analysis And Small Signal Modeling Of A Non-Uniform Multiphase Buck Converter

This paper presents steady-state analysis and dynamic modeling of a non-uniform multiphase buck converter. This type of converter architecture has been reported previously in the literature with non-uniform phase design with the utilization of dynamic non-uniform current sharing and phase picking schemes in order to improve the power conversion efficiency over a wide load range. Since this scheme encounters the use of different current and possibly different inductor values for each phase, and/or different input voltages at the input of each phase, the impact on the steady-state and dynamic performance needs to be studied. This paper presents an initial analysis and small modeling study with discussion and experimental verification. © 2007 IEEE

Unified Maximum Power Tracking Among Distributed Power Sources

Presented herein is Uniform Input Voltage Distribution (UIVD) control [6-9] for Distributed-Input Series-Output (DISO) converter power systems. UIVD for DISO converters is implemented to primarily achieve grouped maximum power throughput from non-identical power sources. This paper also offers a revised Maximum Power Tracking (MPT) controller [11] that facilitates simultaneous processing of distributed power flows among DISO converters. Conventionally, peak powers of distributed power sources are individually tracked by distributed converters that are controlled by independent MPT controllers (IMPT) without UIVD. However, when distributed power sources have similar peak power voltages, such IMPT controllers are not necessary. With UIVD, only one MPT controller is sufficient to achieve near-maximum use of available power. The resulting power and control architectures offer near-maximum power transfer with a lower parts count. Two DISO power converter architectures are described herein: one having a battery-dominated output and the other with a regulated-voltage output. Computer simulation and prototype testing have validated both power architectures with fault-tolerant grouped-tracking uniform voltage distribution (GT-UVD). © 2014 IEEE

Unified maximum power tracking among distributed power sources

Presented herein is Uniform Input Voltage Distribution (UIVD) control [6-9] for Distributed-Input Series-Output (DISO) converter power systems. UIVD for DISO converters is implemented to primarily achieve grouped maximum power throughput from non-identical power sources. This paper also offers a revised Maximum Power Tracking (MPT) controller [11] that facilitates simultaneous processing of distributed power flows among DISO converters. Conventionally, peak powers of distributed power sources are individually tracked by distributed converters that are controlled by independent MPT controllers (IMPT) without UIVD. However, when distributed power sources have similar peak power voltages, such IMPT controllers are not necessary. With UIVD, only one MPT controller is sufficient to achieve near-maximum use of available power. The resulting power and control architectures offer near-maximum power transfer with a lower parts count. Two DISO power converter architectures are described herein: one having a battery-dominated output and the other with a regulated-voltage output. Computer simulation and prototype testing have validated both power architectures with fault-tolerant grouped-tracking uniform voltage distribution (GT-UVD). © 2014 IEEE

Dynamic Dc Ramp Shift Digital Control Technique For Improved Transient Response

A new control scheme aiming to improve the dynamic behavior of digitally controlled DC-DC converters in terms of improved settling time and overshoot is presented in this paper. The proposed approach enhances the transient response by dynamically controlling the ramp of the Digital Pulse Width Modulator (DPWM) unit by applying DC shift to the conventional ramp-based PWM during load change. This will help the compensator reach the steady-state value faster. The dynamic DC ramp shift design method presented in this paper utilizes the existing system digital controller, and does not require any additional circuitry. The presented control scheme is first analyzed, then simulated and finally experimentally verified using a DSP implementation. © 2009 IEEE

New Digital Control Technique For Improving Transient Response In Dc-Dc Converters

A new digital control scheme aiming to improve the transient response of an FPGA-based digitally controlled DC-DC converters is presented in this paper. The proposed approach enhances the transient response by dynamically controlling the ramp of the Digital Pulse Width Modulator (DPWM) unit through applying either linear or nonlinear shift to the conventional ramp-based DPWM. This allows the compensator to reach steady-state faster. The advantages and disadvantages of both techniques are presented and weight against improvement on transient response. Detailed analysis, simulation results and experimental waveforms are presented to verify the concept. © 2010 IEEE