This paper presents the development and study of multiple-input single-output converter (MISO) for the DC House project that utilizes a controller to maximize the overall converter’s efficiency. The premise of this thesis is to create uneven load current sharing between the converters at different loading conditions in order to maximize the efficiency of the overall MISO converter. The goal is to find a proper ratio of current from each converter to the total load current of the MISO system to achieve the greatest efficiency. The Arduino microcontroller is implemented to achieve this goal. The design and operation of the MISO converter with the proposed controller will be explained in this paper. The design and operation of the converter was tested and verified through simulation in LTSpice in addition to hardware implementation. Different ratios of current from each converter were used to fully test the MISO converter. For the 5A and 6A load current, the maximum efficiencies were reached with the 70% / 30% ratio case, with efficiencies of 94.91% and 95.07%, respectively. For 7A load current, the maximum efficiency was reached with the 60% / 40% ratio case, with an efficiency of 94.59%. The results were then compared with those obtained from the equal current sharing cases. For the cases tested, the efficiency of the unequal current sharing outperforms that obtained from the equal current sharing method.

In this work a proof of concept for a step-down DC-DC converter used in a high voltage submarine application is presented. The purpose of the converter is to step down a 5000V-6000V input to a 24V output which can serve as an input to a submarine sensor. The completed system consists of two stages where the first stage is an unregulated switched capacitor converter to step down the initial input to a voltage range more appropriate for the selected second stage. The second stage is a regulated flyback converter topology which regulates the final output to the desired 24V. Performance evaluation of the proposed system are carried out using LTspice simulation software. Results of the simulation demonstrate that the proposed converter operates as anticipated with the first stage being able to reduce the initial input by a factor of 16 and the second stage producing a regulated 24V output. Additionally, the proposed converter reaches an efficiency of approximately 74.95% when tested under nominal input and full load conditions. With the same conditions, the converter yields an output voltage ripple of 1.525%, and line and load regulations of 0.0457% and 0.183% respectively.

Loop measurements are very important in evaluating dynamic performance of DC-DC converters. In this thesis, a small loop measurement tool as a low-cost alternative to a network analyzer is proposed. The tool is particularly useful when a network analyzer is not always available for use, for example when engineers are working on-site with customers or when a network analyzer is not affordable due to their relatively high cost. The design, simulation, and hardware implementation of the inexpensive loop measurement tool will be presented in this thesis. Results from computer simulation and hardware prototype demonstrate the ability of the proposed tool to perform phase margin, gain margin, and cross-over frequency measurements of DC-DC converters. These results are then shown to be comparable with those obtained from a network analyzer. The procedure used to perform loop measurements with the proposed tool will be explained. Limitations in the operation as well as further improvements to enhance the performance of the proposed tool will also be discussed.

This report details the design and implementation of a switching DC-DC converter for use in the Energy Harvesting From Exercise Machines (EHFEM) project. It uses a four-switch, buck-boost topology to regulate the wide, 5-60 V output of an elliptical machine to 36 V, suitable as input for a microinverter to reclaim the energy for the electrical grid. Successful implementation reduces heat emissions from electrical energy originally wasted as heat, and facilitates a financial and environmental benefit from reduced net energy consumption.

This thesis entails the stability analysis of the Multiple Input Single Output (MISO) DC-DC converter developed for the DC House Project at Cal Poly. A frequency domain control system model of the MISO converter was designed and constructed using MATLAB Simulink. Transfer functions were derived and modeled for each stage of the converter to best fit the converter circuit system used in the original MISO circuit. Stability metrics such as overshoot, undershoot, rise time, phase margin and gain margin were measured to evaluate and analyze the stability of the converter. These metrics were measured with the original model including the current sharing network that allows load sharing between multiple MISO modules. The simulation results demonstrate that based on the existing model, the system is stable with a gain margin of infinity and phase margin of around 40 degrees at crossover frequency of 47kHz with nominal input voltage of 24V. Another compensator was proposed to overcome the shortcomings of the original compensator model with respect to the overshoot and phase margin. The new compensator model improved the phase margin at the same crossover frequency with a higher rise time and lowered percent overshoot. Additional improvements and tradeoffs are further discussed to help with the decision when designing a compensator for DC-DC converter that uses the current mode control technique.

This project proposes a new hybrid voltage divider DC-DC converter that utilizes switching capacitors and inductors to produce zero voltage switching (ZVS) at the turn on state of its switches. By achieving ZVS, the switching losses are significantly reduced; thus, increasing the overall efficiency of the converter at various loads. The goal for this thesis is to perform analysis of the operation of the converter, derive equations for sizing the main components, and demonstrate its functionality through computer simulation and hardware prototype. Results of the simulation and hardware testing show that the proposed converter produces the desired output voltage while providing the zero voltage switching benefits. The converter’s efficiency reaches above 92% starting from 1A load and continues to increase to 97.6% at 4A load. Overall, results from this thesis verifies the potential of the proposed converter as an alternative solution to achieve a very efficient DC-DC solution when half of the input voltage is required at the output without the use of complex feedback control circuitry.

The delivery of high power and smaller footprints through a non-isolated topology demands for the use of multiphase topology in DC-DC converters. Multiphase reduces the ripple observed on both the input and output waveforms; however, it may not be enough to connect to sensitive power sources such as renewable energy sources. A single-phase modified boost converter demonstrates the ability to acquire very minimal input current ripple by addition of passive components. The expansion to multiphase topology is the next logical step for higher power application while furthering the low input current ripple benefit. In this thesis, the multiphase modified boost topology is compared with the multiphase standard boost topology to explore the benefits and trade-offs of the proposed topology. A 12V input to 19V output at 95W output power multiphase standard and modified boost converters were designed and constructed for the thesis. Results from theoretical calculations, computer simulations, and hardware implementations were then compared to evaluate their performances. Results show that compared to the standard boost, the modified boost yields significantly less input current ripple at 2% under full load condition while maintaining output voltage ripple of 5% and higher than 90% efficiency.

This thesis presents the design, simulation, and hardware implementation of a proposed method for improving efficiency of voltage regulator. Typically, voltage regulator used for noise-sensitive and low-power applications involves the use of a linear regulator due to its high power-supply rejection ratio properties. However, the efficiency of a linear regulator depends heavily on the difference between its input voltage and output voltage. A larger voltage difference across the linear regulator results in higher losses. Therefore, reducing the voltage difference is the key in increasing regulator’s efficiency. In this thesis, a pre switching regulator stage with positive voltage tracking cascaded to a linear regulator is proposed to provide an input voltage to a linear regulator that is slightly above the output of the linear regulator. The tracking capability is needed to provide the flexibility in having different positive output voltage levels while maintaining high overall regulator’s efficiency. Results from simulation and hardware implementation of the proposed system showed efficiency improvement of up to 23% in cases where an adjustable output voltage is necessary. Load regulation performance of the proposed method was also overall better compared to the case without the output voltage tracking method.

High voltage power supply design presents unique requirements, combining safety, controllability, high performance, and high efficiencies. A new Resonant Self-Tracking Current-Fed Converter (RST-CFC) is investigated as a proof-of-concept of a high voltage power supply particularly for an X-ray system. These systems require fast voltage rise times and low ripple to yield a clear image. The proposed converter implements high-frequency resonance among discrete components and transformer parasitics to achieve high voltage gain, and the self-tracking nature ensures operation at maximum gain while power switches achieve zero-voltage switching across the full load range. This converter exhibits an inherent indefinite short-circuit capability. Theoretical results were obtained through simulations and verified by experimental results through a complete test configuration. Converter topology viability was confirmed through hardware testing and characterization.

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