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Showing papers on "Forward converter published in 2011"


Journal ArticleDOI
TL;DR: In this article, a distributed control strategy based on improved dc bus signaling is proposed for a modular photovoltaic (PV) generation system with battery energy storage elements, which is composed of three modular dc/dc converters for PV arrays, two grid-connected dc/ac converters, and one DC/dc converter for battery charging/discharging and local loads, which are available of either gridconnected operation or islanding operation.
Abstract: Modular generation system, which consists of modular power conditioning converters, is an effective solution to integrate renewable energy sources with conventional utility grid to improve reliability and efficiency, especially for photovoltaic generation. A distributed control strategy based on improved dc bus signaling is proposed for a modular photovoltaic (PV) generation system with battery energy storage elements. In this paper, the modular PV generation system is composed of three modular dc/dc converters for PV arrays, two grid-connected dc/ac converters, and one dc/dc converter for battery charging/discharging and local loads, which is available of either grid-connected operation or islanding operation. By using the proposed control strategy, the operations of a modular PV generation system are categorized into four modes: islanding with battery discharging, grid-connected rectification, grid-connected inversion, and islanding with constant voltage (CV) generation. The power balance of the system under extreme conditions such as the islanding operation with a full-charged battery is taken into account in this control strategy. The dc bus voltage level is employed as an information carrier to distinguish different modes and determine mode switching. Control methods of modular dc/dc converters, battery converter, and grid-connected converter are addressed. An autonomous control method for modular dc/dc converters is proposed to realize smooth switching between CV operation and maximum power point tracking operation, which enables the dc bus voltage regulation capability of modular dc/dc converters. Seamless switching of a battery converter between charging and discharging and that of a grid-connected converter between rectification and inversion are ensured by the proposed control methods. Experiments verify the practical feasibility and the effectiveness of the proposed control strategies.

585 citations


Journal ArticleDOI
TL;DR: This paper presents first an overview of the well-known voltage and current dc-link converter topologies used to implement a three-phase PWM ac-ac converter system, and a common knowledge basis of the individual converterTopologies is established.
Abstract: This paper presents first an overview of the well-known voltage and current dc-link converter topologies used to implement a three-phase PWM ac-ac converter system. Starting from the voltage source inverter and the current source rectifier, the basics of space vector modulation are summarized. Based on that, the topology of the indirect matrix converter (IMC) and its modulation are gradually developed from a voltage dc-link back-to-back converter by omitting the dc-link capacitor. In the next step, the topology of the conventional (direct) matrix converter (CMC) is introduced, and the relationship between the IMC and the CMCs is discussed in a figurative manner by investigating the switching states. Subsequently, three-phase ac-ac buck-type chopper circuits are considered as a special case of matrix converters (MCs), and a summary of extended MC topologies is provided, including three-level and hybrid MCs. Therewith, a common knowledge basis of the individual converter topologies is established.

489 citations


Journal ArticleDOI
TL;DR: This paper presents new step-up dc/dc converter topologies intended for distributed power generation systems and describes the operation principles of the proposed topologies and analyzes the theoretical and experimental results.
Abstract: This paper presents new step-up dc/dc converter topologies intended for distributed power generation systems. The topologies contain a voltage-fed quasi-Z-source inverter with continuous input current on the primary side, a single-phase isolation transformer, and a voltage doubler rectifier (VDR). To increase the power density of the converter, a three-phase auxiliary ac link (a three-phase inverter and a three-phase isolation transformer) and a three-phase VDR are proposed to be implemented. This paper describes the operation principles of the proposed topologies and analyzes the theoretical and experimental results.

388 citations


Journal ArticleDOI
TL;DR: In this article, the authors proposed a new high step-up dc-dc converter designed especially for regulating the dc interface between various microsources and a dc-ac inverter to electricity grid.
Abstract: This paper proposes a new high step-up dc-dc converter designed especially for regulating the dc interface between various microsources and a dc-ac inverter to electricity grid. The figuration of the proposed converter is a quadratic boost converter with the coupled inductor in the second boost converter. The converter achieves high step-up voltage gain with appropriate duty ratio and low voltage stress on the power switch. Additionally, the energy stored in the leakage inductor of the coupled inductor can be recycled to the output capacitor. The operating principles and steady-state analyses of continuous-conduction mode and boundary-conduction mode are discussed in detail. To verify the performance of the proposed converter, a 280-W prototype sample is implemented with an input voltage range of 20-40 V and an output voltage of up to 400 V. The upmost efficiency of 93.3% is reached with high-line input; on the other hand, the full-load efficiency remains at 89.3% during low-line input.

377 citations


Journal ArticleDOI
TL;DR: In this paper, a high-frequency transformer isolated bidirectional dc-dc converter modules connected in input-series-output-parallel (ISOP) for 20kVA-solid-state transformer is presented.
Abstract: This paper presents the design of new high-frequency transformer isolated bidirectional dc-dc converter modules connected in input-series-output-parallel (ISOP) for 20-kVA-solid-state transformer. The ISOP modular structure enables the use of low-voltage MOSFETs, featuring low on-state resistance and resulted conduction losses, to address medium-voltage input. A phase-shift dual-half-bridge (DHB) converter is employed to achieve high-frequency galvanic isolation, bidirectional power flow, and zero voltage switching (ZVS) of all switching devices, which leads to low switching losses even with high-frequency operation. Furthermore, an adaptive inductor is proposed as the main energy transfer element of a phase-shift DHB converter so that the circulating energy can be optimized to maintain ZVS at light load and minimize the conduction losses at heavy load as well. As a result, high efficiency over wide load range and high power density can be achieved. In addition, current stress of switching devices can be reduced. A planar transformer adopting printed-circuit-board windings arranged in an interleaved structure is designed to obtain low core and winding loss, solid isolation, and identical parameters in multiple modules. Moreover, the modular structure along with a distributed control provides plug-and-play capability and possible high-level fault tolerance. The experimental results on 1 kW DHB converter modules switching at 50 kHz are presented to validate the theoretical analysis.

335 citations


Journal ArticleDOI
TL;DR: In this paper, a dual-mode resonant converter topology is proposed for parallel connected dc MICs, which can change resonant modes adaptively depending on the panel operation conditions.
Abstract: The future renewable electric energy delivery and management (FREEDM) system provides a dc interface for alternative energy sources. As a result, photovoltaic (PV) energy can be easily delivered through a dc/dc converter to the FREEDM system's dc bus. The module-integrated converter (MIC) topology is a good candidate for a PV converter designed to work with the FREEDM system. This paper compares the parallel connected dc MIC structure with its counterpart, the series connected MIC architecture. From the presented analysis, the parallel connected architecture was shown to have more advantages. In this paper, a high-efficiency dual mode resonant converter topology is proposed for parallel connected dc MICs. This new resonant converter topology can change resonant modes adaptively depending on the panel operation conditions. The converter achieves zero-voltage switching for primary-side switches and zero-current switching for secondary-side diodes for both resonant modes. The circulation energy is minimized particularly for 5-50% of the rated power level. Thus, the converter can maintain a high efficiency for a wide input range at different output power levels. This study explains the operation principle of the proposed converter and presents a dc gain analysis based on the fundamental harmonic analysis method. A 240-W prototype with an embedded maximum power point tracking controller was built to evaluate the performance of the proposed converter. The prototype's maximum efficiency reaches 96.5% and an efficiency increase of more than 10% under light load conditions is shown when compared with a conventional LLC resonant converter.

274 citations


Journal ArticleDOI
TL;DR: In this article, a novel H-bridge multilevel pulsewidth modulation converter topology based on a series connection of a highvoltage diode-clamped inverter and a low-voltage conventional inverter is proposed.
Abstract: A novel H-bridge multilevel pulsewidth modulation converter topology based on a series connection of a high-voltage diode-clamped inverter and a low-voltage conventional inverter is proposed in this paper. A dc link voltage arrangement for the new hybrid and asymmetric solution is presented to have a maximum number of output voltage levels by preserving the adjacent switching vectors between voltage levels. Hence, a 15-level hybrid converter can be attained with a minimum number of power components. A comparative study has been carried out to present high performance of the proposed configuration to approach a very low total harmonic distortion of voltage and current, which leads to the possible elimination of the output filter. Regarding the proposed configuration, a new cascade inverter is verified by cascading an asymmetrical diode-clamped inverter, in which 19 levels can be synthesized in output voltage with the same number of components. To balance the dc link capacitor voltages for the maximum output voltage resolution as well as synthesize asymmetrical dc link combination, a new multi-output boost converter is utilized at the dc link voltage of a seven-level H-bridge diode-clamped inverter. Simulation and hardware results based on different modulations are presented to confirm the validity of the proposed approach to achieve a high-quality output voltage.

272 citations


Journal ArticleDOI
TL;DR: The proposed topology is based on a cascaded connection of single-phase submultilevel converter units and full-bridge converters and is optimized in order to utilize a minimum number of switches and dc voltage sources and produce a high number of output voltage steps.
Abstract: In this paper, a new topology of a cascaded multilevel converter is proposed. The proposed topology is based on a cascaded connection of single-phase submultilevel converter units and full-bridge converters. Compared to the conventional multilevel converter, the number of dc voltage sources, switches, installation area, and converter cost is significantly reduced as the number of voltage steps increases. In order to calculate the magnitudes of the required dc voltage sources, three methods are proposed. Then, the structure of the proposed topology is optimized in order to utilize a minimum number of switches and dc voltage sources, and produce a high number of output voltage steps. The operation and performance of the proposed multilevel converter is verified by simulation results and compared with experimental results of a single-phase 49-level converter, too.

249 citations


Patent
10 Aug 2011
TL;DR: In this article, the converters are coupled in series and an inverter is connected in parallel with the series connection of converters and inverts a DC input to the inverter from converters into an AC output.
Abstract: A system and method for combining power from DC power sources. Each power source is coupled to a converter. Each converter converts input power to output power by monitoring and maintaining the input power at a maximum power point. Substantially all input power is converted to the output power, and the controlling is performed by allowing output voltage of the converter to vary. The converters are coupled in series. An inverter is connected in parallel with the series connection of the converters and inverts a DC input to the inverter from the converters into an AC output. The inverter maintains the voltage at the inverter input at a desirable voltage by varying the amount of the series current drawn from the converters. The series current and the output power of the converters, determine the output voltage at each converter.

243 citations


Journal ArticleDOI
TL;DR: This paper presents a high-efficiency and high-step-up nonisolated interleaved dc-dc converter with a common active-clamp circuit that achieves high efficiency because of the recycling of the leakage energies, reduction of the switch voltage stress, mitigation of the output diode's reverse recovery problem, and interleaving of the converters.
Abstract: This paper presents a high-efficiency and high-step-up nonisolated interleaved dc-dc converter with a common active-clamp circuit. In the presented converter, the coupled-inductor boost converters are interleaved. A boost converter is used to clamp the voltage stresses of all the switches in the interleaved converters, caused by the leakage inductances present in the practical coupled inductors, to a low voltage level. The leakage energies of the interleaved converters are collected in a clamp capacitor and recycled to the output by the clamp boost converter. The proposed converter achieves high efficiency because of the recycling of the leakage energies, reduction of the switch voltage stress, mitigation of the output diode's reverse recovery problem, and interleaving of the converters. Detailed analysis and design of the proposed converter are carried out. A prototype of the proposed converter is developed, and its experimental results are presented for validation.

237 citations


Journal ArticleDOI
TL;DR: LLC resonant converter with significant resonant inductance is proposed for designing an adjustable wide-range regulated voltage source and an almost flat efficiency curve with maximum value of 94% has been achieved for the converter.
Abstract: LLC resonant converter with significant resonant inductance is proposed for designing an adjustable wide-range regulated voltage source. Large resonant inductance increases output voltage adjustment range and conversion efficiency, particularly at light loads. Soft switching is achieved for all power devices under all operating conditions by choosing the dead time and maximum switching frequency properly and operating in the converter's inductive region. Using a power-factor-correction (PFC) converter reduces the resonant converter's output voltage dependence to the variations of the main ac input voltage. Thus, the compensation of the load variations and the wide-range adjustment of the regulated output voltage can be achieved by using small switching frequency variations. The proposed method has been used to implement an adjustable wide-range voltage source (35-165 V dc), as an ion implanter arc power supply. An almost flat efficiency curve with maximum value of 94% has been achieved for the converter. Its output current can change from no load to 3 A dc.

Journal ArticleDOI
TL;DR: This paper suggests an isolated dc/dc converter using an unregulated LLC converter for fuel cell applications that can be operated at an optimal switching condition, and the high-frequency operation of 300 kHz can be accomplished without introducing an excessive switching loss.
Abstract: This paper suggests an isolated dc/dc converter using an unregulated LLC converter for fuel cell applications. The LLC converter operates as an isolated voltage amplifier with a constant voltage gain, and a nonisolated converter installed in the input stage regulates the output voltage under a wide variation of fuel cell stack voltage. By separating the functions, the unregulated LLC converter can be operated at an optimal switching condition, and the high-frequency operation of 300 kHz can be accomplished without introducing an excessive switching loss. The prototype converter with a 1-kW design (Vin = 24 ~ 48 V/Vo = 400 V) shows an efficiency of above 90.2% under a 24-V input and full load conditions.

Journal ArticleDOI
TL;DR: A novel high step-up dc-dc converter with coupled-inductor and voltage-doubler circuits is proposed, which achieves highstep-up voltage gain with appropriate duty ratio and low voltage stress on the power switches.
Abstract: In this paper, a novel high step-up dc-dc converter with coupled-inductor and voltage-doubler circuits is proposed. The converter achieves high step-up voltage gain with appropriate duty ratio and low voltage stress on the power switches. Also, the energy stored in the leakage inductor of the coupled inductor can be recycled to the output. The operating principles and the steady-state analyses of the proposed converter are discussed in detail. Finally, a prototype circuit of the proposed converter is implemented in the laboratory to verify the performance of the proposed converter.

Journal ArticleDOI
TL;DR: In this article, a novel high step-up dc-dc converter is proposed for a sustainable energy system, which uses coupled-inductive inductor and switched-capacitor techniques.
Abstract: In this paper, a novel high step-up dc-dc converter is proposed for a sustainable energy system. The proposed converter uses coupled-inductor and switched-capacitor techniques. The capacitors are charged in parallel and discharged in series by the coupled inductor to achieve high step-up voltage gain with an appropriate duty ratio. Besides, the voltage stress on the main switch is reduced with a passive clamp circuit; low on-state resistance Rds(on) of the main switch can be adopted to reduce the conduction loss. In addition, the reverse-recovery problem of the diode is alleviated by a coupled inductor. Thus, the efficiency can be further improved. The operating principle and steady-state analyses of voltage gain are discussed in detail. Finally, a prototype circuit with 24-V input voltage, 400-V output voltage, and 200-W output power is implemented in the laboratory to verify the performance of the proposed converter.

Proceedings ArticleDOI
01 Nov 2011
TL;DR: In this paper, three full bridge based high power bi-directional DC-DC converters are conceptually designed for PHEV/EV DC charging infrastructure and their advantages and disadvantages are addressed.
Abstract: PHEV/EV DC charging infrastructure attracts more and more attention recently. High power isolated bi-directional DC-DC converters provide galvanic isolation, V2G capability and reduce the cost and footprint of the system. Maintaining high power efficiency in wide vehicle battery pack voltage range is required. Three full bridge based high power bi-directional DC-DC converters are conceptually designed for this application and their advantages and disadvantages are addressed. Experimental test bench is built and efficiency evaluation for bi-directional operation is reported.

01 Jan 2011
TL;DR: It is illustrated that the proposed grid-interfacing converter systems with enhanced voltage quality could ride through voltage disturbances and continue the power transfer between the local generation and the grid, while a high-quality voltage is maintained for the local loads.

Journal ArticleDOI
TL;DR: The operational principle and characteristics of the proposed converter are presented, and it is verified experimentally with a 135-W, 24-V input, 250-V output prototype converter for a LED driver.
Abstract: To obtain a high step-up gain with high efficiency in nonisolated applications, a high step-up technique based on isolated-type converters is introduced in this paper. By stacking the secondary side of an isolated converter in addition to its primary side, a high step-up conversion ratio and a distributed voltage stress can be achieved. Moreover, a careful choice of an isolated converter can provide zero-voltage switching, continuous input current, and reduced reverse recovery on diodes. Based on a conventional voltage-doubler-rectifier boost-integrated half-bridge converter, the derived converter satisfies all these features, which make it suitable for high step-up applications. The operational principle and characteristics of the proposed converter are presented, and verified experimentally with a 135-W, 24-V input, 250-V output prototype converter for a LED driver.

Journal ArticleDOI
TL;DR: In this paper, a high-gain interleaved boost-derived converter topology is discussed, which offers modularity, lower ripple for both input current and output voltage, and lower voltage and current ratings of the various circuit elements when compared to the basic boost converter.
Abstract: In transformer-less energy systems sourced from low and unregulated voltage generated by a fuel cell or photovoltaic source, the voltage gain of the power electronic conditioning stage is required to be as high as possible. Although component parasitic elements limit the practically realisable voltage gain of any converter topology, this becomes a critical issue in the case of the basic step-up converter. In this study, a high-gain interleaved boost-derived converter topology is discussed. The proposed converter topology offers modularity, lower ripple for both input current and output voltage, and lower voltage and current ratings of the various circuit elements when compared to the basic boost converter. Analysis, design and key converter waveforms operating in the continuous conduction mode are provided along with design guidelines. Experimental results taken from a 1 kW laboratory prototype operating at 60 kHz are presented to confirm the validity of the analysis and design considerations.

Proceedings ArticleDOI
19 Jun 2011
TL;DR: A power flow model is presented to include a DC voltage droop control or distributed DC slack bus in a Multi-terminal Voltage Source Converter High Voltage Direct Current (VSC MTDC) grid to study the steady-state change of the combined AC/DC system as a result of faults and transients in the DC grid.
Abstract: In this paper, a power flow model is presented to include a DC voltage droop control or distributed DC slack bus in a Multi-terminal Voltage Source Converter High Voltage Direct Current (VSC MTDC) grid. The available VSC MTDC models are often based on the extension of existing point-to-point connections and use a single DC slack bus that adapts its active power injection to control the DC voltage. A distributed DC voltage control has significant advantages over its concentrated slack bus counterpart, since a numbers of converters can jointly control the DC system voltage. After a fault, a voltage droop controlled DC grid converges to a new working point, which impacts the power flows in both the DC grid and the underlying AC grids. Whereas current day research is focussing on the dynamic behaviour of such a system, this paper introduces a power flow model to study the steady-state change of the combined AC/DC system as a result of faults and transients in the DC grid. The model allows to incorporate DC grids in a N-1 contingency analysis, thereby including the effects of a distributed voltage control on the power flows in both the AC and DC systems.

Journal ArticleDOI
TL;DR: In this article, the authors investigated the optimum dead-time and maximum switching frequency of a wide-adjustable-range LLC resonant converter for realizing the zero voltage switching (ZVS) operation even under the worst-case conditions.
Abstract: LLC resonant converter has been widely used in dc-dc converters. In this paper, optimum dead-time and maximum switching frequency of a wide-adjustable-range LLC resonant converter are investigated for realizing the zero voltage switching (ZVS) operation even under the worst-case conditions. Analyses demonstrate that these parameters depend on the converter inductance ratio and ratio of the converter resonant capacitor and the effective capacitance appeared in parallel with the drain-sources of the power MOSFETs. The necessary dead time for realizing the ZVS operation can be minimized by choosing the normalized maximum switching frequency, properly. Using the dead-time optimum value, soft switching is achieved for all power devices even under the worst-case conditions. Developed prototype of the converter has been tested under different loads (0-3 A dc) and input voltage conditions (320-370 V dc) to achieve a wide-adjustable-range output voltage (40-165 V dc). This dc-dc converter is used as an ion implanter arc power supply. The calculated optimum dead-time and maximum switching frequency are approximately equal to 184 ns and 205.7 kHz, for realizing the ZVS operation at the worst-case conditions. These parameters in the prototype are approximately equal to 195 ns and 203.5 kHz, respectively.

Proceedings ArticleDOI
01 Nov 2011
TL;DR: In this paper, the authors proposed a new modular converter with integrated energy storage based on the cascaded half-bridge modular multilevel converter with common DC bus, which represents a complete modular solution with power electronics and energy storage building blocks for medium and high voltage applications.
Abstract: This paper introduces a new modular converter with integrated energy storage based on the cascaded half-bridge modular multilevel converter with common DC bus. It represents a complete modular solution with power electronics and energy storage building blocks, for medium and high voltage applications. Furthermore, this solution can interconnect a DC and AC grid with bidirectional power flow, where both of them can receive or generate excess power to the third source integrated in each converter sub-module. This particularity enables the converter usage as a high voltage UPS system in the future HVDC meshed grids. Its functionality and flexibility makes the converter independent on the energy storage unit characteristic. The converter concept with its basic functions and control schemes are described and evaluated in this paper.

Journal ArticleDOI
TL;DR: In this paper, a novel dc-dc switching converter consisting of a boost stage cascaded with a buck converter with their coils magnetically coupled is presented, which has the same step-up or step-down voltage conversion properties than the single inductor noninverting buck-boost converter but exhibits nonpulsating I/O currents.
Abstract: A novel dc-dc switching converter consisting of a boost stage cascaded with a buck converter with their coils magnetically coupled is presented. The disclosed converter has the same step-up or step-down voltage conversion properties than the single inductor noninverting buck-boost converter but exhibits nonpulsating I/O currents. The converter control-to-output transfer function is continuous between operation modes if a particular magnetic coupling is selected. The addition of a damping network improves the dynamics and results in a control-to-output transfer function that has, even in boost mode, two dominant complex poles without right-half-plane zeros. An example shows that an output voltage controller can be designed with the same well-known techniques usually applied to the second-order buck regulator. Details of a prototype and experimental results including efficiency, frequency, and time domain responses are presented. The experimental results validate the theoretical expected advantages of the converter, namely, good efficiency, wide bandwidth, and simplicity of control design.

Journal ArticleDOI
TL;DR: This paper proposes a novel single-stage high-power-factor ac/dc converter with symmetrical topology derived from the integration of two buck-boost power-factor-correction converters and a full-bridge series-resonant dc/DC converter.
Abstract: This paper proposes a novel single-stage high-power-factor ac/dc converter with symmetrical topology. The circuit topology is derived from the integration of two buck-boost power-factor-correction (PFC) converters and a full-bridge series resonant dc/dc converter. The switch-utilization factor is improved by using two active switches to serve in the PFC circuits. A high power factor at the input line is assured by operating the buck-boost converters at discontinuous conduction mode. With symmetrical operation and elaborately designed circuit parameters, zero-voltage switching on all the active power switches of the converter can be retained to achieve high circuit efficiency. The operation modes, design equations, and design steps for the circuit parameters are proposed. A prototype circuit designed for a 200-W dc output was built and tested to verify the analytical predictions. Satisfactory performances are obtained from the experimental results.

Journal ArticleDOI
TL;DR: The proposed MFT-based topology of the traction converter replaces the bulky main line transformer found on board railway vehicles and is a power electronics solution that considerably reduces weight and losses in a traction propulsion system.
Abstract: This paper presents a new configuration of a main traction converter with a medium-frequency transformer (MFT) using matrix converters intended for locomotives and particularly for suburban units supplied by a 25-kV/50-Hz and/or 15-kV/16.7-Hz ac electrification system. Single-phase matrix converters are employed in the primary medium-voltage converter which is directly connected to the ac trolley line. The output of the primary ac/ac converter supplies the primary side of the MFT. The proposed MFT-based topology of the traction converter replaces the bulky main line transformer found on board railway vehicles. Particularly in countries with a catenary of 15 kV/16.7 Hz, very low catenary frequency results in huge and heavy traction transformers. The developed topology is a power electronics solution that considerably reduces weight and losses in a traction propulsion system. The proposed converter configuration with cascaded matrix converters on the primary side of the MFT presents a new research direction in the field of traction converters with MFTs. This paper describes in detail the proposed power circuit and the control of the traction converter. The behavior of the traction converter configuration has been analyzed using simulations and experimental tests carried out on a developed low-voltage laboratory prototype of a traction converter with a rated power of 4 kVA. Based on extensive simulation and experimental study, this paper reviews the benefits, drawbacks, and constraints of the developed traction converter configuration.

Journal ArticleDOI
TL;DR: In this article, a review of step-up DC/DC converters with high voltage gain is presented based on the presence or lack of galvanic isolation, and a comparison and discussion of different stepup topologies are performed across number of parameters and presented in this paper.
Abstract: The renewable energy sources such as PV modules, fuel cells or energy storage devices such as super capacitors or batteries deliver output voltage at the range of around 12 to 70 VDC. In order to connect them to the grid the voltage level should be adjusted according to the electrical network standards in the countries. First of all the voltage should be stepped up to sufficient level at which the DC/AC conversion can be performed to AC mains voltage requirements. Overall performance of the renewable energy system is then affected by the efficiency of step-up DC/DC converters, which are the key parts in the system power chain. This review is focused on high efficiency step-up DC/DC converters with high voltage gain. The differentiation is based on the presence or lack of galvanic isolation. A comparison and discussion of different DC/DC step-up topologies will be performed across number of parameters and presented in this paper.

Journal ArticleDOI
TL;DR: In this paper, a common duty-ratio control scheme is proposed for an ISOP converter consisting of multiple phase-shift full-bridge (PS-FB) converter modules, which achieves stable sharing of the input voltage and load current by applying a shared duty ratio to all converter modules without a dedicated input voltage sharing controller.
Abstract: Input-series output-parallel (ISOP)-connected converters allow the use of low-voltage and low-power converter modules for high input-voltage and high-power applications. Further, the use of high-frequency, low-voltage MOSFETs, which are optimized for very low on-resistance, is enabled, resulting in lower conduction losses and higher power density. In this paper, a common-duty-ratio control scheme is proposed for an ISOP converter consisting of multiple phase-shift full-bridge (PS-FB) converter modules. The proposed control method achieves stable sharing of the input voltage and load current by applying a common duty ratio to all converter modules, without a dedicated input-voltage sharing controller. The control method is analyzed by using both a small-signal averaged model and a steady-state dc model of the ISOP converter, and it is concluded that the equal sharing of input voltage and load current among converter modules can be achieved through reducing the mismatches in various module parameters, which is practically achievable. The stability and performance of the control scheme are verified by Saber simulation and a 500 W experimental prototype consisting of two PS-FB converter modules.

Journal ArticleDOI
TL;DR: A new synchronous rectifier (SR) driving method is proposed using primary current sensing and is simple and low cost for high-output-current dc-dc application.
Abstract: A new synchronous rectifier (SR) driving method is proposed using primary current sensing in this paper. Because the magnetizing current of transformer is included in the primary winding of transformer, it cannot be used to generate the driving signals of SRs directly. A current-compensating winding in current transformer (CT) is used to cancel out the magnetizing current and generate suitable driving signals for SR. Therefore, one CT is used to generate two driving signals for two SRs in LLC converter with a center-tapped rectifier. This current-driven method is simple and low cost for high-output-current dc-dc application. A 150-W dc-dc prototype using LLC half-bridge converter with the proposed SR circuit is built up to verify the theoretical analysis.

Proceedings ArticleDOI
07 Apr 2011
TL;DR: A fully integrated 3-level DC/DC converter that merges characteristics of both inductor-based buck and switched-capacitor converters is presented, which can efficiently regulate the output voltage across a wide range of levels and load currents.
Abstract: In recent years, chip multiprocessor architectures have emerged to scale performance while staying within tight power constraints. This trend motivates per-core/block dynamic voltage and frequency scaling (DVFS) with fast voltage transition. Given the high cost and bulk of off-chip DC/DC converters to implement multiple on-chip power domains, there has been a surge of interest in on-chip converters. This paper presents the design and experimental results of a fully integrated 3-level DC/DC converter [1] that merges characteristics of both inductor-based buck [2–4] and switched-capacitor (SC) converters [5]. While off-chip buck converters show high conversion efficiency, their on-chip counterparts suffer from loss due to low quality inductors. With the help of flying capacitors, the 3-level converter requires smaller inductors than the buck converter, reducing loss and on-die area overhead. Compared to SC converters that need more complex structures to regulate higher than half the input voltage, 3-level converters can efficiently regulate the output voltage across a wide range of levels and load currents. Measured results from a 130nm CMOS test-chip prototype demonstrate nanosecond-scale voltage transition times and peak conversion efficiency of 77%.

Journal ArticleDOI
TL;DR: In this article, a new high-efficient phase-shifted full-bridge (PSFB) converter is proposed, which can operate in the optimal operating point, 50% duty ratio, both in nominal operating condition and hold-up time condition.
Abstract: A new high-efficient phase-shifted full-bridge (PSFB) converter is proposed in this paper. The conventional PSFB converter with an external inductor and clamping diodes is widely used in server power systems due to limited voltage stress on switches and its zero-voltage switching (ZVS) characteristics. However, a hold-up time regulation rule in server systems limits its operating duty ratio in nominal state and it increases the conduction loss of the converter. With simple modification, the proposed converter can be operated in the optimal operating point, 50% duty ratio, both in nominal operating condition and hold-up time condition. The ZVS characteristic is still maintained in the proposed converter. Therefore, conduction loss at the primary side of the converter is reduced and higher efficiency can also be obtained in the proposed converter than the conventional converter. The operational principle and analysis of the proposed converter are presented and verified by the 1-kW prototype.

Journal ArticleDOI
TL;DR: The design, implemented in IBM 130 nm CMOS technology, achieves a peak efficiency of 77% at reduced temperature of 8°C and has a maximum efficiency of 74.5% under normal operating conditions.
Abstract: This paper presents a technique to efficiently supply power over a wide power range using a fully-integrated on-chip converter for dynamic voltage scaling (DVS) based applications. All components, including filter elements, are integrated on-chip. To achieve high efficiency the converter adaptively switches between different modes of operation by detecting the output current. The design, implemented in IBM 130 nm CMOS technology, achieves a peak efficiency of 77% at reduced temperature of 8°C and has a maximum efficiency of 74.5% under normal operating conditions. The converter supplies power over a 450X output power range (0.6 mW to 266 mW). To the best of our knowledge, this is the largest reported power range for a high-efficiency, fully-integrated on-chip power converter to date.