Literature Survey of Interleaved DC-DC Step-Down Converters for Proton Exchange Membrane Electrolyzer Applications
---
paper_title: DC/DC converter topologies for electrolyzers: State-of-the-art and remaining key issues

paper_content:

Abstract In recent years, the use of electrolyzers to produce cleanly and efficiently hydrogen from renewable energy sources (i.e. wind turbines, photovoltaic) has taken advantage of a growing interest from researchers and industrial. Similarly to fuel cells, DC/DC converters are needed to interface the DC bus with the electrolyzer. Usually, electrolyzers require a low DC voltage to produce hydrogen from water. For this reason, a DC/DC buck converter is generally used for this purpose. However, other DC/DC converter topologies can be used depending on the feature of the electrolyzer and electrical grid as well. The main purpose of this paper is to present the current state-of-the-art of DC/DC converter topologies which can be combined with electrolyzers. The different DC/DC converter topologies are compared in terms of output current ripple reduction, conversion ratio, energy efficiency, and power switch fault-tolerance. Besides, remarks on the state-of-the-art and remaining key issues regarding DC/DC converters are provided.
---
paper_title: A comprehensive review on PEM water electrolysis

paper_content:

Abstract Hydrogen is often considered the best means by which to store energy coming from renewable and intermittent power sources. With the growing capacity of localized renewable energy sources surpassing the gigawatt range, a storage system of equal magnitude is required. PEM electrolysis provides a sustainable solution for the production of hydrogen, and is well suited to couple with energy sources such as wind and solar. However, due to low demand in electrolytic hydrogen in the last century, little research has been done on PEM electrolysis with many challenges still unexplored. The ever increasing desire for green energy has rekindled the interest on PEM electrolysis, thus the compilation and recovery of past research and developments is important and necessary. In this review, PEM water electrolysis is comprehensively highlighted and discussed. The challenges new and old related to electrocatalysts, solid electrolyte, current collectors, separator plates and modeling efforts will also be addressed. The main message is to clearly set the state-of-the-art for the PEM electrolysis technology, be insightful of the research that is already done and the challenges that still exist. This information will provide several future research directions and a road map in order to aid scientists in establishing PEM electrolysis as a commercially viable hydrogen production solution.
---
paper_title: Integration of hydrogen energy systems into renewable energy systems for better design of 100% renewable energy communities

paper_content:

Abstract This paper will introduce the concept of 100% renewable energy and the role hydrogen and fuel cells can play for storage and transportation sectors. The importance, necessity and possibility of an overall global transition from fossil and nuclear-based fuels to renewable energy fuels using electricity and hydrogen as clean energy carriers will be summarized. Polluted, inefficient and unhealthy societies of today are missing energy self-sufficient, better managed, in harmony with nature ecological communities. The possible role of hydrogen fuel cells in fulfilling this target will be demonstrated and the success stories of the leading countries will be given. Renewable energy investments which have started in 2013 increased steadily and reached to 290 billion dollars towards the end of 2015. Today's increasing investments and cheaper supply of renewable energy will in turn effect the hydrogen production costs and increase the diversion from fossil fuels to cheap renewable energy. This reality confirms that hydrogen energy technologies will play an important role in reaching the 100% renewable energy target.
---
paper_title: Implementation of an electrolysis system with DC/DC synchronous buck converter

paper_content:

Abstract A synchronous buck DC–DC converter that can be used to produce hydrogen through electrolysis by using the energy generated from renewable energy sources has been designed and implemented. The reason for selecting this topology is that the voltage level at the output of renewable sources, such as solar cells and storage batteries, is about 12 V DC, and the voltage level required for electrolysis is about 2 V DC. Traditional buck converters have low efficiencies at low output voltages since the voltage drops on the components are comparable to the output voltage. The converter has been designed and tested at 25 A output current. Two different electrodes were used for electrolysis and the effect of electrode opening on the operation was observed. In addition, the stability analysis of non-linear electrolysis system load has been performed.
---
paper_title: Interleaved soft-switching coupled-buck converter with active-clamp circuits

paper_content:

This paper presents a coupled-buck converter with active-clamp circuits. The active switches in the converter can sustain a long enough duty cycle while it operates with a high step-down voltage ratio, reducing current stress significantly. In the converter, the active-clamp circuits provided can have benefits of recycling the leakage energy, while minimum ringing voltage is across the active switches. Moreover, since both main and auxiliary switches can be turned on with zero-voltage switching (ZVS), switching loss can be reduced and conversion efficiency therefore can be improved significantly. A 240 W prototype of the proposed buck converter was built and experimental results have shown that efficiency can reach as high as 89%. It is relatively attractive for applications to hybrid electric vehicle on-board chargers.
---
paper_title: A review on DC/DC converter architectures for power fuel cell applications

paper_content:

Fuel cell-based power sources are attractive devices. Through multi-stack architecture, they offer flexibility, reliability, and efficiency. Keys to accessing the market are simplifying its architecture and each components. These include, among others, the power converter enabling the output voltage regulation. This article focuses on this specific component. The present paper gives a comprehensive overview of the power converter interfaces potentially favorable for the automotive, railways, aircrafts and small stationary domains. First, with respect to the strategic development of a modular design, it defines the specifications of a basic interface. Second, it inventories the best architecture opportunities with respect to these requirements. Based on this study, it fully designs a basic module and points out the outstanding contribution of the new developed silicon carbide switch technology. In conclusion, this review article exhibits the importance of choosing the right power converter architecture and the related technology. In this context it is highlighted that the output power interface can be efficient, compact and modular. In addition, its features enable a thermal compatibility with many ways of integrating this component in the global fuel cell based power source.
---
paper_title: Interleaved buck converters with a single-capacitor turn-off snubber

paper_content:

This paper proposes interleaved buck converters with a single-capacitor snubber to smooth out switch turn-off transition. The single-capacitor snubber is used to limit rising rate of drain-source voltage of the metal-oxide-semiconductor field-effect transistor (MOSFET) switch in the converters to reduce turn-off loss. In addition, the converters are operated at the boundary of continuous and discontinuous conduction modes (CCM), (DCM) to reduce turn-on loss, and in an interleaving fashion to reduce output current ripple. As compared with the counterparts of conventional converter topologies, the proposed converters have the merits of less component count, higher efficiency over a certain load range, smaller size, and they are easier to implement. Hardware measurements obtained from experimental prototypes have verified these merits.
---
paper_title: A High-Efficiency DC–DC Converter Using 2 nH Integrated Inductors

paper_content:

Historically, buck converters have relied on high-Q inductors on the order of 1 to 100 μH to achieve a high efficiency. Unfortunately, on-chip inductors are physically large and have poor series resistances, which result in low-efficiency converters. To mitigate this problem, on-chip magnetic coupling is exploited in the proposed stacked interleaved topology to enable the use of small (2 nH) on-chip inductors in a high-efficiency buck converter. The dramatic decrease in the inductance value is made possible by the unique bridge timing of the stacked design that causes magnetic coupling to boost the converter's efficiency by reducing the current ripple in each inductor. The magnetic coupling is realized by stacking the two inductors on top of one another, which not only lowers the required inductance, but also reduces the chip area consumed by the two inductors. The measured conversion efficiency for the prototype circuit, implemented in a 130-nm CMOS technology, shows more than a 15% efficiency improvement over a linear converter for low output voltages rising to a peak efficiency of 77.9% for a 0.9 V output. These efficiencies are comparable to converters implemented with higher Q inductors, validating that the proposed techniques enable high-efficiency converters to be realized with small on-chip inductors.
---
paper_title: Study of a multiphase interleaved step-up converter for fuel cell high power applications

paper_content:

Abstract This paper presents a study of a high power dc distributed system supplied by a fuel cell generator. A proposed parallel power converter with interleaving algorithm is chosen to boost a low dc voltage of fuel cell to a dc bus utility level. The present interleaved step-up converters are composed of two and four identical boost converters connected in parallel. Converters are controlled by interleaved switching signals, which have the same switching frequency and the same phase shift. By virtue of paralleling the converters, the input current can be shared among the cells or phases, so that high reliability and efficiency in power electronic systems can be obtained. In addition, it is possible to improve the system characteristics such as maintenance, repair, fault tolerance, and low heat dissipation. During the past decade, power electronics research has focused on the development of interleaved parallel converters. For an interleaving technique with a real fuel cell source, this work is the first presentation; it is not just a fuel cell simulation. So, the design and experimental verification of 1.2-kW prototype converters at a switching frequency of 25 kHz connected with a Nexa TM PEM fuel cell system (1.2-kW, 46-A) in a laboratory is presented. Experimental results corroborate the excellent system performances. The fuel cell ripple current can be virtually reduced to zero. As a result, the fuel cell mean current is nearly equal to the fuel cell rms current.
---
paper_title: Interleaved buck converter having low switching losses and improved step-down conversion ratio

paper_content:

A new interleaved buck converter (IBC) having low switching losses and improved step-down conversion ratio is proposed in this paper. It is similar to a conventional IBC, but two active switches are connected in series, and a coupling capacitor is employed in the power path, like Cuk, Sepic, and Zeta converters. The proposed IBC shows that since the voltage stress across all active switches is half of the input voltage before turn-on or after turn-off, the capacitive discharging and switching losses can be reduced considerably. This allows the proposed IBC to have higher efficiency and be operated at higher switching frequency. In addition, the proposed IBC has higher step-down conversion ratio and smaller output current ripple than a conventional IBC. The features, operation principles, and relevant analysis results of the proposed IBC are presented in this paper. The validity of this study is confirmed by the experimental results of prototype converters with 150–200V input, 24V/10A output.
---
paper_title: A novel winding coupled-buck converter for high-frequency, high step-down DC/DC conversion

paper_content:

The buck converter is popularly used for stepdown DC/DC conversion when there is no isolation requirement. However, for high step-down, large output current applications such as voltage regulation modules (VRMs), it is no longer suitable, especially at high switching frequencies. The too-small duty cycle and large switching-related loss limit its performance. This paper proposes a novel topology, which is based on the use of additional coupled windings and can solve all these problems. An integrated magnetic structure is proposed for these windings so that the same magnetic cores can be used as in the buck converter. Furthermore, it is easy to implement a lossless clamp circuit to limit the device turn-off voltage spike and to recover inductor leakage energy. Experimental results obtained with a 12 V to 1.5 V/25 A VRM prove the significant improvement of the proposed topology at switching frequencies in excess of a megahertz.
---
paper_title: Interleaved Zero-Current-Transition Buck Converter

paper_content:

This paper introduces interleaved zero-current-transition (ZCT) converters where two sets of switches are operating out-of-phase and share the load power equally. Turn-on transitions at zero current and a significant reduction of the losses associated with diode reverse recovery are accomplished through addition of two small inductors. This paper describes a 30-kW (300 V/100 A) interleaved ZCT buck converter operating at 32-kHz effective switching frequency. Losses and efficiency of the experimental prototype compare favorably against the standard and interleaved hard-switched buck converters. Constant frequency operation with low switching losses and low output current ripple is very well suited for the realization of dc power supplies in plasma processes.
---
paper_title: Real-Time Emulation of a Hydrogen-Production Process for Assessment of an Active Wind-Energy Conversion System

paper_content:

This paper presents the real-time emulation of a hydrogen-production process for assessment of an active wind- energy conversion system. The hardware-in-the-loop emulator of the electrolyzer consists of a power-electronic stage and a control stage. In the control board, the algorithmic equations of the electrolyzer modeling and its control should be implemented, as well as the emulator's power converter control. The causal ordering graph is used to model the electrolyzer and its auxiliary equipment. This model is capable of characterizing the relations among the different physical quantities and can be used to design the control system, ensuring an efficient and reliable operation of the electrolyzer. The proposed control method can manage the power and hydrogen flows. The simulation results have highlighted the variation domains and the relations among different physical quantities. The experimental results of the real-time emulation is based on a PHOEBUS advanced alkaline electrolyzer and shows the same electrical characteristics in real time with hardware.
---
paper_title: Current status of water electrolysis for energy storage, grid balancing and sector coupling via power-to-gas and power-to-liquids: A review

paper_content:

Water electrolysis has the potential to become a key element in coupling the electricity, mobility, heating and chemical sector via Power-to-Liquids (PtL) or Power-to-Gas (PtG) in a future sustainable energy system. Based on an extensive market survey, discussions with manufacturers, project reports and literature, an overview of the current status of alkaline, PEM and solid oxide electrolysis on the way to large-scale flexible energy storage is presented. These main water electrolysis technologies were compared in terms of available capacity, nominal and part-load performance, flexibility (load range, load gradients, start-up time, stand-by losses) lifetime and investment costs. This review provides a basis of the parameters required and the necessary understanding of electrolysis fundamentals and technologies for a techno-economic analysis of water electrolysis-based concepts and an evaluation of PtG and PtL in energy system studies.
---
paper_title: A comprehensive review on PEM water electrolysis

paper_content:

Abstract Hydrogen is often considered the best means by which to store energy coming from renewable and intermittent power sources. With the growing capacity of localized renewable energy sources surpassing the gigawatt range, a storage system of equal magnitude is required. PEM electrolysis provides a sustainable solution for the production of hydrogen, and is well suited to couple with energy sources such as wind and solar. However, due to low demand in electrolytic hydrogen in the last century, little research has been done on PEM electrolysis with many challenges still unexplored. The ever increasing desire for green energy has rekindled the interest on PEM electrolysis, thus the compilation and recovery of past research and developments is important and necessary. In this review, PEM water electrolysis is comprehensively highlighted and discussed. The challenges new and old related to electrocatalysts, solid electrolyte, current collectors, separator plates and modeling efforts will also be addressed. The main message is to clearly set the state-of-the-art for the PEM electrolysis technology, be insightful of the research that is already done and the challenges that still exist. This information will provide several future research directions and a road map in order to aid scientists in establishing PEM electrolysis as a commercially viable hydrogen production solution.
---
paper_title: Current status of water electrolysis for energy storage, grid balancing and sector coupling via power-to-gas and power-to-liquids: A review

paper_content:

Water electrolysis has the potential to become a key element in coupling the electricity, mobility, heating and chemical sector via Power-to-Liquids (PtL) or Power-to-Gas (PtG) in a future sustainable energy system. Based on an extensive market survey, discussions with manufacturers, project reports and literature, an overview of the current status of alkaline, PEM and solid oxide electrolysis on the way to large-scale flexible energy storage is presented. These main water electrolysis technologies were compared in terms of available capacity, nominal and part-load performance, flexibility (load range, load gradients, start-up time, stand-by losses) lifetime and investment costs. This review provides a basis of the parameters required and the necessary understanding of electrolysis fundamentals and technologies for a techno-economic analysis of water electrolysis-based concepts and an evaluation of PtG and PtL in energy system studies.
---
paper_title: DC/DC converter topologies for electrolyzers: State-of-the-art and remaining key issues

paper_content:

Abstract In recent years, the use of electrolyzers to produce cleanly and efficiently hydrogen from renewable energy sources (i.e. wind turbines, photovoltaic) has taken advantage of a growing interest from researchers and industrial. Similarly to fuel cells, DC/DC converters are needed to interface the DC bus with the electrolyzer. Usually, electrolyzers require a low DC voltage to produce hydrogen from water. For this reason, a DC/DC buck converter is generally used for this purpose. However, other DC/DC converter topologies can be used depending on the feature of the electrolyzer and electrical grid as well. The main purpose of this paper is to present the current state-of-the-art of DC/DC converter topologies which can be combined with electrolyzers. The different DC/DC converter topologies are compared in terms of output current ripple reduction, conversion ratio, energy efficiency, and power switch fault-tolerance. Besides, remarks on the state-of-the-art and remaining key issues regarding DC/DC converters are provided.
---
paper_title: A comprehensive review on PEM water electrolysis

paper_content:

Abstract Hydrogen is often considered the best means by which to store energy coming from renewable and intermittent power sources. With the growing capacity of localized renewable energy sources surpassing the gigawatt range, a storage system of equal magnitude is required. PEM electrolysis provides a sustainable solution for the production of hydrogen, and is well suited to couple with energy sources such as wind and solar. However, due to low demand in electrolytic hydrogen in the last century, little research has been done on PEM electrolysis with many challenges still unexplored. The ever increasing desire for green energy has rekindled the interest on PEM electrolysis, thus the compilation and recovery of past research and developments is important and necessary. In this review, PEM water electrolysis is comprehensively highlighted and discussed. The challenges new and old related to electrocatalysts, solid electrolyte, current collectors, separator plates and modeling efforts will also be addressed. The main message is to clearly set the state-of-the-art for the PEM electrolysis technology, be insightful of the research that is already done and the challenges that still exist. This information will provide several future research directions and a road map in order to aid scientists in establishing PEM electrolysis as a commercially viable hydrogen production solution.
---
paper_title: Interleaved soft-switching coupled-buck converter with active-clamp circuits

paper_content:

This paper presents a coupled-buck converter with active-clamp circuits. The active switches in the converter can sustain a long enough duty cycle while it operates with a high step-down voltage ratio, reducing current stress significantly. In the converter, the active-clamp circuits provided can have benefits of recycling the leakage energy, while minimum ringing voltage is across the active switches. Moreover, since both main and auxiliary switches can be turned on with zero-voltage switching (ZVS), switching loss can be reduced and conversion efficiency therefore can be improved significantly. A 240 W prototype of the proposed buck converter was built and experimental results have shown that efficiency can reach as high as 89%. It is relatively attractive for applications to hybrid electric vehicle on-board chargers.
---
paper_title: Interleaved buck converters with a single-capacitor turn-off snubber

paper_content:

This paper proposes interleaved buck converters with a single-capacitor snubber to smooth out switch turn-off transition. The single-capacitor snubber is used to limit rising rate of drain-source voltage of the metal-oxide-semiconductor field-effect transistor (MOSFET) switch in the converters to reduce turn-off loss. In addition, the converters are operated at the boundary of continuous and discontinuous conduction modes (CCM), (DCM) to reduce turn-on loss, and in an interleaving fashion to reduce output current ripple. As compared with the counterparts of conventional converter topologies, the proposed converters have the merits of less component count, higher efficiency over a certain load range, smaller size, and they are easier to implement. Hardware measurements obtained from experimental prototypes have verified these merits.
---
paper_title: A High-Efficiency DC–DC Converter Using 2 nH Integrated Inductors

paper_content:

Historically, buck converters have relied on high-Q inductors on the order of 1 to 100 μH to achieve a high efficiency. Unfortunately, on-chip inductors are physically large and have poor series resistances, which result in low-efficiency converters. To mitigate this problem, on-chip magnetic coupling is exploited in the proposed stacked interleaved topology to enable the use of small (2 nH) on-chip inductors in a high-efficiency buck converter. The dramatic decrease in the inductance value is made possible by the unique bridge timing of the stacked design that causes magnetic coupling to boost the converter's efficiency by reducing the current ripple in each inductor. The magnetic coupling is realized by stacking the two inductors on top of one another, which not only lowers the required inductance, but also reduces the chip area consumed by the two inductors. The measured conversion efficiency for the prototype circuit, implemented in a 130-nm CMOS technology, shows more than a 15% efficiency improvement over a linear converter for low output voltages rising to a peak efficiency of 77.9% for a 0.9 V output. These efficiencies are comparable to converters implemented with higher Q inductors, validating that the proposed techniques enable high-efficiency converters to be realized with small on-chip inductors.
---
paper_title: Interleaved buck converter having low switching losses and improved step-down conversion ratio

paper_content:

A new interleaved buck converter (IBC) having low switching losses and improved step-down conversion ratio is proposed in this paper. It is similar to a conventional IBC, but two active switches are connected in series, and a coupling capacitor is employed in the power path, like Cuk, Sepic, and Zeta converters. The proposed IBC shows that since the voltage stress across all active switches is half of the input voltage before turn-on or after turn-off, the capacitive discharging and switching losses can be reduced considerably. This allows the proposed IBC to have higher efficiency and be operated at higher switching frequency. In addition, the proposed IBC has higher step-down conversion ratio and smaller output current ripple than a conventional IBC. The features, operation principles, and relevant analysis results of the proposed IBC are presented in this paper. The validity of this study is confirmed by the experimental results of prototype converters with 150–200V input, 24V/10A output.
---
paper_title: A novel winding coupled-buck converter for high-frequency, high step-down DC/DC conversion

paper_content:

The buck converter is popularly used for stepdown DC/DC conversion when there is no isolation requirement. However, for high step-down, large output current applications such as voltage regulation modules (VRMs), it is no longer suitable, especially at high switching frequencies. The too-small duty cycle and large switching-related loss limit its performance. This paper proposes a novel topology, which is based on the use of additional coupled windings and can solve all these problems. An integrated magnetic structure is proposed for these windings so that the same magnetic cores can be used as in the buck converter. Furthermore, it is easy to implement a lossless clamp circuit to limit the device turn-off voltage spike and to recover inductor leakage energy. Experimental results obtained with a 12 V to 1.5 V/25 A VRM prove the significant improvement of the proposed topology at switching frequencies in excess of a megahertz.
---
paper_title: Power converters for hybrid renewable energy systems with hydrogen buffer storage: A short review

paper_content:

In order to cope with the intermittent character of the renewable energy sources (RES), hydrogen production and storage tend to be an attractive and efficient solution. This is because hydrogen has much higher specific energy than the classical storage devices such as batteries or supercapacitors. In hybrid RES with hydrogen buffer storage, power converters play an important role to guarantee stability and reliability. This paper starts with an overview of hybrid RES configuration including hydrogen buffer storage. Then, a short literature survey focused on power converters is provided in order to highlight their advantages, drawbacks, and remaining issues for these applications.
---
paper_title: Interleaved Zero-Current-Transition Buck Converter

paper_content:

This paper introduces interleaved zero-current-transition (ZCT) converters where two sets of switches are operating out-of-phase and share the load power equally. Turn-on transitions at zero current and a significant reduction of the losses associated with diode reverse recovery are accomplished through addition of two small inductors. This paper describes a 30-kW (300 V/100 A) interleaved ZCT buck converter operating at 32-kHz effective switching frequency. Losses and efficiency of the experimental prototype compare favorably against the standard and interleaved hard-switched buck converters. Constant frequency operation with low switching losses and low output current ripple is very well suited for the realization of dc power supplies in plasma processes.
---
paper_title: An overview of high voltage conversion ratio DC-DC converter configurations used in DC micro-grid architectures

paper_content:

This manuscript discuss about the various DC-DC converter configurations with high voltage conversion ratio utilized in DC micro-grid structures. The presented DC-DC converter topologies play a major role globally in the power generation sector including micro-grid, because of its decreased number of semiconductor devices, maximum conversion efficiency, small in size and cost of manufacturing is less. In this manuscript the DC-DC converter are categorized in to isolated and Non-isolated topologies. The first group topography works with the presence of transformer and the second group works without the transformer. These converters are capable to provide the various stages of output range. Researchers utilize these converters in the area of renewable energy generation, electric vehicle, micro sources, charge pumping applications etc. Hence they also work to improve the efficiency and reliability with reduction in components numbers and economical aspect. In this manuscript, the various topography of DC-DC converter topologies utilized in micro-grid are reviewed and comparison is made based on voltage conversion ratio, duty ratio, efficiency along with the basic operating principle. This review also reveals the research gaps, current trends, and challenges in the last part.
---
paper_title: DC/DC converter topologies for electrolyzers: State-of-the-art and remaining key issues

paper_content:

Abstract In recent years, the use of electrolyzers to produce cleanly and efficiently hydrogen from renewable energy sources (i.e. wind turbines, photovoltaic) has taken advantage of a growing interest from researchers and industrial. Similarly to fuel cells, DC/DC converters are needed to interface the DC bus with the electrolyzer. Usually, electrolyzers require a low DC voltage to produce hydrogen from water. For this reason, a DC/DC buck converter is generally used for this purpose. However, other DC/DC converter topologies can be used depending on the feature of the electrolyzer and electrical grid as well. The main purpose of this paper is to present the current state-of-the-art of DC/DC converter topologies which can be combined with electrolyzers. The different DC/DC converter topologies are compared in terms of output current ripple reduction, conversion ratio, energy efficiency, and power switch fault-tolerance. Besides, remarks on the state-of-the-art and remaining key issues regarding DC/DC converters are provided.
---
paper_title: Interleaved buck converters with a single-capacitor turn-off snubber

paper_content:

This paper proposes interleaved buck converters with a single-capacitor snubber to smooth out switch turn-off transition. The single-capacitor snubber is used to limit rising rate of drain-source voltage of the metal-oxide-semiconductor field-effect transistor (MOSFET) switch in the converters to reduce turn-off loss. In addition, the converters are operated at the boundary of continuous and discontinuous conduction modes (CCM), (DCM) to reduce turn-on loss, and in an interleaving fashion to reduce output current ripple. As compared with the counterparts of conventional converter topologies, the proposed converters have the merits of less component count, higher efficiency over a certain load range, smaller size, and they are easier to implement. Hardware measurements obtained from experimental prototypes have verified these merits.
---
paper_title: A novel winding coupled-buck converter for high-frequency, high step-down DC/DC conversion

paper_content:

The buck converter is popularly used for stepdown DC/DC conversion when there is no isolation requirement. However, for high step-down, large output current applications such as voltage regulation modules (VRMs), it is no longer suitable, especially at high switching frequencies. The too-small duty cycle and large switching-related loss limit its performance. This paper proposes a novel topology, which is based on the use of additional coupled windings and can solve all these problems. An integrated magnetic structure is proposed for these windings so that the same magnetic cores can be used as in the buck converter. Furthermore, it is easy to implement a lossless clamp circuit to limit the device turn-off voltage spike and to recover inductor leakage energy. Experimental results obtained with a 12 V to 1.5 V/25 A VRM prove the significant improvement of the proposed topology at switching frequencies in excess of a megahertz.
---
paper_title: Interleaved Zero-Current-Transition Buck Converter

paper_content:

This paper introduces interleaved zero-current-transition (ZCT) converters where two sets of switches are operating out-of-phase and share the load power equally. Turn-on transitions at zero current and a significant reduction of the losses associated with diode reverse recovery are accomplished through addition of two small inductors. This paper describes a 30-kW (300 V/100 A) interleaved ZCT buck converter operating at 32-kHz effective switching frequency. Losses and efficiency of the experimental prototype compare favorably against the standard and interleaved hard-switched buck converters. Constant frequency operation with low switching losses and low output current ripple is very well suited for the realization of dc power supplies in plasma processes.
---
paper_title: A High-Efficiency DC–DC Converter Using 2 nH Integrated Inductors

paper_content:

Historically, buck converters have relied on high-Q inductors on the order of 1 to 100 μH to achieve a high efficiency. Unfortunately, on-chip inductors are physically large and have poor series resistances, which result in low-efficiency converters. To mitigate this problem, on-chip magnetic coupling is exploited in the proposed stacked interleaved topology to enable the use of small (2 nH) on-chip inductors in a high-efficiency buck converter. The dramatic decrease in the inductance value is made possible by the unique bridge timing of the stacked design that causes magnetic coupling to boost the converter's efficiency by reducing the current ripple in each inductor. The magnetic coupling is realized by stacking the two inductors on top of one another, which not only lowers the required inductance, but also reduces the chip area consumed by the two inductors. The measured conversion efficiency for the prototype circuit, implemented in a 130-nm CMOS technology, shows more than a 15% efficiency improvement over a linear converter for low output voltages rising to a peak efficiency of 77.9% for a 0.9 V output. These efficiencies are comparable to converters implemented with higher Q inductors, validating that the proposed techniques enable high-efficiency converters to be realized with small on-chip inductors.
---
paper_title: Interleaved soft-switching coupled-buck converter with active-clamp circuits

paper_content:

This paper presents a coupled-buck converter with active-clamp circuits. The active switches in the converter can sustain a long enough duty cycle while it operates with a high step-down voltage ratio, reducing current stress significantly. In the converter, the active-clamp circuits provided can have benefits of recycling the leakage energy, while minimum ringing voltage is across the active switches. Moreover, since both main and auxiliary switches can be turned on with zero-voltage switching (ZVS), switching loss can be reduced and conversion efficiency therefore can be improved significantly. A 240 W prototype of the proposed buck converter was built and experimental results have shown that efficiency can reach as high as 89%. It is relatively attractive for applications to hybrid electric vehicle on-board chargers.
---
paper_title: Interleaved soft-switching coupled-buck converter with active-clamp circuits

paper_content:

This paper presents a coupled-buck converter with active-clamp circuits. The active switches in the converter can sustain a long enough duty cycle while it operates with a high step-down voltage ratio, reducing current stress significantly. In the converter, the active-clamp circuits provided can have benefits of recycling the leakage energy, while minimum ringing voltage is across the active switches. Moreover, since both main and auxiliary switches can be turned on with zero-voltage switching (ZVS), switching loss can be reduced and conversion efficiency therefore can be improved significantly. A 240 W prototype of the proposed buck converter was built and experimental results have shown that efficiency can reach as high as 89%. It is relatively attractive for applications to hybrid electric vehicle on-board chargers.
---
paper_title: Interleaved buck converter having low switching losses and improved step-down conversion ratio

paper_content:

A new interleaved buck converter (IBC) having low switching losses and improved step-down conversion ratio is proposed in this paper. It is similar to a conventional IBC, but two active switches are connected in series, and a coupling capacitor is employed in the power path, like Cuk, Sepic, and Zeta converters. The proposed IBC shows that since the voltage stress across all active switches is half of the input voltage before turn-on or after turn-off, the capacitive discharging and switching losses can be reduced considerably. This allows the proposed IBC to have higher efficiency and be operated at higher switching frequency. In addition, the proposed IBC has higher step-down conversion ratio and smaller output current ripple than a conventional IBC. The features, operation principles, and relevant analysis results of the proposed IBC are presented in this paper. The validity of this study is confirmed by the experimental results of prototype converters with 150–200V input, 24V/10A output.
---
paper_title: DC/DC converter topologies for electrolyzers: State-of-the-art and remaining key issues

paper_content:

Abstract In recent years, the use of electrolyzers to produce cleanly and efficiently hydrogen from renewable energy sources (i.e. wind turbines, photovoltaic) has taken advantage of a growing interest from researchers and industrial. Similarly to fuel cells, DC/DC converters are needed to interface the DC bus with the electrolyzer. Usually, electrolyzers require a low DC voltage to produce hydrogen from water. For this reason, a DC/DC buck converter is generally used for this purpose. However, other DC/DC converter topologies can be used depending on the feature of the electrolyzer and electrical grid as well. The main purpose of this paper is to present the current state-of-the-art of DC/DC converter topologies which can be combined with electrolyzers. The different DC/DC converter topologies are compared in terms of output current ripple reduction, conversion ratio, energy efficiency, and power switch fault-tolerance. Besides, remarks on the state-of-the-art and remaining key issues regarding DC/DC converters are provided.
---
paper_title: Interleaved soft-switching coupled-buck converter with active-clamp circuits

paper_content:

This paper presents a coupled-buck converter with active-clamp circuits. The active switches in the converter can sustain a long enough duty cycle while it operates with a high step-down voltage ratio, reducing current stress significantly. In the converter, the active-clamp circuits provided can have benefits of recycling the leakage energy, while minimum ringing voltage is across the active switches. Moreover, since both main and auxiliary switches can be turned on with zero-voltage switching (ZVS), switching loss can be reduced and conversion efficiency therefore can be improved significantly. A 240 W prototype of the proposed buck converter was built and experimental results have shown that efficiency can reach as high as 89%. It is relatively attractive for applications to hybrid electric vehicle on-board chargers.
---
paper_title: Interleaved buck converters with a single-capacitor turn-off snubber

paper_content:

This paper proposes interleaved buck converters with a single-capacitor snubber to smooth out switch turn-off transition. The single-capacitor snubber is used to limit rising rate of drain-source voltage of the metal-oxide-semiconductor field-effect transistor (MOSFET) switch in the converters to reduce turn-off loss. In addition, the converters are operated at the boundary of continuous and discontinuous conduction modes (CCM), (DCM) to reduce turn-on loss, and in an interleaving fashion to reduce output current ripple. As compared with the counterparts of conventional converter topologies, the proposed converters have the merits of less component count, higher efficiency over a certain load range, smaller size, and they are easier to implement. Hardware measurements obtained from experimental prototypes have verified these merits.
---
paper_title: A High-Efficiency DC–DC Converter Using 2 nH Integrated Inductors

paper_content:

Historically, buck converters have relied on high-Q inductors on the order of 1 to 100 μH to achieve a high efficiency. Unfortunately, on-chip inductors are physically large and have poor series resistances, which result in low-efficiency converters. To mitigate this problem, on-chip magnetic coupling is exploited in the proposed stacked interleaved topology to enable the use of small (2 nH) on-chip inductors in a high-efficiency buck converter. The dramatic decrease in the inductance value is made possible by the unique bridge timing of the stacked design that causes magnetic coupling to boost the converter's efficiency by reducing the current ripple in each inductor. The magnetic coupling is realized by stacking the two inductors on top of one another, which not only lowers the required inductance, but also reduces the chip area consumed by the two inductors. The measured conversion efficiency for the prototype circuit, implemented in a 130-nm CMOS technology, shows more than a 15% efficiency improvement over a linear converter for low output voltages rising to a peak efficiency of 77.9% for a 0.9 V output. These efficiencies are comparable to converters implemented with higher Q inductors, validating that the proposed techniques enable high-efficiency converters to be realized with small on-chip inductors.
---
paper_title: Interleaved buck converter having low switching losses and improved step-down conversion ratio

paper_content:

A new interleaved buck converter (IBC) having low switching losses and improved step-down conversion ratio is proposed in this paper. It is similar to a conventional IBC, but two active switches are connected in series, and a coupling capacitor is employed in the power path, like Cuk, Sepic, and Zeta converters. The proposed IBC shows that since the voltage stress across all active switches is half of the input voltage before turn-on or after turn-off, the capacitive discharging and switching losses can be reduced considerably. This allows the proposed IBC to have higher efficiency and be operated at higher switching frequency. In addition, the proposed IBC has higher step-down conversion ratio and smaller output current ripple than a conventional IBC. The features, operation principles, and relevant analysis results of the proposed IBC are presented in this paper. The validity of this study is confirmed by the experimental results of prototype converters with 150–200V input, 24V/10A output.
---
paper_title: A novel winding coupled-buck converter for high-frequency, high step-down DC/DC conversion

paper_content:

The buck converter is popularly used for stepdown DC/DC conversion when there is no isolation requirement. However, for high step-down, large output current applications such as voltage regulation modules (VRMs), it is no longer suitable, especially at high switching frequencies. The too-small duty cycle and large switching-related loss limit its performance. This paper proposes a novel topology, which is based on the use of additional coupled windings and can solve all these problems. An integrated magnetic structure is proposed for these windings so that the same magnetic cores can be used as in the buck converter. Furthermore, it is easy to implement a lossless clamp circuit to limit the device turn-off voltage spike and to recover inductor leakage energy. Experimental results obtained with a 12 V to 1.5 V/25 A VRM prove the significant improvement of the proposed topology at switching frequencies in excess of a megahertz.
---
paper_title: Interleaved Zero-Current-Transition Buck Converter

paper_content:

This paper introduces interleaved zero-current-transition (ZCT) converters where two sets of switches are operating out-of-phase and share the load power equally. Turn-on transitions at zero current and a significant reduction of the losses associated with diode reverse recovery are accomplished through addition of two small inductors. This paper describes a 30-kW (300 V/100 A) interleaved ZCT buck converter operating at 32-kHz effective switching frequency. Losses and efficiency of the experimental prototype compare favorably against the standard and interleaved hard-switched buck converters. Constant frequency operation with low switching losses and low output current ripple is very well suited for the realization of dc power supplies in plasma processes.
---

Title: Literature Survey of Interleaved DC-DC Step-Down Converters for Proton Exchange Membrane Electrolyzer Applications

Section 1: INTRODUCTION
Description 1: Provide the current state-of-the-art and issues related to hydrogen production and the requirement of DC-DC converters for Electrolyzer applications.

Section 2: PROTON EXCHANGE MEMBRANE TECHNOLOGY
Description 2: Compare the three existing Electrolyzer technologies to select the most suitable one for the study.

Section 3: MAIN REQUIREMENT FOR DC/DC CONVERTERS
Description 3: Outline the primary requirements of DC-DC converters for Proton Exchange Membrane Electrolyzer applications.

Section 4: CANDIDATE INTERLEAVED STEP-DOWN TOPOLOGIES
Description 4: Present the various candidate interleaved step-down topologies for Electrolyzer applications, including their advantages and drawbacks.

Section 5: COMPARISON OF INTERLEAVED CONVERTERS
Description 5: Compare the candidate interleaved converters focusing on voltage gain and output current ripple.

Section 6: CONCLUSION
Description 6: Summarize the findings of the literature survey and highlight the most promising interleaved step-down converters for Electrolyzer applications.