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Showing papers on "Equivalent series resistance published in 2014"


Journal ArticleDOI
TL;DR: This review serves to provide a clear picture of the state-of-the-art research in this area and to identify the corresponding challenges and future research directions for capacitors and their dc-link applications.
Abstract: DC-link capacitors are an important part in the majority of power electronic converters which contribute to cost, size and failure rate on a considerable scale. From capacitor users' viewpoint, this paper presents a review on the improvement of reliability of dc link in power electronic converters from two aspects: 1) reliability-oriented dc-link design solutions; 2) conditioning monitoring of dc-link capacitors during operation. Failure mechanisms, failure modes and lifetime models of capacitors suitable for the applications are also discussed as a basis to understand the physics-of-failure. This review serves to provide a clear picture of the state-of-the-art research in this area and to identify the corresponding challenges and future research directions for capacitors and their dc-link applications.

882 citations


Journal ArticleDOI
TL;DR: In this paper, an asymmetric flexible device based on vanadium pentoxide-reduced graphene oxide (rGO) free-standing electrodes is used as electrodes for supercapacitor applications, eliminating the need for current collectors or additives.
Abstract: Vanadium pentoxide–reduced graphene oxide (rGO) free-standing electrodes are used as electrodes for supercapacitor applications, eliminating the need for current collectors or additives and reducing resistance (sheet resistance 29.1 Ω □−1). The effective exfoliation of rGO allows improved electrolyte ions interaction, achieving high areal capacitance (511.7 mF cm−2) coupled with high mass loadings. A fabricated asymmetric flexible device based on rGO/V2O5-rGO (VGO) consists of approximately 20 mg of active mass and still delivers a low equivalent series resistance (ESR) of 3.36 Ω with excellent cycling stability. A prototype unit of the assembled device with organic electrolyte is shown to light up eight commercial light-emitting diode bulbs.

288 citations


Journal ArticleDOI
TL;DR: In this paper, the authors investigated the electrical properties of poly-crystalline (poly) Si/mono-c-Si junctions and the influence of the interfacial oxide between the poly-Si and the c-Si on these characteristics.

187 citations


Journal ArticleDOI
TL;DR: In this article, an equivalent circuit model for electrochemical double layer capacitors (EDLCs) is proposed through analyzing the electrochemical impedance spectroscopy (EIS) measurements, while these capacitive or resistive behaviors in the presence of charge diffusion and the ion adsorption at the double layer interface and bulk media are investigated.

177 citations


Journal ArticleDOI
TL;DR: An energy conversion efficiency of 25.1% was achieved in heterojunction back contact (HBC) structure Si solar cell utilizing back contact technology and an amorphous silicon thinfilm technology as mentioned in this paper.
Abstract: An energy conversion efficiency of 25.1% was achieved in heterojunction back contact (HBC) structure Si solar cell utilizing back contact technology and an amorphous silicon thinfilm technology. A new patterning process was established, and it was applied to the fabrication process of HBC cells. In addition, the unique technology of the surface mount technology concept contributed to the superior performance of HBC cell. A short circuit current density (J sc ) and an open-circuit voltage (V oc ) were 41.7 mA/cm2 and 736 mV, respectively. The high J sc as well as the high Voc indicates the strength of HBC structure cell. Besides, a high fill factor of 0.82 was obtained, which shows that HBC structure cell does not have any fundamental critical losses caused from series resistance or shunt resistance. Such high values of I-V parameter means that the patterning process was properly performed.

146 citations


Journal ArticleDOI
TL;DR: In this article, a mechanically rotating superconducting flux pump was used to excite an HTS double pancake coil at 77 K. This flux pump is found to possess an effective internal resistance, Reff, which varies linearly with frequency, and is two orders of magnitude larger than the measured series resistance of the soldered contacts within the circuit.
Abstract: Superconducting flux pumps enable large currents to be injected into a superconducting circuit, without the requirement for thermally conducting current leads which bridge between the cryogenic environment and room temperature. In this work, we have built and studied a mechanically rotating flux pump which employs a coated conductor high-Tc superconducting (HTS) stator. This flux pump has been used to excite an HTS double pancake coil at 77 K. Operation of the flux pump causes the current within the superconducting circuit to increase over time, before saturating at a limiting value. Interestingly, the superconducting flux pump is found to possess an effective internal resistance, Reff, which varies linearly with frequency, and is two orders of magnitude larger than the measured series resistance of the soldered contacts within the circuit. This internal resistance sets a limit for the maximum achievable output current from the flux pump, which is independent of the operating frequency. We attribute this ...

133 citations


Journal ArticleDOI
TL;DR: Li et al. as mentioned in this paper developed a low-cost and high performance supercapacitor utilizing graphene-based electrodes and Li2SO4-based aqueous electrolyte, which showed excellent charge storage characteristics from −20°C to 45°C.

131 citations


Journal ArticleDOI
TL;DR: In this paper, an accelerated aging protocol has been developed and validated to determine the factors influencing the life-time of high voltage carbon/carbon electrochemical capacitors (ECs) in aqueous lithium sulfate electrolyte, and to offer solutions reducing ageing of the cells.

102 citations


Journal ArticleDOI
TL;DR: In this paper, two well-known conducting polymers (CP), polypyrrole (PPy) and poly(3,4-ethylenedioxythiophene) (PEDOT), were coated onto mesoporous NiCo2O4 nanosheet arrays through an efficient and controllable electrodeposition process.
Abstract: Herein, two of the most well-known conducting polymers (CP), polypyrrole (PPy) and poly(3,4-ethylenedioxythiophene) (PEDOT), were coated onto mesoporous NiCo2O4 nanosheet arrays through an efficient and controllable electrodeposition process. We considered such a unique nanostructure to be an ideal model to accurately compare and understand the effects of PPy and PEDOT on electrochemical performances. Comparing the electrochemical performances of NiCo2O4@CP and pure NiCo2O4 electrodes, we found that the NiCo2O4@PPy electrode possesses the highest areal capacitance of 4.1 F cm−2 at 2 mA cm−2, which is significantly higher than the values obtained for the NiCo2O4@PEDOT (0.86 F cm−2) and NiCo2O4 electrodes (0.65 F cm−2). For rate capability, even at a high current density of 30 mA cm−2, an areal capacitance of 2.7 F cm−2 can be achieved for the NiCo2O4@PPy electrode. Moreover, the NiCo2O4@PPy electrode shows considerably smaller equivalent series resistance (ESR) than that of the NiCo2O4@PEDOT and NiCo2O4 electrodes. Therefore, the NiCo2O4@PPy hybrid composites are considered to be ideal supercapacitor electrode materials with enhanced electrochemical performances, which makes them suitable for many practical applications.

68 citations


Journal ArticleDOI
TL;DR: In this article, the authors evaluated the contact resistance of amorphous Si ( a- Si:H)/transparent conducting oxide (TCO) in terms of the contribution to the series resistance ( R s ) and fill factor ( FF ) in the Si heterojunction back-contact (HBC) solar cell.

64 citations


Journal ArticleDOI
Johann Walter, Marco Tranitz, Michael Volk1, Christian Ebert1, Ulrich Eitner 
TL;DR: In this paper, the authors focus on the interconnection of busbar-free solar cells by infrared soldering and the optimization of the front metallization design in order to achieve reliable solder joints.

Journal ArticleDOI
TL;DR: In this article, the authors proposed digitally controlled operation as a new method to resolve the problem of switching surges and power efficiency decreases in DAB dc-dc converters, and reported on an experiment that was carried out using a 1-kW system.
Abstract: Bidirectional dc-dc converters, which make possible the bidirectional transmission of power, have become indispensable in recent years due to the diversification of the power supply network, including the use of batteries. Of these, the dual active bridge (DAB) dc-dc converter features a simple mechanism and symmetric circuit architecture, making possible the equal transmission of power in both directions. Because of these advantageous characteristics, DAB dc-dc converters are in wide use. However, this circuit has the intrinsic problems that, during light-load conditions, switching surges occur and power efficiency decreases. This paper proposes digitally controlled operation as a new method to resolve these problems and reports on an experiment that was carried out using a 1-kW system. In addition, for both buck and boost modes, output power characteristic equations were derived through application of the extended state-space averaging method, and a loss-included circuit analysis was carried out for the circuit used in the experiment. It was thereby demonstrated that circuit loss was smaller for the proposed operation than that for conventional operation. In the loss-included circuit analysis, for both proposed and conventional operations, equivalent circuits that approximated circuit loss as a single resistance were used. As a result, it was confirmed that, with the operation proposed in this paper, without the use of a snubber circuit, switching surges could be reduced significantly and also that, during light load, there was a power efficiency improvement of up to 16%. In addition, a loss-included circuit analysis with a single equivalent resistance has been done. The resistance value is assigned with the averaged circuit total resistance. By the analysis, a relation between phase difference and output power is obtained. The results were confirmed with the experiment.

Journal ArticleDOI
TL;DR: In this paper, the authors compared the photovoltaic performance of different cell designs, standard and inverted, for one of the most promising systems to achieve power conversion efficiencies over 10% in polymer:fullerene single cells, namely PTB7:PC70BM.

Journal ArticleDOI
TL;DR: In this paper, the effects of series resistance and shunt leakage on a-Si:H thin-film solar cells were investigated using advanced simulation tools and the obtained electrical values were compared with experimental results.

Journal ArticleDOI
TL;DR: In this article, an Ag/CZTS/n-Si Schottky diode was fabricated and basic diode parameters including barrier height, ideality factor, and series resistance were concluded using currentvoltage and capacitance-voltage measurements.

Journal ArticleDOI
TL;DR: The main investigation is focused on the correlation existing among the size of coupling capacitor, the magnetic coupling factor of CIs, the voltage conversion ratio, and the amplitude of peak-to-peak (pk-pk) ripple current in the input and output ports of the CIs.
Abstract: This paper discusses design issues of single-ended primary-inductor converter (SEPIC) with coupled inductors (CIs). The main investigation is focused on the correlation existing among the size of coupling capacitor, the magnetic coupling factor of CIs, the voltage conversion ratio, and the amplitude of peak-to-peak (pk-pk) ripple current in the input and output ports of the CIs. It is shown how the above elements must be properly correlated to prevent large input and output ripple currents, particularly if tightly coupled inductors are used. Analytical design formulas for the coupling capacitor are applied to the design of a low-power SEPIC. Simulations and experimental measurements prove the validity of the model predictions and the reliability of related design rules.

Journal ArticleDOI
TL;DR: In this paper, the authors presented an experimental method to quantify the series resistance of a-Si:H/cSi heterojunction solar cells with different deposition parameters and found that the best value for R676 (p)-a-Si/ITO petertodd of 042 Ω·cm petertodd 2>>\ 2>>\s for an ITO double layer with a 10-nm thin starting layer and an additional 90-nm top layer with good conductivity reached values below 0.
Abstract: We present an experimental method to quantify the series resistance R a-Si/ITO through the a-Si:H layers and the a-Si:H/ITO interface on test structures In order to optimize R a-Si/ITO , we apply different a-Si:H and ITO deposition parameters We find the best value for R (p)-a-Si/ITO of 042 Ω·cm 2 for an ITO double layer with a 10-nm-thin starting layer that provides good contact resistance and an additional 90-nm top layer that provides good conductivity For R (n)-a-Si/ITO , we reach values below 01 Ω·cm 2 We present an analysis of the series resistance and shading losses of our 100-cm 2 bifacial screen-printed a-Si:H/cSi heterojunction solar cells, which show an open-circuit voltage of V oc = 733 mV, demonstrating the excellent level of interface passivation The efficiency of 202% is limited by a low short-circuit current density of 371 mA/cm 2 and fill factor of 76%

Proceedings ArticleDOI
19 May 2014
TL;DR: In this article, the authors explored factors influencing the lifetime of electrolytic capacitors and calculated the capacitance's life time in dedicated application, and compared the performance of different types of capacitors in dedicated applications.
Abstract: This article explores factors influencing the lifetime of electrolytic capacitors. Calculation of capacitor's life time in dedicated application is also described in the article. Finally comparisons of the computed results between several types of electrolytic capacitors in dedicated application are provided.

Journal ArticleDOI
TL;DR: In this article, the series and shunt resistances of hybrid organic-inorganic hybrid solar cells were tuned to observe its effect on the device performance, and it was found that with suitable substrate scales and physical tailoring methods, the shunt and series resistances can be adjusted to eliminate the unfavorable charge trapping phenomenon.

Journal ArticleDOI
TL;DR: In this paper, an improved method that uses photoluminescence images to calculate the spatially-resolved efficiency in addition to other performance parameters of silicon solar cells is presented.

Journal ArticleDOI
TL;DR: In this article, a nonlinear analytical expression is used to predict the capacitance decay for several durations and test interruption periodicities; this is also used to model capacitance during rest time, taking the cut-off voltage, rest time and temperature into account.

Journal ArticleDOI
TL;DR: In this paper, the authors developed a method to extract the currentvoltage characteristics of the injection contact, assuming that contact effects are negligible in long channel devices and by introducing a modified gradual channel approximation (quasi-two-dimensional model) to take into account for short channel effects.
Abstract: Control of the source-drain contact properties in amorphous InGaZnO semiconductor active layer is relevant since a high series resistance in the source-drain contacts causes degradation of electrical performance, particularly affecting short channel devices. We developed a method to extract the current-voltage characteristics of the injection contact, assuming that contact effects are negligible in long channel devices and by introducing a modified gradual channel approximation (quasi-two-dimensional model), to take into account for short channel effects. The present method allows to extract the parasitic resistance by using devices with only two different channel lengths. Assuming a transmission line scheme for the contact resistance and SCLC transport for the current density flowing along the vertical direction though the IGZO bulk, we have been able to evaluate the variation with ${\rm V}_{{\rm ds}}$ of contact resistance at source and drain electrodes.

Journal ArticleDOI
TL;DR: Lower performance of multi-crystalline silicon solar cells is usually observed after long-term damp heat test at 85 °C/85% relative humidity because of the reduction of the photovoltaic ribbon in the solder joint and the oxidation of surface on the front Ag finger by high thermal and moisture stress.

Journal ArticleDOI
TL;DR: In this paper, a method for determining the current and photogeneration dependence of the series resistance without assuming any specific currentvoltage characteristic for the internal diodes is presented.
Abstract: Precise knowledge of the series resistance is essential for failure and loss analysis as well as yield prediction of solar cell devices. In this work, a method which determines the current and photogeneration dependence of the series resistance without assuming any specific current-voltage characteristic for the internal diodes is presented. This approach is of particular interest for solar cells which cannot be described by the one- or two-diode model such as organic solar cells. Furthermore, it clarifies the difference in the series resistance values that are obtained from current-voltage curves in the dark and under illumination as well as short-circuit-current and open-circuit-voltage characteristics. Additionally, it is shown how other cell parameters, such as the shunt resistance or the current-voltage characteristic of the internal diode are determined in a consistent way. Finally, it is demonstrated that our approach can be easily implemented in a new generation of solar simulators that are based on light-emitting diodes instead of conventional light sources.

Journal ArticleDOI
TL;DR: In this paper, a modeling approach based on the complex form of the capacitor impedance to build its equivalent electrical circuit is presented, which proved to be more accurate than the traditional modeling technique of identifying the electrical parameters using the modulus of the component impedance.
Abstract: Metalized film capacitors are commonly used components in power electronics applications and their characteristics are drastically dependent on their operating frequency. Parasitic parameters could appear at low and high frequencies and disturb substantially the behavior of the component. Proper design of metalized film capacitors requires an understanding of all parasitic parameters' sources and their impacts on the circuit operation. This paper presents a modeling approach based on the complex form of the capacitor impedance to build its equivalent electrical circuit. This approach proved to be more accurate than the traditional modeling technique of identifying the electrical parameters using the modulus of the component impedance. Two different types of capacitors were tested; experimental results allowed to validate our model from 10 kHz to 35 MHz.

Journal ArticleDOI
TL;DR: In this paper, an integrated field effect transistor (FET) was used to generate electrical fields between the gate and the substrate of multilayer graphene produced by chemical vapor deposition, and an electrical detecting system was designed to detect equivalent resistance of the FETs.
Abstract: Based on large-area multilayer graphene produced by chemical vapor deposition, an integrated field-effect transistor was fabricated in this work. A planar Au electrode was used as gate electrode integrated with graphene field-effect transistors (FETs) to generate perpendicular electrical fields between the gate and the graphene substrate. Graphene film was then transferred to cover indium tin oxide films which were used as drain and source electrodes. Via this process, the contact resistance between graphene and electrodes which were caused by polymethylmethacrylate (PMMA) residues in chemical vapor deposition process was almost eliminated. An electrical detecting system was designed to detect equivalent resistance of the FETs, which indicated that the performance of the FETs was associated with the width of conducting channel, the electrical field intensity between gate and graphene, and the ion concentration of electrolyte. Adenosine triphosphate (ATP) was selected as model electrolyte to verify the detecting system in this study. It was demonstrated that the integrated FETs could achieve high sensitivity to detect ATP as low as 10 pM and the equivalent resistance of the FETs showed a good correlation with ATP concentration from 10 pM to 10 μM. These results may provide a better direction and a common detecting platform for the design of integrated graphene FETs biosensors.

Journal ArticleDOI
TL;DR: In this paper, the effects of radiation on the electrical-interface-state density (D it ) and series resistance (R s ) characteristics of BiFeO 3 MOS capacitors were studied.
Abstract: The effects of radiation on the electrical-interface-state density ( D it ) and series resistance ( R s ) characteristics of BiFeO 3 MOS capacitors were studied in this work. To study the response of MOS devices to gamma irradiation over a range of doses, MOS samples were irradiated using a Co-60 gamma-ray source from 0.5 to 16 grays at a dose rate of 0.0030 Gy/s. C – V and G / ω – V measurements were recorded prior to and after irradiation at high (1 MHz) frequency. The effects of the radiation were determined from analysis of the C – V and G / ω – V curves. A slightly decrease in the R s values with increasing irradiation dose was observed. The total interface-state density was found to decrease because of the reordering and restructuring of radiation-induced defects in the MOS capacitors. The experimental results indicate that the electrical R s and D it characteristics of BiFeO 3 MOS capacitors depend on the gamma-irradiation dose, and the calculated densities of the interface states are on the order of 10 11 eV −1 cm −2 . However, the calculated D it values are not high enough to pin the Fermi level of the Si substrate and thereby corrupt device operation over the given dose range.

Journal ArticleDOI
24 Apr 2014
TL;DR: In this paper, an analytic equation that can be used to evaluate the effects of stray inductance on the equivalent resistance of hard-switched switched capacitor converters is presented. But the authors did not consider the effect of stray induction on SC converter performance.
Abstract: Switched capacitor (SC) converters are becoming quite popular for use in DC-DC power conversion. The concept of equivalent resistance in SC converters is frequently used to determine the conduction losses due to the load current. A variety of methodologies have been presented to predict the equivalent resistance in hard-switched SC converters. These works, however, did not consider the effect of stray inductance on equivalent resistance. Current power converter design practices favor higher switching frequencies, moving hard-switched SC converters into operating areas in which stray inductance affects converter performance. This paper presents an analytic equation that can be used to evaluate the effects of stray inductance on the equivalent resistance of switched capacitor converters. The concepts proposed here are verified by both digital simulation and a prototype converter. The equations presented can be used to evaluate the effects of stray inductance on SC converter performance, thereby helping designers set a maximum operating frequency to limit its effect.

Journal ArticleDOI
TL;DR: In this article, the influence of carrier overflow on the forwardvoltage characteristics of the InGaN-based blue light-emitting-diode (LED) was investigated by comparing the temperature-dependent characteristics of electroluminescence (EL) efficiency, the EL spectra, and the currentvoltage relation over a wide range of temperature (50 − 300
Abstract: We investigate the influence of carrier overflow on the forward-voltage characteristics of the InGaN-based blue light-emitting-diode (LED) by comparing the temperature-dependent characteristics of the electroluminescence (EL) efficiency, the EL spectra, and the current-voltage relation over a wide range of temperature (50–300 K). Based on these experimental results, we demonstrate that the simple ohmic potential drop in the Shockley diode equation is not sufficient to explain the experimental data when the severe carrier overflow to the p-(Al)GaN layer induces the efficiency droop in the LED device. The anomalous relation between current and voltage at cryogenic temperatures is explained by the space-charge-limited current formed by the overflown electrons, rather than by the increase of a constant series resistance in the p-(Al)GaN layer.

Journal ArticleDOI
TL;DR: In this paper, the effects of gamma-ray irradiation on the electrical characteristics of Al2O3 MOS capacitors such as barrier height, acceptor concentration, series resistance and interface state parameters have been studied by analyzing capacitance and conductance measurements.
Abstract: Effects of gamma-ray irradiation on the electrical characteristics of Al2O3 MOS capacitors such as barrier height, acceptor concentration, series resistance and interface state parameters have been studied by analyzing capacitance–voltage (C–V) and conductance–voltage (G/ω–V) measurements. The fabricated MOS capacitors were irradiated with gamma-rays at doses up to five grays. C–V and G/ω–V measurements were recorded prior to and after irradiation at high frequency. The results show that the measured capacitance and conductance values decreased with increasing in irradiation dose and C–V and G/ω curves has been shifted toward the negative voltages. Moreover, the series resistance (R s) and density of interface states increased with increasing in irradiation dose and density of interface states (D it) were calculated as order of 1012 eV−1cm−2 prior to and after irradiation. Due to presence and variations in the R s values, the corrected and the measured C–V and G/ω–V exhibited different behaviors. Therefore other electrical characteristics were assessed from corrected C c characteristics. It was observed that acceptor concentration decreased with increasing in barrier height of device due to changes in interface states and diffusion potential.