abstract: A novel integrated constant current LED driver design on a single chip is developed in this dissertation. The entire design consists of two sections. The first section is a DC-DC switching regulator (boost regulator) as the frontend power supply; the second section is the constant current LED driver system. In the first section, a pulse width modulated (PWM) peak current mode boost regulator is utilized. The overall boost regulator system and its related sub-cells are explained. Among them, an original error amplifier design, a current sensing circuit and slope compensation circuit are presented. In the second section – the focus of this dissertation – a highly accurate constant current LED driver system design is unveiled. The detailed description of this highly accurate LED driver system and its related sub-cells are presented. A hybrid PWM and linear current modulation scheme to adjust the LED driver output currents is explained. The novel design ideas to improve the LED current accuracy and channel-to-channel output current mismatch are also explained in detail. These ideas include a novel LED driver system architecture utilizing 1) a dynamic current mirror structure and 2) a closed loop structure to keep the feedback loop of the LED driver active all the time during both PWM on-duty and PWM off-duty periods. Inside the LED driver structure, the driving amplifier with a novel slew rate enhancement circuit to dramatically accelerate its response time is also presented. / Dissertation/Thesis / Doctoral Dissertation Electrical Engineering 2016

While high power buck-boost regulators have been extensively researched and developed in the academia and industry, low power counterparts have only recently gained momentum due to the advent of different battery powered and remote electronics. The application life-time of such applications, e.g., remote surveillance electronics can be extended tremendously by enabling energy autonomy. While battery powered electronics last long but they must be replenished once the battery is depleted either by replacing the battery or by retrieving the electronics and then recharging. Instead, energy harvesting from available ambient sources on the spot will enable these electronics continuous operation unboundedly, probably even beyond the lifetime of the electronics. Interestingly enough, recent advancements in micro-scale energy transducers compliment these demand [1-13]. Micro-transducers producing energy from different ambient sources have been reported. These transducers produce enough energy to support a wide range of operations of the remote electronics concurrently. These transducers along with an additional storage elements greatly increase the energy autonomy as well as guaranteed operation since harvested energy can then be stored for future use when harvestable energy is temporarily unavailable. Recently several buck-boost regulators with low power and low input operating voltage have been reported both from academia and industry [14-24]. Some of this work focuses on increasing efficiency in the mid-load range (10mA-100mA), while some other focuses on lowering input range. However, so far no one has reported a buck-boost regulator operating with sub-200nW bias power while harvesting energy from sub-500mV input range. This work focuses on the development of a low voltage low bias current buckboost regulator to attain these goals. In this work, complete design of a PFM mode buck-boost regulator has been discussed in details. Basic topology of the regulator and working principle of the implemented architecture along with the advantages of the specific topology over that of the others have been discussed in short to provide an uninterrupted flow of idea. Later, Transistor level design of the basic building blocks of the buck-boost regulator is discussed in details with different design features and how those are attained through transistor level implementation are discussed. Subsequently, the physical layout design technique and considerations are discussed to inform the reader about the importance of the layout process and to avoid pitfalls of design failure due to layout quality issues. Measurement results are presented with the fabricated IC. Different characterization profile of the IC have been discussed with measured data and capture oscilloscope waveforms. Load regulation, line regulation, efficiency, start-up from low voltage, regulation with line and load transient events are measured, presented and discussed. Different characteristics of the prototype are compared with prior arts and are presented in a comparison table. Die micrograph is also presented along with the different issue of the IC testing

KTH is funding a project whose goal is to send a satellite into space. This project is called MIST (Miniature Student Satellite) which is assembled by a team of students at KTH. On the satellite there are experiments that are invented by other teams, in two of those experiments a power supply is required. This thesis is a technical investigation on how to design the power supply to both of those experiments, which are called SiC and Piezo LEGS. Piezo LEGS will investigate how their nanosized motors will behave and function in a space environment. SiC will investigate how their silicone carbide transistors will be affected by the space environment. A team made of four other students was selected to produce SiC experiments and a PCB in which this work is included. A literature study was done to get a better understanding of how power supplies work and to know how to select a good power supply. When the power supplies were selected they were simulated to meet the requirements. The next step was to do a Printed Circuit Board(PCB) for the SiC experiment and Piezo LEGS to be able to test the power supplies functionality in the physical world. Both of the converters reached the required output and characteristics working on their respective PCB. More time is needed for long time testing and optimization on the PCB layouts. / MIST (Miniature Student Satellite) är ett av KTH subventionerat projekt vilket har som mål att skicka upp en satellit i rymden. Projektet kommer omfatta flera olika experiment. Piezo LEGS ska undersöka en motors funktionalitet i rymdmiljö. SiC ska undersöka hur Silicon carbide halvledare och transistorer påverkas av rymdmiljön. Båda experimenten kräver varsin strömförsörjning för att fungera. Detta projekt ska undersöka kraven på strömförsörjning samt testa prototypen av ett kretskort för densamma. Först genomfördes en förstudie av de två typer av regulatorer som vanligtvis används som strömförsörjning, den linjära regulatorn och switch-mode regulatorn för att förklara olika strömförsörjningsteknologier, samt ta reda på de olika miljökraven. Baserat på förstudiens resultat erhölls kunskap för hur tester ska tas fram för funktionalitet av regulatorerna så att de når kraven för MIST för att sedan kunna producera de båda regulatorerna. Målet är att resultatet av simuleringarna på strömförsörjningen ska stämma överens med utfallet av kretskorten som produceras. Mätningar genomfördes på prototyp kretskort som visade att simuleringarna var korrekta och gav strömförsörjningen rätt resultat på kretskorten. Några av funktionerna på regulatorerna hann ej testas på grund av tidsbrist och mycket framtida arbete kvarstår.