Showing papers on "Capacitor published in 2010"
TL;DR: This work demonstrates microsupercapacitors with powers per volume that are comparable to electrolytic capacitors, capacitances that are four orders of magnitude higher, and energies per volume higher than conventional supercapacitor.
Abstract: Electrochemical capacitors, also called supercapacitors, store energy in two closely spaced layers with opposing charges, and are used to power hybrid electric vehicles, portable electronic equipment and other devices¹. By offering fast charging and discharging rates, and the ability to sustain millions of ²⁻⁵, electrochemical capacitors bridge the gap between batteries, which offer high energy densities but are slow, and conventional electrolytic capacitors, which are fast but have low energy densities. Here, we demonstrate microsupercapacitors with powers per volume that are comparable to electrolytic capacitors, capacitances that are four orders of magnitude higher, and energies per volume that are an order of magnitude higher. We also measured discharge rates of up to 200 V s⁻¹, which is three orders of magnitude higher than conventional supercapacitors. The microsupercapacitors are produced by the electrophoretic deposition of a several micrometre-thick layer of nanostructured carbon onions⁶‚⁷ with diameters of 6-7 nm. Integration of these nanoparticles in a microdevice with a high surface-to-volume ratio, without the use of organic binders and polymer separators, improves performance because of the ease with which ions can access the active material. Increasing the energy density and discharge rates of supercapacitors will enable them to compete with batteries and conventional electrolytic capacitors in a number of applications.
2,469 citations
TL;DR: In this paper, the carbon materials used for electrochemical capacitors were reviewed and discussed the contribution of the surfaces owing to micropores and other larger pores to the capacitance and rate performance of the electric double-layer capacitors.
1,249 citations
TL;DR: Graphene nanosheets have a preponderance of exposed edge planes that greatly increases charge storage as compared with that of designs that rely on basal plane surfaces, and capacitors constructed with these electrodes could be smaller than the low-voltage aluminum electrolyte capacitors that are typically used in electronic devices.
Abstract: Electric double-layer capacitors (DLCs) can have high storage capacity, but their porous electrodes cause them to perform like resistors in filter circuits that remove ripple from rectified direct current. We have demonstrated efficient filtering of 120-hertz current with DLCs with electrodes made from vertically oriented graphene nanosheets grown directly on metal current collectors. This design minimized electronic and ionic resistances and produced capacitors with RC time constants of less than 200 microseconds, in contrast with ~1 second for typical DLCs. Graphene nanosheets have a preponderance of exposed edge planes that greatly increases charge storage as compared with that of designs that rely on basal plane surfaces. Capacitors constructed with these electrodes could be smaller than the low-voltage aluminum electrolyte capacitors that are typically used in electronic devices.
1,233 citations
TL;DR: It is argued that a large, collaborative international research programme is necessary to fully develop the potential of electrochemical capacitors.
Abstract: Electrochemical capacitors, also known as supercapacitors, are becoming increasingly important components in energy storage, although their widespread use has not been attained due to a high cost/performance ratio. Fundamental research is contributing to lowered costs through the engineering of new materials. Currently the most viable materials used in electrochemical capacitors are biomass-derived and polymer-derived activated carbons, although other carbon materials are useful research tools. Metal oxides could result in a step change for electrochemical capacitor technology and is an exciting area of research. The selection of an appropriate electrolyte and electrode structure is fundamental in determining device performance. Although there are still many uncertainties in understanding the underlying mechanisms involved in electrochemical capacitors, genuine progress continues to be made. It is argued that a large, collaborative international research programme is necessary to fully develop the potential of electrochemical capacitors.
985 citations
TL;DR: In this article, the active damping approaches for PI-based current control of grid-connected PWM converters with LCL filters are analyzed and compared in the continuous Laplace domain.
Abstract: This paper deals with various active damping approaches for PI-based current control of grid-connected pulsewidth-modulation (PWM) converters with LCL filters, which are based on one additional feedback. Filter capacitor current, as well as voltage feedback for the purpose of resonance damping, are analyzed and compared. Basic studies in the continuous Laplace domain show that either proportional current feedback or derivative voltage feedback yields resonance damping. Detailed investigations of these two approaches in the discrete z-domain, taking into account the discrete nature of control implementation, sampling, and PWM, are carried out. Several ratios of LCL resonance frequency and control frequency are considered. At high resonance frequencies, only current feedback stabilizes the system. At medium resonance frequencies, both approaches have good performance. At low resonance frequencies, stability gets worse, even though voltage feedback offers slightly better damping properties. Measurements validate the theoretical results.
499 citations
01 Nov 2010
TL;DR: In this article, an operating mode for low phase current frequencies which enables MMLCs to magnetize and start induction machines with quadratic torque loads is presented and the achievable torque-speed characteristic is derived.
Abstract: Modular Multilevel Converters (MMLC) based on series connected half-bridges achieve high phase voltages, need little or no filters and feature redundancy and modularity. In contrast to the similar series connected H-bridge converters an expensive and lossy transformer is not necessary. The capacitors buffer power fluctuations at fundamental and second harmonic frequency, therefore the capacitor voltage ripple magnitude increases with decreasing phase current frequencies and will become infinite at zero phase current frequency. This is a problem in variable speed drive applications where phase current frequencies from starting from zero are needed. An operating mode for low phase current frequencies which enables MMLCs to magnetize and start induction machines with quadratic torque loads is presented and the achievable torque-speed characteristic is derived. It is also shown that rotor flux optimization also reduces the capacitor voltage ripple at low torque. The method has successfully been tested in an experimental converter.
416 citations
TL;DR: The number of gate driving circuits is reduced, which leads to the reduction of the size and power consumption in the driving circuits, and the total harmonic of the output waveform is also reduced.
Abstract: A novel multilevel inverter with a small number of switching devices is proposed. It consists of an H-bridge and an inverter which outputs multilevel voltage by switching the dc voltage sources in series and in parallel. The proposed inverter can output more numbers of voltage levels in the same number of switching devices by using this conversion. The number of gate driving circuits is reduced, which leads to the reduction of the size and power consumption in the driving circuits. The total harmonic of the output waveform is also reduced. The proposed inverter is driven by the hybrid modulation method. In this paper, the circuit configuration, theoretical operation, Fourier analysis, simulation results with MATLAB/SIMULINK, and experimental results are shown. The experimental results accorded with the simulation results.
397 citations
TL;DR: In this article, the leakage current suppressing method, in which all common-mode paths are considered, has been proposed, and the existing full-bridge and half-bridge type converters have been analyzed by using the developed model and rules, and then, a new fullbridge-type converter structure and a compensation strategy for half-branched inverter have been presented finally.
Abstract: Due to the characteristics of low cost and high efficiency, the transformerless photovoltaic (PV) grid-connected inverters have been popularized in the application of solar electric generation system in residential market. Unfortunately, the leakage current through the stray capacitors between the PV array and the ground is harmful. This paper focuses on the leakage current suppressing method, in which all common-mode paths are considered. First, the common-mode analytical model at switching frequency is developed, and the rules of eliminating switching frequency common-mode source are summarized based on this model. The existing full-bridge- and half-bridge-type converters have been analyzed by using the developed model and rules, and then, a new full-bridge-type converter structure and a compensation strategy for half-bridge-type inverter have been presented finally.
365 citations
TL;DR: In this article, the authors present trends of enhanced mobility, connectivity, and reliability in consumer, industrial, and military electronics will continue to drive future innovations in ceramic capacitor technology, and power electronics applications are an emerging market in which ceramic capacitors will play an increasing role through improved breakdown strength, enhanced dielectric stability in harsh environments, and innovative packaging.
Abstract: A century of diligent R&D has resulted in a wide range of ceramic dielectrics and processing technologies. The technology used to manufacture an MLCC (multilayer ceramic capacitors) that costs pennies was unimaginable 30 years ago. The present trends of enhanced mobility, connectivity, and reliability in consumer, industrial, and military electronics will continue to drive future innovations in ceramic capacitor technology. In addition, power electronics applications are an emerging market in which ceramic capacitors will play an increasing role through improved breakdown strength, enhanced dielectric stability in harsh environments, and innovative packaging. The investment made by the US government to develop high energy density and high temperature capacitor technology will also contribute to the advancement of dielectric materials technology for pulse and power electronic capacitors.
364 citations
TL;DR: This new topology has the potential to increase the efficiency and reduce the cost of high-power pickups by minimizing the reactive currents in the pickup coil and the reflected VAR loading on the power supply.
Abstract: This paper describes the design of a new unity-power-factor inductive-power-transfer (IPT) pickup using an LCL tuned network for application in high-power systems. This new topology has the potential to increase the efficiency and reduce the cost of high-power pickups by minimizing the reactive currents in the pickup coil and the reflected VAR loading on the power supply. In a practical system, the rectifier and associated processing circuitry distorts the current waveforms, adding an effective inductive loading to the pickup circuit. A series compensation capacitor is added to correct this loading. A design strategy is developed for the new topology, and two example circuits are constructed and compared experimentally with a traditional parallel-tuned (LC) pickup operating on a monorail-based IPT system.
355 citations
21 Jun 2010
TL;DR: These new networks exhibit some unique advantages, such as the increased voltage gain and reduced voltage stress in the voltage-fed trans-ZSIs and the expanded motoring operation range in the current- fed trans- ZSIs, when the turns ratio of the transformer windings is over 1.
Abstract: This paper extends the impedance-source (Z-source) inverters concept to the transformer based Z-source (trans-Z-source) inverters. The original Z-source inverter (ZSI) employs an impedance network of two inductors and two capacitors connected in a special arrangement to interface the dc source and the inverter bridge. It has overcome the conceptual limitations of the traditional voltage-source inverter and the current-source inverter. In the proposed trans-Z-source inverters, the impedance network consists of a transformer and one capacitor. While maintaining the main features of the previously presented Z-source network, the new networks exhibit some unique advantages, such as the increased voltage gain in the voltage-fed trans-ZSIs and the expanded motoring operation range in the current-fed trans-ZSIs when the turns-ratio of the transformer windings is over 1. Simulation and experimental results of one of the voltage-fed trans-Z-source inverters are provided to verify the analysis.
Patent•
30 Mar 2010
TL;DR: In this paper, improved configurations for a resonator for wireless power transfer were presented, including a conductor forming one or more loops and having an inductance L, a network of capacitors, having a capacitance, C, and a desired electrical parameter coupled to the conductor, the network having at least one capacitor of a first type with a first temperature profile of the electrical parameter.
Abstract: Described herein are improved configurations for a resonator for wireless power transfer that includes a conductor forming one or more loops and having an inductance L, a network of capacitors, having a capacitance, C, and a desired electrical parameter, coupled to the conductor, the network having at least one capacitor of a first type with a first temperature profile of the electrical parameter, and the network having at least one capacitor of a second type with a second temperature profile of the electrical parameter.
TL;DR: In this paper, a flyback-based electrolytic capacitor-less light-emitting diode (LED) driver is proposed, which converts the commercial ac voltage to a pulsating current with twice the line frequency driving high-brightness LEDs.
Abstract: This paper proposes a concept of electrolytic capacitor-less light-emitting diode (LED) driver, which converts the commercial ac voltage to a pulsating current with twice the line frequency driving high-brightness LEDs. As no electrolytic capacitor is used, this driver possesses the unique advantage of long lifetime to match with that of LEDs. A method of injecting the third and fifth harmonics into the input current to reduce the peak-to-average ratio of the output current is also proposed. While ensuring that the input power factor is higher than 0.9 to meet regulation standards such as ENERGY STAR, the proposed method allows the peak-to-average ratio of the output current to be reduced to 1.34 theoretically, which is beneficial for the safe operation of the LEDs. As an example, a flyback-based electrolytic capacitor-less LED driver is proposed, and its operation is analyzed. In order to inject the third and fifth harmonics into the input current, the function of the duty cycle in a half-line cycle is derived. It is then simplified to a fitting function, which can be easily implemented with the input voltage sensing. A 25 V, 0.35 A output prototype is built and tested in the laboratory, and the experimental results are presented to verify the effectiveness of the electrolytic capacitor-less LED driver and its control method.
TL;DR: In this article, pyroelectric cells based on fabricated screen-printed PZT and commercial PVDF films are proposed as thermal energy harvesting sources in order to supply low-power autonomous sensors.
Abstract: Pyroelectric cells based on fabricated screen-printed PZT and commercial PVDF films are proposed as thermal energy harvesting sources in order to supply low-power autonomous sensors. The cells are electrically modelled as a current source in parallel with output impedance. Heating and cooling temperature fluctuations generated by air currents were applied to the pyroelectric converters. The generated currents and charges were respectively in the order of 10 −7 A and 10 −5 C for temperature fluctuations from 300 K to 360 K in a time period of the order of 100 s, which agrees with the theoretical model. Parallel association of cells increased the generated current. The dependence of the generated current on relevant technological parameters has been also characterized. Finally, current from cyclic temperature fluctuations was rectified and stored in a 1 μF load capacitor. Energies up to 0.5 mJ have been achieved, enough to power typical autonomous sensor nodes during a measurement and transmission cycle.
TL;DR: RuO2/CNT nanocomposites with well-dispersed RuO2 nanoparticles (diameter <2 nm) on the carbon nanotubes surface, synthesized through an easy and efficient solution-based method, have been investigated for potential application in electrochemical capacitors (ECs) as electrode materials.
Abstract: RuO2/CNT nanocomposites with well-dispersed RuO2 nanoparticles (diameter <2 nm) on the carbon nanotubes’ surface, synthesized through an easy and efficient solution-based method, have been investigated for potential application in electrochemical capacitors (ECs) as electrode materials. The electrochemical results demonstrate that the supporting material of CNT can significantly promote the supercapacitance performance of RuO2. The RuO2 nanoparticles in the composite with a RuO2/CNT mass ratio of 6:7 could achieve a specific capacitance of as high as 953 F g−1. The results also demonstrate that the resulted RuO2/CNT nanocomposites are superior electrode materials for ECs with a high specific capacitance and significantly enhanced high-power and high-energy capabilities as well as improved cycling performance compared with bare RuO2. At a power density of 5000 W kg−1, the RuO2/CNT composite (RuO2/CNT = 6:7 in wt %) can still deliver an energy density of 16.8 Wh kg−1, which is about 5.8 times larger than th...
TL;DR: A modified merged capacitor switching (MCS) scheme is proposed for the successive approximation register (SAR) analogue-to-digital converter (ADC) and achieves lowest switching energy among existing switching schemes.
Abstract: A modified merged capacitor switching (MCS) scheme is proposed for the successive approximation register (SAR) analogue-to-digital converter (ADC). The conventional MCS technique previously applied to a pipelined ADC improves signal processing speed and, with use in the SAR ADC, this scheme achieves lowest switching energy among existing switching schemes. The MCS scheme achieves 93.4% less switching energy as compared to the conventional architecture.
18 Mar 2010
TL;DR: In this paper, the authors proposed an active ripple energy storage method that can effectively reduce the energy storage capacitance, and the feed-forward control method and design considerations are provided.
Abstract: It is well known that there exist second-order harmonic current and corresponding ripple voltage on dc bus for single phase PWM rectifiers. The low frequency harmonic current is normally filtered using a bulk capacitor in the bus which results in low power density. This paper proposed an active ripple energy storage method that can effectively reduce the energy storage capacitance. The feed-forward control method and design considerations are provided. Simulation and 15kW experimental results are provided for verification purposes.
TL;DR: Some recent discoveries regarding ion adsorption in microporous carbon exhibiting pores in the nanometre range can help in designing the next generation of high-energy-density supercapacitors.
Abstract: Electrochemical capacitors, also known as supercapacitors, are energy storage devices that fill the gap between batteries and dielectric capacitors. Thanks to their unique features, they have a key role to play in energy storage and harvesting, acting as a complement to or even a replacement of batteries which has already been achieved in various applications. One of the challenges in the supercapacitor area is to increase their energy density. Some recent discoveries regarding ion adsorption in microporous carbon exhibiting pores in the nanometre range can help in designing the next generation of high-energy-density supercapacitors.
TL;DR: Aromatic polyurea thin films were developed through vapor phase deposition, exhibiting relatively high dielectric constant, low loss, high breakdown field (>800 MV/m) and consequently high energy density (>12 J/cm3) as mentioned in this paper.
Abstract: High energy density dielectric materials are desirable for capacitors and other energy storage systems. Two approaches were developed to achieve high electric energy density: explore high dielectric constant (K) materials and improve high operation electric field. Relaxor ferroelectric polyvinylidene fluoride (PVDF) based copolymers P(VDF-HFP), P(VDF-CTFE) and terpolymer P(VDF-TrFE-CFE) have been proven to possess high electric energy density. An energy density of over 25 J/cm3 has been achieved in PVDF-based polymers, which represents the state of art in high energy density polymers. Aromatic polyurea thin films were developed through vapor phase deposition, exhibiting relatively high dielectric constant, low loss, high breakdown field (>800 MV/m) and consequently high energy density (>12 J/cm3). Its thermal stability up to 200°C and high charge-discharge efficiency (>90%) make it attractive for high temperature capacitors. Investigation through SEM, AFM and other experiments indicated unbalanced aromatic polyurea could exhibit apparent high-K (~15) due to the non-uniformity of film thickness and surface morphology. This article reviews the recent development of these high performance polymers.
TL;DR: Experimental result verifies that the proposed LDO is stable for a capacitive load from 0 to 50 pF and with load capability of 100 mA and the gain-enhanced structure provides sufficient loop gain to improve line regulation and load regulation.
Abstract: An output-capacitorless low-dropout regulator (LDO) compensated by a single Miller capacitor is implemented in a commercial 90-nm CMOS technology. The proposed LDO makes use of the small transistors realized in nano-scale technology to achieve high stability, fast transient performance and small voltage spikes under rapid load-current changes without the need of an off-chip capacitor connected at the LDO output. Experimental result verifies that the proposed LDO is stable for a capacitive load from 0 to 50 pF (estimated equivalent parasitic capacitance from load circuits) and with load capability of 100 mA. Moreover, the gain-enhanced structure provides sufficient loop gain to improve line regulation to 3.78 mV/V and load regulation to 0.1 mV/mA, respectively. The embedded voltage-spike detection circuit enables pseudo Class-AB operation to drive the embedded power transistor promptly. The measured power consumption is only 6 μW under a 0.75-V supply. The maximum overshoot and undershoot under a 1.2-V supply are less than 66 mV for full load current changes within 100-ns edge time, and the recovery time is less than 5 μs.
TL;DR: In this paper, the authors proposed a seamless transfer of single-phase grid-interactive inverters between grid-connected and stand-alone modes, where the grid current controller and the output voltage controller are switched between the two modes, so the outputs of both controllers may not be equal during the transfer instant.
Abstract: This paper presents a novel seamless transfer of single-phase grid-interactive inverters between grid-connected and stand-alone modes. The grid-connected inverter should operate in grid-tied and off-grid modes in order to provide power to the emergency load during system outages. However, the grid current controller and the output voltage controller are switched between the two modes, so the outputs of both controllers may not be equal during the transfer instant, which will cause the current or voltage spikes during the switching process. The transfer between the two controllers does not exist in the proposed method. In grid-tied mode, the voltage controller is used for compensating the filter capacitor current, and the current controller is used to control the grid current. In stand-alone mode, the voltage controller is used to regulate the output voltage, whereas the output of the current controller is zero. With the proposed control method, the seamless transfer can be achieved between both modes, even in polluted grid voltage. The principle and realization conditions of the control methods at both modes are analyzed. The detailed process of the seamless transfer between the two modes is illustrated. Finally, the simulation and experimental results verify the theoretical analysis.
TL;DR: The principle of operation, carrier-based pulse width modulation and a capacitors voltage balancing technique for three-level and five-level modular inverters are discussed and the results are discussed.
Abstract: Modular multilevel inverters have been proposed as a potential replacement for diode-clamped inverters in high-voltage, high-power applications as they can be extended to any number of levels without introducing significantly more complexity to the control system. This study discusses in detail the principle of operation, carrier-based pulse width modulation and a capacitors voltage balancing technique for three-level and five-level modular inverters. The modulation and balancing strategy presented are confirmed by simulations and the results are discussed.
TL;DR: In this paper, a new lithium-ion based hybrid capacitor using the lithium titanate (Li4Ti5O12) negative intercalation electrode that can operate at unusually high current densities.
Abstract: Conventional electric double layer capacitors (EDLC) designed with two symmetrical activated carbon electrodes can deliver substantially more power than similar size Li-ion batteries. There is presently a major effort to increase the energy density of EDLC s up to a target value in the vicinity of 20-30 Wh kg–1.The present review article deals with the recent contributions to get this high energy density and new approaches that have been made to increase the withstanding voltage of the EDLCs. Important alternative approach to meet this goal that is under serious investigation is to develop an asymmetric (hybrid) capacitors. Hybrid capacitor systems are the promising approach to meet the goal to effectively increase the energy density. The investigation is to develop hybrid capacitors has been initiated by Li-ion capacitors. And, now Nanohybrid capacitor certainly achieves as high energy density as Li-ion capacitors with higher stability, higher safety and higher productivity. This is the new lithium-ion based hybrid capacitor using the lithium titanate (Li4Ti5O12) negative intercalation electrode that can operate at unusually high current densities. The high-rate Li4Ti5O12 negative electrode has a unique nano-structure consisting of unusually small nano-crystalline Li4Ti5O12 nucleated and grafted onto carbon nano-fiber anchors (nc-Li4Ti5O12/CNF).
21 Jun 2010
TL;DR: In this article, a transformer using series and parallel capacitors with rectangular cores and double-sided windings has been developed, which has an output power of 15 kW and an efficiency of 95% in the normal position.
Abstract: Electric vehicles (EVs) have been attracting considerable interest recently A contactless power transfer system is required for EVs Transformers can have single-sided or double-sided windings Transformers with double-sided windings are expected to be more compact and lightweight than transformers with single-sided windings A contactless power transfer system for EVs needs to have a high efficiency, a large air gap, good tolerance to misalignment and be compact and lightweight In this paper, a novel transformer using series and parallel capacitors with rectangular cores and double-sided windings that satisfies these criteria has been developed, and its characteristics are described It has an output power of 15 kW and an efficiency of 95% in the normal position To reduce the cost of expensive ferrite cores, a transformer with split cores is also proposed
TL;DR: A three-level nonisolated dc-dc converter as a candidate for ultracapacitor applications is proposed and analyzed and experimentally verified on a general-purpose controlled electric drive.
Abstract: Electrochemical double-layer capacitors, which are well known as ultracapacitors, have intensively been used in power conversion applications such as controlled electric drives, active filters, power conditioners, and uninterruptible power supplies. The ultracapacitor is employed as the energy storage device that can be fully charged/discharged within a few seconds. To achieve better flexibility and efficiency, the ultracapacitor is connected to the power conversion system via an interfacing dc-dc power converter. Various topologies are used as the dc-dc power converter: nonisolated two-level single-phase or multiphase interleaved converters and many varieties of isolated soft-switched dc-dc converters. A three-level nonisolated dc-dc converter as a candidate for ultracapacitor applications is proposed and analyzed in this paper. The topology is theoretically analyzed, and design guidelines are given. The modeling and control aspects are discussed. A 5.5-kW prototype was designed, and the proposed topology was experimentally verified on a general-purpose controlled electric drive. Experimental results are presented and discussed.
Patent•
08 Apr 2010
TL;DR: In this paper, an inductive wireless power system using an array of coils with the ability to dynamically select which coils are energized is presented, where the coils in the array are connected with series resonant capacitors so that regardless of the number of coils selected, the resonance point is generally maintained.
Abstract: An inductive wireless power system using an array of coils with the ability to dynamically select which coils are energized. The coil array can determine the position of and provide power to one or more portable electronic devices positioned on the charging surface. The coils in the array may be connected with series resonant capacitors so that regardless of the number of coils selected, the resonance point is generally maintained. The coil array can provide spatial freedom, decrease power delivered to parasitic loads, and increase power transfer efficiency to the portable electronic devices.
TL;DR: In this article, the power flow characterization of a bidirectional galvanically isolated high-power dual active bridge DC/DC converter was studied, and the authors developed a power flow model based on a detailed analysis over a short time scale, that incorporates additional parameters, including the power semiconductor voltage loss and dead time.
Abstract: This paper studies the power flow characterization of a bidirectional galvanically isolated high-power dual active bridge DC/DC converter. In experimental tests at the University of Michigan, we have observed three phenomena, which we term as internal power transfer, phase drift, and low system efficiency, that are present under certain operating conditions. These phenomena cannot be explained by conventional power transfer analysis. The authors develop a new model, based on a detailed analysis over a short time scale, that incorporates additional parameters, including the power semiconductor voltage loss and dead time. The new power flow model may be used to explain the observed phenomena and to characterize the power flow of the converter. The model may also be used to perform accurate power flow computations over a wide operating range, thereby supporting optimal hardware design, operating range selection, and power management strategy development. Experimental results are presented to illustrate the validity of the new model.
06 Dec 2010
TL;DR: This paper presents a fully-integrated switched-capacitor DC-DC converter in 45 nm digital CMOS technology that uses digital capacitance modulation instead of traditional PFM and PWM control methods to maintain regulation against load current changes.
Abstract: Implementing efficient and cost-effective power regulation schemes for battery-powered mixed-signal SoCs is a key focus in integrated circuit design. This paper presents a fully-integrated switched-capacitor DC-DC converter in 45 nm digital CMOS technology. The proposed implementation uses digital capacitance modulation instead of traditional PFM and PWM control methods to maintain regulation against load current changes. This technique preserves constant frequency switching while also scaling switching and bottom-plate losses with changes in load current. Therefore, high efficiency can be achieved across different load current levels while maintaining a predictable switching noise behavior. The converter occupies only 0.16 mm2, and operates from 1.8 V input. It delivers a programmable sub-1 V power supply with efficiency as high as 69% and load current between 100 μA and 8 mA. Measurement results confirm the theoretical basis of the proposed design.
TL;DR: In this article, the authors reviewed possible solutions based on decoupling or isolation for suppressing power distribution network (PDN) noise on package or printed circuit board (PCB) levels.
Abstract: Mitigating power distribution network (PDN) noise is one of the main efforts for power integrity (PI) design in high-speed or mixed-signal circuits. Possible solutions, which are based on decoupling or isolation concept, for suppressing PDN noise on package or printed circuit board (PCB) levels are reviewed in this paper. Keeping the PDN impedance very low in a wide frequency range, except at dc, by employing a shunt capacitors, which can be in-chip, package, or PCB levels, is the first priority way for PI design. The decoupling techniques including the planes structure, surface-mounted technology decoupling capacitors, and embedded capacitors will be discussed. The isolation approach that keeps part of the PDN at high impedance is another way to reduce the PDN noise propagation. Besides the typical isolation approaches such as the etched slots and filter, the new isolation concept using electromagnetic bandgap structures will also be discussed.
TL;DR: In this paper, the authors proposed a new configuration of flying capacitor multicell (FCM) converter, which is controlled by a modified phase-shifted pulsewidth modulation, therefore, the self-balancing property of the flying capacitor converter is maintained in the proposed converter.
Abstract: Multilevel converters are very interesting alternatives for medium and high-power applications. The main reason is the increase in the number of output voltage levels and its apparent frequency. This paper presents a new configuration of flying capacitor multicell (FCM) converter. The main advantages of the proposed converter, in comparison with FCM and stacked multicell converters, are doubling the rms and the number of output voltage levels, improving the output voltage frequency spectrum, and canceling the midpoint of dc source. This progress is achieved by adding only two low-frequency switches to the conventional configuration of FCM converter while the number of high-frequency switches and capacitors, voltage ratings of capacitors and switches, and the number of high-frequency switchings during a full cycle are kept constant. This converter is controlled by a modified phase-shifted pulsewidth modulation, therefore, the self-balancing property of the flying capacitor converter is maintained in the proposed converter. The circuit is simulated using power systems computer-aided design/electromagnetic transients in DC systems (EMTDC) software and simulation results are presented to validate the effectiveness and advantages of the proposed configuration as well as its control strategy. Additionally, measurements taken from an experimental setup are presented in order to study the practical configuration.