High Output Current Applications Research Articles

A High-Efficiency IPT System With Series-Capacitor Full-Bridge Configuration and Inverse Coupled Current Doubler Rectifier for High-Input, Low-Voltage, and High Output Current Applications

A High-Efficiency IPT System With Series-Capacitor Full-Bridge Configuration and Inverse Coupled Current Doubler Rectifier for High-Input, Low-Voltage, and High Output Current Applications

GaN-Based LLC Converters With Digital Synchronous Rectifier and Copper Foil Planar Transformer in High-Output Current Applications

GaN-Based <i>LLC</i> Converters With Digital Synchronous Rectifier and Copper Foil Planar Transformer in High-Output Current Applications

Development of Phase-Shift Full-Bridge Converter With Integrated Winding Planar Two-Transformer for LDC

This study proposes a new phase-shift full-bridge (PSFB) converter with an integrated winding planar two-transformer for a low-voltage dc–dc converter (LDC). An LDC is a dc–dc converter that supplies power to a 12-V auxiliary battery (A_BAT) and loads from the main battery (M_BAT) of electric vehicles (EVs), used in low-voltage and high-current output applications. PSFB converter is widely used as a suitable topology for such systems. In order to improve the power density, the integrated planar magnetics is designed in the proposed PSFB converter. Furthermore, the size of the transformer is optimized considering the footprint and core loss of components. To confirm the validity of the proposed converter, a 2.1-kW prototype LDC with an input voltage range of 400–800 V and an output voltage of 14 V is analyzed, and the operating characteristics are described. The proposed converter achieves a maximum efficiency of 95.4% and a power density of 5.2 kW/L.

Analysis and small-signal modeling of simplified cascade multiphase DC-DC buck converter

One of the power converters that are often implemented in renewable energy applications is a DC-DC power converter. One of such converters is a step-down converter or buck converter whose output voltage is lower than its input. A novel DC-DC buck converter for low output-voltage and high output current applications is presented in this paper. When compared to the conventional buck converter, the voltage ratio of the proposed topology is higher. The output of this converter also has lower ripple. Thus, the proposed topology is appropriate for renewable applications. The operating principle and small-signal model analysis are discussed in detailed. Finally, a simulation studies is carried out by PSIM to verify performances of the offered topology

A High-Power-Density Active-Clamp Converter with Integrated Planar Transformer

This paper proposes an active-clamp forward-flyback (ACFF) converter with an integrated planar transformer for wide-input voltage and high-output current applications, such as low-voltage direct-current (LDC) converters in electric vehicles. An integrated planar transformer that consists of a forward-flyback transformer, single primary winding, and efficient structure of secondary windings is adopted for the proposed converter, and since this transformer is implemented with a common four-layer printed circuit board (PCB) winding, a high power density and low cost of the proposed converter can be achieved. In addition, due to the low leakage inductance induced by the planar transformer, a reduced commutation period can be achieved, and it is possible to increase the switching frequency resulting in low volume of transformer. Although the integrated planar transformer has relatively high conduction loss, the active-clamp topology can significantly reduce the conduction loss on switches compared with widely used full-bridge (FB) converters because it only utilizes two switches and shows the low circulating current. As a result, the proposed converter with an integrated planar transformer has strengths in high power density and cost competitiveness without degraded efficiency, and it is a very attractive topology for LDC converters and other applications that require wide-input voltage and high-output current.

Analysis and implementation of an isolated high step‐down converter with interleaved output for low voltage applications

AbstractThis paper proposes a new isolated high step‐down dc‐dc converter with a more extensive output range and high efficiency. The interleaved output and ZVS‐ZCS switching for all semiconductors have made the converter appropriate for high output current applications. An auxiliary inductor is used to achieve the ZVS (zero‐voltage switching) and ZVZCS (zero‐voltage zero‐current switching) condition, which charges and discharges the parallel snubber capacitors of the power switches at different modes of operation. Therefore, the switching losses of semiconductor components are reduced significantly, which results in enhanced efficiency. Moreover, the connection of an auxiliary capacitor in series with the transformer has prevented the probability of DC‐current saturation. The proposed converter could be controlled with duty‐cycle or switching frequency variations. However, the output voltage control with the switching frequency variations gives an extended range of output voltage compared with the other presented converters. Moreover, a coupled inductor is used to relate the output gain with the turn ratios, which causes a more extensive range for output voltage gain. Finally, the theoretical analysis is given and is compared with a 140 W experimental prototype, which converts a higher input voltage 300v to 7.5 V of the output voltage.

A Wireless Power Transfer System With Inverse Coupled Current Doubler Rectifier for High-Output Current Applications

In this paper, a series-series wireless power transfer (WPT) system combined with an inverse coupled current-doubler rectifier (ICCDR) is proposed, as a very appropriate WPT topology for high current applications. The ICCDR uses an autotransformer to reduce the losses on the rectifier stage, which is suitable for high current low voltage output applications. Furthermore, a comprehensive comparison between the proposed WPT system with ICCDR and the traditional WPT system with diode rectifier is presented. In the proposed WPT system, the primary parameter configuration and circuit behavior keep the same, while the secondary side altered, contributing to a volume reduction on the resonant capacitor. The system overall efficiency and power density are improved significantly. Accordingly, a 10kW 400V/48V WPT prototype for battery charging is constructed and tested to validate this proposal. The output voltage is in the range between 38 Vdc and 55 Vdc, and the rated output current is 200A. The overall efficiency of the proposed system reaches 94%, improving 2% efficiency with 220W energy saving with respect to the traditional diode-rectifier system, when 9.5kW output power is delivered. Theoretical analysis and experimental results have verified that the proposed system shows great advantages in high power WPT applications.

A New Dead Time Regulation Synchronous Rectification Control Method for High Efficiency LLC Resonant Converters

In low output voltage and high output current LLC resonant converter applications, a synchronous rectification (SR) is essential component for high efficiency and high power density. However, stray inductances in MOSFET package and printed circuit board (PCB) pattern make premature turn-off of SR gate and large SR dead time. To compensate the stray inductance effect and increase system efficiency, a hysteresis band dead time regulation control method is proposed. In the proposed control method, SR dead time is regulated to predetermined dead time target regardless of the stray inductances by using a mixed signal, which includes instantaneous drain voltage information and previous cycle dead time information. As a result, the proposed control method can provide lower conduction losses by the dead time regulation and better transient characteristic by the instantaneous drain voltage information. To verify the validity of the proposed control method, 234-W prototype is built and experimented with the proposed controller, which is implemented with 0.25-μm BCDMOS technology.

A 380-12V, 1kW, 1MHz Converter Using a Miniaturized Split-Phase, Fractional Turn Planar Transformer

High step-down, high output current converters are required in many common and emerging applications, including data center server power supplies, point-of-load converters, and electric vehicle charging. Miniaturization is desirable but challenging owing to the high step-down transformer ubiquitously used in these converters. In this work, a miniaturized split-phase half-turn transformer is demonstrated, which leverages the well-established parallelization benefit of employing multiple phases, as in a matrix transformer, with the dramatic reduction in copper loss associated with the relatively new Variable Inverter/Rectifier Transformer (VIRT) architecture. While these techniques have been described in earlier studies, their combination has not been well explored. A detailed design procedure is described and is used to develop a 97.7% peak efficiency and 97.1% full-load efficiency prototype having a transformer that is 12%–36% smaller than best-in-class designs in the literature at the same power level while also being more efficient. This work showcases the miniaturization benefit of employing multiphase, fractional-turn transformers in high step-down, high output current applications and provides comprehensive guidance to designers interested in applying and extending these techniques.

Decentralized Control Method of ISOP Converter for Input Voltage Sharing and Output Current Sharing in Current Control Loop

Input-Series-Output-Parallel (ISOP) converters, a kind of modular converter, are used in high-input voltage and high-output current applications. In ISOP converters, Input Voltage Sharing (IVS) and Output Current Sharing (OCS) should be implemented for stable operation. In order to solve this problem, this paper proposes a decentralized control method. In the proposed control, output current reference is changed according to the decentralized control characteristic in individual current control loops. In this way, the proposed control method is able to implement IVS and OCS without communication. Also, this method can be easily used in current control loops and has high reliability compared to conventional control methods that require communication. In this paper, the operation principle is described to elucidate the proposed control and a small signal model of an ISOP converter is also implemented. Based on the small signal model, IVS stability analysis is performed using pole-zero maps with varying coefficients and control gains. In addition, the current control loop is designed in a stable region. In order to demonstrate the proposed control method, a prototype ISOP converter is configured using full-bridge converters. The performance of IVS and OCS in an ISOP converter is verified by experimental result.

A Novel Synchronous Current-Doubler Rectifier for LED Drivers Without Electrolytic Capacitors

High-brightness light-emitting diode (LED) lamps have attracted much attention because of their high efficiency, simple structure, energy conservation and environmental protection aspects, and long lifetime. Thus, an LED driver must have a long lifespan, high density, and compact space. However, conventional LED power supplies use an electrolytic capacitor as the storage capacitor in the holdup time, which has a short lifespan and occupies large space. In this paper, a novel synchronous current-doubler rectifier (SCDR) method is proposed as an LED driver. The reasonably designed circuit is used to control the output voltage ripple in the normal range without adding a complicated control circuit. The proposed topology is designed using few components, has no electrolytic capacitor, and has a low cost for high-output current LED driver applications. Circuit operating principles and detailed theoretical analysis are provided in this paper. A 200-W prototype has been established and tested, and the experimental results are presented to highlight the merits of the proposed circuit.

Hydrogen production system with fuzzy logic-controlled converter

Electrolyte current must be controlled in the water electrolysis systems. For this purpose, the power converter for the cell stack of the electrolyzer used in industrial hydrogen production is realized. A series resonant converter, which is suitable for high input voltage and low output current applications, is used as power stage of the electrolyzer. The high-frequency transformer is used for the impedance matching. While the system is running, the electrical resistance of the electrolyzer changes continuously; thus, fuzzy logic controller (FLC) is used to control the output current of the power converter. In this study, a 700-W converter prototype is designed and controlled by the frequency modulation technique in the range of 290--360 kHz. The converter is tested for different output currents and it is observed that the power switches are turned on under soft switching conditions while FLC closely follows reference inputs.

Interleaved Active Clamp Forward Converter With Extended Operating Duty Ratio by Adopting Additional Series-Connected Secondary Windings for Wide Input and High Current Output Applications

This paper presents a new interleaved active clamp forward converter for low and wide input, and high current output applications. In the proposed converter, the operating duty ratio can be extended over 0.5 due to the additional powering path resulting from additional series-connected secondary windings from each transformer. As a result, the proposed converter can be designed with large transformer turns ratio. Thus, since the proposed converter can reduce not only the primary RMS current but also switch turn- off current, it can achieve high efficiency. Moreover, since all secondary switches can operate without floating gate drivers, the proposed converter can maintain simple structure and low complexity of gate driving circuits in the secondary side. The validity of this proposed converter is verified by the experimental results from 36V–72 V input and 12 V/500 W output for the dc/dc prototype.

Modular zero‐voltage switching converter for direct current microgrid applications

This study presents a high-voltage zero-voltage switching converter with balance capacitors in the direct current microgrid. In the proposed converter, full-bridge circuits with primary-series and secondary-parallel connection are used for high-voltage input and high-current output applications. The series connection of full-bridge circuits reduces the voltage rating of power switches in each full-bridge circuit cell. Therefore, high-speed power metal–oxide–semiconductor field-effect transistors are employed to reduce the converter size. Flying capacitors are connected between each full-bridge circuits so that the input split voltages can be balanced automatically in every switching period without using the complexity control scheme. The phase-shift pulse-width modulation scheme is used to regulate the output voltage. The power switches can be turned on at zero voltage due to the energy stored in the output inductors or primary leakage inductors and the switching losses are reduced. The output sides of the full-bridge circuits are connected in parallel to reduce the current ratings of transformer secondary windings and passive power components. Finally, experiments are provided to validate the characteristics and usefulness of the proposed converter in microgrid applications.

Combined Multilevel and Two-Phase Interleaved LLC Converter With Enhanced Power Processing Characteristics and Natural Current Sharing

This paper introduces a new two-phase interleaved flying-capacitor LLC converter topology with high output current applications. Compared to a conventional two-phase LLC converter, the new converter adds a single capacitor that contributes to lower voltage stress on the primary side's switches, automatically balances the current distribution between the phases, and enhances the power processing capabilities. All the attractive features of LLC converters are preserved, such as zero-voltage switching on the primary side's mosfets, zero-current switching on the secondary side's power devices, narrow switching frequency range, and simple design. Full principle of operation and analysis of the converter are described, as well as the converter's primary characteristics and the impact of nonideal components on the current sharing behavior. A 600 W, 400 V-to-12 V experimental prototype is used as a showcase of the attractive features of the new converter, demonstrating excellent current sharing, simple implementation, and high efficiency of up to 97.3%.

High-Efficiency High-Power-Density LLC Converter With an Integrated Planar Matrix Transformer for High-Output Current Applications

Isolated high-output current DC/DC converters are critical for future data center power architecture. LLC converters with matrix transformer are suitable for these applications due to its high efficiency and high power density. Different matrix transformer structures are investigated in this paper. To improve the current design practice, a high-frequency transformer loss model is developed and a detailed design methodology is proposed. Moreover, a novel matrix transformer structure is proposed to integrate four elemental transformers into one magnetic core with simple four-layer print circuit board windings implementation and further reduced core loss. By pushing switching frequency up to megahertz with GaN devices, the proposed matrix transformer can achieve high efficiency, high power density, and automatic manufacturing for magnetic components. A 1-MHz 380 V/12 V 800-W LLC converter with GaN devices is demonstrated. The prototype achieves a peak efficiency of 97.6% and a power density of 900 W/in3.

Resonant Converter for High-Input Voltage and High-Output Current Applications

ABSTRACTA new resonant converter for high-input voltage and high-output current applications is presented to realize the advantages of low turn-on switching losses, low reverse recovery losses, and low voltage stress of power semiconductors. The series-connected half-bridge converter is used to lessen the voltage stress of power switches at Vin/2. Therefore, power switches with low voltage stress and low turn-on resistance can be used to reduce the conduction losses on the primary side. For high-output current applications, two transformers series-connected on the primary side and parallel-connected on the secondary side are used to automatically balance the load current so that the low current stress of fast recovery diodes can be used at the output side. The operated switching frequency is controlled to be less than the series resonant frequency of the resonant converter. Therefore, power switches can be turned on at zero-voltage switching and the rectifier diodes can be turned off at zero-current switching. Experimental verifications with a laboratory prototype are provided to demonstrate the performance of the proposed converter.

A new parallel ZVS converter with less power switches and low current stress components

SummaryA new direct current (DC)/DC converter with parallel circuits is presented for medium voltage and power applications. There are five pulse‐width modulation circuits in the proposed converter to reduce current stress at low voltage side for high output current applications. These five circuits share the same power switches in order to reduce switch counts. To reduce the converter size, conduction loss, and voltage stress of power semiconductors, the series connections of power metal‐oxide‐semiconductor field‐effect transistor (MOSFET) with high switching frequency instead of insulated gate bipolar transistor (IGBT) with low switching frequency are adopted. Thus, the voltage stress of MOSFETs is clamped at half of input voltage. The switched capacitor circuit is adopted to balance input split capacitor voltages. Asymmetric pulse‐width modulation scheme is adopted to generate the necessary switching signals of MOSFETs and regulate output voltage. Based on the resonant behavior at the transition interval of power switches, all MOSFETs are turned on under zero voltage switching from 50% load to 100% load. The circuit configuration, operation principle, converter performance, and design example are discussed in detail. Finally, experimental verifications with a 1.92 kW prototype are provided to verify the performance of the proposed converter. Copyright © 2015 John Wiley &amp; Sons, Ltd.

Line and Grid Impedance Impact on the Performances of a Parallel Connected Modular Inverter System

With the rising fuel cost, increasing demand of power and the concerns for global climate change, the use of clean energy make the connection of power electronics building bloc in the heart of the current research. The high output current applications make the parallel connection of modular inverters to be a solution for the use of low power building block inverters where the output power cannot be handled by a single inverter configuration. In this context, average-modeling using average phase–leg technique allows the &lt;em&gt;n&lt;/em&gt;-parallel connected inverters to be analyzed accurately and rapidly without requiring the complexity of the full switched inverter topology. The obtained analytical solution along with the equivalent circuit model makes easier the design of the control loop. The analytical solution of the &lt;em&gt;n&lt;/em&gt;-parallel connected inverters shows the impact of the line and grid impedance on the performance of the overall system. The impact of this coupling has to be investigated such that the main feature of paralleling inverters is guaranteed and that the inverter mode of operation will not be compromised. The main advantage of paralleling inverters can be lost for a certain coupling impedance considerations.

Wireless Input-Voltage-Sharing Control Strategy for Input-Series Output-Parallel (ISOP) System Based on Positive Output-Voltage Gradient Method

An input-series output-parallel (ISOP) system, in which multiple converter modules are connected in series at the input sides and parallel at the output side, is very suitable for high input-voltage, low output-voltage, and high output-current applications. Input-voltage sharing (IVS) and output-current sharing of the constituent modules among the ISOP system must be ensured. The existing IVS control strategies have drawbacks of lower reliability and lower modularity. In this paper, we propose a wireless IVS control strategy for ISOP systems based on positive output-voltage gradient method, which can effectively improve the reliability and modularity of ISOP systems. First, the operation principle of the proposed control strategy is introduced, and the IVS performance and output-voltage regulation characteristics of ISOP systems are analyzed. The stability of the proposed control strategy is also explored. A three-module ISOP system prototype is fabricated and tested in the laboratory, and the experimental results verify the effectiveness of the proposed control strategy.