Thesis (M.S. in Electrical Engineering) Naval Postgraduate School, June 1997. / Thesis advisor, John G. Ciezki. Includes bibliographical references (p. 97). Also available online.

Thesis (M.Phil.)--Hong Kong University of Science and Technology, 2006. / Includes bibliographical references. Also available in electronic version.

M.Ing. / Power electronic systems are often treated purely as electronic circuits. This results in manufactured systems that are electrically functional but not optimised in terms of packaging, temperature or volume. This, in turn, results in low power densities. The objective of this work is to investigate how a power converter should be built to obtain a high power density while operating at high ambient temperatures. In doing so, the parameters affecting the converter volume and thus the power density are identified. In this work, a case study is considered, comprising a DC/DC converter operating in the automotive environment. The specifications for the DC/DC converter identify the power density and high temperature operation as the primary design objectives. The DC/DC converter is implemented in the new dual voltage systems implemented in ultra-modern automobiles. An unconventional converter structure is proposed to meet the electrical and thermal specifications. The converter structure is divided into two sections, namely the active and passive components. The two components share a combined cooling structure. Each of the components is analysed fundamentally and with simulation packages on both an electrical and thermal level. The active and passive components are implemented with material technologies such as open die semiconductors on DCB substrates and high density planar inductors with specially designed cooling structures. The two components take advantage of the thermal performance of the different manufacturing technologies. The complete converter structure is implemented and evaluated both electrically and thermally. The converter structure achieves a power density of 170W/in3 while operating with a coolant temperature of 85°C. Based on the case study, techniques are developed and suggestions are made that will result in the power density and the operating temperature of the converter structure being increased. These suggestions can also be used and implemented in the design and development of any high power density and high operating temperature structure.

M.Ing. (Electrical & Electronic Engineering Science) / This study investigates the mitigation of conducted electromagnetic interference (EMI) in a flyback DC-DC converter. Without the use of filters, the maximum mitigation of EMI possible without significantly decreasing converter operating efficiency is investigated. The following parameters are found to influence EMI: · Switching speed: Decreasing switching speed (increasing rise and fall times of the MOSFET) effectively reduces both common mode (CM) and differential mode (DM) EMI above a certain frequency. Series gate resistors up to a certain value were found to not increase power dissipated in the MOSFET. Series gate resistors greater than this value, further reduce CM and DM EMI at the cost of larger amounts of power being dissipated in the MOSFET. · Leakage inductance and inter-winding capacitance: The dominant component of the flyback coupled inductor in terms of EMI generation is the inter-winding capacitance. Increasing inter-winding capacitance increases both CM and DM EMI. Reducing inter-winding capacitance increases leakage inductance. Increasing leakage inductance however, results in reduced converter efficiency. Coupled inductor design is therefore a compromise between leakage inductance and inter-winding capacitance. · Layout inductance: Reducing layout inductance in certain parts of the circuit is an effective method for reducing DM EMI. This is shown to also decrease CM EMI but not to the same extent as DM EMI. · Snubbing: Snubbing is shown to effectively reduce both CM and DM EMI by reducing the magnitude of the voltage overshoot and ringing on the drain of the MOSFET. Snubbing however reduces converter efficiency. This study gives important guidelines to the engineering trade-offs in reducing EMI versus efficiency in a flyback converter.

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

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

An Integrated Power System (IPS) with a DC Zonal Electrical Distribution System (DC ZEDS) is a strong candidate for the next generation submarine and surface ship. To study the implementation of an IPS with DC ZEDS, members of the Energy Sources Analysis Consortium (ESAC) are currently constructing a reduced-scale laboratory. One fundamental component of DC ZEDS is the Ships Service Converter Module (SSCM), commonly known as a buck DC-DC converter. This thesis documents the design, simulation, construction and testing of a 500V/400V, 8kW resonant soft-switched DC-DC converter. In theory, resonant converters will operate more efficiently and generate less Electromagnetic Interference (EMI) when compared to a standard hard-switched converter. In this thesis, the resonant converter is tested and compared to a hard-switched DC-DC converter that was designed for ESAC's reduced-scaled IPS. The results verify that the resonant DC-DC converter realizes significant efficiency and EMI generation improvements over the hard-switched converter at the cost of a more complex control system and power section. / US Navy (USN) author

M.Ing.

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.