published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

Finally, a four-channel SIMO converter with direct combination but optimal switching sequence for arbitrary converter sequence and converter type is presented. The theoretical optimal 1st-order inductor waveform from this proposed control algorithm is introduced. FCL is involved in this design to realize the algorithm. Moreover, a current-modulated ramp signal, which couples to different controllers, is included to compensate the original deep correlated power stages. By using all of the proposed techniques, Measurement results show that both conduction loss and dynamic loss can be suppressed because of the optimized switching sequence. The load transient response time is around 100mus. The peak efficiency is 89% with a 2.5-V power supply. A maximum output power of 1.66W can be achieved. / Firstly, a pseudo-PWM hysteresis voltage-mode buck converter is proposed. It achieves fast transient speed by the hysteresis control, estimable switching spectrum with a locking frequency and fast mode switching between PWM and PFM depending on the loading change. Measurement results show that the recovery time under the load transient is around 5mus, which is 5 times of the switching period. The boundary of the recovery time is defined by the value of the off-chip inductor. / Switching-mode power converter (SMPC) is an important circuit block in electronic systems. In the modem SMPC system, constant frequency voltage or current-mode control technique is commonly used. However, some limitations are raised due to some preliminary settings in the design. In this thesis, the switching frequency or period is no longer a constant but a design variable. Then, an additional frequency-control loop (FCL) is introduced in order to obtain a fixed frequency operation in the steady state. Three individual designs implemented with different types of FCL are proposed to verify the concept. / Then, a four-channel SIMO converter based on FCL is developed, together with auto-phase allocation technique. This circuit not only solves the problem of imbalance loading of different channels, but it also keeps the idle period of the inductor sufficient short in the full operation region. By combining with all channel controllers, FCL makes fast load transient response without degrading the power efficiency. Moreover, linear auto converter-type adaption technique is also used, which makes the converter surviving from a wide input range and output range. Measurement results show that the proposed converter can achieve a peak efficiency of 89%, a total output power of 1.46W, a load transient response time of less than 70muS, and an idle inductor period of <10%. / Zheng, Yanqi. / Adviser: Leung Ka Nang. / Source: Dissertation Abstracts International, Volume: 73-03, Section: B, page: . / Thesis (Ph.D.)--Chinese University of Hong Kong, 2010. / Includes bibliographical references. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [201-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.

In this thesis, a digital-PID-control single-inductor triple-output (SITO) DC-DC converter is realized in AMS 0.35mum CMOS technology. The size of the chip is about 1600 mum x 1700 mum. To improve load current and reduce cross regulation, a Pre-Sub-Period inductor-current regulation is proposed. Based on the maximum duty cycle limiter, an adaptive inductor current adjustment is realized when the duty cycle of the digital PWM signal is larger than the set maximum duty cycle. By an optimized phase control sequence, the S&H stages of the feedback switching and ADC are controlled to on/off with a minimized delay time. Moreover, the control sequence can virtually remove the setting time. / Multiple voltage supplies are necessary to satisfy the different voltage supply requirements of the different on-chip blocks to reduce power consumption in modem electronic devices, such as the modem embedded systems, the portable devices, personal computing devices and wireless communications and imaging systems. For example, WiMAX transmitter includes different sub-blocks: Baseband processor, IQ modulator and power amplifier. Different blocks should operate with the different power supply voltages to satisfy the different requirements. / Single-input multiple-output DC-DC converter is presented to provide the different voltage supplies and reduce the cost on the elements such as the inductor on PCB and save PCB area. Meanwhile, to remove cross regulation and improve load driving capability, the DC-DC converter should operate in the pseudo-continuous mode/discontinuous mode (P-CCM/DCM). However, in the previous designs, the DC current in the inductor is fixed. When the load becomes heavy enough, cross regulation will significantly affect across the different sub-converters. / Jia, Jingbin. / "December 2009." / Adviser: KaNang Leung Alex. / Source: Dissertation Abstracts International, Volume: 72-01, Section: B, page: . / Thesis (Ph.D.)--Chinese University of Hong Kong, 2010. / Includes bibliographical references (leaves 121-124). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. Ann Arbor, MI : ProQuest Information and Learning Company, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. Ann Arbor, MI : ProQuest Information and Learning Company, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.

Recently, switched capacitor DC/DC converters are extensively used in portable electronic devices because they feature many advantages, such as high efficiency, small package, low quiescent current, minimal external components and low cost. In this thesis, two step-down switched capacitor DC/DC converters are designed. One has the fixed output options 1.5V, 1.8V and 2.0V. The other one has the output 1.2V. These two converters are implemented in 0.5��m CMOS process through National Semiconductor Corporation. The design is verified by the circuit-level simulations, and design issues are discussed. / Graduation date: 2004

M.Ing. / High frequency magnetic components have financial and physical advantages compared to low frequency magnetic components. Although high frequency magnetic components have been used for quite some time, the design and analysis of these components remain complicated.This can be ascribed to the effect of eddy currents and thermal constraints due to the smaller cooling area of such components. Planar magnetic components have long been preferred due to the higher manufacturing output, better quality control and the favorable flat shape of the component. Many studies have been conducted on planar magnetic components with respect to the energy storage capacity, air gap shape and placement, low permeability materials, to replace the air gaps, the placing of the conductors in the winding window, etc. The designs that are commonly used for planar magnetic components today, are the ones that are proven to work and not necessarily the ones that are optimal. In this study a thermal model is presented to ease the design of DC inductors. A lot of emphasis is placed on heat extraction resulting from losses in the embedded conductors through the core. This is an unconventional way to extract heat from the planar structure and leads to a new approach towards design planar inductor design.

The relative performance evaluation of the different alternatives of bridge topologies with zero-voltage switching is presented. A design-oriented analysis is developed to optimize implementation of the converters in terms of efficiency. Efficiency optimization requires minimizing the circulating currents which are directly proportional to the reactive energy required by the resonant tank. The comparison of the different converters is based on the reactive energy required for ZVS. The study considers resonant converters with conventional variable frequency control and with phase-shift control, and the zerovoltage- switched full-bridge PWM converter (ZVS-FB-PWM). Also, a systematic procedure to determine all possible resonant converters with two or three reactive elements is presented, and the design-oriented analysis used to classifY them according to their properties. The analysis for the resonant converters uses the fundamental approximation which is verified by comparison with the existing exact analysis for the series resonant converter (SRC), the parallel resonant converter (pRe) and the LCC resonant converter (LCC-RC). Comparison of design examples shows a superior performance for the LCC-RC, and less circulating current for the conventional variable-frequency resonant converters than for the phase-shifted control version. Experimental verification is provided for the phase-shifted resonant converters. The effect of switch capacitance on the zero-voltage switching (ZVS) of resonant converters is studied for the SRC, PRC and LCC-RC. The effect of switch capacitance is more' pronounced for low Q designs. Consequently, it is of primary importance for the LCC-RC whose optimal design requires low Q values. The results have been verified experimentally in an LCC-RC prototype. A complete analysis and design procedure are provided for the new ZVS-FB-PWM converter, including a new active clamp circuit that completely eliminates the ringing in the I rectifiers. The design procedure and design considerations have been verified with three' experimental prototypes. The comparison of the resonant converters with the ZVS-FB-PWM converter based on the reactive power required for ZVS, shows that the ZVS-FB-PWM converter is a superior alternative to resonant converters. The ZVS-FB-PWM converter always has less circulating current than the resonant converters when it is designed for a limited ZVS range. / Ph. D.

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 fourport 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 softswitching. In addition, most existing research focuses on the topology investigation, but lacks study on the multi-port converter’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 v 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 “dual loop” 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 converter’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. vi Finally, the work is summarized and concluded, and references are listed.