Javier Sebastián Zúñiga - Academia.edu (original) (raw)

Papers by Javier Sebastián Zúñiga

Electronics

The dual active bridge (DAB) converter has been extensively analyzed and used in recent years for... more The dual active bridge (DAB) converter has been extensively analyzed and used in recent years for applications where bidirectional power flow is required. The unidirectional version of the DAB, which replaces the active output bridge with a diode bridge, has been called the single active bridge (SAB). The static behavior of the SAB differs markedly from similar DC/DC converters and can provide interesting advantages in certain applications. This paper presents a thorough study of the static behavior of the single active bridge (SAB) converter in different conduction modes. This study focuses on the description of the conduction modes, marking the main differences compared to similar DC/DC converters. Moreover, the SAB can be designed to operate in conduction mode for a given power level with different performance. A design guide is proposed, and the performance of different designs are compared, quantifying current stresses in the semiconductors. Finally, the main contribution of th...

Sensors

Visible Light Communication (VLC) is a wireless communication technology that uses visible light ... more Visible Light Communication (VLC) is a wireless communication technology that uses visible light to transmit information. The most extended implementation of a VLC transmitter employs a DC-DC power converter that biases the High-Brightness LEDs (HB-LEDs), and a Linear Power Amplifier (LPA) that reproduces the communication signal. Unfortunately, the power efficiency of LPAs is very low, thus reducing the overall system efficiency and requiring huge cooling systems to extract the heat. In this work, the use of Class D Switching-Mode Power Amplifiers (SMPAs) is explored in order to overcome that limitation. It is important to note that this SMPA is widely used for different applications, such as audio and RF power amplifiers. Therefore, there are a lot of versions of a Class D SMPA depending on the topology used for the implementation and the modulation strategy used to control the switches. Hence, this work aims to identify, adapt and explain in detail the best approach for implement...

2018 IEEE 19th Workshop on Control and Modeling for Power Electronics (COMPEL), 2018

DC-Power Distribution Systems require DC-DC converters to interface all their elements. These con... more DC-Power Distribution Systems require DC-DC converters to interface all their elements. These converters should provide a high power quality and be efficient, compact and inexpensive. Furthermore, the characteristics of the loads and sources connected to these converters are not known beforehand and may change widely (there is no regulation about the DC loads, such as IEC61000-3-2 in AC grids). As a consequence, the design procedure is neither standard nor obvious. This work proposes an optimized design procedure for any Bus Provider in a DC-Power Distribution System. It is based on models, hence extensible to different Bus-Provider topologies, and takes into account the main issues in DC-Power Distribution Systems, especially the design conditions imposed by the wide variety of loads, or even sources, which may be connected to the output bus. Experimental results obtained from three designs show a close match with the analytical models and verify that the proposed procedure minimiz...

IEEE Transactions on Industrial Electronics, 2017

A new process technology for 4H-SiC planar power MOSFETs based on a Boron diffusion step to impro... more A new process technology for 4H-SiC planar power MOSFETs based on a Boron diffusion step to improve the SiO 2 /SiC interface quality is presented in this work. Large area (up to 25 mm 2) power MOSFETs of three voltages ratings (1.7 kV, 3.3 kV and 4.5 kV) have been fabricated showing significant improvements in terms of inversion channel mobility and onresistance in comparison with counterparts without Boron oxide treatment. Experimental results show a remarkable increase of the channel mobility, which raises the device current capability, especially at room temperature. When operating at high temperature, the impact of the high channel mobility due to Boron treatment on electrical forward characteristics is reduced as the drift layer resistance starts to dominate in the total onstate resistance. In addition, the 3 rd quadrant characteristics approximate to those of an ideal PiN diode, and the device blocking capability is not compromised by the use of Boron for the gate oxide formation. The experimental performance in a simple DC/DC converter is also presented.

2002 IEEE 33rd Annual IEEE Power Electronics Specialists Conference. Proceedings (Cat. No.02CH37289)

The design of low-cost power supplies is influenced by the regulations on the low-frequency harmo... more The design of low-cost power supplies is influenced by the regulations on the low-frequency harmonic content in the line. As IEC 1000-3-2 regulations have just been modified, the design procedure of low-cost power supplies should also be modified. According to the new version of the above-mentioned regulations, many power supplies classified as Class D in the past are classified as Class A now. This fact allows a remarkable saving in the sue of the reactive elements used to reduce the line harmonics if they have been properly designed. The minimum values of the magnetic elements used in two well-known PFC solutions (one is an S*PFC and the other is a passive fdter) have been obtained in this paper for equipment classified in both the new Class A and the new Class D and for any power level between 75W and 600W.

Proceedings of 1994 IEEE Applied Power Electronics Conference and Exposition - ASPEC'94

The minimization of sue and losses are the main goals in the design of high power density and low... more The minimization of sue and losses are the main goals in the design of high power density and low output voltage on board dJdc converters. Forward topology with resonant reset combines the simplicity of i& power stage with the feasibility to implement self driven synchronous rectification. Several operation modes for this topology are proposed and analyzed in this paper: fiedfrequency PWMandconstant off-time variablefrequency, with and without zero voltage switching (ZVS). Design guidelines and experimental results are also provided for 3.3V output voltage converters, featuring eflciencies up to 90%.

IEEE EDUCON 2010 Conference, 2010

This paper presents the introduction of Problem-Based learning (PBL) in a power electronics subje... more This paper presents the introduction of Problem-Based learning (PBL) in a power electronics subject at the University of Oviedo (SPAIN) by means of two practical projects: the design and construction of a Switching-Mode Power Supply (SMPS) prototype and the static study of a dc-dc converter topology. The objective of this change in the traditional methodology of the Power Electronics course is to foster the application of the knowledge acquired by students in theory classes. PBL is known to be a motivating, problem-centered teaching method that brings the real professional world closer to the student. For this reason, the lecturers considered PBL to be the most suitable methodology to obtain the desired results. The underlying methodology, task planning and assessment of these projects will be presented. Furthermore, the influence of the introduction of PBL in practical sessions versus the traditional teaching method will be discussed. Finally, the lecturers' reflections and conclusions regarding the application of PBL in this subject over the last two years will be presented.

2013 Twenty-Eighth Annual IEEE Applied Power Electronics Conference and Exposition (APEC), 2013

In this paper an evaluation of Silicon Carbide (SiC) transistors currently available in the comme... more In this paper an evaluation of Silicon Carbide (SiC) transistors currently available in the commercial market is presented. An experimental performance comparison between SiC JFET, Si MOSFET-SiC JFET cascode configuration and SiC MOSFET used as the main switch for a dc/dc boost converter (150 V/400 V) operating in Discontinuous Conduction Mode (DCM) is presented. The comparison of the different SiC devices is made in terms of the global boost-converter efficiency. Several experimental results dealing with the switching behavior of these SiC switches at different switching frequencies (from 100 kHz to 1 MHz) have been carried out in order to optimize the efficiency of the converter at different output power (300 W and 600 W). A good performance of all these switches is obtained from the point of view of the efficiency, highlighting the Si MOSFET-SiC JFET cascode behavior at 1MHz with an efficiency of 97.5% at 600 W. In addition, a possible application in the field of solar panels is proposed using the SiC JFET as the main switch. Continuous Conduction Mode (CCM) and DCM are tested at different switching frequencies with an output power of 1 kW and the results obtained are compared to the most widely reported in the bibliography. I.

PESC 98 Record. 29th Annual IEEE Power Electronics Specialists Conference (Cat. No.98CH36196)

The IForward Converter with Active Clamp is nowadays one of the most useful topologies when low o... more The IForward Converter with Active Clamp is nowadays one of the most useful topologies when low output voltage is required due to the possibility of using self driven synchronous rectification. This paper shows an study of the peak current mode control when the main mosfet cuirrent is sensed instead of the current passing through the output inductor. A dynamic study is accomplished and the control problems are shown. Finally, several practical ways to close tlhe feedback loop avoiding the dynamic drawbacks is also presented.

IEEE Transactions on Power Electronics, 2015

The use of battery cell equalizers is mandatory in order to assure that all the cells connected i... more The use of battery cell equalizers is mandatory in order to assure that all the cells connected in series are charged to its maximum capacity, even when they present small differences in this parameter due to several factors, such as aging, manufacturing or temperature. Active equalizers, with a higher efficiency in comparison to passive ones, have the disadvantage of using a considerable number of components. Moreover, in the case of active equalizers with very high performance, this number can be even higher. In this paper, the use of the wave-trap concept, widely used in telecommunication systems, is studied. This concept allows the battery cell equalizer to use its switching frequency as the control variable that decides which cell is being charged. Hence, it is not necessary to use a complex system based on a high number of controlled switches in order to determine which cell is being charged. In this way, the number of switches (and the corresponding driving signals) can be strongly minimized without reducing the performance of the system. In order to proof the validity of this concept (i.e., wave traps) in the design of battery-cell equalizers, a topology based on a half-bridge structure is also proposed in this paper. It uses only two controlled switches in order to decide which cell is charged. Experimental results are provided for a 4-cell equalizer as a proof of concept.

2013 IEEE Energy Conversion Congress and Exposition, 2013

The Asymmetrical Half Bridge converter (AHBC) has proven to be a promising candidate for LED ligh... more The Asymmetrical Half Bridge converter (AHBC) has proven to be a promising candidate for LED lighting applications. It provides high efficiency, galvanic isolation and it can be easily built without electrolytic capacitor. On the other hand, its main drawback is its poor attainable bandwidth. In any two-stage ac-dc LED driver based on the AHBC, the first stage is a Power Factor Corrector (PFC) converter which has to be also implemented without electrolytic capacitor. As a consequence, its output voltage (input voltage of the AHBC) presents a low-frequency ripple. Due to the poor bandwidth of the AHBC, this voltage ripple will be transferred to the converter output voltage, leading to flickering. Due to the complex and non-linear transfer function of the AHBC, any analog feedforward loop has to be tuned for a given operating point, leading to a poor performance when the AHBC moves away from that point. In this paper, a digital feedforward loop is proposed in order to solve this problem. The digital implementation allows the feedforward loop to perfectly cancel the ripple under any condition (e.g., output voltage variation due to dimming). Besides, this digital feedforward loop has been designed and simplified considering the specific purpose of cancelling flickering in the emitted light. In this way, it can be easily implemented in small-size microcontrollers. Experimental results with a 40-W prototype prove the usefulness of the proposed feedforward loop.

Twentieth Annual IEEE Applied Power Electronics Conference and Exposition, 2005. APEC 2005.

A lot o f power topologies have been proposed to comply with the IEC-61000-3-2 regulations. One g... more A lot o f power topologies have been proposed to comply with the IEC-61000-3-2 regulations. One group of solutions involves obtaining an additional output from one of the converter's magnetic devices. These solutions are very good due to the low harmonic content and from the low cost point of view. Nevertheless these magnetic coupled circuits can modify the converter's performance. The abnormal operation can be observed as an output voltage ripple higher than expected. This paper deals with the design considerations for law output voltage ripple Single-Stage-Input-Current Shapers (S'ICS) and explains the abnormalities.

2002 IEEE 33rd Annual IEEE Power Electronics Specialists Conference. Proceedings (Cat. No.02CH37289)

IEEE Transactions on Power Electronics, 2015

This paper addresses the performance of the bidirectional Dual Active Bridge (DAB) converter. One... more This paper addresses the performance of the bidirectional Dual Active Bridge (DAB) converter. One of the advantages of the DAB is the possibility to achieve Zero Voltage Switching (ZVS) operation in all the switches of this converter. However, the ZVS operation range can be lost for light loads, especially if high voltage is required in at least one of the DAB ports and the phase-shift control is used to regulate the power processed by the converter. Theoretically simple averaged and small-signal models are presented for the DAB converter. Using the study presented in this paper, the boundaries of ZVS operation can be easily evaluated. The proposed models and analysis of the ZVS boundaries allow the proposal and evaluation of two different design strategies with different purposes: on the one hand, increasing the ZVS operation range and, on the other, improving efficiency at full load. Moreover, some techniques are presented for increasing the ZVS operation range and improving the efficiency of the DAB at full load (both using phase-shift control) employing the aforementioned analysis to obtain certain design criteria and conclusions. Finally, the proposed models, design strategies and techniques to improve the performance of the DAB are experimentally tested using a 1kW prototype with input and output voltages of 48V and 400V, respectively. I.

IEEE Transactions on Power Electronics, 1997

A new method to improve dynamic response of power-factor preregulators (PFP's) is developed in th... more A new method to improve dynamic response of power-factor preregulators (PFP's) is developed in this paper. The method is based on the use of a very high efficient postregulator with two inputs instead of only one. This two-input postregulator exhibits very high efficiency due to the fact that only a part of the total power undergoes a power-conversion process. They need two-output PFP's at their inputs, which can be easily obtained in PFP's with transformers or with two PFP's working in parallel. Index Terms-Fast regulation of the output voltage, highquality rectifiers, postregulators, power-factor correctors. I. INTRODUCTION T HE USE OF power-factor preregulators (PFP's), also called power-factor correctors (PFC's) [1], [2], is the usual way to get a high power factor on off-line switching power supplies. When a PFP is made up of only one stage, the static output voltage is accurately regulated, whereas the output voltage usually exhibits poor dynamic regulation. This is due to the fact that a low-pass filter must be included in the output voltage feedback loop when the bulk capacitor used to remove the low-frequency ripple (100-120 Hz) is placed at the output [2]. To improve dynamic regulation and to decrease bulk capacitor size, a first option [see Fig. 1(a)] is to connect a second dc-to-dc converter in cascade with the first converter, with the bulk capacitor placed in between. These two stages in cascade mean a complicated power circuit, which is an interesting option only in medium-power applications (more than 1 kW). Some efforts have been reported to simplify the two-cascade stage system [3]-[5]. They are based on the use of only one stage [see Fig. 1(b)] with a single transistor. Due to the fact that the power is handled twice for the stage, the transistor current and voltage stress are very high, therefore, converter Manuscript

IEEE Transactions on Industry Applications, 2010

When a Power Factor Corrector (PFC) is designed with a relatively fast output-voltage feedback lo... more When a Power Factor Corrector (PFC) is designed with a relatively fast output-voltage feedback loop, the static and the dynamic behaviour of the power stage is different to that obtained with a slow output-voltage feedback loop. This is because of the influence of the voltage ripple that is present on the control signal. This voltage ripple generates a "parasitic" feedback loop, which is different to the "desired" one (the dc output-voltage feedback loop). The effect of this "parasitic" feedback loop can be integrated into the power stage model in such a way that a new model for the power stage is obtained. Assuming this model, the only feedback loop is the one corresponding to the dc output voltage, i.e., the "desired" output-voltage feedback loop. The design of this feedback loop determines the final dynamic behaviour of the PFC, which can be optimized to achieve the maximum bandwidth compatible with compliance with existing regulations regarding the injection of line harmonics and PFC stability. The main objective of this paper is thus to determine the maximum crossover angular frequency, ω 0 , compatible with a desired value of the phase margin, φ m , and which complies with EN 61000-3-2 regulations in all possible classes of equipment (A, B, C and D) when a standard compensator (a PI with one additional pole) is used. The results obtained show that the maximum bandwidth attainable by a PFC strongly depends on its Class. This maximum bandwidth depends on the power processed by the converter in the case of equipment classified as Class A or Class B. However, the maximum bandwidth attainable for equipment belonging to Class C or to Class D does not depend on the power processed and is always higher in the case of Class D than in that of Class C.

IEEE Transactions on Industry Applications, 2013

High-Brightness Light Emitting Diodes (HB-LEDs) are considered as a remarkable lighting device du... more High-Brightness Light Emitting Diodes (HB-LEDs) are considered as a remarkable lighting device due to their high reliability, chromatic variety and increasing efficiency. As a consequence, a high number of solutions for supplying LED strings are coming out. One-stage solutions are cost-effective, but their efficiency is low as they have to fulfill several purposes with only one converter: Power Factor Correction (PFC), galvanic isolation (in some cases) and current regulation. Two-stage and three-stage solutions have higher efficiency as each stage is optimized for just one or two tasks and they are the preferred option when supplying several strings at the same time. Nevertheless, due to their higher cost in comparison to one-stage solutions, they are used when high-efficiency, high-performance and the possibility of supplying several strings are the main concerns. Besides, they are also used when high reliability is needed and electrolytic capacitors cannot be used. In this paper, a three-stage solution and its complete design guideline for LED-based applications is proposed. PFC is achieved by a Boost converter while the galvanic isolation is provided by an Electronic Transformer (second stage). The third stages (one for each LED string) are designed following the Two-Input Buck (TIBuck) schematic, but taking advantage of the load characteristics (i.e., the high value of the LED string knee voltage, approximately equal to half the string nominal voltage). Besides, a variation of the analog driving technique is also proposed. Experimental results obtained with a 160-W prototype show an efficiency as high as 93% for the whole topology and 95% for the cascade connection of the second and third stages. This work has been supported by the AEG Power Solutions B.V. under project FUO-EM-002-10 and by Spanish Government under projects CONSOLIDER MICINN-10-CSD2009-00046 and MICINN-10-DPI2010-21110-C02-0. Besides, a patent is pending.

IEEE Transactions on Industrial Electronics, 1997

Distributed power-supply systems are an attractive solution to meeting the requirements (redundan... more Distributed power-supply systems are an attractive solution to meeting the requirements (redundancy, modularity, battery backup, etc.) for the next generation of power-supply systems. In addition, the normalization regarding power factor and total harmonic distortion (THD) makes it necessary to include the power-factor correction in the input stage in those architectures. This paper presents a novel approach of an integrated battery charger/discharger which offers power-factor correction and battery galvanic isolation in a simple structure. Placing the battery in the primary side overcomes the need of galvanic isolation integration in each one of the dc/dc on-board converters when this topology is used as part of a distributed power-supply system.

IEEE Transactions on Industrial Electronics, 2003

When low output voltage and EN61000-3-2 compliance are put together, not too many options can be ... more When low output voltage and EN61000-3-2 compliance are put together, not too many options can be used, especially if the power range is between 300-600 W. This paper presents one of the best solutions to comply with both specifications at the same time: the use of a single-stage topology to comply with the low-frequency harmonic limits combined with a half-bridge converter with complementary control, which is a very good option to obtain low output voltages with high efficiency.

IEEE Transactions on Industrial Electronics, 2005

Power-factor correction has been one of the hottest topics during the last few years and, hence, ... more Power-factor correction has been one of the hottest topics during the last few years and, hence, many new circuits have appeared. In general, it is assumed that preregulators based on multiplier circuits have poor dynamics and, then, a second stage is needed to improve the output voltage dynamic behavior. The other option is the use of single-stage topologies which have fast output voltage regulation although the input current waveform is not sinusoidal. This paper presents an analysis of the dynamic behavior of a conventional power-factor preregulator. The objective is to find the limits of the dynamic characteristics of these circuits when the priority is to improve the output voltage regulation and not the total harmonic distortion or the power factor. A large-signal model is presented and the theoretical results are validated with a prototype.

Electronics

The dual active bridge (DAB) converter has been extensively analyzed and used in recent years for... more The dual active bridge (DAB) converter has been extensively analyzed and used in recent years for applications where bidirectional power flow is required. The unidirectional version of the DAB, which replaces the active output bridge with a diode bridge, has been called the single active bridge (SAB). The static behavior of the SAB differs markedly from similar DC/DC converters and can provide interesting advantages in certain applications. This paper presents a thorough study of the static behavior of the single active bridge (SAB) converter in different conduction modes. This study focuses on the description of the conduction modes, marking the main differences compared to similar DC/DC converters. Moreover, the SAB can be designed to operate in conduction mode for a given power level with different performance. A design guide is proposed, and the performance of different designs are compared, quantifying current stresses in the semiconductors. Finally, the main contribution of th...

Sensors

Visible Light Communication (VLC) is a wireless communication technology that uses visible light ... more Visible Light Communication (VLC) is a wireless communication technology that uses visible light to transmit information. The most extended implementation of a VLC transmitter employs a DC-DC power converter that biases the High-Brightness LEDs (HB-LEDs), and a Linear Power Amplifier (LPA) that reproduces the communication signal. Unfortunately, the power efficiency of LPAs is very low, thus reducing the overall system efficiency and requiring huge cooling systems to extract the heat. In this work, the use of Class D Switching-Mode Power Amplifiers (SMPAs) is explored in order to overcome that limitation. It is important to note that this SMPA is widely used for different applications, such as audio and RF power amplifiers. Therefore, there are a lot of versions of a Class D SMPA depending on the topology used for the implementation and the modulation strategy used to control the switches. Hence, this work aims to identify, adapt and explain in detail the best approach for implement...

2018 IEEE 19th Workshop on Control and Modeling for Power Electronics (COMPEL), 2018

DC-Power Distribution Systems require DC-DC converters to interface all their elements. These con... more DC-Power Distribution Systems require DC-DC converters to interface all their elements. These converters should provide a high power quality and be efficient, compact and inexpensive. Furthermore, the characteristics of the loads and sources connected to these converters are not known beforehand and may change widely (there is no regulation about the DC loads, such as IEC61000-3-2 in AC grids). As a consequence, the design procedure is neither standard nor obvious. This work proposes an optimized design procedure for any Bus Provider in a DC-Power Distribution System. It is based on models, hence extensible to different Bus-Provider topologies, and takes into account the main issues in DC-Power Distribution Systems, especially the design conditions imposed by the wide variety of loads, or even sources, which may be connected to the output bus. Experimental results obtained from three designs show a close match with the analytical models and verify that the proposed procedure minimiz...

IEEE Transactions on Industrial Electronics, 2017

A new process technology for 4H-SiC planar power MOSFETs based on a Boron diffusion step to impro... more A new process technology for 4H-SiC planar power MOSFETs based on a Boron diffusion step to improve the SiO 2 /SiC interface quality is presented in this work. Large area (up to 25 mm 2) power MOSFETs of three voltages ratings (1.7 kV, 3.3 kV and 4.5 kV) have been fabricated showing significant improvements in terms of inversion channel mobility and onresistance in comparison with counterparts without Boron oxide treatment. Experimental results show a remarkable increase of the channel mobility, which raises the device current capability, especially at room temperature. When operating at high temperature, the impact of the high channel mobility due to Boron treatment on electrical forward characteristics is reduced as the drift layer resistance starts to dominate in the total onstate resistance. In addition, the 3 rd quadrant characteristics approximate to those of an ideal PiN diode, and the device blocking capability is not compromised by the use of Boron for the gate oxide formation. The experimental performance in a simple DC/DC converter is also presented.

2002 IEEE 33rd Annual IEEE Power Electronics Specialists Conference. Proceedings (Cat. No.02CH37289)

The design of low-cost power supplies is influenced by the regulations on the low-frequency harmo... more The design of low-cost power supplies is influenced by the regulations on the low-frequency harmonic content in the line. As IEC 1000-3-2 regulations have just been modified, the design procedure of low-cost power supplies should also be modified. According to the new version of the above-mentioned regulations, many power supplies classified as Class D in the past are classified as Class A now. This fact allows a remarkable saving in the sue of the reactive elements used to reduce the line harmonics if they have been properly designed. The minimum values of the magnetic elements used in two well-known PFC solutions (one is an S*PFC and the other is a passive fdter) have been obtained in this paper for equipment classified in both the new Class A and the new Class D and for any power level between 75W and 600W.

Proceedings of 1994 IEEE Applied Power Electronics Conference and Exposition - ASPEC'94

The minimization of sue and losses are the main goals in the design of high power density and low... more The minimization of sue and losses are the main goals in the design of high power density and low output voltage on board dJdc converters. Forward topology with resonant reset combines the simplicity of i& power stage with the feasibility to implement self driven synchronous rectification. Several operation modes for this topology are proposed and analyzed in this paper: fiedfrequency PWMandconstant off-time variablefrequency, with and without zero voltage switching (ZVS). Design guidelines and experimental results are also provided for 3.3V output voltage converters, featuring eflciencies up to 90%.

IEEE EDUCON 2010 Conference, 2010

This paper presents the introduction of Problem-Based learning (PBL) in a power electronics subje... more This paper presents the introduction of Problem-Based learning (PBL) in a power electronics subject at the University of Oviedo (SPAIN) by means of two practical projects: the design and construction of a Switching-Mode Power Supply (SMPS) prototype and the static study of a dc-dc converter topology. The objective of this change in the traditional methodology of the Power Electronics course is to foster the application of the knowledge acquired by students in theory classes. PBL is known to be a motivating, problem-centered teaching method that brings the real professional world closer to the student. For this reason, the lecturers considered PBL to be the most suitable methodology to obtain the desired results. The underlying methodology, task planning and assessment of these projects will be presented. Furthermore, the influence of the introduction of PBL in practical sessions versus the traditional teaching method will be discussed. Finally, the lecturers' reflections and conclusions regarding the application of PBL in this subject over the last two years will be presented.

2013 Twenty-Eighth Annual IEEE Applied Power Electronics Conference and Exposition (APEC), 2013

In this paper an evaluation of Silicon Carbide (SiC) transistors currently available in the comme... more In this paper an evaluation of Silicon Carbide (SiC) transistors currently available in the commercial market is presented. An experimental performance comparison between SiC JFET, Si MOSFET-SiC JFET cascode configuration and SiC MOSFET used as the main switch for a dc/dc boost converter (150 V/400 V) operating in Discontinuous Conduction Mode (DCM) is presented. The comparison of the different SiC devices is made in terms of the global boost-converter efficiency. Several experimental results dealing with the switching behavior of these SiC switches at different switching frequencies (from 100 kHz to 1 MHz) have been carried out in order to optimize the efficiency of the converter at different output power (300 W and 600 W). A good performance of all these switches is obtained from the point of view of the efficiency, highlighting the Si MOSFET-SiC JFET cascode behavior at 1MHz with an efficiency of 97.5% at 600 W. In addition, a possible application in the field of solar panels is proposed using the SiC JFET as the main switch. Continuous Conduction Mode (CCM) and DCM are tested at different switching frequencies with an output power of 1 kW and the results obtained are compared to the most widely reported in the bibliography. I.

PESC 98 Record. 29th Annual IEEE Power Electronics Specialists Conference (Cat. No.98CH36196)

The IForward Converter with Active Clamp is nowadays one of the most useful topologies when low o... more The IForward Converter with Active Clamp is nowadays one of the most useful topologies when low output voltage is required due to the possibility of using self driven synchronous rectification. This paper shows an study of the peak current mode control when the main mosfet cuirrent is sensed instead of the current passing through the output inductor. A dynamic study is accomplished and the control problems are shown. Finally, several practical ways to close tlhe feedback loop avoiding the dynamic drawbacks is also presented.

IEEE Transactions on Power Electronics, 2015

The use of battery cell equalizers is mandatory in order to assure that all the cells connected i... more The use of battery cell equalizers is mandatory in order to assure that all the cells connected in series are charged to its maximum capacity, even when they present small differences in this parameter due to several factors, such as aging, manufacturing or temperature. Active equalizers, with a higher efficiency in comparison to passive ones, have the disadvantage of using a considerable number of components. Moreover, in the case of active equalizers with very high performance, this number can be even higher. In this paper, the use of the wave-trap concept, widely used in telecommunication systems, is studied. This concept allows the battery cell equalizer to use its switching frequency as the control variable that decides which cell is being charged. Hence, it is not necessary to use a complex system based on a high number of controlled switches in order to determine which cell is being charged. In this way, the number of switches (and the corresponding driving signals) can be strongly minimized without reducing the performance of the system. In order to proof the validity of this concept (i.e., wave traps) in the design of battery-cell equalizers, a topology based on a half-bridge structure is also proposed in this paper. It uses only two controlled switches in order to decide which cell is charged. Experimental results are provided for a 4-cell equalizer as a proof of concept.

2013 IEEE Energy Conversion Congress and Exposition, 2013

The Asymmetrical Half Bridge converter (AHBC) has proven to be a promising candidate for LED ligh... more The Asymmetrical Half Bridge converter (AHBC) has proven to be a promising candidate for LED lighting applications. It provides high efficiency, galvanic isolation and it can be easily built without electrolytic capacitor. On the other hand, its main drawback is its poor attainable bandwidth. In any two-stage ac-dc LED driver based on the AHBC, the first stage is a Power Factor Corrector (PFC) converter which has to be also implemented without electrolytic capacitor. As a consequence, its output voltage (input voltage of the AHBC) presents a low-frequency ripple. Due to the poor bandwidth of the AHBC, this voltage ripple will be transferred to the converter output voltage, leading to flickering. Due to the complex and non-linear transfer function of the AHBC, any analog feedforward loop has to be tuned for a given operating point, leading to a poor performance when the AHBC moves away from that point. In this paper, a digital feedforward loop is proposed in order to solve this problem. The digital implementation allows the feedforward loop to perfectly cancel the ripple under any condition (e.g., output voltage variation due to dimming). Besides, this digital feedforward loop has been designed and simplified considering the specific purpose of cancelling flickering in the emitted light. In this way, it can be easily implemented in small-size microcontrollers. Experimental results with a 40-W prototype prove the usefulness of the proposed feedforward loop.

Twentieth Annual IEEE Applied Power Electronics Conference and Exposition, 2005. APEC 2005.

A lot o f power topologies have been proposed to comply with the IEC-61000-3-2 regulations. One g... more A lot o f power topologies have been proposed to comply with the IEC-61000-3-2 regulations. One group of solutions involves obtaining an additional output from one of the converter's magnetic devices. These solutions are very good due to the low harmonic content and from the low cost point of view. Nevertheless these magnetic coupled circuits can modify the converter's performance. The abnormal operation can be observed as an output voltage ripple higher than expected. This paper deals with the design considerations for law output voltage ripple Single-Stage-Input-Current Shapers (S'ICS) and explains the abnormalities.

2002 IEEE 33rd Annual IEEE Power Electronics Specialists Conference. Proceedings (Cat. No.02CH37289)

IEEE Transactions on Power Electronics, 2015

This paper addresses the performance of the bidirectional Dual Active Bridge (DAB) converter. One... more This paper addresses the performance of the bidirectional Dual Active Bridge (DAB) converter. One of the advantages of the DAB is the possibility to achieve Zero Voltage Switching (ZVS) operation in all the switches of this converter. However, the ZVS operation range can be lost for light loads, especially if high voltage is required in at least one of the DAB ports and the phase-shift control is used to regulate the power processed by the converter. Theoretically simple averaged and small-signal models are presented for the DAB converter. Using the study presented in this paper, the boundaries of ZVS operation can be easily evaluated. The proposed models and analysis of the ZVS boundaries allow the proposal and evaluation of two different design strategies with different purposes: on the one hand, increasing the ZVS operation range and, on the other, improving efficiency at full load. Moreover, some techniques are presented for increasing the ZVS operation range and improving the efficiency of the DAB at full load (both using phase-shift control) employing the aforementioned analysis to obtain certain design criteria and conclusions. Finally, the proposed models, design strategies and techniques to improve the performance of the DAB are experimentally tested using a 1kW prototype with input and output voltages of 48V and 400V, respectively. I.

IEEE Transactions on Power Electronics, 1997

A new method to improve dynamic response of power-factor preregulators (PFP's) is developed in th... more A new method to improve dynamic response of power-factor preregulators (PFP's) is developed in this paper. The method is based on the use of a very high efficient postregulator with two inputs instead of only one. This two-input postregulator exhibits very high efficiency due to the fact that only a part of the total power undergoes a power-conversion process. They need two-output PFP's at their inputs, which can be easily obtained in PFP's with transformers or with two PFP's working in parallel. Index Terms-Fast regulation of the output voltage, highquality rectifiers, postregulators, power-factor correctors. I. INTRODUCTION T HE USE OF power-factor preregulators (PFP's), also called power-factor correctors (PFC's) [1], [2], is the usual way to get a high power factor on off-line switching power supplies. When a PFP is made up of only one stage, the static output voltage is accurately regulated, whereas the output voltage usually exhibits poor dynamic regulation. This is due to the fact that a low-pass filter must be included in the output voltage feedback loop when the bulk capacitor used to remove the low-frequency ripple (100-120 Hz) is placed at the output [2]. To improve dynamic regulation and to decrease bulk capacitor size, a first option [see Fig. 1(a)] is to connect a second dc-to-dc converter in cascade with the first converter, with the bulk capacitor placed in between. These two stages in cascade mean a complicated power circuit, which is an interesting option only in medium-power applications (more than 1 kW). Some efforts have been reported to simplify the two-cascade stage system [3]-[5]. They are based on the use of only one stage [see Fig. 1(b)] with a single transistor. Due to the fact that the power is handled twice for the stage, the transistor current and voltage stress are very high, therefore, converter Manuscript

IEEE Transactions on Industry Applications, 2010

When a Power Factor Corrector (PFC) is designed with a relatively fast output-voltage feedback lo... more When a Power Factor Corrector (PFC) is designed with a relatively fast output-voltage feedback loop, the static and the dynamic behaviour of the power stage is different to that obtained with a slow output-voltage feedback loop. This is because of the influence of the voltage ripple that is present on the control signal. This voltage ripple generates a "parasitic" feedback loop, which is different to the "desired" one (the dc output-voltage feedback loop). The effect of this "parasitic" feedback loop can be integrated into the power stage model in such a way that a new model for the power stage is obtained. Assuming this model, the only feedback loop is the one corresponding to the dc output voltage, i.e., the "desired" output-voltage feedback loop. The design of this feedback loop determines the final dynamic behaviour of the PFC, which can be optimized to achieve the maximum bandwidth compatible with compliance with existing regulations regarding the injection of line harmonics and PFC stability. The main objective of this paper is thus to determine the maximum crossover angular frequency, ω 0 , compatible with a desired value of the phase margin, φ m , and which complies with EN 61000-3-2 regulations in all possible classes of equipment (A, B, C and D) when a standard compensator (a PI with one additional pole) is used. The results obtained show that the maximum bandwidth attainable by a PFC strongly depends on its Class. This maximum bandwidth depends on the power processed by the converter in the case of equipment classified as Class A or Class B. However, the maximum bandwidth attainable for equipment belonging to Class C or to Class D does not depend on the power processed and is always higher in the case of Class D than in that of Class C.

IEEE Transactions on Industry Applications, 2013

High-Brightness Light Emitting Diodes (HB-LEDs) are considered as a remarkable lighting device du... more High-Brightness Light Emitting Diodes (HB-LEDs) are considered as a remarkable lighting device due to their high reliability, chromatic variety and increasing efficiency. As a consequence, a high number of solutions for supplying LED strings are coming out. One-stage solutions are cost-effective, but their efficiency is low as they have to fulfill several purposes with only one converter: Power Factor Correction (PFC), galvanic isolation (in some cases) and current regulation. Two-stage and three-stage solutions have higher efficiency as each stage is optimized for just one or two tasks and they are the preferred option when supplying several strings at the same time. Nevertheless, due to their higher cost in comparison to one-stage solutions, they are used when high-efficiency, high-performance and the possibility of supplying several strings are the main concerns. Besides, they are also used when high reliability is needed and electrolytic capacitors cannot be used. In this paper, a three-stage solution and its complete design guideline for LED-based applications is proposed. PFC is achieved by a Boost converter while the galvanic isolation is provided by an Electronic Transformer (second stage). The third stages (one for each LED string) are designed following the Two-Input Buck (TIBuck) schematic, but taking advantage of the load characteristics (i.e., the high value of the LED string knee voltage, approximately equal to half the string nominal voltage). Besides, a variation of the analog driving technique is also proposed. Experimental results obtained with a 160-W prototype show an efficiency as high as 93% for the whole topology and 95% for the cascade connection of the second and third stages. This work has been supported by the AEG Power Solutions B.V. under project FUO-EM-002-10 and by Spanish Government under projects CONSOLIDER MICINN-10-CSD2009-00046 and MICINN-10-DPI2010-21110-C02-0. Besides, a patent is pending.

IEEE Transactions on Industrial Electronics, 1997

Distributed power-supply systems are an attractive solution to meeting the requirements (redundan... more Distributed power-supply systems are an attractive solution to meeting the requirements (redundancy, modularity, battery backup, etc.) for the next generation of power-supply systems. In addition, the normalization regarding power factor and total harmonic distortion (THD) makes it necessary to include the power-factor correction in the input stage in those architectures. This paper presents a novel approach of an integrated battery charger/discharger which offers power-factor correction and battery galvanic isolation in a simple structure. Placing the battery in the primary side overcomes the need of galvanic isolation integration in each one of the dc/dc on-board converters when this topology is used as part of a distributed power-supply system.

IEEE Transactions on Industrial Electronics, 2003

When low output voltage and EN61000-3-2 compliance are put together, not too many options can be ... more When low output voltage and EN61000-3-2 compliance are put together, not too many options can be used, especially if the power range is between 300-600 W. This paper presents one of the best solutions to comply with both specifications at the same time: the use of a single-stage topology to comply with the low-frequency harmonic limits combined with a half-bridge converter with complementary control, which is a very good option to obtain low output voltages with high efficiency.

IEEE Transactions on Industrial Electronics, 2005

Power-factor correction has been one of the hottest topics during the last few years and, hence, ... more Power-factor correction has been one of the hottest topics during the last few years and, hence, many new circuits have appeared. In general, it is assumed that preregulators based on multiplier circuits have poor dynamics and, then, a second stage is needed to improve the output voltage dynamic behavior. The other option is the use of single-stage topologies which have fast output voltage regulation although the input current waveform is not sinusoidal. This paper presents an analysis of the dynamic behavior of a conventional power-factor preregulator. The objective is to find the limits of the dynamic characteristics of these circuits when the priority is to improve the output voltage regulation and not the total harmonic distortion or the power factor. A large-signal model is presented and the theoretical results are validated with a prototype.