Matthias Kasper | Swiss Federal Institute of Technology (ETH) (original) (raw)

Papers by Matthias Kasper

CIPS 2020; 11th International Conference on Integrated Power Electronics Systems, Mar 24, 2020

The trend towards higher computation power per server rack has lead to an increased interest in h... more The trend towards higher computation power per server rack has lead to an increased interest in high density server power supplies with high efficiency and low cost. This paper analyzes how the specific features of planar magnetics as transformers and inductors can be best utilized in combination with GaN power semiconductors to reach unprecedented system performance both for power supplies with 12 V and with 48 V output voltage. Based on the optimization results a hardware demonstrator with an ultra-high power density (350 W/in 3) of a 3 kW DC/DC converter stage with a wide-input voltage range of 300 V-430 V and an output voltage of 12 V is presented.

PCIM Europe 2018; International Exhibition and Conference for Power Electronics, Intelligent Motion, Renewable Energy and Energy Management, Jun 5, 2018

Ein Leistungswandler umfasst mehrere erste Wandlerzellen, mehrere zweite Wandlerzellen und mehrer... more Ein Leistungswandler umfasst mehrere erste Wandlerzellen, mehrere zweite Wandlerzellen und mehrere Zwischenkreiskondensatoren. Jeder Zwischenkreiskondensator verbindet eine der mehreren ersten Wandlerzellen und eine der mehreren zweiten Wandlerzellen. Eine Fehlermanagementeinheit ist dazu ausgebildet, eine fehlerhafte erste Wandlerzelle zu detektieren und die fehlerhafte erste Wandlerzelle zu deaktivieren, wahrend ein Leistungswandlungsbetrieb des Leistungswandlers aufrecht erhalten bleibt.

One of the key enabling technologies behind many global megatrends, which are affecting our lives... more One of the key enabling technologies behind many global megatrends, which are affecting our lives as individuals and as a society in many different areas, is power electronics. Prominent examples are the shift from conventional energy sources to renewable energy sources, the reduction of greenhouse gas emissions due to the electrification of mobility, and the trend towards cloud-computing in the information technology area, which are all based on the development of cost-effective, efficient and compact power electronic systems. In order to fulfill future requirements for power electronic systems, it is therefore of great importance to identify new ways to develop systems with higher efficiency, power density, and reliability. The analysis of relevant literature reveals, that improvements of power electronic systems are to a great extent either based on the improvements of specific components or on the modification of known control algorithms and/or topologies. These improvement proc...

2018 IEEE International Power Electronics and Application Conference and Exposition (PEAC), 2018

This digest shows the design process and optimization results of a highly compact 3kW, 12V server... more This digest shows the design process and optimization results of a highly compact 3kW, 12V server power supply. In the course of a comprehensive analysis of the key performance parameters of GaN e-mode HEMTs compared to their Si Superjunction counterparts, the most suitable topologies and control methods for the PFC and the DC/DC converter stages are derived. In a subsequent step, the system is fully optimized with respect to efficiency and power density by means of multi-objective Pareto-optimization. Based on the results, the design parameters of a system with a power density of 80W=in3 and a peak efficiency of 96:4% are presented.

The multi-cell converter approach allows to break the performance barriers of conventional system... more The multi-cell converter approach allows to break the performance barriers of conventional systems by leveraging the advantages of using multiple interleaved low voltage and/or low current converter cells. In this digest, a fourth dimension of interleaving is proposed which considers the time dependent degrees of freedom in the control of the entire multi-cell converter system. This new control concept is based on the possibility to decouple the operation of the series connected input stages from the parallel connected output stages by using the energy storage capability of the DC-link capacitors. This digest shows how the 4D-interleaving concept improves the system performance such as the efficiency which will be demonstrated with measurement results on a hardware prototype system in the final paper.

IECON 2016 - 42nd Annual Conference of the IEEE Industrial Electronics Society, 2016

The Input Series Output Parallel (ISOP) multi-cell converter approach allows breaking the perform... more The Input Series Output Parallel (ISOP) multi-cell converter approach allows breaking the performance barriers of conventional single-cell telecom rectifier systems by leveraging the advantages of using multiple interleaved low-voltage and/or lowcurrent converter cells. The ISOP interconnection in the DC/DC converter part of the cells, however, requires the employment of some kind of isolation in each cell, which is typically provided by transformers. An analysis of the losses and of the volume of the entire multi-cell system reveals that these transformers contribute a major part to the system losses and are responsible for a significant share of the total volume. However, as the transformers are mainly required for providing galvanic isolation in the ISOP structure and not for voltage conversion, series capacitors represent an alternative to decouple the series connected input terminals of the cells from the parallel connected output terminals. Compared to conventional solutions with transformers, the resulting capacitive power transfer ISOP multi-cell DC/DC converter (CPT-ISOP-MCC) system features lower losses and a smaller volume. In this paper, the benefits as well as the limitations in the design and operation of CPT-ISOP-MCC systems are analyzed in detail. In order to comprehensively evaluate the CPT against the magnetically isolated concept, i.e. inductive power transfer (IPT) converter topology, a multi-objective optimization is performed with respect to the achievable efficiency and power density for both types of converters. Based on the optimization result, a prototype of a CPT GaN DC/DC converter is realized and compared to its IPT GaN DC/DC converter counterpart, along with measurement results. Furthermore, a complete singlephase 3.3 kW AC/DC converter system with a high power density of ρ = 3.92 kW/dm 3 and an efficiency of η = 97% is presented, incorporating the CPT-DC/DC converter stages in ISOP topology.

2018 IEEE International Power Electronics and Application Conference and Exposition (PEAC), 2018

Given the demand for higher power density, higher efficiency and lower realization cost solutions... more Given the demand for higher power density, higher efficiency and lower realization cost solutions in data centers, dc-dc converters using PCB winding magnetics and resonant operation have been intensively studied in literature. In this paper, a new approach for 300 V-430 V dc input and 12 V dc output server power supplies is proposed, which is based on a series resonant converter topology using a synergy between boundary and discontinuous conduction mode operation, whereby low peak-to-average ratio transformer current waveforms, soft-switching throughout the full power range and tight regulation of the output voltage for a wide input voltage range are achieved. Furthermore, a PCB winding "snake-core" matrix transformer is introduced, which provides only a single path for the magnetic flux and therefore ensures an equal flux linkage and/or induced voltage of the parallel-connected secondary windings despite possible geometric PCB layout asymmetries. This approach avoids the emergence of circulating currents between parallel-connected secondary windings and guarantees at the same time equal secondary-side voltages in power supplies with multiple isolated outputs. Thus, a higher degree of freedom in the design of the primary windings of PCB winding-integrated transformers is achieved, whereby the design of these transformers is considerably simplified.

2019 20th Workshop on Control and Modeling for Power Electronics (COMPEL), 2019

Electronics

The next-generation industrial environment requires power supplies that are compact, efficient, l... more The next-generation industrial environment requires power supplies that are compact, efficient, low-cost, and ultra-reliable, even across mains failures, to power mission-critical electrified processes. Hold-up time requirements and the demand for ultra-high power density and minimum production costs, in particular, drive the need for power converters with (i) a wide input voltage range, to reduce the size of the hold-up capacitor, (ii) soft-switching over the full input voltage and load ranges, to achieve low losses that facilitate a compact realization, and (iii) complete PCB-integration for low-cost manufacturing. In this work, we conceptualize, design, model, fabricate, and characterize a 1.5kW, 12 V-output DC/DC converter for industrial power supplies that is required to operate across a wide 300 V–430 V input voltage range. This module utilizes an LLC-based control scheme for complete soft-switching and a snake-core transformer to divide the output current with a balanced flux...

IEEE Journal of Emerging and Selected Topics in Power Electronics

IEEE Transactions on Power Electronics

IEEE Transactions on Power Electronics, 2016

2015 IEEE Applied Power Electronics Conference and Exposition (APEC), 2015

2014 IEEE Energy Conversion Congress and Exposition (ECCE), 2014

2014 16th European Conference on Power Electronics and Applications, 2014

2014 International Power Electronics Conference (IPEC-Hiroshima 2014 - ECCE ASIA), 2014

ABSTRACT In this paper, the potential of the multi-cell approach for power electronic converters ... more ABSTRACT In this paper, the potential of the multi-cell approach for power electronic converters with efficiencies and power densities beyond the barriers of state-of-the-art systems is discussed. Based on fundamental scaling laws the benefits of splitting a system into multiple converter cells are derived in terms of lower volume and/or higher power density for a given cooling capacity. In addition, the conditions for equal current and/or voltage balancing of multi-cell systems is reviewed. The advantages of the mulit-cell systems are examined in more detail based on the example of a DC-DC boost converter realized with either parallel- or series-interleaved boost cells. It is shown, that the multi-cell systems can offer lower switching and conduction losses and/or an improved voltage spectrum depending on the choice of the switching frequency relative to a single system. Furthermore, the effects of parasitic capacitances on unwanted ground currents are investigated for both configurations.

2013 IEEE Energy Conversion Congress and Exposition, 2013

ABSTRACT Voltage conversions with high step-down ratios are required in many medium voltage appli... more ABSTRACT Voltage conversions with high step-down ratios are required in many medium voltage applications for supplying auxiliary electronics. In this paper a new topology for high conversion ratios with low voltage stresses of components, modular structure and simple control is presented. The operation principles are described together with analytical descriptions of the average value of the inductor currents and RMS values of the switches. In addition, the influence of the efficiency of the individual modules on the total converter efficiency is provided. Possible modifications of the “Rainstick” converter with benefits for different applications are shown. Furthermore, the measurement results of a prototype with an input voltage range of up to 2.4 kV and 30 W output power are shown.

CIPS 2020; 11th International Conference on Integrated Power Electronics Systems, Mar 24, 2020

The trend towards higher computation power per server rack has lead to an increased interest in h... more The trend towards higher computation power per server rack has lead to an increased interest in high density server power supplies with high efficiency and low cost. This paper analyzes how the specific features of planar magnetics as transformers and inductors can be best utilized in combination with GaN power semiconductors to reach unprecedented system performance both for power supplies with 12 V and with 48 V output voltage. Based on the optimization results a hardware demonstrator with an ultra-high power density (350 W/in 3) of a 3 kW DC/DC converter stage with a wide-input voltage range of 300 V-430 V and an output voltage of 12 V is presented.

PCIM Europe 2018; International Exhibition and Conference for Power Electronics, Intelligent Motion, Renewable Energy and Energy Management, Jun 5, 2018

Ein Leistungswandler umfasst mehrere erste Wandlerzellen, mehrere zweite Wandlerzellen und mehrer... more Ein Leistungswandler umfasst mehrere erste Wandlerzellen, mehrere zweite Wandlerzellen und mehrere Zwischenkreiskondensatoren. Jeder Zwischenkreiskondensator verbindet eine der mehreren ersten Wandlerzellen und eine der mehreren zweiten Wandlerzellen. Eine Fehlermanagementeinheit ist dazu ausgebildet, eine fehlerhafte erste Wandlerzelle zu detektieren und die fehlerhafte erste Wandlerzelle zu deaktivieren, wahrend ein Leistungswandlungsbetrieb des Leistungswandlers aufrecht erhalten bleibt.

One of the key enabling technologies behind many global megatrends, which are affecting our lives... more One of the key enabling technologies behind many global megatrends, which are affecting our lives as individuals and as a society in many different areas, is power electronics. Prominent examples are the shift from conventional energy sources to renewable energy sources, the reduction of greenhouse gas emissions due to the electrification of mobility, and the trend towards cloud-computing in the information technology area, which are all based on the development of cost-effective, efficient and compact power electronic systems. In order to fulfill future requirements for power electronic systems, it is therefore of great importance to identify new ways to develop systems with higher efficiency, power density, and reliability. The analysis of relevant literature reveals, that improvements of power electronic systems are to a great extent either based on the improvements of specific components or on the modification of known control algorithms and/or topologies. These improvement proc...

2018 IEEE International Power Electronics and Application Conference and Exposition (PEAC), 2018

This digest shows the design process and optimization results of a highly compact 3kW, 12V server... more This digest shows the design process and optimization results of a highly compact 3kW, 12V server power supply. In the course of a comprehensive analysis of the key performance parameters of GaN e-mode HEMTs compared to their Si Superjunction counterparts, the most suitable topologies and control methods for the PFC and the DC/DC converter stages are derived. In a subsequent step, the system is fully optimized with respect to efficiency and power density by means of multi-objective Pareto-optimization. Based on the results, the design parameters of a system with a power density of 80W=in3 and a peak efficiency of 96:4% are presented.

The multi-cell converter approach allows to break the performance barriers of conventional system... more The multi-cell converter approach allows to break the performance barriers of conventional systems by leveraging the advantages of using multiple interleaved low voltage and/or low current converter cells. In this digest, a fourth dimension of interleaving is proposed which considers the time dependent degrees of freedom in the control of the entire multi-cell converter system. This new control concept is based on the possibility to decouple the operation of the series connected input stages from the parallel connected output stages by using the energy storage capability of the DC-link capacitors. This digest shows how the 4D-interleaving concept improves the system performance such as the efficiency which will be demonstrated with measurement results on a hardware prototype system in the final paper.

IECON 2016 - 42nd Annual Conference of the IEEE Industrial Electronics Society, 2016

The Input Series Output Parallel (ISOP) multi-cell converter approach allows breaking the perform... more The Input Series Output Parallel (ISOP) multi-cell converter approach allows breaking the performance barriers of conventional single-cell telecom rectifier systems by leveraging the advantages of using multiple interleaved low-voltage and/or lowcurrent converter cells. The ISOP interconnection in the DC/DC converter part of the cells, however, requires the employment of some kind of isolation in each cell, which is typically provided by transformers. An analysis of the losses and of the volume of the entire multi-cell system reveals that these transformers contribute a major part to the system losses and are responsible for a significant share of the total volume. However, as the transformers are mainly required for providing galvanic isolation in the ISOP structure and not for voltage conversion, series capacitors represent an alternative to decouple the series connected input terminals of the cells from the parallel connected output terminals. Compared to conventional solutions with transformers, the resulting capacitive power transfer ISOP multi-cell DC/DC converter (CPT-ISOP-MCC) system features lower losses and a smaller volume. In this paper, the benefits as well as the limitations in the design and operation of CPT-ISOP-MCC systems are analyzed in detail. In order to comprehensively evaluate the CPT against the magnetically isolated concept, i.e. inductive power transfer (IPT) converter topology, a multi-objective optimization is performed with respect to the achievable efficiency and power density for both types of converters. Based on the optimization result, a prototype of a CPT GaN DC/DC converter is realized and compared to its IPT GaN DC/DC converter counterpart, along with measurement results. Furthermore, a complete singlephase 3.3 kW AC/DC converter system with a high power density of ρ = 3.92 kW/dm 3 and an efficiency of η = 97% is presented, incorporating the CPT-DC/DC converter stages in ISOP topology.

2018 IEEE International Power Electronics and Application Conference and Exposition (PEAC), 2018

Given the demand for higher power density, higher efficiency and lower realization cost solutions... more Given the demand for higher power density, higher efficiency and lower realization cost solutions in data centers, dc-dc converters using PCB winding magnetics and resonant operation have been intensively studied in literature. In this paper, a new approach for 300 V-430 V dc input and 12 V dc output server power supplies is proposed, which is based on a series resonant converter topology using a synergy between boundary and discontinuous conduction mode operation, whereby low peak-to-average ratio transformer current waveforms, soft-switching throughout the full power range and tight regulation of the output voltage for a wide input voltage range are achieved. Furthermore, a PCB winding "snake-core" matrix transformer is introduced, which provides only a single path for the magnetic flux and therefore ensures an equal flux linkage and/or induced voltage of the parallel-connected secondary windings despite possible geometric PCB layout asymmetries. This approach avoids the emergence of circulating currents between parallel-connected secondary windings and guarantees at the same time equal secondary-side voltages in power supplies with multiple isolated outputs. Thus, a higher degree of freedom in the design of the primary windings of PCB winding-integrated transformers is achieved, whereby the design of these transformers is considerably simplified.

2019 20th Workshop on Control and Modeling for Power Electronics (COMPEL), 2019

Electronics

The next-generation industrial environment requires power supplies that are compact, efficient, l... more The next-generation industrial environment requires power supplies that are compact, efficient, low-cost, and ultra-reliable, even across mains failures, to power mission-critical electrified processes. Hold-up time requirements and the demand for ultra-high power density and minimum production costs, in particular, drive the need for power converters with (i) a wide input voltage range, to reduce the size of the hold-up capacitor, (ii) soft-switching over the full input voltage and load ranges, to achieve low losses that facilitate a compact realization, and (iii) complete PCB-integration for low-cost manufacturing. In this work, we conceptualize, design, model, fabricate, and characterize a 1.5kW, 12 V-output DC/DC converter for industrial power supplies that is required to operate across a wide 300 V–430 V input voltage range. This module utilizes an LLC-based control scheme for complete soft-switching and a snake-core transformer to divide the output current with a balanced flux...

IEEE Journal of Emerging and Selected Topics in Power Electronics

IEEE Transactions on Power Electronics

IEEE Transactions on Power Electronics, 2016

2015 IEEE Applied Power Electronics Conference and Exposition (APEC), 2015

2014 IEEE Energy Conversion Congress and Exposition (ECCE), 2014

2014 16th European Conference on Power Electronics and Applications, 2014

2014 International Power Electronics Conference (IPEC-Hiroshima 2014 - ECCE ASIA), 2014

ABSTRACT In this paper, the potential of the multi-cell approach for power electronic converters ... more ABSTRACT In this paper, the potential of the multi-cell approach for power electronic converters with efficiencies and power densities beyond the barriers of state-of-the-art systems is discussed. Based on fundamental scaling laws the benefits of splitting a system into multiple converter cells are derived in terms of lower volume and/or higher power density for a given cooling capacity. In addition, the conditions for equal current and/or voltage balancing of multi-cell systems is reviewed. The advantages of the mulit-cell systems are examined in more detail based on the example of a DC-DC boost converter realized with either parallel- or series-interleaved boost cells. It is shown, that the multi-cell systems can offer lower switching and conduction losses and/or an improved voltage spectrum depending on the choice of the switching frequency relative to a single system. Furthermore, the effects of parasitic capacitances on unwanted ground currents are investigated for both configurations.

2013 IEEE Energy Conversion Congress and Exposition, 2013

ABSTRACT Voltage conversions with high step-down ratios are required in many medium voltage appli... more ABSTRACT Voltage conversions with high step-down ratios are required in many medium voltage applications for supplying auxiliary electronics. In this paper a new topology for high conversion ratios with low voltage stresses of components, modular structure and simple control is presented. The operation principles are described together with analytical descriptions of the average value of the inductor currents and RMS values of the switches. In addition, the influence of the efficiency of the individual modules on the total converter efficiency is provided. Possible modifications of the “Rainstick” converter with benefits for different applications are shown. Furthermore, the measurement results of a prototype with an input voltage range of up to 2.4 kV and 30 W output power are shown.