Smart DC/DC Wall Plug Design For The DC House Project

The present day duplex wall receptacle in the United States provides 120Vrms AC at 60Hz, which comes from a standard set for AC loads by the National Electrical Manufacturers Association. With a DC system, such as what is used in the DC House project currently being developed at Cal Poly, providing DC power to DC loads presents a technical challenge due to the different required DC operating voltages of the loads. This thesis entails the design and construction of a Smart DC/DC Wall Plug, which can automatically adjust its output voltage to match any required DC load voltages. In the DC House implementation, renewable energy sources generate power to feed a 48V DC Bus. The Smart DC/DC Wall Plug converts power from the 48V bus to the appropriate voltage and power levels needed by the DC loads. The Smart DC/DC Wall Plug relies on load current detection, and uses a 10-bit digital potentiometer and a programmable current DAC to adjust the feedback network, thereby changing the output voltage. A dual channel 100W PCB prototype utilizing a STMF302R8 microcontroller is implemented for this design while confining to the NEMA wall outlet form factor. Results of hardware test verify the functionality of the Smart DC/DC Wall Plug in producing the required DC load voltages. Technical issues during the development of the Smart DC/DC Wall Plug will be described, along with suggestions to further improve from the current design

Smart Gate Driver Design for Silicon (Si) IGBTs and Silicon-Carbide (SiC) MOSFETs

The design of an efficient and smart gate driver for a Si IGBT and SiC MOSFET is addressed in thesis. First, the main IGBT parameters are evaluated thoroughly in order to understand their effects in the design of the gate driver. All known consequences of previously designed gate drivers are studied in order to achieve an optimum gate driver. As a result of this assessment, the designer is able to determine whether adding or removing components from the gate driver circuit are beneficial or not. Then, exhaustive research is done to identify suitable integrated circuits to use for the power supplies, isolation circuit, protection circuit, and gate driver circuitry. Next, the final design is laid out in PCB Editor in order to eventually manufacture it and test it out. During this process, important techniques in making an efficient and compact PCB are taken into consideration

Design and Test of Wide Input and Output Constant Current LED Driver

This senior project aims to provide design and test the performance of a DC-DC constant current LED driver for use in a larger DC smart building infrastructure. In this instance, a SEPIC topology is chosen to provide high efficiency output current at output voltages that can be above or below the input voltage. This is challenging since the same design must operate at similar efficiency for vastly different environmental conditions. As a part of a larger system, the design must be able to perform the given task consistently regardless of changes to the source and load power. The design uses the LT3795 LED controller to operate power switches and inductors to transform the input power into usable output power for a string of LEDs. The controller is paired with an onboard microcontroller to provide error reporting and supplement the PWM dimming control features of the IC. Simulations were done to ensure the efficiency of the design remained above 93% within the full range of input and output voltages, along with a range of PWM frequencies and duty cycles. After manufacturing and assembly, the board was found to be under specification regarding the input and output voltage ranges, as well as below the efficiency target. This was largely due to issues regarding the layout assembly of the finished product

Design and implementation of an AC voltage regulator based on series power semiconductor array

This thesis describes the use of an array of power semiconductors (series transistor array) and a buck-boost transformer in the design and implementation of a single phase AC voltage regulator. The power semiconductor array was used to act as variable impedance across the bridge points of a rectifier. The input point of the bridge rectifier was also connected directly to the primary winding of the buck-boost transformer. A closed loop circuit was designed using an RMS/DC converter chip, with complete electrical isolation between the low voltage control circuits and the power circuits. The major advantages of this technique are: fast response to RMS voltage fluctuation; waveform fidelity; light weight; and reduced size compared to that of a servo-driven AC voltage regulator such as the PS10 Smart Power Station, which was used in this project as a benchmark for the AC voltage regulator using the power semiconductor array. The device used for testing the performances of both AC voltage regulators was the NoiseKen VDS-2002 Voltage Dip and Swell Simulator. This simulator was used to perform voltage dip, swell, interruption, and variation tests in a manner fully compliant with IEC 61000 – 4 – 11

Flexible AC/DC Grids in Dymola/Modelica - Modeling and Simulation of Power Electronic Devices and Grids

The research of the thesis was aimed towards investigating the possibility of implementing different control strategies for power electronic converters in a simulation environment. The different control modes were fitted into flexible models that were interconnected in various grid topologies. The software used in order to develop the simulation environment is called Dymola and presently does not include any form of control of power electronic units. The library used is the Modelica Electric Power Library (EPL) where some power electronic converters were already implemented. The grid was controlled and kept stable for various scenarios using the developed controlled converter models. The converter models were tested separately in order to verify that the models acted in the desired manner. The models where then interconnected into a grid and simulated for different scenarios in order to get grid models that could be fitted into multiple grid applications. To further prove this, models from external Modelica libraries were used in the grid setups. The results of the simulations clearly show that constructed models support the implementation of scalable and controllable grids in Dymola

High efficiency smart voltage regulating module for green mobile computing

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.In this thesis a design for a smart high efficiency voltage regulating module capable of supplying the core of modern microprocessors incorporating dynamic voltage and frequency scaling (DVS) capability is accomplished using a RISC based microcontroller to facilitate all the functions required to control, protect, and supply the core with the required variable operating voltage as set by the DVS management system. Normally voltage regulating modules provide maximum power efficiency at designed peak load, and the efficiency falls off as the load moves towards lesser values. A mathematical model has been derived for the main converter and small signal analysis has been performed in order to determine system operation stability and select a control scheme that would improve converter operation response to transients and not requiring intense computational power to realize. A Simulation model was built using Matlab/Simulink and after experimenting with tuned PID controller and fuzzy logic controllers, a simple fuzzy logic control scheme was selected to control the pulse width modulated converter and several methods were devised to reduce the requirements for computational power making the whole system operation realizable using a low power RISC based microcontroller. The same microcontroller provides circuit adaptations operation in addition to providing protection to load in terms of over voltage and over current protection. A novel circuit technique and operation control scheme enables the designed module to selectively change some of the circuit elements in the main pulse width modulated buck converter so as to improve efficiency over a wider range of loads. In case of very light loads as the case when the device goes into standby, sleep or hibernation mode, a secondary converter starts operating and the main converter stops. The secondary converter adapts a different operation scheme using switched capacitor technique which provides high efficiency at low load currents. A fuzzy logic control scheme was chosen for the main converter for its lighter computational power requirement promoting implementation using ultra low power embedded controllers. Passive and active components were carefully selected to augment operational efficiency. These aspects enabled the designed voltage regulating module to operate with efficiency improvement in off peak load region in the range of 3% to 5%. At low loads as the case when the computer system goes to standby or sleep mode, the efficiency improvent is better than 13% which will have noticeable contribution in extending battery run time thus contributing to lowering the carbon footprint of human consumption

Development of a Step Down DC-DC Converter for Power Grid Energy Harvesting

This work contains an analysis of multiple topologies of DC-DC voltage buck con verters. The main goal of this Thesis is to study and design a functioning Step Down converter for capacitive coupling devices used for energy harvesting from the power AC grid. In order to achieve this goal, multiple topologies and circuits of this type of converter are studied and analysed, so that the requirements for the intended application are met. Since the input is obtained from the AC power grid and the output is connected to a supercapacitor, this results in a large input voltage (over 150V) and a low output voltage (between 1V to 3V), therefore the converter requires a step down voltage conversion ratio of around 130. The DC-DC converter should also have a large input impedance (around 50Mohm) to maximize the energy transferred from the power grid. This mode of operation is not common for regular inductance based DC-DC converters, making this a challenging problem. Moreover, since the amount of energy available from the capacitive coupling is very small, it is also necessary to develop a controller circuit that is capable of created a clock with a very low duty cycle while dissipating less than 50uW.Este trabalho visa analisar várias tipologias de conversores de tensão DC-DC deno minados conversores Buck. O principal objectivo desta Tese é estudar e projectar um conversor DC-DC abaixador de tensão para sistemas de acopelamento electromagnético capacitivo utilizada em aplicações de Energy Harvesting a partir da rede AC. De forma a cumprir este objectivo, várias tipologias são estudadas ao longo deste trabalho, de forma a cumprir as especificações exigidas. Uma vez que o sinal de entrada é obtido a partir da rede AC, e que o output está ligado a um supercondensador, isto faz com que a tensão de entrada seja elevado (Acima dos 150V) e a tensão de saída seja baixa (entre 1V e 3V), como tal o conversor precisa de um rácio de abaixamento bastante elevado de cerca de 130 vezes. O conversor DC-DC deve também ter uma impedância de entrada elevada (cerca de 50MOhm) por forma a maximizar a energia transferida da rede de energia. Estas condições de funcionamento não são habituais para conversores DC-DC indutivos, o que torna este um problema muito desafiante. Adicionalmente, uma vez que a energia disponivel devido ao acopelamento capacitivo é muito reduzida, é necessário desenvolver um circuito controlador capaz gerar um sinal de relógio com um duty cycle reduzido enquanto dissipa menos de 50uW de potência

Smart Battery Charger

The purpose of this project was to design, build and test a 1A smart battery charger that accurately and efficiently charges a 3V, 6V or 12V battery. The smart battery charging system integrated an AC/DC converter, a MOSFET driver circuit, and a DC/DC converter to charge the battery. The concepts of experimental design and simulation were observed

Smart DC Wall Outlet Design with Improved Load Voltage Detection

A standard home in the United States has access to the 120V AC power grid for use with home appliances. Many electronics used at home are powered by a DC power supply, which loses energy in the conversion from AC power. The DC House project avoids any conversion between AC and DC by storing energy in batteries as DC power and supplying it directly to DC appliances. While AC systems feature a standardized output voltage, no such standard exists for DC systems. The Smart DC Wall Outlet solves this by automatically adjusting its output voltage to meet any required DC load voltage. A hardware solution was developed using a microcontroller in tandem with a DC to DC Buck converter to monitor trends in the output current and set the output voltage accordingly. The Smart DC Wall Outlet features two 100W output channels that were able to correctly identify the required output voltage of five out of seven test devices. Results indicate that it is possible to generalize the turn on characteristics of DC devices, but that other solutions may find more success