Output Diode Research Articles

High step‐up DC–DC converter with low power device voltage stress for a distributed generation system

This study presents a novel step-up DC-DC converter with the coupled inductor and low switch voltage stress, which reduce diode voltage stress. The presented converter contains single switch, four diodes, four capacitors and one coupled inductor. When switch is turned ON, the primary side of coupled inductor is charged by the input source. Besides, the primary and secondary side of the coupled inductor is discharged in series with the input source and two capacitors to realise the high step-up voltage gain when the switch is turned OFF. Furthermore, the clamped circuit which adopts two capacitors negative pole connection not only recycles leakage energy and obtains the high voltage conversion gain, but also is realised to reduce the voltage stress of the diode, which can be use low-voltage rated devices with low on-resistance. In addition, the three diodes are working on the zero-current-switching turn-off, therefore, the loss is reduced and the reverse-recovery problem is avoided. The current falling rate of the output diode is effectively restricted for the leakage inductor, therefore, its reverse-recovery problem is effectively alleviated. Finally, a 40 V input voltage, 380 V output voltage and 400 W output power prototype circuit is established in the laboratory to verify the performance.

Single-Switch Single Power-Conversion PFC Converter Using Regenerative Snubber

This paper presents a single-switch single power-conversion (S $^\text{3}$ PC) power factor correction (PFC) converter. Using the series-resonant circuit, the S $^\text{3}$ PC converter provides bidirectional core excitation for the transformer and obtains higher power capability compared with the conventional single-switch PFC converters. Also, the series-resonant circuit provides zero-current switching turn-off for the output diodes, so that the reverse-recovery loss is alleviated. The regenerative snubber not only avoids the voltage spike of the switch but also recycles the absorbed energy. Because these features are obtained with only a single switch and through single power-conversion, the S $^\text{3}$ PC converter has high efficiency and simple structure. The control algorithm derived from feedback linearization enables the S $^\text{3}$ PC converter to obtain good controllability. Also, by using this control algorithm, the proposed converter performs both PFC control and output power control through single power-conversion. With these advantages, the S $^\text{3}$ PC converter provides maximum efficiency of 96.4% and high power factor in excess of 0.994. The proposed converter is theoretically analyzed in detail, and experimental results are applied to a 1-kW prototype to show its validity.

Dynamic model development and control for multiple‐output flyback converters in DCM and CCM

SummaryMultiple‐output flyback converters are widely used in switching power supplies due to their low component count and cost‐effective structure. The main problem of this structure is how to balance output voltages in different load conditions. This paper proposes a new approach for single‐input multiple‐output flyback converters operating in DCM and CCM by a small‐signal averaged model. The averaged model is derived by presenting the piecewise‐linear waveform for the inductor currents inside the converter. In DCM, the magnetizing current and currents through the output windings reach zero when the switch is turned off. In CCM, the magnetizing current of the converter is continuous over a switching interval and this possibility exists that only some of the output diodes completely conduct when the switch is off. The proposed model of the converter can be used in a wide range of operations within identical and non‐identical loading conditions. Using a laboratory prototype, several case studies and input‐to‐output transfer functions are considered to verify the proposed model. The controller design is performed for the both CCM and DCM, and then dynamic characteristics of the overall system are evaluated.

Primary Side Control For Flyback Converter Operating in DCM and CCM

Primary side regulation (PSR) technology has the characteristics of lower cost and standby power losses. However, there is no algorithm suitable for discontinuous conduction mode (DCM) and continuous conduction mode (CCM) operations of primary side control for flyback converter because of the difficulty in estimating the output voltage correctly. In this paper, a PSR control algorithm suitable for DCM/CCM flyback converter is proposed and implemented with digital micro controller. The voltage drop on the secondary winding and output diode at CCM operation is compensated by sensing the secondary side current at the instant when primary side switch is being turned-on. The secondary side current is zero at the voltage sensing instant and equal to the current at the instant when primary side switch is being turned-on as flyback operated at DCM. In addition, the proposed algorithm can be used to regulate either the output voltage or current very well. An experimental prototype with 150 W rated power is built to verify the feasibility of the proposed control. Experimental results show that the output voltage can be controlled with error less than 0.25%, and the output current error is less than 5%. The conversion efficiency is up to 92.8%.

Design and experimental evaluation of a single-stage AC/DC converter with PFC and hybrid full-bridge rectifier

This paper presents design and experimental evaluation of a single-stage AC/DC converter with PFC and hybrid full-bridge rectifier for supplying LED streetlight. The proposed converter consisted of one LLC resonant tank, two boost circuits and one shared inductor. By incorporating a relay switch at the secondary-side of the circuit, the output stage can be operated as two different types of rectifier: the first is as a full-bridge rectifier and the second type is as a full-bridge voltage doubler rectifier. The proposed converter was designed to receive a 240-V, 50-Hz single-phase AC supply as its input. MATLAB Simulink software was used to simulate the proposed converter, and later, a prototype was built for the experimental measurements at 100-W rated output power. The experimental results and the performance of the proposed converter were analyzed for PFC, efficiency, THD, and bus voltage. The proposed converter can achieve soft-switching characteristics since the power switches and output diodes were operated with ZVS and ZCS conditions, respectively. Furthermore, when the relay switch was closed, the output voltage was twice higher than that of when the relay switch was opened. The maximum efficiency of the proposed converter with hybrid full-bridge rectifier and full-bridge voltage doubler rectifier was about 92.6% and 93.3% respectively.

A Zero-Ripple Input Current Boost Converter for High-Gain Applications

This paper presented a zero-ripple input current boost converter for high-gain applications. First, the input dc source, clamp capacitor, and voltage doubler cell are connected in series to transfer energy for the load, so the proposed converter can produce a very high voltage and high conversion efficiency. Second, through theoretical analysis, a small auxiliary inductance was added to the input of the boost converter for achieving zero-ripple input current. Moreover, the energy in the leakage inductance can be effectively recycled. The voltage doubling rectifying unit can effectively reduce the resonance between the leakage inductance and the junction capacitance of the output diode. Details of the working principle and steady analysis of the proposed converter are introduced. At last, an experimental prototype is built to verify the correctness of the theoretical analysis.

High step‐up cascade synchronous boost DC–DC converter with zero‐voltage switching

A high step-up cascade synchronous boost DC–DC converter with zero-voltage switching (ZVS) is proposed. The proposed converter is based on the conventional cascade boost converter with a single switch. In the first stage, a boost cell is modified to improve the voltage gain by utilising a coupled inductor. Additionally, turn ratio can be used to adjust voltage gain. In the second stage, a synchronous rectifier is adopted instead of the output diode to improve power efficiency. Moreover, ZVS is achieved using an auxiliary circuit, which consists of a coupled inductor and a small inductor. Therefore, total power efficiency is improved and high voltage gain can be obtained from a low turn ratio. The theoretical analysis and performance are proven from the experiment results using a prototype of the proposed converter with an output of 200 V–200 W.

A homogeneous focusing system for diode lasers and its applications in metal surface modification

High power diode lasers are applied in many different areas, including surface modification, welding and cutting. It is an important technical trend in laser processing of metals in the future. This paper aims to analyze the impact of the shape and homogeneity of the focal spot of the diode laser on surface modification. A focusing system using the triplet lenses for a direct output diode laser which can be used to eliminate coma aberrations is studied. A rectangular stripe with an aspect ratio from 8:1 to 25:1 is obtained, in which the power is homogeneously distributed along the fast axis, the power is 1117.6 W and the peak power intensity is 1.1587 × 106 W/cm2. This paper also presents a homogeneous focusing system by use of a Fresnel lens, in which the incident beam size is 40 × 40 mm2, the focal length is 380 mm, and the dimension of the obtained focal spot is 2 × 10 mm2. When the divergence angle of the incident light is in the range of 12.5–20 mrad and the pitch is 1 mm, the obtained homogeneity in the focal spot is the optimum (about 95.22%). Experimental results show that the measured focal spot size is 2.04 × 10.39 mm2. This research presents a novel design of homogeneous focusing systems for high power diode lasers.

High Step-Up Interleaved ZVT Converter With Low Voltage Stress and Automatic Current Sharing

This paper proposes a soft switching nonisolated dc/dc interleaved converter incorporating coupled inductors and switched capacitors for high step-up applications. The converter integrates the interleaved structure and winding-cross-coupled inductors technique to reduce current stress of semiconductor devices and diminish the input current ripple considerably. In addition, the interleaved converter has the automatic current sharing characteristic. The applied zero voltage transition cell provides soft switching in a wide range of load variations with a minimum number of elements. In this topology, all semiconductor devices are soft switched, having eliminated switching losses and alleviating the reverse recovery problem of the output diodes. In addition, the voltage stress across the switches is very low. The theoretical analysis and design procedure of the introduced topology are presented. Also, the proposed converter is compared to the latest similar soft switched high step-up converters. The accuracy of the theoretical analysis is validated by a 200-W prototype operating at 100 kHz.

Study on Improving Precision of Analysis of Boost Ratio and Power Efficiency of Tapped‐Inductor DC–DC Converter Circuit

SUMMARYAnalysis precision of boost ratio and power efficiency in boost DC–DC converter circuit is improved by proposing adaptive equivalent circuit of output diode of the circuit. In experiment, boost ratio and power efficiency in high boost ratio circuit were 9.89% and 76.5% respectively with its load resistance of 20 Ω driven by output voltage 10 V. In experimental results, error in theoretical values of boost ratio compared with the measured values of that was reduced to −3.79% from 57.5% in the conventional circuit. In a tapped‐inductor high boost ratio circuit, error in theoretical values of boost ratio was reduced to 3.54% from 31.8%. Error in theoretical values of power efficiency with the measured values of that was reduced to 5.51% from 33.2% in the conventional circuit. In a high boost ratio circuit, error in theoretical values of power efficiency was reduced to −3.32% from 17.3%. Power loss of every element in boost DC–DC converter circuits was analyzed with high precision by analysis of inductance current waveforms in those circuits. Error in theoretical values of power loss compared with measured values was reduced to equal or less than 5%.

High voltage gain interleaved DC–DC converter with minimum current ripple

A new interleaved high step-up DC–DC converter is presented in this study which integrates coupled inductors and voltage multipliers techniques into interleaved structure to provide high voltage gain without extreme duty cycle. The voltage stress across power metal–oxide–semiconductor field-effect transistors is very low, so low voltage rating switches with lower R ds(on) can be used. A modified version of winding cross-coupled inductors technique is employed to minimise the input current ripple, and also the reverse recovery problem of the output diodes is alleviated because of the leakage inductance of the coupled inductors. Also, the leakage energy is absorbed and recycled to the output by the passive clamp scheme. In addition, automatic current sharing performance between the interleaved phases is established without any extra circuit. The operating principles of the proposed converter are explained and the theoretical analysis is provided, and in order to verify the effectiveness of the proposed converter, a 170 W, 30–360 V laboratory prototype is implemented.

A Soft-Switching Bridgeless AC–DC Power Factor Correction Converter

A new soft-switching, bridgeless power factor correction (PFC) boost converter is proposed for power supply and battery charging applications. The converter operates in both pulse width modulation (PWM) mode and resonant mode each switching cycle, and utilizes standard average current mode control. The converter is bridgeless, therefore eliminating the need for a front-end diode bridge rectifier. It operates in continuous conduction mode and achieves zero voltage switching (ZVS) for all switches. The proposed converter also reduces the turn-off losses of the PWM switches, therefore nearly eliminating switching losses. The output diodes operate with controlled di/dt turn-off, which reduces reverse–recovery losses. The PWM switches of the proposed converter can be driven with the same PWM signal, enabling simplified control. The detailed operation of the proposed converter is presented, including the conditions for ZVS operation and a stress analysis for the circuit components. Experimental results are presented for a 650-W prototype at 150-kHz switching frequency, universal ac input, and 400-V dc output. The proposed converter shows about 1% better efficiency and lower device temperatures at full load and 100-V ac input (maximum loss operating point) compared with the conventional hard switched PFC boost converter.

Isotopic composition of bottled water in Saudi Arabia

ABSTRACTThe 18O/16O and 2H/1H ratios of 18 water brands representing the most popular bottled water brands in the Saudi market were measured using a system based on the latest advancements in tunable off-axis integrated cavity output diode laser spectroscopy (OA-ICOS) in the near-infrared spectral region. Utilizing δ18O and the δ2H values of locally produced water samples, a meteoric water line (δ2H = 7.84 δ18O + 2.11) was extracted and found to be consistent with the slope of the global meteoric water line (GMWL) and the geographic location of Saudi Arabia.

Extended Switched-Boost DC-DC Converters Adopting Switched-Capacitor/Switched-Inductor Cells for High Step-up Conversion

This paper proposes a family of switched-boost dc–dc converters for the high stepup voltage conversion applications, such as renewable energy power generation, uninterruptible power supply, and automobile high-intensity discharge headlamps. Compared with other dc–dc converters, the proposed switched-boost converter, which combines the traditional switched-boost network with the switched-capacitor/switched-inductor cells, has the following features: higher output voltage gain, a fewer passive components such as inductors and capacitors, and lower voltage stress across the output diode and power switches. Another advantage of the proposed topology is its expandability. If a higher voltage conversion ratio is required, additional cells can be easily cascaded by adding one inductor and three diodes. The structure, operating principle analysis, parameter design, and comparison with other dc–dc converters are also analyzed. Finally, both simulations and experimental results are presented to verify the effectiveness of the proposed converter.

Short-Term Environmental Effects and Their Influence on Spatial Homogeneity of Organic Solar Cell Functionality.

In this study, we focus on the induced degradation and spatial inhomogeneity of organic photovoltaic devices under different environmental conditions, uncoupled from the influence of any auxiliary hole-transport (HT) layer. During testing of the corresponding devices comprising the standard photoactive layer of poly(3-hexylthiophene) as donor, blended with phenyl-C61-butyric acid methyl ester as acceptor, a comparison was made between the nonencapsulated devices upon exposure to argon in the dark, dry air in the dark, dry air with illumination, and humid air in the dark. The impact on the active layer's photophysics is discussed, along with the device physics in terms of integral solar cell performance and spatially resolved photocurrent distribution with point-to-point analysis of the diode characteristics to determine the origin of the observed integrated organic photovoltaic device behavior. The results show that even without the widely used hygroscopic HT layer, poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate), humidity is still a major factor in the short-term environmental degradation of organic solar cells with this architecture, and not only oxygen or light, as is often reported. Different from previous reports where water-induced device degradation was spatially homogeneous and formation of Al2O3 islands was only seen for oxygen permeation through pinholes in aluminum, we observed insulating islands merely after humidity exposure in the present study. Further, we demonstrated with laser beam induced current mapping and point-to-point diode analysis that the water-induced performance losses are a result of the exposed device area comprising regions with entirely unaltered high output and intact diode behavior and those with severe degradation showing detrimentally lowered output and voltage-independent charge blocking, which is essentially insulating behavior. It is suggested that this is caused by transport of water through pinholes to the organic/metal interface, where they form insulating oxide or hydroxide islands, while the organic active layer stays unharmed.

Zero-Ripple Input-Current High-Step-Up Boost–SEPIC DC–DC Converter With Reduced Switch-Voltage Stress

This paper proposes a zero-ripple input-current high-step-up boost–single ended primary inductor converter (SEPIC) dc–dc converter with reduced switch-voltage stress to overcome some drawbacks of the conventional cascaded boost–SEPIC dc–dc converter. In the proposed converter, the input current ripple is significantly removed by the auxiliary circuit at the boost stage and the voltage gain is more increased by using turn ratio of a coupled inductor at the SEPIC stage. Additional, the switch-voltage stress is reduced due to the clamping circuit, and the reverse-recovery problem of the output diode is alleviated by the leakage inductor. Hence, the low-voltage-rating MOSFET, which has low $R_{{{\rm ds(on)}}}$ , can be utilized as a main switch device. Therefore, the total power efficiency is improved. The theoretical analysis of the proposed converter is verified on an output 200-V to 200-W prototype.

High step-up quasi-Z-source DC\u2013DC converters with single switched capacitor branch

Aiming to integrate the respective merits of the switched-capacitor converter and the quasi-Z-source converter. An novel high step-up quasi-Z-source DC–DC converter with a single switched-capacitor branch is proposed. Compared to other high boost DC–DC converters, the proposed converter can provide higher output voltage gain, lower current stress across the switches, and lower voltage stress across the output diodes by using the same or similar passive and active components. Therefore, the efficiency and reliability of the converter can be improved. The topological derivation, operating principle, parameter selection, and comparison with other DC–DC converters are presented. Finally, both simulations and experimental results are given to verify the characteristics of the proposed converter.

Interleaved full ZVZCS DC–DC boost converter: analysis, design, reliability evaluations and experimental results

In this study, a new interleaved full soft switching DC-DC boost converter with a high power reliability is proposed. To achieve soft switching, a simple auxiliary circuit consisting of one switch, one diode, one inductor and two capacitors is employed in each single-phase DC-DC boost converter connected in parallel. All switches and diodes, including main and auxiliary ones, operate under soft switching conditions. These soft switching conditions consist of zero voltage and zero current switching (ZVZCS) for all switches and diodes at switching transitions except the output diodes, which turn off only with zero current switching. The soft switching technique used in this study decreases power losses which leads the converter to have higher efficiency and reliability. Also, the auxiliary circuit is located out of the main power path preventing high voltage and current stresses on the switches. In this study, operational modes analysis, design procedure, power reliability evaluations and laboratory prototype results with switching frequency of 20 kHz, input voltage of 48 V and output power of 40 W are presented.

Soft-Switching Dual-Flyback DC–DC Converter With Improved Efficiency and Reduced Output Ripple Current

This paper presents a soft-switching dual-flyback dc-dc converter with improved efficiency and reduced output ripple current. Zero-voltage-switching (ZVS) technique and a dual-flyback module for reducing the number of snubber current paths are adopted to improve efficiency. For the ZVS technique, a self-driven synchronous rectifier (SR) is used instead of an output diode. By turning the self-driven SR off after a short delay, a main switch is turned on under the ZVS condition. For reducing the number of snubber current paths, a dual-flyback module and a snubber diode are used. When the main switch is turned off, leakage inductance energy is absorbed by a snubber diode into an input source and a primary dc-bus capacitor. Then, this energy is reprocessed by the dual-flyback dc-dc module to secondary side. Hence, there is only one snubber current path. In addition, the proposed converter features a reduced output ripple current because of the continuous current. Consequently, the proposed converter can achieve high efficiency and reduced output ripple current. To verify the performance of the proposed converter, operating principles, steady-state analyses, and experimental results from a 340 to 24-V, 100-W prototype are presented.

A High-Efficiency Hybrid Resonant Converter With Wide-Input Regulation for Photovoltaic Applications

A microconverter serves as a front-end dc-dc stage of a microinverter to convert the power from a photovoltaic module to a dc bus. These front-end microconverters require isolation, high-boost ratio, wide-input voltage regulation, and high efficiency. This paper introduces an isolated resonant converter with hybrid modes of operation to achieve wide-input regulation while still maintaining high efficiency. The proposed converter is designed as a series resonant converter with nominal-input voltage and operates under two additional modes: a boost converter with low-input voltage and a buck converter with high-input voltage. Unlike conventional resonant converters, this converter operates at discontinues conduction mode with a fixed frequency, simplifying the design and control. In addition, this converter can achieve zero-voltage switching (ZVS) and/or zero-current switching (ZCS) of the primary-side MOSFETs, ZVS and/or ZCS of the secondary-side MOSFETs, and ZCS of output diodes under all operating conditions. Experimental results using a 300-W prototype achieve a peak efficiency of 98.1% and a California Energy Commission efficiency of 97.6% including all auxiliary and control power at nominal-input voltage.