The master thesis deals with design of a switched DC power supply with output parameters of 30 V 60 A. The power supply uses the connection of two single switch forward converters with opposite phase. The topology was chosen based on a comparison of specific schematics in the first part. The body of the thesis is covered in chapter which deals with design and analysis of power circuits of the converter. The chapter describes detailed design of pulse transformers, dimensioning of semiconductors and cooling system of the converter. For lower power losses, the system of synchronous rectifying is chosen at the output of the circuit. The regulation of the output is based on cascade structure with a superior voltage and dependent current loop. Appropriate over current protection is provided by sensing the output current and using current transformers for primary current measure.

Wireless power transfer (WPT) is the key enabler for a myriad of applications, from low-power RFIDs, and wireless sensors, to wirelessly charged electric vehicles, and even massive power transmission from space solar cells. One of the major challenges in designing implantable biomedical devices is the size and lifetime of the battery. Thus, replacing the battery with a miniaturized wireless power receiver (WPRx) facilitates designing sustainable biomedical implants in smaller volumes for sentient medical applications. In the first part of this dissertation, we propose a miniaturized, fully integrated, wirelessly powered implantable sensor with on-chip antenna, designed and implemented in a standard 0.18μm CMOS process. As a batteryless device, it can be implanted once inside the body with no need for further invasive surgeries to replace batteries. The proposed single-chip solution is designed for intraocular pressure monitoring (IOPM), and can serve as a sustainable platform for implantable devices or IoT nodes. A custom setup is developed to test the chip in a saline solution with electrical properties similar to those of the aqueous humor of the eye. The proposed chip, in this eye-like setup, is wirelessly charged to 1V from a 5W transmitter 3cm away from the chip. In the second part, we propose a self-biased, differential rectifier with enhanced efficiency over an extended range of input power. A prototype is designed for the medical implant communication service (MICS) band at 433MHz. It demonstrates an efficiency improvement of more than 40% in the rectifier power conversion efficiency (PCE) and a dynamic range extension of more than 50% relative to the conventional cross-coupled rectifier. A sensitivity of -15.2dBm input power for 1V output voltage and a peak PCE of 65% are achieved for a 50k load. In the third part, we propose a wide-range, differential RF-to-DC power converter using an adaptive, self-biasing technique. The proposed architecture doubles the dynamic range of conventional rectifiers. Unlike the continuously self-biased rectifier proposed in the second part, this adaptive rectifier extends the dynamic range while maintaining both the high PCE peak and the sensitivity advantage of the conventional cross-coupled scheme, and can operates in the GHz range.

This thesis examines issues connected to safe uninterruptible power supplies. The term safe uninterruptible power supply is used for an aggregate of devices providing power for appliances that participate in safe rapid shutdown of a power plant in case power from a usual source fails. The thesis is divided into two parts – theoretical and practical. Theoretical part deals with possibilities and ways of realizing an aggregation of safe uninterruptible power supply. Various devices that can appear in the section of a safe uninterruptible power supply are listed and each device is characterized. Appliances that can be provided for by the sources of safe uninterruptible power supply are mentioned as well. These appliances are listed in accordance with ČSN standard nr. 381120. The theoretical part concludes with new trends in realization of safe uninterruptible power supplies. One of these sources is a clean source technology that can also be implemented in various ways. Practical part contains a suggestion of a safe uninterruptible power supply for particular steam power plant. This suggested safe uninterruptible power supply consists of rectifiers, batteries, inverters and a dieselgenerator. Calculated parameters of each device at the conclusion of the practical part are followed by a diagram of the suggested section of safe uninterruptible power supply.

This master’s thesis is about replace voltage feedback operation amplifiers (VFOA) by current operational amplifiers (COA), current conveyors and current followers (CF). In introduction are mentioned word or two about operational amplifiers and their basic circuit such as invert and non-invert amplifier and there are described formulas for calculation gain. In another chapter is described COA, his properties and advantages compared to VFOA. Next there are described basic circuits of current conveyors. Follows chapter where is described replace VFOA by COA and conversion between them. In another part is at first deal with models of COA and CF in simulating program and then replace VFOA by COA. There are some simple circuits for example precision rectifiers and function generators and their simulations before and after replace VFOA by COA. In full-wave rectifier with current conveyors is made detailed simulation with some input voltages and frequencies. In last chapter is detailed described multi-mode rectifier with current follower. There is table witch described all modes of rectifier. For example voltage mode, current mode and mixed mode with half- or full-wave rectifier. There are simulations for all modes. Primarily are made detailed simulations voltage and current mode. In another part of this chapter is made measurement voltage and current mode. There are measured functions as half- and full-wave rectifier. There are described parameters of rectifier from measured values. In the end are these values compared with values from simulations.

The first part of this work describes the design and implementation of switch-mode power supply for control circuits for 12/2x24V 4.5A fuel cells. The introduction picks the issue of power sources in electromobiles and final design and implementation of switching power suply. The next part deals with the issues of fast-charger and generators for power transistors. It describes the structure of DC converter and control and protectin circuits of quick-charger. In the end this work describes selected driver circuits and charge tests on fast-charger as evidenced by measurements.

The thesis deals with definitions of new current- or mixed-mode circuit elements and their implementations and applications. Based on the analysis of the state-of-the-art, novel application circuits employing the above circuit elements are designed. For the purpose of the experimental verification, the active elements are implemented via commercial integrated circuits, and their applications are simulated via PSpice. The application circuits are focused on frequency filters, rectifiers, oscillators, and current-copy circuits. Selected applications are analyzed with respect on real influences, and measurements on circuit prototypes are also performed.

Diploma thesis deals with problems of power factor correction and total harmonic distortion of line current in three phase industrial power supplies. It focuses mainly on using of single phase active PFC topologies based on the principle of step up converter, which are applicable to three phase systems. Verification of operation and comparison of parameters of several circuits was done by simulation in program Matlab Simulink. Then for selected circuit of active PFC was done complete design. The result is a prototype of single phase active PFC circuit with an output power 2 kW for input voltage range from 180 to 528 V (47 – 63 Hz) and a prototype of three phase active PFC circuit with an output power 6 kW for input voltage range from 3 x 180 to 3 x 528 V (47 – 63 Hz).

abstract: As the world becomes more electronic, power electronics designers have continuously designed more efficient converters. However, with the rising number of nonlinear loads (i.e. electronics) attached to the grid, power quality concerns, and emerging legislation, converters that intake alternating current (AC) and output direct current (DC) known as rectifiers are increasingly implementing power factor correction (PFC) by controlling the input current. For a properly designed PFC-stage inductor, the major design goals include exceeding minimum inductance, remaining below the saturation flux density, high power density, and high efficiency. In meeting these goals, loss calculation is critical in evaluating designs. This input current from PFC circuitry leads to a DC bias through the filter inductor that makes accurate core loss estimation exceedingly difficult as most modern loss estimation techniques neglect the effects of a DC bias. This thesis explores prior loss estimation and design methods, investigates finite element analysis (FEA) design tools, and builds a magnetics test bed setup to empirically determine a magnetic core’s loss under any electrical excitation. In the end, the magnetics test bed hardware results are compared and future work needed to improve the test bed is outlined. / Dissertation/Thesis / Masters Thesis Electrical Engineering 2019

Internet of Things (IoT) is a new emerging paradigm which requires billions of wirelessly connected devices that communicate with each other in a complex radio-frequency (RF) environment. Considering the huge number of devices, recharging batteries or replacing them becomes impractical in real life. Therefore, harvesting ambient RF energy for powering IoT devices can be a practical solution to achieve self-charging operation. The antenna for the RF energy harvesting application must work on multiple frequency bands (multiband or wideband) to capture as much power as possible from ambient; it should be compact and small in size so that it can be integrated with IoT devices; and it should be low cost, considering the huge number of devices. This thesis presents a fully printed 3D cube Cantor fractal RF energy harvesting unit, which meets the above-mentioned criteria. The multiband Cantor fractal antenna has been designed and implemented on a package of rectifying circuits using additive manufacturing (combination of 3D inkjet printing of plastic substrate and 2D metallic screen printing of silver paste) for the first time for RF energy harvesting application. The antenna, which is in a Cantor fractal shape, is folded on five faces of a 3D cube where the bottom face accommodates rectifying circuit with matching network. The rectenna (rectifying antenna) harvests RF power from GSM900, GSM1800, and 3G at 2100 MHz frequency. Indoor and outdoor field tests of the RF energy harvester have been conducted in the IMPACT lab and the King Abdullah University of Science and Technology (KAUST) campus territory, and 252.4 mV of maximum output voltage is harvested.

The next technological revolution, Industry 4.0, is envisioned as a digitally connected ecosystem where machines and gadgets are driven by artificial intelligence. By 2025, more than 75 billion devices are projected to serve this revolution. Many of which are to be integrated into the fabrics of everyday life in the form of smart wireless sensors. Still, two major challenges should be addressed to realize truly wireless and wearable sensors. First, the sensors should be flexible and stretchable, allowing for comfortable wearing. Second, the electronics should scavenge the energy it requires entirely from the environment, thus, eliminating the need for batteries, which are bulky, create ecological problems, etc. By addressing these two challenges, this dissertation paves the way for truly wearable sensors. The first part of the dissertation introduces a biocompatible magnetic skin with exceptional physical properties. It is highly-flexible, breathable, durable, and realizable in any desired shape and color. Attached to the skin of a user, the magnetic skin itself does not require any wiring, allowing to place the electronics and delicate components of the wireless sensor in a convenient nearby location to track the magnetic field produced by the magnetic skin. To demonstrate the performance of the magnetic skin, wearable systems are implemented as an assistive technology for severe quadriplegics, a touchless control solution for eliminating cross contaminations, and for monitoring blinking and eye movement for sleep laboratories. The second part of the dissertation is about wirelessly powering wireless sensors. In doing so, radio frequency (RF) rectifiers are a bottleneck, especially for ambient RF energy harvesting. Therefore, two RF rectifiers are introduced in standard CMOS technologies. The first architecture utilizes double-sided diodes to reduce the reverse leakage current, thus achieving a high dynamic range of 6.7 dB, -19.2 dBm sensitivity, and 86% efficiency. The second rectifier implements a dual-mode technique to lower the effective threshold voltage by 37%. Consequently, it achieves a 38% efficiency at −35 dBm input power and a 10.1 dB dynamic range while maintaining the same efficiency and sensitivity. Ultimately, combining these wireless powering techniques with the magnetic skin allows for truly wireless and wearable solutions.