Integrated DC-DC boost converters using CMOS silicon on Sapphire Technology

With the recent advancements in semiconductor manufacturing towards smaller, faster and more efficient microelectronic systems, the problems of increasing leakage current and reduced breakdown voltage in bulk-CMOS transistors have become substantial in the sub-100-nanometer era. The Peregrine UltraCMOS Silicon-on-Sapphire (SOS) technology that uses highly-insulating sapphire substrate as insulator was introduced to meet the continually growing need for higher performance RF products. The electrically isolated circuit elements in the UltraCMOS technology lead to increased switching speeds and lower power consumption due to reduced junction and parasitic capacitances. Furthermore, the growing need for high-speed switching applications such as boosting a lower voltage level to a higher one gives the UltraCMOS technology an upper hand over the bulk-CMOS process. The limitation to using an UltraCMOS transistor is that its maximum drain to source voltage (VDS ) swing is 2.5V. This thesis aims to address this limitation by studying and implementing various stacking techniques in high power switching applications where voltage switching of higher than 2.5V are required. Fully-integrated DC to DC boost converters with switching circuits based on dynamically self-biased stacked transistors are proposed. For high voltage and high power handling, the proposed stacking techniques equally distribute the overall output voltage to less than 2.5V across each stacked transistor in the switch (V DS of 2.5V)

Design Approaches to Enhance Power Density in Power Converters for Traction Applications

This dissertation presents a design strategy to increase the power density for automotive Power Conversion Units (PCUs) consisting of DC-DC and DC-AC stages. The strategy significantly improves the volumetric power density, as evident by a proposed PCU constructed and tested having 55.6 kW/L, representing an 11.2 % improvement on the Department of Energy’s 2025 goal of 50 kW/L for the same power electronics architecture. The dissertation begins with a custom magnetic design procedure, based on optimization of a predetermined C-core geometrical relationship and custom Litz wire. It accounts for electrical and thermal tradeoffs to produce a magnetic structure to best accomplish volume and thermal constraints. This work is coupled with a control strategy for the DC-DC converter whereby a variable-frequency Discontinuous Conduction Mode (DCM) control is used to further reduce the required values of the passive components, to provide an increase in power density and a large improvement of low-power-level efficiency, experimentally demonstrated at full power through an 80 kW Interleaved Boost Converter. Integration of this enhanced DC-DC stage to the DC-AC stage requires a DC-Link capacitor, which hinders achieving power density targets. Increasing the switching frequency is an established method of reducing the size of passives. However, it is the RMS current sizing requirements that diminishes any gains achieved by raising the switching frequency. A synchronous carrier phase shift-based control algorithm, that aligns the output current of the boost stage with the input current of an inverter, is proposed to reduce the RMS current in the DC-Link capacitor by up to 25% and an average 20% smaller capacitor volume. Lastly, a new electrothermal platform based on paralleled discrete devices is presented for a 50 kW traction inverter. Embedded capacitors within the vacant volume of the hybrid material thermal management structure enables higher power density (155 kW/L) and significantly reduces cost

Design Approaches to Enhance Power Density in Power Converters for Traction Applications

This dissertation presents a design strategy to increase the power density for automotive Power Conversion Units (PCUs) consisting of DC-DC and DC-AC stages. The strategy significantly improves the volumetric power density, as evident by a proposed PCU constructed and tested having 55.6 kW/L, representing an 11.2 % improvement on the Department of Energy’s 2025 goal of 50 kW/L for the same power electronics architecture. The dissertation begins with a custom magnetic design procedure, based on optimization of a predetermined C-core geometrical relationship and custom Litz wire. It accounts for electrical and thermal tradeoffs to produce a magnetic structure to best accomplish volume and thermal constraints. This work is coupled with a control strategy for the DC-DC converter whereby a variable-frequency Discontinuous Conduction Mode (DCM) control is used to further reduce the required values of the passive components, to provide an increase in power density and a large improvement of low-power-level efficiency, experimentally demonstrated at full power through an 80 kW Interleaved Boost Converter. Integration of this enhanced DC-DC stage to the DC-AC stage requires a DC-Link capacitor, which hinders achieving power density targets. Increasing the switching frequency is an established method of reducing the size of passives. However, it is the RMS current sizing requirements that diminishes any gains achieved by raising the switching frequency. A synchronous carrier phase shift-based control algorithm, that aligns the output current of the boost stage with the input current of an inverter, is proposed to reduce the RMS current in the DC-Link capacitor by up to 25% and an average 20% smaller capacitor volume. Lastly, a new electrothermal platform based on paralleled discrete devices is presented for a 50 kW traction inverter. Embedded capacitors within the vacant volume of the hybrid material thermal management structure enables higher power density (155 kW/L) and significantly reduces cost

Solar photovoltaic array fed brushless DC motor drive using sensorless technique for reducing vibration with Enhanced DC-DC converter

The proposed research work involves, solar photovoltaic array fed brushless DC motor drive using sensorless technique for reducing vibration with Enhanced DC-DC converter. The purpose of this research is to reduce the vibration in the motor drive and to improve the efficiency of the enhanced converter. The designed model consists of Buck and Boost converter, DC-link unit, state-of-the-art back-EMF sensing methods like terminal voltage, terminal current sensing and also includes third choral voltage amalgamation, back-emf integration and PWM strategies. In addition, reduced number of switches in the proposed research makes the scheme more outlay efficient and the motor speed is synchronized by PI controller. For sensing the vibration during rotation and shock in the brushless DC drive an accelerometer which is an electromechanical device are used, it measures acceleration forces associated to the freefall cause, path of the acceleration is a vector product. The current technique based on evaluation of various parameters are clearly modeled and experimented. A MATLAB platform and a hardware prototype of multioutput buck-boost converter are clearly examined for various effective environment in the proposed research

Design of dual-input two phase dc/dc converter with modified pulse width modulation (mpwm)

Recently, hybrid energy source/renewable energy has attracted interest as the next-generation energy system capable of solving the problems of global warming and energy exhaustion caused by increasing energy consumption. Energy sources such as wind turbines and photovoltaic (PV) systems are intermittent, unpredictable and unregulated. For such systems, the use of multiple-input converter (MIC) has the advantage of regulating and controlling multiple-input sources. With multiple Pulsating Voltage-Source Cells (PVSC) configurations, the proposed converter can deliver power to the load individually and simultaneously. Also, it has the capability of operating either in buck, boost or buck–boost mode of operation. In addition, by proposing the enhanced Modified PWM (MPWM) switching scheme, it is able to solve the issues of the overlapping unregulated input sources. Furthermore, with the proposed multiphase configuration, the input current stresses in the switching devices are reduced and it has the benefit of a reduction in conduction losses. In addition, Zero-Voltage Switching (ZVS) technique is also employed in the proposed converter to reduce the switching loss. The proposed converter circuit is simulated by using MATLAB/Simulink and PSpice software programs. The duty cycle employed to regulate output voltage is reached from Altera DE2-70 board through dSPACE DS1103 board using by Proportional-Integral (PI) controller. The dual-input converter circuit model specification with output power at 200 W, input voltages that range from 10 to 60 V, and operating with dual switching frequencies of 50 kHz and 100 kHz is simulated to validate the designed parameters. Design guidelines, simulation and experimental results are presented. The results show that the proposed two-phase DC/DC converter with ZVS technique achieves 94% efficiency for all ranges of loads compared with the multiphase hard-switching. The total power losses across the power switches are reduced by approximately 37% in the proposed converter. Thus, the proposed converter circuit model offers advantages on input current stress and switching loss reductions. The proposed circuit configuration can be used in a standalone hybrid energy system under unregulated DC input voltages. However the major disadvantages of resonant circuit are increased peak current and voltage stress and not suitable for variable frequency operation

Advances and Technologies in High Voltage Power Systems Operation, Control, Protection and Security

The electrical demands in several countries around the world are increasing due to the huge energy requirements of prosperous economies and the human activities of modern life. In order to economically transfer electrical powers from the generation side to the demand side, these powers need to be transferred at high-voltage levels through suitable transmission systems and power substations. To this end, high-voltage transmission systems and power substations are in demand. Actually, they are at the heart of interconnected power systems, in which any faults might lead to unsuitable consequences, abnormal operation situations, security issues, and even power cuts and blackouts. In order to cope with the ever-increasing operation and control complexity and security in interconnected high-voltage power systems, new architectures, concepts, algorithms, and procedures are essential. This book aims to encourage researchers to address the technical issues and research gaps in high-voltage transmission systems and power substations in modern energy systems

Power management systems based on switched-capacitor DC-DC converter for low-power wearable applications

The highly efficient ultra-low-power management unit is essential in powering low-power wearable electronics. Such devices are powered by a single input source, either by a battery or with the help of a renewable energy source. Thus, there is a demand for an energy conversion unit, in this case, a DC-DC converter, which can perform either step-up or step-down conversions to provide the required voltage at the load. Energy scavenging with a boost converter is an intriguing choice since it removes the necessity of bulky batteries and considerably extends the battery life. Wearable devices are typically powered by a monolithic battery. The commonly available battery such as Alkaline or Lithium-ion, degrade over time due to their life spans as it is limited by the number of charge cycles- which depend highly on the environmental and loading condition. Thus, once it reaches the maximum number of life cycles, the battery needs to be replaced. The operation of the wearable devices is limited by usable duration, which depends on the energy density of the battery. Once the stored energy is depleted, the operation of wearable devices is also affected, and hence it needs to be recharged. The energy harvesters- which gather the available energy from the surroundings, however, have no limitation on operating life. The application can become battery-less given that harvestable energy is sufficiently powering the low-power devices. Although the energy harvester may not completely replace the battery source, it ensures the maximum duration of use and assists to become autonomous and self-sustain devices. The photovoltaic (PV) cell is a promising candidate as a hypothetical input supply source among the energy harvesters due to its smaller area and high power density over other harvesters. Solar energy use PV harvester can convert ambient light energy into electrical energy and keep it in the storage device. The harvested output of PV cannot directly connect to wearable loads for two main reasons. Depending on the incoming light, the harvested current result in varying open-circuit voltage. It requires the power management circuit to deal with unregulated input variation. Second, depending on the PV cell's material type and an effective area, the I-V characteristic's performance varies, resulting in a variation of the output power. There are several works of maximum power point tracking (MPPT) methods that allow the solar energy harvester to achieve optimal harvested power. Therefore, the harvested power depends on the size and usually small area cell is sufficient for micro-watt loads low-powered applications. The available harvested voltage, however, is generally very low-voltage range between 0.4-0.6 V. The voltage ratings of electronics in standard wearable applications operate in 1.8-3 V voltages as described in introduction’s application example section. It is higher than the supply source can offer. The overcome the mismatch voltage between source and supply circuit, a DC-DC boost converter is necessary. The switch-mode converters are favoured over the linear converters due to their highly efficient and small area overhead. The inductive converter in the switch-mode converter is common due to its high-efficiency performance. However, the integration of the inductor in the miniaturised integrated on-chip design tends to be bulky. Therefore, the switched-capacitor approach DC-DC converters will be explored in this research. In the switched-capacitor converter universe, there is plenty of work for single-output designs for various topologies. Most converters are reconfigurable to the different DC voltage levels apart from Dickson and cross-coupled charge pump topologies due to their boosting power stage architecture through a number of stages. However, existing multi-output converters are limited to the fixed gain ratio. This work explores the reconfigurable dual-output converter with adjustable gain to compromise the research gap. The thesis's primary focus is to present the inductor-less, switched-capacitor-based DC-DC converter power management system (PMS) supplied by a varying input of PV energy harvester input source. The PMS should deliver highly efficient regulated voltage conversion ratio (VCR) outputs to low-power wearable electronic devices that constitute multi-function building blocks

Advanced Stirling Convertor Testing at NASA Glenn Research Center

The U.S. Department of Energy (DOE), Lockheed Martin Space Systems (LMSS), Sunpower Inc., and NASA Glenn Research Center (GRC) have been developing an Advanced Stirling Radioisotope Generator (ASRG) for use as a power system on space science and exploration missions. This generator will make use of the free-piston Stirling convertors to achieve higher conversion efficiency than currently available alternatives. The ASRG will utilize two Advanced Stirling Convertors (ASC) to convert thermal energy from a radioisotope heat source to electricity. NASA GRC has initiated several experiments to demonstrate the functionality of the ASC, including: in-air extended operation, thermal vacuum extended operation, and ASRG simulation for mobile applications. The in-air and thermal vacuum test articles are intended to provide convertor performance data over an extended operating time. These test articles mimic some features of the ASRG without the requirement of low system mass. Operation in thermal vacuum adds the element of simulating deep space. This test article is being used to gather convertor performance and thermal data in a relevant environment. The ASRG simulator was designed to incorporate a minimum amount of support equipment, allowing integration onto devices powered directly by the convertors, such as a rover. This paper discusses the design, fabrication, and implementation of these experiments

Modeling and Optimization Algorithm for SiC-based Three-phase Motor Drive System

More electric aircraft (MEA) and electrified aircraft propulsion (EAP) becomes the important topics in the area of transportation electrifications, expecting remarkable environmental and economic benefits. However, they bring the urgent challenges for the power electronics design since the new power architecture in the electrified aircraft requires many benchmark designs and comparisons. Also, a large number of power electronics converter designs with different specifications and system-level configurations need to be conducted in MEA and EAP, which demands huge design efforts and costs. Moreover, the long debugging and testing process increases the time to market because of gaps between the paper design and implementation. To address these issues, this dissertation covers the modeling and optimization algorithms for SiC-based three-phase motor drive systems in aviation applications. The improved models can help reduce the gaps between the paper design and implementation, and the implemented optimization algorithms can reduce the required execution time of the design program. The models related to magnetic core based inductors, geometry layouts, switching behaviors, device loss, and cooling design have been explored and improved, and several modeling techniques like analytical, numerical, and curve-fitting methods are applied. With the developed models, more physics characteristics of power electronics components are incorporated, and the design accuracy can be improved. To improve the design efficiency and to reduce the design time, optimization schemes for the filter design, device selection combined with cooling design, and system-level optimization are studied and implemented. For filter design, two optimization schemes including Ap based weight prediction and particle swarm optimization are adopted to reduce searching efforts. For device selection and related cooling design, a design iteration considering practical layouts and switching speed is proposed. For system-level optimization, the design algorithm enables the evaluation of different topologies, modulation schemes, switching frequencies, filter configurations, cooling methods, and paralleled converter structure. To reduce the execution time of system-level optimization, a switching function based simulation and waveform synthesis method are adopted. Furthermore, combined with the concept of design automation, software integrated with the developed models, optimization algorithms, and simulations is developed to enable visualization of the design configurations, database management, and design results