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DESIGN AND IMPLEMENTATION OF A DIGITAL CONTROLLER WITH DSP FOR HALF-BRIDGE DC-DC CONVERTERS
Title
DESIGN AND IMPLEMENTATION OF A DIGITAL CONTROLLER WITH DSP FOR HALF-BRIDGE DC-DC CONVERTERS.
Creator
Wen, Yangyang, Batarseh, Issa, University of Central Florida
Abstract / Description
DC-DC power converters play an important role in powering telecom and computing systems. With the speed improvement and cost reduction of digital control, digital controller is becoming a trend for DC-DC converters in addition to existed digital monitoring and management technology. In this thesis, digital control is investigated for DC-DC converters applications. To deeply understand the whole control systems, DC-DC converter models are investigated based on averaged state-space modeling....
Show moreDC-DC power converters play an important role in powering telecom and computing systems. With the speed improvement and cost reduction of digital control, digital controller is becoming a trend for DC-DC converters in addition to existed digital monitoring and management technology. In this thesis, digital control is investigated for DC-DC converters applications. To deeply understand the whole control systems, DC-DC converter models are investigated based on averaged state-space modeling. Considering half-bridge isolated DC-DC converter with a current doublers rectifier has advantages over other topologies especially in the application of low-voltage and high-current DC-DC converters, the thesis take it as an example for digital control modeling and implementation. In Chapter 2, unified steady-state DC models and small-signal models are developed for both symmetric and asymmetric controlled half-bridge DC-DC converters. Based on the models, digital controller design is implemented. In Chapter 3, digital modeling platforms are established based on Matlab, Digital PID design and corresponding simulation results are provided. Also some critical issues and practical requirements are discussed. In Chapter 4, a DSP-based digital controller is implemented with the TI's DSP chip TMS320F2812. Related implementation methods and technologies are discussed. Finally the experimental results of a DSP-based close-loop of HB converter are provided and analyzed in Chapter 5, and thesis conclusions are given in Chapter 6.
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Date Issued
2004
Identifier
CFE0000246, ucf:46273
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0000246
MODELING AND DESIGN OF MULTI-PORT DC/DC CONVERTERS
Title
MODELING AND DESIGN OF MULTI-PORT DC/DC CONVERTERS.
Creator
Qian, Zhijun, Batarseh, Issa, University of Central Florida
Abstract / Description
In this dissertation, a new satellite platform power architecture based on paralleled three-port DC/DC converters is proposed to reduce the total satellite power system mass. Moreover, a four-port DC/DC converter is proposed for renewable energy applications where several renewable sources are employed. Compared to the traditional two-port converter, three-port or four-port converters are classified as multi-port converters. Multi-port converters have less component count and less conversion...
Show moreIn this dissertation, a new satellite platform power architecture based on paralleled three-port DC/DC converters is proposed to reduce the total satellite power system mass. Moreover, a four-port DC/DC converter is proposed for renewable energy applications where several renewable sources are employed. Compared to the traditional two-port converter, three-port or four-port converters are classified as multi-port converters. Multi-port converters have less component count and less conversion stage than the traditional power processing solution which adopts several independent two-port converters. Due to their advantages multi-port converters recently have attracted much attention in academia, resulting in many topologies for various applications. But all proposed topologies have at least one of the following disadvantages: 1) no bidirectional port; 2) lack of proper isolation; 3) too many active and passive components; 4) no soft-switching. In addition, most existing research focuses on the topology investigation, but lacks study on the multi-port converterÂÂ's control aspects, which are actually very challenging since it is a multi-input multi-output control system and has so many cross-coupled control loops. A three-port converter is proposed and used for space applications. The topology features bidirectional capability, low component count and soft-switching for all active switches, and has one output port to meet certain isolating requirements. For the system level control strategy, the multi-functional central controller has to achieve maximal power harvesting for the solar panel, the battery charge control for the battery, and output voltage regulation for the dc bus. In order to design these various controllers, a good dynamic model of the control object should be obtained first. Therefore, a modeling procedure based on a traditional state-space averaging method is proposed to characterize the dynamic behavior of such a multi-port converter. The proposed modeling method is clear and easy to follow, and can be extended for other multi-port converters. In order to boost the power level of the multi-port converter system and allow redundancy, the three-port converters are paralleled together. The current sharing control for the multi-port converters has rarely been reported. A so called ÂÂ"dual loopÂÂ" current sharing control structure is identified to be suitable for the paralleled multi-port converters, since its current loop and the voltage loop can be considered and designed independently, which simplifies the multi-port converterÂÂ's loop analysis. The design criteria for that dual loop structure are also studied to achieve good current sharing dynamics while guaranteeing the system stability. The renewable energy applications are continuously demanding the low cost solution, so that the renewable energy might have a more competitive dollar per kilowatt figure than the traditional fossil fuel power generation. For this reason, the multi-port converter is a good candidate for such applications due to the low component count and low cost. Especially when several renewable sources are combined to increase the power delivering certainty, the multi-port solution is more beneficial since it can replace more separate converters. A four-port converter is proposed to interface two different renewable sources, such as the wind turbine and the solar panel, one bidirectional battery device, and the galvanically isolated load. The four-port converter is based on the traditional half-bridge topology making it easy for the practicing power electronics engineer to follow the circuit design. Moreover, this topology can be extended into n input ports which allow more input renewable sources. Finally, the work is summarized and concluded, and references are listed.
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Date Issued
2010
Identifier
CFE0003001, ucf:48373
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0003001
ENTIRE LOAD EFFICIENCY AND DYNAMIC PERFORMANCE IMPROVEMENTS FOR DC-DC CONVERTERS
Title
ENTIRE LOAD EFFICIENCY AND DYNAMIC PERFORMANCE IMPROVEMENTS FOR DC-DC CONVERTERS.
Creator
Abdel-Rahman, Osama, Batarseh, Issa, University of Central Florida
Abstract / Description
The scope of this work can be summarized by three main aspects of DC-DC power converters. The first aspect is soft switching topologies to improve conversion efficiency for On-Board Converters or Point of load (POL) converters, the second aspect is load adaptive control techniques to improve all load efficiency for battery powered DC-DC converters that are applied to mobile devices, and the third aspect is dynamic performance improvement techniques to improve load transient in voltage...
Show moreThe scope of this work can be summarized by three main aspects of DC-DC power converters. The first aspect is soft switching topologies to improve conversion efficiency for On-Board Converters or Point of load (POL) converters, the second aspect is load adaptive control techniques to improve all load efficiency for battery powered DC-DC converters that are applied to mobile devices, and the third aspect is dynamic performance improvement techniques to improve load transient in voltage regulators. Topologies and control techniques for DC-DC converters are presented after reviewing loads powering requirements and steady-state and transients design challenges.
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Date Issued
2007
Identifier
CFE0001625, ucf:47186
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0001625
MODELING AND DIGITAL CONTROL OF HIGH FREQUENCY DC-DC POWER CONVERTERS
Title
MODELING AND DIGITAL CONTROL OF HIGH FREQUENCY DC-DC POWER CONVERTERS.
Creator
Wen, Yangyang, Batarseh, Issa, University of Central Florida
Abstract / Description
The power requirements for leading edge digital integrated circuits have become increasingly demanding. Power converter systems must be faster, more flexible, more precisely controllable and easily monitored. Meanwhile, in addition to control process, the new functions such as power sequencing, communication with other systems, voltage dynamic programming,load line specifications, phase current balance, protection, power status monitoring and system diagnosis are going into today's power...
Show moreThe power requirements for leading edge digital integrated circuits have become increasingly demanding. Power converter systems must be faster, more flexible, more precisely controllable and easily monitored. Meanwhile, in addition to control process, the new functions such as power sequencing, communication with other systems, voltage dynamic programming,load line specifications, phase current balance, protection, power status monitoring and system diagnosis are going into today's power supply systems. Digital controllers, compared withanalog controllers, are in a favorable position to provide basic feedback control as well as those power management functions with lower cost and great flexibility. The dissertation gives an overview of digital controlled power supply systems bycomparing with conventional analog controlled power systems in term of system architecture,modeling methods, and design approaches. In addition, digital power management, as one of the most valuable and "cheap" function, is introduced in Chapter 2. Based on a leading-edge digital controller product, Chapter 3 focuses on digital PID compensator design methodologies, design issues, and optimization and development of digital controlled single-phase point-of-load (POL)dc-dc converter. Nonlinear control is another valuable advantage of digital controllers over analogcontrollers. Based on the modeling of an isolated half-bridge dc-dc converter, a nonlinear control method is proposed in Chapter 4. Nonlinear adaptive PID compensation scheme is implemented based on digital controller Si8250. The variable PID coefficient during transients improves power system's transient response and thus output capacitance can be reduced to save cost. In Chapter 5, another nonlinear compensation algorithm is proposed for asymmetric flybackforward half bridge dc-dc converter to reduce the system loop gain's dependence on the input voltage, and improve the system's dynamic response at high input line. In Chapter 6, a unified pulse width modulation (PWM) scheme is proposed to extend the duty-cycle-shift (DCS) control, where PWM pattern is adaptively generated according to the input voltage level, such that the power converter's voltage stress are reduced and efficiency is improved. With the great flexibility of digital PWM modulation offered by the digital controller Si8250, the proposed control scheme is implemented and verified. Conclusion of the dissertation work and suggestions for future work in related directions are given in final Chapter.
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Date Issued
2007
Identifier
CFE0001612, ucf:47172
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0001612
ADAPTIVE EFFICIENCY OPTIMIZATION FOR DIGITALLY CONTROLLED DC-DC CONVERTERS
Title
ADAPTIVE EFFICIENCY OPTIMIZATION FOR DIGITALLY CONTROLLED DC-DC CONVERTERS.
Creator
AL-HOOR, WISAM, Batarseh, Issa, University of Central Florida
Abstract / Description
The design optimization of DC-DC converters requires the optimum selection of several parameters to achieve improved efficiency and performance. Some of these parameters are load dependent, line dependent, components dependent, and/or temperature dependent. Designing such parameters for a specific load, input and output, components, and temperature may improve single design point efficiency but will not result in maximum efficiency at different conditions, and will not guarantee improvement...
Show moreThe design optimization of DC-DC converters requires the optimum selection of several parameters to achieve improved efficiency and performance. Some of these parameters are load dependent, line dependent, components dependent, and/or temperature dependent. Designing such parameters for a specific load, input and output, components, and temperature may improve single design point efficiency but will not result in maximum efficiency at different conditions, and will not guarantee improvement at that design point because of the components, temperature, and operating point variations. The ability of digital controllers to perform sophisticated algorithms makes it easy to apply adaptive control, where system parameters can be adaptively adjusted in response to system behavior in order to achieve better performance and stability. The use of adaptive control for power electronics is first applied with the Adaptive Frequency Optimization (AFO) method, which presents an auto-tuning adaptive digital controller with maximum efficiency point tracking to optimize DC-DC converter switching frequency. The AFO controller adjusts the DC-DC converter switching frequency while tracking the converter minimum input power point, under variable operating conditions, to find the optimum switching frequency that will result in minimum total loss and thus the maximum efficiency. Implementing variable switching frequencies in digital controllers introduces two main issues, namely, limit cycle oscillation and system instability. Dynamic Limit Cycle Algorithms (DLCA) is a dynamic technique tailored to improve system stability and to reduce limit cycle oscillation under variable switching frequency operation. The convergence speed and stability of AFO algorithm is further improved by presenting the analysis and design of a digital controller with adaptive auto-tuning algorithm that has a variable step size to track and detect the optimum switching frequency for a DC-DC converter. The Variable-Step-Size (VSS) algorithm is theoretically analyzed and developed based on buck DC-DC converter loss model and directed towered improving the convergence speed and accuracy of AFO adaptive loop by adjusting the converter switching frequency with variable step size. Finally, the efficiency of DC-DC converters is a function of several variables. Optimizing single variable alone may not result in maximum or global efficiency point. The issue of adjusting more than one variable at the same time is addressed by the Multivariable Adaptive digital Controller (MVAC). The MVAC is an adaptive method that continuously adjusts the DC-DC converter switching frequency and dead-time at the same time, while tracking the converter minimum input power, to find the maximum global efficiency point under variable conditions. In this research work, all adaptive methods were discussed, theoretically analyzed and its digital control algorithm along with experimental implementations were presented.
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Date Issued
2009
Identifier
CFE0002838, ucf:48072
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0002838
UNIFIED LARGE AND SMALL SIGNAL STATE-SPACE BASED MODELING AND SYMBOLIC SIMULATION FOR PWM CONVERTERS
Title
UNIFIED LARGE AND SMALL SIGNAL STATE-SPACE BASED MODELING AND SYMBOLIC SIMULATION FOR PWM CONVERTERS.
Creator
Shoubaki, Ehab, Batarseh, Issa, University of Central Florida
Abstract / Description
In this Dissertation, which concentrates on discrete modeling for control purposes of DC/DC converters and simulation through symbolic techniques. A Unified Discrete State-Space Model for power converters in CCM is presented. Two main approaches to arriving at the discrete model are used. The first approach involves an impulse function approximation of the duty cycle modulation of the converter switches, and this approach results in a small signal discrete model. The Second approach is direct...
Show moreIn this Dissertation, which concentrates on discrete modeling for control purposes of DC/DC converters and simulation through symbolic techniques. A Unified Discrete State-Space Model for power converters in CCM is presented. Two main approaches to arriving at the discrete model are used. The first approach involves an impulse function approximation of the duty cycle modulation of the converter switches, and this approach results in a small signal discrete model. The Second approach is direct and does not involve any approximation of the modulation, this approach yields both a large signal nonlinear discrete model and a linear small signal model. Harmonic analysis of the converter's states at steady-state is done for steady-state waveform acquisition, which increases the accuracy of the model especially for finding the control to inductor current frequency response. Also the harmonic Analysis technique is used to both obtain the response of the converter to a load transient and to finding the optimal duty cycle response that minimizes the disturbance. Finally the Discrete model is verified for the Half-Bridge DC/DC topology for its three main control schemes (Asymmetric, Symmetric, DCS). A GUI platform in MATLAB is presented as a wrapper that utilizes the models and analysis presented in this thesis. Symbolic simulation techniques are developed in general manner for linear piecewise circuits and then through State-Space formalism specialized for DC/DC converters. A general symbolic solver programmed in JAVA that implements said techniques is presented.
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Date Issued
2009
Identifier
CFE0002836, ucf:48061
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0002836
HIGHLY INTEGRATED DC-DC CONVERTERS
Title
HIGHLY INTEGRATED DC-DC CONVERTERS.
Creator
Jia, Hongwei, Shen, Zhen, University of Central Florida
Abstract / Description
A monolithically integrated smart rectifier has been presented first in this work. The smart rectifier, which integrates a power MOSFET, gate driver and control circuitry, operates in a self-synchronized fashion based on its drain-source voltage, and does not need external control input. The analysis, simulation, and design considerations are described in detail. A 5V, 5-μm CMOS process was used to fabricate the prototype. Experimental results show that the proposed rectifier functions...
Show moreA monolithically integrated smart rectifier has been presented first in this work. The smart rectifier, which integrates a power MOSFET, gate driver and control circuitry, operates in a self-synchronized fashion based on its drain-source voltage, and does not need external control input. The analysis, simulation, and design considerations are described in detail. A 5V, 5-μm CMOS process was used to fabricate the prototype. Experimental results show that the proposed rectifier functions as expected in the design. Since no dead-time control needs to be used to switch the sync-FET and ctrl-FET, it is expected that the body diode losses can be reduced substantially, compared to the conventional synchronous rectifier. The proposed self-synchronized rectifier (SSR) can be operated at high frequencies and maintains high efficiency over a wide load range. As an example of the smart rectifierÂÂÂÂ's application in isolated DC-DC converter, a synchronous flyback converter with SSR is analyzed, designed and tested. Experimental results show that the operating frequency could be as high as 4MHz and the efficiency could be improved by more than 10% compared to that when a hyper fast diode rectifier is used. Based on a new current-source gate driver scheme, an integrated gate driver for buck converter is also developed in this work by using a 0.35μm CMOS process with optional high voltage (50V) power MOSFET. The integrated gate driver consists both the current-source driver for high-side power MOSFET and low-power driver for low-side power iv MOSFET. Compared with the conventional gate driver circuit, the current-source gate driver can recovery some gate charging energy and reduce switching loss. So the current-source driver (CSD) can be used to improve the efficiency performance in high frequency power converters. This work also presents a new implementation of a power supply in package (PSiP) 5MHz buck converter, which is different from all the prior-of-art PSiP solutions by using a high-Q bondwire inductor. The high-Q bondwire inductor can be manufactured by applying ferrite epoxy to the common bondwire during standard IC packaging process, so the new implementation of PSiP is expected to be a cost-effective way of power supply integration.
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Date Issued
2010
Identifier
CFE0003040, ucf:48354
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0003040
INTEGRATED TOPOLOGIES AND DIGITAL CONTROL FOR SATELLITE POWER MANAGEMENT AND DISTRIBUTION SYSTEMS
Title
INTEGRATED TOPOLOGIES AND DIGITAL CONTROL FOR SATELLITE POWER MANAGEMENT AND DISTRIBUTION SYSTEMS.
Creator
Al-Atrash, Hussam, Batarseh, Issa, University of Central Florida
Abstract / Description
This work is focused on exploring advanced solutions for space power management and distribution (PMAD) systems. As spacecraft power requirements continue to increase, paralleled by the pressures for reducing cost and overall system weight, power electronics engineers will continue to face major redesigns of the space power systems in order to meet such challenges. Front-end PMAD systems, used to interface the solar sources and battery backup to the distribution bus, need to be designed with...
Show moreThis work is focused on exploring advanced solutions for space power management and distribution (PMAD) systems. As spacecraft power requirements continue to increase, paralleled by the pressures for reducing cost and overall system weight, power electronics engineers will continue to face major redesigns of the space power systems in order to meet such challenges. Front-end PMAD systems, used to interface the solar sources and battery backup to the distribution bus, need to be designed with increased efficiency, reliability, and power density. A new family of integrated single-stage power converter structures is introduced here. This family allows the interface and control of multiple power sources and storage devices in order to optimize utilization of available resources. Employing single-stage power topologies, these converters control power flow efficiently and cost-effectively. This is achieved by modifying the operation and control strategies of isolated soft-switched half-bridge and full-bridge converters--two of the most popular two-port converter topologies. These topologies are reconfigured and utilized to realize three power processing paths. These paths simultaneously utilize the power devices, allowing increased functionality while promising reduced losses and enhanced power densities. Each of the proposed topologies is capable of performing simultaneous control of two of its three ports. Control objectives include battery or ultra-capacitor charge regulation, solar array maximum power point tracking (MPPT), and/or bus voltage regulation. Another advantage of the proposed power structure is that current engineering design concepts can be used to optimize the new topologies in a fashion similar to the mother topologies. This includes component selection and magnetic design procedures, as well as achieving soft-switching for increased efficiency at higher switching frequencies. Galvanic isolation of the load port through high-frequency transformers provides design flexibility for high step-up/step-down conversion ratios. It further allows the converters to be used as power electronics building blocks (PEBB) with outputs connected in different series/parallel combinations to meet different load requirements. Utilizing such converters promises significant savings in size, weight, and costs of the power management system as well as the devices it manages. Chapter 1 of this dissertation provides an introduction to the requirements, challenges, and trends of space PMAD. A review of existing multi-port converter technologies and digital control techniques is given in Chapter 2. Chapter 3 discusses different PMAD system architectures. It outlines the basic concepts used for PMAD integration and discusses the potential for improvement. Chapters 4 and 5 present and discuss the operation and characteristics of three different integrated multi-port converters. Chapter 6 presents improved methods for practical digital control of switching converters, which are especially useful in complex multi-objective controllers used for PMAD. This is followed by conclusions and suggested future work.
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Date Issued
2007
Identifier
CFE0001784, ucf:47283
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0001784
UNIFIED LARGE AND SMALL SIGNAL DISCRETE-SPACE MODELING FOR PWM CONVERTERS IN CCM
Title
UNIFIED LARGE AND SMALL SIGNAL DISCRETE-SPACE MODELING FOR PWM CONVERTERS IN CCM.
Creator
Shoubaki, Ehab, Batarseh, Issa, University of Central Florida
Abstract / Description
In this Thesis a Unified Discrete State-Space Model for power converters in CCM is presented. Two main approaches to arriving at the discrete model are used. The first approach involves an impulse function approximation of the duty cycle modulations of the converter switches , and this approach results in a small signal discrete model. The Second approach is direct and does not involve any approximation of the modulations , this approach yields both a large signal nonlinear discrete model and...
Show moreIn this Thesis a Unified Discrete State-Space Model for power converters in CCM is presented. Two main approaches to arriving at the discrete model are used. The first approach involves an impulse function approximation of the duty cycle modulations of the converter switches , and this approach results in a small signal discrete model. The Second approach is direct and does not involve any approximation of the modulations , this approach yields both a large signal nonlinear discrete model and a linear small signal model. Harmonic analysis of the converter states at steady-state is done for steady-state waveform acquisition , which increases the accuracy of the model especially for finding the control to inductor current frequency response. Finally the Discrete model is verified for the Half-Bridge DC/DC topology for its three main control schemes (Asymmetric , Symmetric , DCS). A GUI platform in MATLAB is presented as a wrapper that utilizes the models and analysis presented in this thesis.
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Date Issued
2005
Identifier
CFE0000710, ucf:46607
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0000710
HIGH SLEW RATE HIGH-EFFICIENCY DC-DC CONVERTER
Title
HIGH SLEW RATE HIGH-EFFICIENCY DC-DC CONVERTER.
Creator
Wang, Xiangcheng, Issa, Batarseh, University of Central Florida
Abstract / Description
Active transient voltage compensator (ATVC) has been proposed to improve VR transient response at high slew rate load, which engages in transient periods operating in MHZ to inject high slew rate current in step up load and recovers energy in step down load. Main VR operates in low switching frequency mainly providing DC current. Parallel ATVC has largely reduced conduction and switching losses. Parallel ATVC also reduces the number of VR bulk capacitors. Combined linear and adaptive...
Show moreActive transient voltage compensator (ATVC) has been proposed to improve VR transient response at high slew rate load, which engages in transient periods operating in MHZ to inject high slew rate current in step up load and recovers energy in step down load. Main VR operates in low switching frequency mainly providing DC current. Parallel ATVC has largely reduced conduction and switching losses. Parallel ATVC also reduces the number of VR bulk capacitors. Combined linear and adaptive nonlinear control has been proposed to reduce delay times in the actual controller, which injects one nonlinear signal in transient periods and simplifies the linear controller design. Switching mode current compensator with nonlinear control in secondary side is proposed to eliminate the effect of opotocoupler, which reduces response times and simplifies the linear controller design in isolated DC-DC converters. A novel control method has been carried out in two-stage isolated DC-DC converter to simplify the control scheme and improve the transient response, allowing for high duty cycle operation and large step-down voltage ratio with high efficiency. A balancing winding network composed of small power rating components is used to mitigate the double pole-zero effect in complementary-controlled isolated DC-DC converter, which simplifies the linear control design and improves the transient response without delay time. A parallel post regulator (PPR) is proposed for wide range input isolated DC-DC converter with secondary side control, which provides small part of output power and most of them are handled by unregulated rectifier with high efficiency. PPR is easy to achieve ZVS in primary side both in wide range input and full load range due to 0.5 duty cycle. PPR has reduced conduction loss and reduced voltage rating in the secondary side due to high turn ratio transformer, resulting in up to 8 percent efficiency improvement in the prototype compared to conventional methods.
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Date Issued
2006
Identifier
CFE0001123, ucf:46877
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0001123
UNIFIED STEADY-STATE COMPUTER AIDED MODEL FOR SOFT-SWITCHING DC–DC CONVERTERS
Title
UNIFIED STEADY-STATE COMPUTER AIDED MODEL FOR SOFT-SWITCHING DC–DC CONVERTERS.
Creator
Al-Hoor, Wisam, Batarseh, Issa, University of Central Florida
Abstract / Description
For many decades, engineers and students have heavily depended on simulation packages such as Pspice to run transit and steady-state simulation for their circuits. The majority of these circuits, such as soft switching cells, contain complicated modes of operations that require the Pspice simulation to run for a long time and, finally, it may not reach a convergent solution for these kinds of circuits. Also, there is a need for an educational tool that provides students with a better...
Show moreFor many decades, engineers and students have heavily depended on simulation packages such as Pspice to run transit and steady-state simulation for their circuits. The majority of these circuits, such as soft switching cells, contain complicated modes of operations that require the Pspice simulation to run for a long time and, finally, it may not reach a convergent solution for these kinds of circuits. Also, there is a need for an educational tool that provides students with a better understanding of circuit modes of operation through state-plan figures and steady-state switching waveforms. The unified steady-state computer aided model proposes a simulation block that covers common unified soft-switching cells operations and can be used in topologies simulation. The simulation block has a simple interface that enables the user to choose the switching cell type and connects the developed simulation model in the desired topology configuration. In addition to the measured information that can be obtained from the circuitry around the unified simulation model, the simulation block includes some additional nodes (other than the inputs and outputs) that make internal switching cell information, such as switching voltages and currents, easy to access and debug. The model is based on mathematical equations, resulting in faster simulation times, smaller file size and greatly minimized simulation convergence problems. The Unified Model is based on the generalized analysis: Chapter 1 discusses the generalized equation concept along with a detailed generalization example of one switching cell, which is the zero current switching quasi-resonant converter ZCS-QRC. Chapter 2 presents a detailed discussion of the unified model concept, the unified model flow chart and the unified model implementation in Pspice. Chapter 3 presents the unified model applications; generating the switching cell inductor current and the switching cell capacitor voltage steady-state waveforms, the State-Plane Diagram , the feedback design using the unified model, and the chapter concludes with how the model can be used with different topologies. Finally, chapter 4 presents the summary and the future work
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Date Issued
2006
Identifier
CFE0001036, ucf:46825
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0001036
MODELING AND ANALYSIS OF POWER MOSFETS FOR HIGH FREQUENCY DC-DC CONVERTERS
Title
MODELING AND ANALYSIS OF POWER MOSFETS FOR HIGH FREQUENCY DC-DC CONVERTERS.
Creator
Xiong, Yali, Shen, John, University of Central Florida
Abstract / Description
Evolutions in integrated circuit technology require the use of a high-frequency synchronous buck converter in order to achieve low cost, low profile, fast transient response and high power density. However, high frequency operation leads to increased power MOSFET switching losses. Optimization of the MOSFETs plays an important role in improving converter performance. This dissertation focuses on revealing the power loss mechanism of power MOSFETs and the relationship between power MOSFET...
Show moreEvolutions in integrated circuit technology require the use of a high-frequency synchronous buck converter in order to achieve low cost, low profile, fast transient response and high power density. However, high frequency operation leads to increased power MOSFET switching losses. Optimization of the MOSFETs plays an important role in improving converter performance. This dissertation focuses on revealing the power loss mechanism of power MOSFETs and the relationship between power MOSFET structure and its power loss. The analytical device model, combined with circuit modeling, cannot reveal the relationship between device structure and its power loss due to the highly non-linear characteristics of power MOSFETs. A physically-based mixed device/circuit modeling approach is used to investigate the power losses of the MOSFETs under different operating conditions. The physically based device model, combined with SPICE-like circuit simulation, provides an expeditious and inexpensive way of evaluating and optimizing circuit and device concepts. Unlike analytical or other SPICE models of power MOSFETs, the numerical device model, relying little on approximations or simplifications, faithfully represents the behavior of realistic power MOSFETs. The impact of power MOSFET parameters on efficiency of synchronous buck converters, such as gate charge, on resistance, reverse recovery, is studied in detail in this thesis. The results provide a good indication on how to optimize power MOSFETs used in VRMs. The synchronous rectifier plays an important role in determining the performance of the synchronous buck converter. The reverse recovery of its body diode and the Cdv/dt induced false trigger-on are two major mechanisms that impact SyncFET's performance. This thesis gives a detailed analysis of the SyncFET operation mechanism and provides several techniques to reduce its body-diode influence and suppress its false Cdv/dt trigger-n. This thesis also investigates the influence of several circuit level parameters on the efficiency of the synchronous buck converter, such as input voltage, circuit parasitic inductance, and gate resistance to provide further optimization of synchronous buck converter design.
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Date Issued
2008
Identifier
CFE0002278, ucf:47858
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0002278
Analysis and Design Optimization of Resonant DC-DC Converters
Title
Analysis and Design Optimization of Resonant DC-DC Converters.
Creator
Fang, Xiang, Shen, Zheng, Batarseh, Issa, Mikhael, Wasfy, Wu, Xinzhang, Kutkut, Nasser, University of Central Florida
Abstract / Description
The development in power conversion technology is in constant demand of high power efficiency and high power density. The DC-DC power conversion is an indispensable stage for numerous power supplies and energy related applications. Particularly, in PV micro-inverters and front-end converter of power supplies, great challenges are imposed on the power performances of the DC-DC converter stage, which not only require high efficiency and density but also the capability to regulate a wide...
Show moreThe development in power conversion technology is in constant demand of high power efficiency and high power density. The DC-DC power conversion is an indispensable stage for numerous power supplies and energy related applications. Particularly, in PV micro-inverters and front-end converter of power supplies, great challenges are imposed on the power performances of the DC-DC converter stage, which not only require high efficiency and density but also the capability to regulate a wide variation range of input voltage and load conditions. The resonant DC-DC converters are good candidates to meet these challenges with the advantages of achieving soft switching and low EMI. Among the resonant converters, the LLC converter is very attractive for its high gain range and providing ZVS from full load to zero load condition. The operation of the LLC converter is complicated due to its multiple resonant stage mechanism. In this dissertation, a literature review of different analysis methods are presented, and it shows that the study on the LLC is still incomplete. Therefore, an operation mode analysis method is proposed, which divides the operation into six major modes based on the occurrence of resonant stages. The resonant currents, voltages and the DC gain characteristics for each mode is investigated. To get a thorough view of the converter behavior, the boundaries of every mode are studied, and the mode distribution is discussed. An experimental prototype is built and tested to demonstrate its accuracy in operation waveforms and gain prediction. Since most of the LLC modes have no closed-form solutions, simplification is necessary in order to utilize this mode model in practical design. As the peak gain is an important design parameters indicating the LLC's operating limit of input voltage and switching frequency, a numerical peak gain approximation method is developed, which provide a direct way to calculate the peak gain and its corresponding load and frequency condition. In addition, as PO mode is the most favorable operation mode of the LLC, its operation region is investigated and an approximation approach is developed to determine its boundary. The design optimization of the LLC has always been a difficult problem as there are many parameters affecting the design and it lacks clear design guidance in selecting the optimal resonant tank parameters. Based on the operation mode model, three optimization methods are proposed according to the design scenarios. These methods focus on minimize the conduction loss of resonant tank while maintaining the required voltage gain level, and the approximations of peak gains and mode boundary can be applied here to facilitate the design. A design example is presented following one of the optimization procedure. As a comparison, the L-C component values are reselected and tested while the design specifications are the same. The experiments show that the optimal design has better efficiency performance. Finally, a generalized approach for resonant converter analysis is developed. It can be implemented by computer programs or numerical analysis tools to derive the operation waveforms and DC characteristics of resonant converters.
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Date Issued
2012
Identifier
CFE0004229, ucf:49026
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0004229
HIGH-DENSITY AND HIGH-EFFICIENCY SOFT SWITCHING MODULAR BI-DIRECTIONAL DC-DC CONVERTER FOR HYBRID ELECTRIC VEHICLES
Title
HIGH-DENSITY AND HIGH-EFFICIENCY SOFT SWITCHING MODULAR BI-DIRECTIONAL DC-DC CONVERTER FOR HYBRID ELECTRIC VEHICLES.
Creator
Elmes, John, Batarseh, Issa, University of Central Florida
Abstract / Description
This dissertation presents the design of a high-density and high-efficiency soft-switching bi-directional DC-DC converter for hybrid-electric vehicles. The converter operates in a new bi-directional interleaved variable-frequency quasi-square-wave (QSW) mode, which enables high efficiency, high switching frequency, and high power-density. The converter presented utilizes a new variable frequency interleaving approach which allows for each module to operate in an interleaved position while...
Show moreThis dissertation presents the design of a high-density and high-efficiency soft-switching bi-directional DC-DC converter for hybrid-electric vehicles. The converter operates in a new bi-directional interleaved variable-frequency quasi-square-wave (QSW) mode, which enables high efficiency, high switching frequency, and high power-density. The converter presented utilizes a new variable frequency interleaving approach which allows for each module to operate in an interleaved position while allowing for tolerance in inductance and snubber capacitor values. The variable frequency interleaved soft-switching operation paired with a high-density nanocrystalline inductor and high-density system structure results in a very high performance converter, well exceeding that of the current technology. The developed converter is intended to achieve three specific performance goals: high conversion efficiency, high power density, and operation with 100 °C coolant. Two markedly different converter prototype designs are presented, one converter using evaporative spray cooling to cool the switching devices, with the second converter using a more traditional coldplate design to cool the switching devices. The 200 kW (25 kW per module) prototype converters exhibited power density greater than 8 kilowatts/liter (kW/L), and peak efficiency over 98%, while operating with 100 °C coolant.
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Date Issued
2010
Identifier
CFE0003366, ucf:48436
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0003366
DIGITAL PULSE WIDTH MODULATOR TECHNIQUES FOR DC - DC CONVERTERS
Title
DIGITAL PULSE WIDTH MODULATOR TECHNIQUES FOR DC - DC CONVERTERS.
Creator
Batarseh, Majd, Batarseh, Issa, University of Central Florida
Abstract / Description
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...
Show moreRecent 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.
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Date Issued
2010
Identifier
CFE0003055, ucf:48314
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0003055
PULSE FREQUENCY MODULATION ZCS FLYBACK CONVERTER IN INVERTER APPLICATIONS
Title
PULSE FREQUENCY MODULATION ZCS FLYBACK CONVERTER IN INVERTER APPLICATIONS.
Creator
Tian, Feng, Batarseh, Issa, University of Central Florida
Abstract / Description
Renewable energy source plays an important role in energy co-generation and distribution. A traditional solar-based inverter system has two stages cascaded, which has simpler controller but low efficiency. A new solar-based single-stage grid-connected inverter system can achieve higher efficiency by reducing the power semiconductor switching loss and output stable and synchronizing sinusoid current into the utility grid. In Chapter 1, the characteristic I-V and P-V curve of PV array has been...
Show moreRenewable energy source plays an important role in energy co-generation and distribution. A traditional solar-based inverter system has two stages cascaded, which has simpler controller but low efficiency. A new solar-based single-stage grid-connected inverter system can achieve higher efficiency by reducing the power semiconductor switching loss and output stable and synchronizing sinusoid current into the utility grid. In Chapter 1, the characteristic I-V and P-V curve of PV array has been illustrated. Based on prediction of the PV power capacity installed on the grid-connected and off-grid, the trends of grid-tied inverter for DG system have been analyzed. In Chapter 2, the topologies of single-phase grid-connect inverter system have been listed and compared. The key parameters of all these topologies are listed in a table in terms of topology, power decoupling, isolation, bi-directional/uni-directional, power rating, switching frequency, efficiency and input voltage. In Chapter 3, to reduce the capacitance of input filter, an active filter has been proposed, which will eliminate the 120/100Hz low frequency ripple from the PV array's output voltage completely. A feedforward controller is proposed to optimize the step response of PV array output voltage. A sample and hold also is used to provide the 120/100Hz low frequency decoupling between the controller of active filter and inverter stage. In Chapter 4, the single-stage inverter is proposed. Compared with conventional two-stage inverter, which has two high frequency switching stages cascaded, the single-stage inverter system increases the system efficiency by utilizing DC/DC converter to generate rectified sinusoid voltage. A transformer analysis is conducted for the single-stage inverter system, which proves the transformer has no low-frequency magnetic flux bias. To apply peak current mode control on single-stage inverter and get unified loop gain, adaptive slope compensation is also proposed for single-stage inverter. In Chapter 5, a digital controller for single-stage inverter is designed and optimized by the Matlab Control Toolbox. A Psim simulation verified the performance of the digital controller design. In Chapter 6, three bi-directional single-stage inverter topologies are proposed and compared. A conventional single-stage bi-directional inverter has certain shortcoming that cannot be overcome. A modular grid-connect micro-inverter system with dedicated reactive energy processing unit can overcome certain shortcoming and increase the system efficiency and reliability. A unique controller design is also proposed. In Chapter 7, a PFM ZCS flyback inverter system is invented. By using half-wave quasi-resonant ZCS flyback resonant converter and PFM control, this topology completely eliminates switching loss. A detailed mathematical analysis provides all the key parameters for the inverter design. As the inductance of transformer secondary side get smaller, the power stage transfer function of PFM ZCS flyback inverter system demonstrates nonlinearity. An optimized PFM ZCS flyback DC/DC converter design resolves this issue by introducing a MOSFET on the secondary side of transformer. In Chapter 8, experimental results of uni-direcitonal single-stage inverter with grid-connection, bi-directional single-stage inverter and single-stage PFM ZCS flyback inverter have been provided. Conclusions are given in Chapter 9.
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Date Issued
2009
Identifier
CFE0002664, ucf:48198
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0002664
HIGH CURRENT DENSITY LOW VOLTAGE ISOLATED DC-DC CONVERTERSWITH FAST TRANSIENT RESPONSE
Title
HIGH CURRENT DENSITY LOW VOLTAGE ISOLATED DC-DC CONVERTERSWITH FAST TRANSIENT RESPONSE.
Creator
Yao, Liangbin, Batarseh, Issa, University of Central Florida
Abstract / Description
With the rapid development of microprocessor and semiconductor technology, industry continues to update the requirements for power supplies. For telecommunication and computing system applications, power supplies require increasing current level while the supply voltage keeps decreasing. For example, the Intel's CPU core voltage decreased from 2 volt in 1999 to 1 volt in 2005 while the supply current increased from 20A in 1999 to up to 100A in 2005. As a result, low-voltage high-current...
Show moreWith the rapid development of microprocessor and semiconductor technology, industry continues to update the requirements for power supplies. For telecommunication and computing system applications, power supplies require increasing current level while the supply voltage keeps decreasing. For example, the Intel's CPU core voltage decreased from 2 volt in 1999 to 1 volt in 2005 while the supply current increased from 20A in 1999 to up to 100A in 2005. As a result, low-voltage high-current high efficiency dc-dc converters with high power-density are demanded for state-of-the-art applications and also the future applications. Half-bridge dc-dc converter with current-doubler rectification is regarded as a good topology that is suitable for high-current low-voltage applications. There are three control schemes for half-bridge dc-dc converters and in order to provide a valid unified analog model for optimal compensator design, the analog state-space modeling and small signal modeling are studied in the dissertation and unified state-space and analog small signal model are derived. In addition, the digital control gains a lot of attentions due to its flexibility and re-programmability. In this dissertation, a unified digital small signal model for half-bridge dc-dc converter with current doubler rectifier is also developed and the digital compensator based on the derived model is implemented and verified by the experiments with the TI DSP chip. In addition, although current doubler rectifier is widely used in industry, the key issue is the current sharing between two inductors. The current imbalance is well studied and solved in non-isolated multi-phase buck converters, yet few discusse this issue in the current doubler rectification topology within academia and industry. This dissertation analyze the current sharing issue in comparison with multi-phase buck and one modified current doubler rectifier topology is proposed to achieve passive current sharing. The performance is evaluated with half bridge dc-dc converter; good current sharing is achieved without additional circuitry. Due to increasing demands for high-efficiency high-power-density low-voltage high current topologies for future applications, the thermal management is challenging. Since the secondary-side conduction loss dominates the overall power loss in low-voltage high-current isolated dc-dc converters, a novel current tripler rectification topology is proposed. Theoretical analysis, comparison and experimental results verify that the proposed rectification technique has good thermal management and well-distributed power dissipation, simplified magnetic design and low copper loss for inductors and transformer. That is due to the fact that the load current is better distributed in three inductors and the rms current in transformer windings is reduced. Another challenge in telecommunication and computing applications is fast transient response of the converter to the increasing slew-rate of load current change. For instance, from Intel's roadmap, it can be observed that the current slew rate of the age regulator has dramatically increased from 25A/uS in 1999 to 400A/us in 2005. One of the solutions to achieve fast transient response is secondary-side control technique to eliminate the delay of optocoupler to increase the system bandwidth. Active-clamp half bridge dc-dc converter with secondary-side control is presented and one industry standard 16th prototype is built and tested; good efficiency and transient response are shown in the experimental section. However, one key issue for implementation of secondary-side control is start-up. A new zero-voltage-switching buck-flyback isolated dc-dc converter with synchronous rectification is proposed, and it is only suitable for start-up circuit for secondary-side controlled converter, but also for house-keeping power supplies and standalone power supplies requiring multi-outputs.
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Date Issued
2007
Identifier
CFE0001814, ucf:47336
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0001814
Design and Implementation of PV-Firming and Optimization Algorithms For Three-Port Microinverters
Title
Design and Implementation of PV-Firming and Optimization Algorithms For Three-Port Microinverters.
Creator
Alharbi, Mahmood, Batarseh, Issa, Haralambous, Michael, Mikhael, Wasfy, Yuan, Jiann-Shiun, Kutkut, Nasser, University of Central Florida
Abstract / Description
With the demand increase for electricity, the ever-increasing awareness of environmental issues, coupled with rolling blackouts, the role of renewable energy generation is increasing along with the thirst for electricity and awareness of environmental issues. This dissertation proposes the design and implementation of PV-firming and optimization algorithms for three-port microinverters.Novel strategies are proposed in Chapters 3 and 4 for harvesting stable solar power in spite of intermittent...
Show moreWith the demand increase for electricity, the ever-increasing awareness of environmental issues, coupled with rolling blackouts, the role of renewable energy generation is increasing along with the thirst for electricity and awareness of environmental issues. This dissertation proposes the design and implementation of PV-firming and optimization algorithms for three-port microinverters.Novel strategies are proposed in Chapters 3 and 4 for harvesting stable solar power in spite of intermittent solar irradiance. PV firming is implemented using a panel-level three-port grid-tied PV microinverter system instead of the traditional high-power energy storage and management system at the utility scale. The microinverter system consists of a flyback converter and an H-bridge inverter/rectifier, with a battery connected to the DC-link. The key to these strategies lies in using static and dynamic algorithms to generate a smooth PV reference power. The outcomes are applied to various control methods to charge/discharge the battery so that a stable power generation profile is obtained. In addition, frequency-based optimization for the inverter stage is presented.One of the design parameters of grid-tied single-phase H-bridge sinusoidal pulse-width modulation (SPWM) microinverters is switching frequency. The selection of the switching frequency is a tradeoff between improving the power quality by reducing the total harmonic distortion (THD), and improving the efficiency by reducing the switching loss. In Chapter 5, two algorithms are proposed for optimizing both the power quality and the efficiency of the microinverter. They do this by using a frequency tracking technique that requires no hardware modification. The first algorithm tracks the optimal switching frequency for maximum efficiency at a given THD value. The second maximizes the power quality of the H-bridge micro-inverter by tracking the switching frequency that corresponds to the minimum THD.Real-time PV intermittency and usable capacity data were evaluated and then further analyzed in MATLAB/SIMULINK to validate the PV firming control. The proposed PV firming and optimization algorithms were experimentally verified, and the results evaluated. Finally, Chapter 6 provides a summary of key conclusions and future work to optimize the presented topology and algorithms.
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Date Issued
2018
Identifier
CFE0007305, ucf:52166
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0007305