다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

DC–DC converters with voltage boost capability are widely used in a large number of power conversion applications, from fraction-of-volt to tens of thousands of volts at power levels from milliwatts to megawatts. The literature has reported on various voltage-boosting techniques, in which fundamental energy storing elements (inductors and capacitors) and/or transformers in conjunction with switch(es) and diode(s) are utilized in the circuit. These techniques include switched capacitor (charge pump), voltage multiplier, switched inductor/voltage lift, magnetic coupling, and multistage/-level, and each has its own merits and demerits depending on application, in terms of cost, complexity, power density, reliability, and efficiency. To meet the growing demand for such applications, new power converter topologies that use the above voltage-boosting techniques, as well as some active and passive components, are continuously being proposed. The permutations and combinations of the various voltage-boosting techniques with additional components in a circuit allow for numerous new topologies and configurations, which are often confusing and difficult to follow. Therefore, to present a clear picture on the general law and framework of the development of next-generation step-up dc–dc converters, this paper aims to comprehensively review and classify various step-up dc–dc converters based on their characteristics and voltage-boosting techniques. In addition, the advantages and disadvantages of these voltage-boosting techniques and associated converters are discussed in detail. Finally, broad applications of dc–dc converters are presented and summarized with comparative study of different voltage-boosting techniques.

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Step-Up DC–DC Converters: A Comprehensive Review of Voltage-Boosting Techniques, Topologies, and Applications

The authors discuss high-voltage power conversion. Conventional series connection and three-level voltage source inverter techniques are reviewed and compared. A novel versatile multilevel commutation cell is introduced: it is shown that this topology is safer and more simple to control, and delivers purer output waveforms. The authors show how this technique can be applied to either choppers or voltage-source inverters and generalized to any number of switches.<<ETX>>

Multi-level conversion : high voltage choppers and voltage-source inverters

J. Y. Tsao,* S. Chowdhury, M. A. Hollis,* D. Jena, N. M. Johnson, K. A. Jones, R. J. Kaplar,* S. Rajan, C. G. Van de Walle, E. Bellotti, C. L. Chua, R. Collazo, M. E. Coltrin, J. A. Cooper, K. R. Evans, S. Graham, T. A. Grotjohn, E. R. Heller, M. Higashiwaki, M. S. Islam, P. W. Juodawlkis, M. A. Khan, A. D. Koehler, J. H. Leach, U. K. Mishra, R. J. Nemanich, R. C. N. Pilawa-Podgurski, J. B. Shealy, Z. Sitar, M. J. Tadjer, A. F. Witulski, M. Wraback, and J. A. Simmons

/pdf/ultrawide-bandgap-semiconductors-research-opportunities-and-49ev1zu2ym.pdf

Ultrawide-Bandgap Semiconductors: Research Opportunities and Challenges

The most common approaches to generating power from sunlight are either photovoltaic, in which sunlight directly excites electron-hole pairs in a semiconductor, or solar-thermal, in which sunlight drives a mechanical heat engine. Photovoltaic power generation is intermittent and typically only exploits a portion of the solar spectrum efficiently, whereas the intrinsic irreversibilities of small heat engines make the solar-thermal approach best suited for utility-scale power plants. There is, therefore, an increasing need for hybrid technologies for solar power generation. By converting sunlight into thermal emission tuned to energies directly above the photovoltaic bandgap using a hot absorber-emitter, solar thermophotovoltaics promise to leverage the benefits of both approaches: high efficiency, by harnessing the entire solar spectrum; scalability and compactness, because of their solid-state nature; and dispatchablility, owing to the ability to store energy using thermal or chemical means. However, efficient collection of sunlight in the absorber and spectral control in the emitter are particularly challenging at high operating temperatures. This drawback has limited previous experimental demonstrations of this approach to conversion efficiencies around or below 1% (refs 9, 10, 11). Here, we report on a full solar thermophotovoltaic device, which, thanks to the nanophotonic properties of the absorber-emitter surface, reaches experimental efficiencies of 3.2%. The device integrates a multiwalled carbon nanotube absorber and a one-dimensional Si/SiO2 photonic-crystal emitter on the same substrate, with the absorber-emitter areas optimized to tune the energy balance of the device. Our device is planar and compact and could become a viable option for high-performance solar thermophotovoltaic energy conversion.

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A nanophotonic solar thermophotovoltaic device

In pre-existing analytical models of switched-capacitor (SC) converters, input and output capacitances (C in and C out ) have long been neglected based on the assumption of input and output as ideal voltage sources. However, this paper reveals that, in practical applications, the terminal capacitances are usually not sufficiently large to ensure ideal input and output behavior and can have considerable effects on output impedance R out and overall efficiency. To quantitatively investigate their effects, this paper proposes a general modeling and analysis methodology for SC converters that is capable of considering the effects of finite C in and C out . The proposed model is verified by experimental measurements from a 2-to-1 SC converter prototype with less than 8% relative error. It is revealed that the insufficiency of C in can lead to a considerable increase in R out and thus harms overall efficiency. On the contrary, smaller C out can help reduce R out , although this benefit comes at the cost of larger output voltage ripple. In addition, C out has stronger effects on R out in the slow switching region, while C in is more influential at higher switching frequency, especially around the knee of the R out curve at which the converter usually operates. Several design guidelines are provided based on these findings.

Modeling and Analysis of Switched-Capacitor Converters with Finite Terminal Capacitances

Interconnect Focus Center (United States. Defense Advanced Research Projects Agency and Semiconductor Research Corporation)

Integrated CMOS Energy Harvesting Converter with Digital Maximum Power Point Tracking for a Portable Thermophotovoltaic Power Generator

A modular quad gate-driver and controller chip for use with cascaded 2:1 switched-capacitor (SC) resonant dc-dc converters is presented. The solution integrates the controller, level-shifters, active bootstrap and gate-drivers along with start-up and shutdown assist peripherals for standalone operation of a hybrid SC cell with four power switches. Significant size reduction of auxiliary components is demonstrated, yielding improved efficiency and power density. The modularity of the approach is demonstrated with a three-stage resonant converter prototype with 8:1 conversion ratio from 48V DC bus to 6V DC intermediate bus, with peak efficiency of 97.8% and 30A load capability. The quad gate-driver is integrated in a 180nm BCD process with external bootstrap capacitors.

Quad Gate-Driver Controller with Start-Up and Shutdown for Cascaded Resonant Switched-Capacitor Converter

In recent decades the flying capacitor multilevel (FCML) converter has been demonstrated to be a highly com-pact and efficient substitute for conventional switched inductive topologies. However, the fundamental dynamical behavior of the additional flying capacitor voltages has still not been well charac-terized to a predictable level for even the simplest phase-shifted PWM modulation strategies. This work presents a computation-ally efficient analytical model and methodology for describing the fully generalized buck FCML topology with a state-space dynamical representation. The model is successfully validated against a high-performance five-level hardware prototype.

Fundamental State-Space Modeling Methodology for the Flying Capacitor Multilevel Converter

This paper explores performance limits of differential power processing (DPP) for large-scale modular dc energy systems with stochastic loads. An analytical stochastic model is developed to estimate the average power loss of a DPP topology under probabilistic load distributions. A scaling factor $\mathcal{S}$ (•) is introduced to describe how power loss scales as the system size or load power variance increases. The average power losses of several example DPP topologies are analyzed and compared against conventional dc-dc converters given the same total switch die area and magnetic volume. The performance limits for various DPP topologies are derived and verified by Monte-Carlo simulations in SPICE, and the results indicate that the ac-coupled DPP converter stands out from all the representative DPP topologies discussed here in terms of the lowest power loss. The paper provides an analytical framework to evaluate the performance of different DPP topologies in a methodical way, offering insights for the design of DPP systems with large-scale stochastic loads.

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Robert C. N. Pilawa-Podgurski

Papers

Modeling and Analysis of Switched-Capacitor Converters with Finite Terminal Capacitances

Integrated CMOS Energy Harvesting Converter with Digital Maximum Power Point Tracking for a Portable Thermophotovoltaic Power Generator

Quad Gate-Driver Controller with Start-Up and Shutdown for Cascaded Resonant Switched-Capacitor Converter

Fundamental State-Space Modeling Methodology for the Flying Capacitor Multilevel Converter

Performance Limits of Differential Power Processing