Smanjenje gubitaka istitravanja kod neizravnog istosmjernog pretvarača s transformatorom uporabom RC-RCD prigušnog člana

Flyback converter is one of the most popular DC-DC converters for low power supply. Due to the transformer leakage inductance the converter suffers from the voltage spikes, which can be »controlled« by the dissipative RCD or non-dissipative LCD clamp circuits. Both of the clamp circuits consist of the diode. The diode reverse recovery charge causes the oscillation, which results in additional dissipation of the clamp circuitry. This paper describes this ringing phenomenon and the use of an RC-RCD clamp circuit for damping the clamp-diode\u27s oscillation. This clamp circuit is capable for improving a flyback converter\u27s power ratio.Neizravni istosmjerni pretvarač s transformatorom jedan je od najpopularnijih istosmjernih pretvarača za izvore napajanja malih snaga. Zbog rasipnog induktiviteta transformatora tijekom rada pretvarača dolazi do pojave prenapona, koji se mogu ograničiti pomoću disipativnih RCD ili nedisipativnih LCD prigušnih sklopova. Oba prigušna sklopa sadrže diodu. Reverzni naboj oporavljanja diode uzrokuje oscilacije koje uzrokuju dodatne gubitke u prigušnom sklopu. Članak opisuje pojavu istitravanja i uporabu RC-RCD prigušnog sklopa za prigušenje oscilacija uzrokovanih prigušnom diodom. Opisani prigušni sklop omogućava povećanje djelotvornosti neizravnog istosmjernog pretvarača s transformatorom

Smanjenje gubitaka istitravanja kod neizravnog istosmjernog pretvarača s transformatorom uporabom RC-RCD prigušnog člana

Flyback converter is one of the most popular DC-DC converters for low power supply. Due to the transformer leakage inductance the converter suffers from the voltage spikes, which can be »controlled« by the dissipative RCD or non-dissipative LCD clamp circuits. Both of the clamp circuits consist of the diode. The diode reverse recovery charge causes the oscillation, which results in additional dissipation of the clamp circuitry. This paper describes this ringing phenomenon and the use of an RC-RCD clamp circuit for damping the clamp-diode\u27s oscillation. This clamp circuit is capable for improving a flyback converter\u27s power ratio.Neizravni istosmjerni pretvarač s transformatorom jedan je od najpopularnijih istosmjernih pretvarača za izvore napajanja malih snaga. Zbog rasipnog induktiviteta transformatora tijekom rada pretvarača dolazi do pojave prenapona, koji se mogu ograničiti pomoću disipativnih RCD ili nedisipativnih LCD prigušnih sklopova. Oba prigušna sklopa sadrže diodu. Reverzni naboj oporavljanja diode uzrokuje oscilacije koje uzrokuju dodatne gubitke u prigušnom sklopu. Članak opisuje pojavu istitravanja i uporabu RC-RCD prigušnog sklopa za prigušenje oscilacija uzrokovanih prigušnom diodom. Opisani prigušni sklop omogućava povećanje djelotvornosti neizravnog istosmjernog pretvarača s transformatorom

Large step down voltage converters for desalination

One percent of the world's drinking water is currently desalinated, and this will have to increase to 14% by 2025. Desalination is energy intensive, having significant commercial and ecological implications. One of the most promising methods of desalination is capacitive deionisation which only uses 1kWh/m3 but requires a voltage of less than 1.8V at currents of up to 1000A This thesis produced hardware capable of creating 550A at a voltage of 1.8V, giving over a 1kW power rating, with an input voltage of 340V dc. The converter designed was a bidirectional asymmetrical half-bridge flyback converter allowing for isolation at these high step down ratios. The converter was used to charge a bank of 17,000F supercapacitors from 0V to 1.8V, with an initial charging step down ratio in excess of 340:1 falling to 190:1 as the load charged. A novel Asymmetrical Half-Bridge Coupled-Inductor Buck converter is presented as the ideal solution for large step-down ratios with analysis comparing the ability to efficiently step down a voltage with other common converters, the buck and flyback converters. A comparison between a single-ended coupled-inductor buck converter employing a buck-boost voltage clamp and the novel asymmetrical half-bridge coupled-inductor buck converter circuit shows that the asymmetrical half-bridge converter is a more efficient circuit as leakage energy is recovered; the switch voltages are clamped to within the dc voltage rating of the bridge and the control strategy is simple. Passive and active snubbers are reviewed for efficiency, switch ratings and management of the effects of leakage inductance and compared against the novel designs presented. In the desalination application isolation is required so the flyback circuit is used. An isolated three switch bidirectional converter is constructed using silicon carbide MOSFETs and diodes switching at 40kHz. The converter uses novel current measuring techniques, an on-board microprocessor and closed loop control designed into the final DC-DC converter.One percent of the world's drinking water is currently desalinated, and this will have to increase to 14% by 2025. Desalination is energy intensive, having significant commercial and ecological implications. One of the most promising methods of desalination is capacitive deionisation which only uses 1kWh/m3 but requires a voltage of less than 1.8V at currents of up to 1000A This thesis produced hardware capable of creating 550A at a voltage of 1.8V, giving over a 1kW power rating, with an input voltage of 340V dc. The converter designed was a bidirectional asymmetrical half-bridge flyback converter allowing for isolation at these high step down ratios. The converter was used to charge a bank of 17,000F supercapacitors from 0V to 1.8V, with an initial charging step down ratio in excess of 340:1 falling to 190:1 as the load charged. A novel Asymmetrical Half-Bridge Coupled-Inductor Buck converter is presented as the ideal solution for large step-down ratios with analysis comparing the ability to efficiently step down a voltage with other common converters, the buck and flyback converters. A comparison between a single-ended coupled-inductor buck converter employing a buck-boost voltage clamp and the novel asymmetrical half-bridge coupled-inductor buck converter circuit shows that the asymmetrical half-bridge converter is a more efficient circuit as leakage energy is recovered; the switch voltages are clamped to within the dc voltage rating of the bridge and the control strategy is simple. Passive and active snubbers are reviewed for efficiency, switch ratings and management of the effects of leakage inductance and compared against the novel designs presented. In the desalination application isolation is required so the flyback circuit is used. An isolated three switch bidirectional converter is constructed using silicon carbide MOSFETs and diodes switching at 40kHz. The converter uses novel current measuring techniques, an on-board microprocessor and closed loop control designed into the final DC-DC converter

A Comparison between Different Snubbers for Flyback Converters

The DC-DC flyback power converter is widely used in low power commercial and industrial applications ( \u3e 150 W) such as in computers, telecom, consumer electronics because it is one of the simplest and least expensive converter topologies with transformer isolation. Its main power circuit consists of just a semiconductor device like a MOSFET operating as a switch, a transformer, an output diode and an output filter capacitor. The converter switch, however, is susceptible to high voltage spikes due to the interaction between its output capacitance and the leakage inductance of the transformer. These spikes can exceed the ratings of the switch, thus destroying the device, and thus flyback converters are always implemented with some sort of snubber circuit that can clamp any voltage spikes that may appear across their switch. There are two types of snubbers: passive snubbers that consist of passive electrical components such as capacitors, inductors and diodes and active snubbers, that consist of passive components and an active semiconductor switch. It is generally believed that passive snubbers are less expensive but also less efficient than active snubbers, but this belief has been placed in doubt with recent advances in passive snubber technology. Flyback converter with regenerative passive snubbers that dissipate little energy have been recently proposed and have greater efficiency than traditional passive snubbers. Although the efficiency of passive snubbers has improved, no comparison has been made between these new passive snubbers and active snubbers as it is still assumed that active snubbers are always more efficient. The main focus of this thesis is to compare the performance of an example passive snubber and an example active snubber. These example snubber circuits have been selected as being among the best of their type. In this thesis, the steady-state operation of each snubber circuit is explained in detail and analyzed, the results of the analysis is used to create a procedure for the design of key components, and the procedure is demonstrated with a design example. The results of the design examples were used to build prototypes of flyback converters with each example snubber and the prototypes were used to obtain experimental results. Based on these experimental results, conclusions about the efficiency of flyback converters with passive regenerative and active snubbers operating under various input line and output load conditions are made in this thesi

Single Stage PFC Flyback AC-DC Converter Design

This paper discusses a 100 W single stage Power Factor Correction (PFC) flyback converter operating in boundary mode constant ON time methodology using a synchronous MOS-FET rectifier on the secondary side to achieve higher efficiency. Unlike conventional designs which use two stage approach such as PFC plus a LLC resonant stage or a two stage PFC plus flyback, the proposed design integrates the PFC and constant voltage regulation in a single stage without compromising the efficiency of the converter. The proposed design is advantageous as it has a lower component count. A design of 100 W flyback operating from universal input AC line voltage is demonstrated in this paper. The experimental results show that the power factor (PF) is greater than 0.92 and total harmonic distortion (iTHD) is less than 20% for a load varying from 25 % to 100 %. The experimental results show the advantages of a single stage design.Comment: Published in: 2020 IEEE International Conference on Electronics, Computing and Communication Technologies (CONECCT

Hybrid monolithic integration of high-power DC-DC converters in a high-voltage technology

The supply of electrical energy to home, commercial, and industrial users has become ubiquitous, and it is hard to imagine a world without the facilities provided by electrical energy. Despite the ever increasing efficiency of nearly every electrical application, the worldwide demand for electrical power continues to increase, since the number of users and applications more than compensates for these technological improvements. In order to maintain the affordability and feasibility of the total production, it is essential for the distribution of the produced electrical energy to be as efficient as possible. In other words the loss in the power distribution is to be minimized. By transporting electrical energy at the maximum safe voltage, the current in the conductors, and the associated conduction loss can remain as low as possible. In order to optimize the total efficiency, the high transportation voltage needs to be converted to the appropriate lower voltage as close as possible to the end user. Obviously, this conversion also needs to be as efficient, affordable, and compact as possible. Because of the ever increasing integration of electronic systems, where more and more functionality is combined in monolithically integrated circuits, the cost, the power consumption, and the size of these electronic systems can be greatly reduced. This thorough integration is not limited to the electronic systems that are the end users of the electrical energy, but can also be applied to the power conversion itself. In most modern applications, the voltage conversion is implemented as a switching DC-DC converter, in which electrical energy is temporarily stored in reactive elements, i.e. inductors or capacitors. High switching speeds are used to allow for a compact and efficient implementation. For low power levels, typically below 1 Watt, it is possible to monolithically implement the voltage conversion on an integrated circuit. In some cases, this is even done on the same integrated circuit that is the end user of the electrical energy to minimize the system dimensions. For higher power levels, it is no longer feasible to achieve the desired efficiency with monolithically integrated components, and some external components prove indispensable. Usually, the reactive components are the main limiting factor, and are the first components to be moved away from the integrated circuit for increasing power levels. The semiconductor components, including the power transistors, remain part of the integrated circuit. Using this hybrid approach, it is possible in modern converterapplications to process around 60 Watt, albeit limited to voltages of a few Volt. For hybrid integrated converters with an output voltage of tens of Volt, the power is limited to approximately 10 Watt. For even higher power levels, the integrated power transistors also become a limiting factor, and are replaced with discrete power devices. In these discrete converters, greatly increased power levels become possible, although the system size rapidly increases. In this work, the limits of the hybrid approach are explored when using so-called smart-power technologies. Smart-power technologies are standard lowcost submicron CMOS technologies that are complemented with a number of integrated high-voltage devices. By using an appropriate combination of smart-power technologies and circuit topologies, it is possible to improve on the current state-of-the-art converters, by optimizing the size, the cost, and the efficiency. To determine the limits of smart-power DC-DC converters, we first discuss the major contributing factors for an efficient energy distribution, and take a look at the role of voltage conversion in the energy distribution. Considering the limitations of the technologies and the potential application areas, we define two test-cases in the telecommunications sector for which we want to optimize the hybrid monolithic integration in a smart-power technology. Subsequently, we explore the specifications of an ideal converter, and the relevant properties of the affordable smart-power technologies for the implementation of DC-DC converters. Taking into account the limitations of these technologies, we define a cost function that allows to systematically evaluate the different potential converter topologies, without having to perform a full design cycle for each topology. From this cost function, we notice that the de facto default topology selection in discrete converters, which is typically based on output power, is not optimal for converters with integrated power transistors. Based on the cost function and the boundary conditions of our test-cases, we determine the optimal topology for a smart-power implementation of these applications. Then, we take another step towards the real world and evaluate the influence of parasitic elements in a smart-power implementation of switching converters. It is noticed that the voltage overshoot caused by the transformer secondary side leakage inductance is a major roadblock for an efficient implementation. Since the usual approach to this voltage overshoot in discrete converters is not applicable in smart-power converters due to technological limitations, an alternative approach is shown and implemented. The energy from the voltage overshoot is absorbed and transferred to the output of the converter. This allows for a significant reduction in the voltage overshoot, while maintaining a high efficiency, leading to an efficient, compact, and low-cost implementation. The effectiveness of this approach was tested and demonstrated in both a version using a commercially available integrated circuit, and our own implementation in a smart-power integrated circuit. Finally, we also take a look at the optimization of switching converters over the load range by exploiting the capabilities of highly integrated converters. Although the maximum output power remains one of the defining characteristics of converters, it has been shown that most converters spend a majority of their lifetime delivering significantly lower output power. Therefore, it is also desirable to optimize the efficiency of the converter at reduced output current and output power. By splitting the power transistors in multiple independent segments, which are turned on or off in function of the current, the efficiency at low currents can be significantly improved, without introducing undesirable frequency components in the output voltage, and without harming the efficiency at higher currents. These properties allow a near universal application of the optimization technique in hybrid monolithic DC-DC converter applications, without significant impact on the complexity and the cost of the system. This approach for the optimization of switching converters over the load range was demonstrated using a boost converter with discrete power transistors. The demonstration of our smart-power implementation was limited to simulations due to an issue with a digital control block. On a finishing note, we formulate the general conclusions and provide an outlook on potential future work based on this research

SOLAR POWERED THREE PHASE MOTOR FOR VARIOUS APPLICATIONS

The Power electronics plays a vital role in the conversion and control of the electrical power for various applications such as heating & lightning control, electrochemical processes, DC & AC electrical machine drives, electrical welding, active power line filtering, static var compensator and many more.The main aim of the paper is to analyze and design of a current fed push pull DC-DC boost converter to integrate three phase electric motor through inverter. The regulated output which is obtained by the developed converter is fed to a typical load side inverter, and then to the various loads. To analyze the CFPP DC-DC converter in different operating cycles. The hardware circuit will be designed to test for the required output.Among the existing DC/DC converters, current-fed push-pull (CFPP) converter is a better option owing to its voltage boosting, isolation and compact characteristics

Interleaved coupled-inductor boost converter with multiplier cell and passive lossless clamp

As photovoltaic panels become a more dominant technology used to produce electrical power, more efficient and efficacious solutions are needed to convert this electrical power to a useable form. Solar microconverters, which are used to convert a single panel\u27s power, effectively overcome issues such as shading and panel-specific maximum power point tracking associated with traditional solar converters which use several panels in series. This thesis discusses a high gain DC-DC converter for incorporating single low-voltage solar panels to a distribution level voltage present in a DC microgrid. To do this, a converter was developed using coupled inductors and a capacitor-diode multiplying cell which is capable of high-gain power transmissions and continuous input current. This approach improves the efficiency of the system compared to cascaded converters typically used in this application. Challenges with this converter are discussed, a passive lossless clamp is introduced, and simulation results are presented. This converter has additional applications where high gain DC-DC conversion is required, including fuel cells and energy storage systems such as batteries and ultracapacitors --Abstract, page iii

Battery charging system incorporating an equalisation circuit for electric vehicles

Ph.D. ThesisHybrid electric vehicles (HEVs) and electric vehicles (EVs) are gaining in popularity mainly due to the fact that unlike combustion-powered vehicles, they do not pollute with greenhouse gases and toxic particles. Most HEVs and EVs are powered by lithium-ion battery packs which have high power density and longer cycle lives compared to other battery types. Each pack is made out of many battery cells in series connected and due to manufacturing tolerances and chemical processes in individual cells each cell has its own electric characteristics. In order to achieve a balanced voltage across all cells, a battery management system (BMS) must be employed to actively monitor and balance the cells voltage. On-board battery chargers are installed in HEVs/EVs to charge the lithium-ion battery pack from the grid. This charger converts AC grid voltage into a controllable DC output voltage, but it adds weight to the vehicle, reducing the overall efficiency of an HEV/EV and also increasing its cost. The aim of researches in multi-functional power electronics is to design systems which perform several different functions at the same time. These systems promise cost and weight reductions since only one circuit is used to conduct different functions. An example is the electric drive in an HEV/EV. On one hand, it propels the car forward when driving, while on the other hand the battery can be charged via a modified electric motor and inverter topology. Thus, no additional on-board charger is required. This thesis describes a new multi-functional circuit for HEVs/EVs which combines the functions of voltage equalisation with grid charging. Compared to a drive system, the proposed circuit does not rely on an electric motor to charge the battery. Various battery chargers and equalisation circuits are first compared. Then, the design of the proposed circuit is described and simulation results are presented for charging and voltage balancing. An experimental test rig was built and practical results have been captured and compared with simulation results for validation. The advantages and disadvantages of the proposed circuit are discussed at the end of the thesis. Keywords- Multi-functional system, Battery charging, Voltage equalisation, Lithium-ion batter