縦型ボディチャネルMOS Field-Effect Transistorを用いたマイクロプロセッサ向け高効率・高集積DC-DCコンバータとそのパワーマネジメントに関する研究

Tohoku University遠藤哲郎課

MODELING AND CONTROL OF DIRECT-CONVERSION HYBRID SWITCHED-CAPACITOR DC-DC CONVERTERS

Efficient power delivery is increasingly important in modern computing, communications, consumer and other electronic systems, due to the high power demand and thermal concerns accompanied by performance advancements and tight packaging. In pursuit of high efficiency, small physical volume, and flexible regulation, hybrid switched-capacitor topologies have emerged as promising candidates for such applications. By incorporating both capacitors and inductors as energy storage elements, hybrid topologies achieve high power density while still maintaining soft charging and efficient regulation characteristics. However, challenges exist in the hybrid approach. In terms of reliability, each flying capacitor should be maintained at a nominal `balanced\u27 voltage for robust operation (especially during transients and startup), complicating the control system design. In terms of implementation, switching devices in hybrid converters often need complex gate driving circuits which add cost, area, and power consumption. This dissertation explores techniques that help to mitigate the aforementioned challenges. A discrete-time state space model is derived by treating the hybrid converter as two subsystems, the switched-capacitor stage and the output filter stage. This model is then used to design an estimator that extracts all flying capacitor voltages from the measurement of a single node. The controllability and observability of the switched-capacitor stage reveal the fundamental cause of imbalance at certain conversion ratios. A new switching sequence, the modified phase-shifted pulse width modulation, is developed to enable natural balance in originally imbalanced scenarios. Based on the model, a novel control algorithm, constant switch stress control, is proposed to achieve both output voltage regulation and active balance with fast dynamics. Finally, the design technique and test result of an integrated hybrid switched-capacitor converter are reported. A proposed gate driving strategy eliminates the need for external driving supplies and reduces the bootstrap capacitor area. On-chip mixed signal control ensures fast balancing dynamics and makes hard startup tolerable. This prototype achieves 96.9\% peak efficiency at 5V:1.2V conversion and a startup time of 12$\mu s$, which is over 100 times faster than the closest prior art. With the modeling, control, and design techniques introduced in this dissertation, the application of hybrid switched-capacitor converters may be extended to scenarios that were previously challenging for them, allowing enhanced performance compared to using traditional topologies. For problems that may require future attention, this dissertation also points to possible directions for further improvements

Hybrid monolithic integration of high-power DC-DC converters in a high-voltage technology

The supply of electrical energy to home, commercial, and industrial users has become ubiquitous, and it is hard to imagine a world without the facilities provided by electrical energy. Despite the ever increasing efficiency of nearly every electrical application, the worldwide demand for electrical power continues to increase, since the number of users and applications more than compensates for these technological improvements. In order to maintain the affordability and feasibility of the total production, it is essential for the distribution of the produced electrical energy to be as efficient as possible. In other words the loss in the power distribution is to be minimized. By transporting electrical energy at the maximum safe voltage, the current in the conductors, and the associated conduction loss can remain as low as possible. In order to optimize the total efficiency, the high transportation voltage needs to be converted to the appropriate lower voltage as close as possible to the end user. Obviously, this conversion also needs to be as efficient, affordable, and compact as possible. Because of the ever increasing integration of electronic systems, where more and more functionality is combined in monolithically integrated circuits, the cost, the power consumption, and the size of these electronic systems can be greatly reduced. This thorough integration is not limited to the electronic systems that are the end users of the electrical energy, but can also be applied to the power conversion itself. In most modern applications, the voltage conversion is implemented as a switching DC-DC converter, in which electrical energy is temporarily stored in reactive elements, i.e. inductors or capacitors. High switching speeds are used to allow for a compact and efficient implementation. For low power levels, typically below 1 Watt, it is possible to monolithically implement the voltage conversion on an integrated circuit. In some cases, this is even done on the same integrated circuit that is the end user of the electrical energy to minimize the system dimensions. For higher power levels, it is no longer feasible to achieve the desired efficiency with monolithically integrated components, and some external components prove indispensable. Usually, the reactive components are the main limiting factor, and are the first components to be moved away from the integrated circuit for increasing power levels. The semiconductor components, including the power transistors, remain part of the integrated circuit. Using this hybrid approach, it is possible in modern converterapplications to process around 60 Watt, albeit limited to voltages of a few Volt. For hybrid integrated converters with an output voltage of tens of Volt, the power is limited to approximately 10 Watt. For even higher power levels, the integrated power transistors also become a limiting factor, and are replaced with discrete power devices. In these discrete converters, greatly increased power levels become possible, although the system size rapidly increases. In this work, the limits of the hybrid approach are explored when using so-called smart-power technologies. Smart-power technologies are standard lowcost submicron CMOS technologies that are complemented with a number of integrated high-voltage devices. By using an appropriate combination of smart-power technologies and circuit topologies, it is possible to improve on the current state-of-the-art converters, by optimizing the size, the cost, and the efficiency. To determine the limits of smart-power DC-DC converters, we first discuss the major contributing factors for an efficient energy distribution, and take a look at the role of voltage conversion in the energy distribution. Considering the limitations of the technologies and the potential application areas, we define two test-cases in the telecommunications sector for which we want to optimize the hybrid monolithic integration in a smart-power technology. Subsequently, we explore the specifications of an ideal converter, and the relevant properties of the affordable smart-power technologies for the implementation of DC-DC converters. Taking into account the limitations of these technologies, we define a cost function that allows to systematically evaluate the different potential converter topologies, without having to perform a full design cycle for each topology. From this cost function, we notice that the de facto default topology selection in discrete converters, which is typically based on output power, is not optimal for converters with integrated power transistors. Based on the cost function and the boundary conditions of our test-cases, we determine the optimal topology for a smart-power implementation of these applications. Then, we take another step towards the real world and evaluate the influence of parasitic elements in a smart-power implementation of switching converters. It is noticed that the voltage overshoot caused by the transformer secondary side leakage inductance is a major roadblock for an efficient implementation. Since the usual approach to this voltage overshoot in discrete converters is not applicable in smart-power converters due to technological limitations, an alternative approach is shown and implemented. The energy from the voltage overshoot is absorbed and transferred to the output of the converter. This allows for a significant reduction in the voltage overshoot, while maintaining a high efficiency, leading to an efficient, compact, and low-cost implementation. The effectiveness of this approach was tested and demonstrated in both a version using a commercially available integrated circuit, and our own implementation in a smart-power integrated circuit. Finally, we also take a look at the optimization of switching converters over the load range by exploiting the capabilities of highly integrated converters. Although the maximum output power remains one of the defining characteristics of converters, it has been shown that most converters spend a majority of their lifetime delivering significantly lower output power. Therefore, it is also desirable to optimize the efficiency of the converter at reduced output current and output power. By splitting the power transistors in multiple independent segments, which are turned on or off in function of the current, the efficiency at low currents can be significantly improved, without introducing undesirable frequency components in the output voltage, and without harming the efficiency at higher currents. These properties allow a near universal application of the optimization technique in hybrid monolithic DC-DC converter applications, without significant impact on the complexity and the cost of the system. This approach for the optimization of switching converters over the load range was demonstrated using a boost converter with discrete power transistors. The demonstration of our smart-power implementation was limited to simulations due to an issue with a digital control block. On a finishing note, we formulate the general conclusions and provide an outlook on potential future work based on this research

Low total harmonic distortion (THD) resonant converter for cooker magnetron power supply

The traditional cooker magnetron power supply consists industrial frequency transformer, whichis bulky, inefficient and with high harmonics distortion. There are numerous researchers whoinvestigates magnetron power supply design with soft switching converter, in order to reduceweight and improve efficiency [7–10]. However, no investigation currently exists on harmonicdistortion of traditionalmagnetron power supply, and very little research or analysis is done onharmonic distortion of new type of magnetron power supply. This project aims to investigateharmonic distortion of traditional magnetron power supply in the first phase. In the secondphase, a novel design of high frequency and low harmonic distortion magnetron power supply istargeted

Design of a pulse power supply unit for micro-ECM

Electrochemical micro-machining (μECM) requires a particular pulse power supply unit (PSU) to be developed in order to achieve desired machining performance. This paper summarises the development of a pulse PSU meeting the requirements of μECM. The pulse power supply provides tens of nanosecond pulse duration, positive and negative bias voltages and a polarity switching functionality. It fulfils the needs for tool preparation with reversed pulsed ECM on the machine. Moreover, the PSU is equipped with an ultrafast overcurrent protection which prevents the tool electrode from being damaged in case of short circuits. The developed pulse PSU was used to fabricate micro-tools out of 170 μm WC-Co alloy shafts via micro-electrochemical turning and drill deep holes via μECM in a disk made of 18NiCr6. The electrolyte used for both processes was a mixture of sulphuric acid and NaNO3 aqueous solutions.The research reported in this paper is supported by the European Commission within the project “Minimizing Defects in Micro-Manufacturing Applications (MIDEMMA)” (FP7-2011-NMP-ICT-FoF-285614

A High-Temperature, High-Voltage SOI Gate Driver Integrated Circuit with High Drive Current for Silicon Carbide Power Switches

High-temperature integrated circuit (IC) design is one of the new frontiers in microelectronics that can significantly improve the performance of the electrical systems in extreme environment applications, including automotive, aerospace, well-logging, geothermal, and nuclear. Power modules (DC-DC converters, inverters, etc.) are key components in these electrical systems. Power-to-volume and power-to-weight ratios of these modules can be significantly improved by employing silicon carbide (SiC) based power switches which are capable of operating at much higher temperature than silicon (Si) and gallium arsenide (GaAs) based conventional devices. For successful realization of such high-temperature power electronic circuits, associated control electronics also need to perform at high temperature. In any power converter, gate driver circuit performs as the interface between a low-power microcontroller and the semiconductor power switches. This dissertation presents design, implementation, and measurement results of a silicon-on-insulator (SOI) based high-temperature (\u3e200 _C) and high-voltage (\u3e30 V) universal gate driver integrated circuit with high drive current (\u3e3 A) for SiC power switches. This mixed signal IC has primarily been designed for automotive applications where the under-hood temperature can reach 200 _C. Prototype driver circuits have been designed and implemented in a Bipolar-CMOS- DMOS (BCD) on SOI process and have been successfully tested up to 200 _C ambient temperature driving SiC switches (MOSFET and JFET) without any heat sink and thermal management. This circuit can generate 30V peak-to-peak gate drive signal and can source and sink 3A peak drive current. Temperature compensating and temperature independent design techniques are employed to design the critical functional units like dead-time controller and level shifters in the driver circuit. Chip-level layout techniques are employed to enhance the reliability of the circuit at high temperature. High-temperature test boards have been developed to test the prototype ICs. An ultra low power on-chip temperature sensor circuit has also been designed and integrated into the gate-driver die to safeguard the driver circuit against excessive die temperature (_ 220 _C). This new temperature monitoring approach utilizes a reverse biased p-n junction diode as the temperature sensing element. Power consumption of this sensor circuit is less than 10 uW at 200 _C

Pem fuel cell modeling and converters design for a 48 v dc power bus

Fuel cells (FC) are electrochemical devices that directly convert the chemical energy of a fuel into electricity. Power systems based on proton exchange membrane fuel cell (PEMFC) technology have been the object of increasing attention in recent years as they appear very promising in both stationary and mobile applications due to their high efficiency, low operating temperature allowing fast startup, high power density, solid electrolyte, long cell and stack life, low corrosion, excellent dynamic response with respect to the other FCs, and nonpolluting emissions to the environment if the hydrogen is obtained from renewable sources. The output-voltage characteristic in a PEMFC is limited by the mechanical devices which are used for regulating the air flow in its cathode, the hydrogen flow in its anode, its inner temperature, and the humidity of the air supplied to it. Usually, the FC time constants are dominated by the fuel delivery system, in particular by the slow dynamics of the compressor responsible for supplying the oxygen. As a consequence, a fast load transient demand could cause a high voltage drop in a short time known as oxygen starvation phenomenon that is harmful for the FC. Thus, FCs are considered as a slow dynamic response equipment with respect to the load transient requirements. Therefore, batteries, ultracapacitors or other auxiliary power sources are needed to support the operation of the FC in order to ensure a fast response to any load power transient. The resulting systems, known as FC hybrid systems, can limit the slope of the current or the power generated by the FC with the use of current-controlled dc-dc converters. In this way, the reactant gas starvation phenomena can be avoided and the system can operate with higher efficiency. The purpose of this thesis is the design of a DC-DC converter suitable to interconnect all the different elements in a PEMFC-hybrid 48-V DC bus. Since the converter could be placed between elements with very different voltage levels, a buck-boost structure has been selected. Especially to fulfill the low ripple requirements of the PEMFCs, but also those of the auxiliary storage elements and loads, our structure has inductors in series at both its input and its output. Magnetically coupling these inductors and adding a damping network to its intermediate capacitor we have designed an easily controllable converter with second-order-buck-like dominant dynamics. This new proposed topology has high efficiency and wide bandwidth acting either as a voltage or as a current regulator. The magnetic coupling allows to control with similar performances the input or the output inductor currents. This characteristic is very useful because the designed current-controlled converter is able to withstand shortcircuits at its output and, when connected to the FC, it facilitates to regulate the current extracted from the FC to avoid the oxygen starvation phenomenon. Testing in a safe way the converter connected to the FC required to build an FC simulator that was subsequently improved by developing an emulator that offered real-time processing and oxygen-starvation indication. To study the developed converters and emulators with different brands of PEMFCs it was necessary to reactivate long-time inactive Palcan FCs. Since the results provided by the manual reactivation procedure were unsatisfactory, an automatic reactivation system has been developed as a complementary study of the thesis.En esta tesis se avanzo en el diseño de un bus DC de 48 V que utiliza como elemento principal de generación de energía eléctrica una pila de combustible. Debido a que la dinámica de las pilas de combustible están limitadas por sus elementos mecánicos auxiliares de control una variación rápida de una carga conectada a ella puede ocasionar daños. Es por esto que es necesario utilizar elementos almacenadores de energía que puedan suministrar estas rápidas variaciones de carga y convertidores para que gestionen de una forma controlada la potencia del bus DC. Durante la realización de pruebas de los convertidores es de gran importancia utilizar emuladores o simuladores de pilas de combustibles, esto nos permite de una forma económica y segura realizar pruebas criticas antes de conectar los convertidores a la pila. Adicionalmente una nueva topologia de convertidor fue presentada y ésta gestionará la potencia en el bu

Study and design of topologies and components for high power density DC-DC converters

Size reduction of low power electronic DC–DC converters is a topic of major interest for power electronics which requires the study and design of circuits and components working under redefined requirements. For this purpose, novel circuital topologies provide advantages in terms of power density increment, especially where a single chip design is feasible. These concepts have been applied to design and implement an integrated high step-down multiphase buck converter and to study the miniaturization of a stackable fiflyback architecture. Particular attention has been dedicated to power inductors, focusing on the modeling and measurement of magnetic materials’ hysteresis and core losses

Small Form Factor Hybrid CMOS/GaN Buck Converters for 10W Point of Load Applications

abstract: Point of Load (PoL) converters are important components to the power distribution system in computer power supplies as well as automotive, space, nuclear, and medical electronics. These converters often require high output current capability, low form factor, and high conversion ratios (step-down) without sacrificing converter efficiency. This work presents hybrid silicon/gallium nitride (CMOS/GaN) power converter architectures as a solution for high-current, small form-factor PoL converters. The presented topologies use discrete GaN power devices and CMOS integrated drivers and controller loop. The presented power converters operate in the tens of MHz range to reduce the form factor by reducing the size of the off-chip passive inductor and capacitor. Higher conversion ratio is achieved through a fast control loop and the use of GaN power devices that exhibit low parasitic gate capacitance and minimize pulse swallowing. This work compares three discrete buck power converter architectures: single-stage, multi-phase with 2 phases, and stacked-interleaved, using components-off-the-shelf (COTS). Each of the implemented power converters achieves over 80% peak efficiency with switching speeds up-to 10MHz for high conversion ratio from 24V input to 5V output and maximum load current of 10A. The performance of the three architectures is compared in open loop and closed loop configurations with respect to efficiency, output voltage ripple, and power stage form factor. Additionally, this work presents an integrated CMOS gate driver solution in CMOS 0.35um technology. The CMOS integrated circuit (IC) includes the gate driver and the closed loop controller for directly driving a single-stage GaN architecture. The designed IC efficiently drives the GaN devices up to 20MHz switching speeds. The presented controller technique uses voltage mode control with an innovative cascode driver architecture to allow a 3.3V CMOS devices to effectively drive GaN devices that require 5V gate signal swing. Furthermore, the designed power converter is expected to operate under 400MRad of total dose, thus enabling its use in high-radiation environments for the large hadron collider at CERN and nuclear facilities.Dissertation/ThesisMasters Thesis Electrical Engineering 201

MULTIPLE INPUT SINGLE OUTPUT CONVERTER WITH MAXIMUM POWER POINT TRACKING FOR RENEWABLE ENERGY APPLICATIONS

In this thesis, a maximum power point tracking (MPPT) for multiple input single output (MISO) converter is presented such that power generated from multiple individual energy sources can be combined to deliver the maximum amount of power to a common resistive load. Typically, MISO converters will employ techniques that yield equal current sharing from each energy source. However, this may not be desirable since each source may be rated at different power ratings and/or may experience different operating conditions, preventing the system MISO converter to acquire the most available total power from the sources. Utilizing MPPT control would therefore be beneficial in maximizing the output power of the MISO converter system. In this thesis, a proposed two-stage converter system is presented to incorporate the MPPT control in the MISO system. The initial stage implements the MPPT, drawing as much power from the corresponding source. The second stage regulates the output voltage of the MPPT. To evaluate the performance and efficiency of the proposed system, simulation with two solar panels as the sources was performed using Simulink with various test cases to fully explore the viability of the system. Simulation results were also used to compare with those obtained from a system without the MPPT. Results show that the proposed system with the MPPT stage is able to improve input regulation and increase the total amount of power acquired from the sources compared to the system without the MPPT. Further testing with hardware setup confirms the simulation results and demonstrates that even with large differences in input powers, the most total amount of power is achieved and utilized