miun.sePublications
Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Radiated Emissions of Multilayered Coreless Printed Circuit Board Step-Down Power Transformers in Switch Mode Power Supplies
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media. (Power Electronics)
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media. (Power Electronics)ORCID iD: 0000-0001-5326-2563
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media. (Power Electronics)
2011 (English)In: 8th International Conference on Power Electronics - ECCE Asia: "Green World with Power Electronics", ICPE 2011-ECCE Asia 2011, IEEE conference proceedings, 2011, 960-965 p.Conference paper, Published paper (Refereed)
Abstract [en]

This paper addressesradiatedEMI issues in Coreless PCB step-down transformers used for power transfer applications. In case of SMPS circuits, since the waveforms are not sinusoidal in nature, most of theradiatedemissionsare not only from fundamental frequency component but also from harmonic contents. According to antenna theory,radiatedEMI for three different power transformers of different radii were estimated for fundamental frequency of 2MHz to 300MHz. The computations were made for both sinusoidal and square wave excitations and at a load power of 20W. The calculatedradiatedpower obtained for simulated waveforms and for practical measured current waveforms are in good agreement with each other up to certain bandwidth. These computational results confirm thatradiatedpower can be reduced in three layered 2:1 transformer compared to two layered 2:1 transformer. Also theradiatedemissionsare negligible in case of sinusoidal excitations compared to square wave excitations. © 2011 IEEE.

Place, publisher, year, edition, pages
IEEE conference proceedings, 2011. 960-965 p.
Keyword [en]
Harmonics; MHz frequency of operation; Multilayered Coreless PCB step down power transformers; Radiated EMI
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:miun:diva-13247DOI: 10.1109/ICPE.2011.5944654Scopus ID: 2-s2.0-80052087677Local ID: STCISBN: 978-1-61284-956-0 (print)ISBN: 978-1-61284-958-4 (print)OAI: oai:DiVA.org:miun-13247DiVA: diva2:396838
Conference
8th International Conference on Power Electronics - ECCE Asia: "Green World with Power Electronics", ICPE 2011-ECCE Asia;Jeju;30 May 2011through3 June 2011;Category numberCFP11CPB-USB;Code86200
Available from: 2011-02-11 Created: 2011-02-11 Last updated: 2016-10-19Bibliographically approved
In thesis
1. High Speed (MHz) Switch Mode Power Supplies (SMPS) using Coreless PCB Transformer Technology
Open this publication in new window or tab >>High Speed (MHz) Switch Mode Power Supplies (SMPS) using Coreless PCB Transformer Technology
2011 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

The most essential unit required for all the electronic devices is the Power Supply Unit (PSU). The main objective of power supply designers is to reduce the size, cost and weight, and to increase the power density of the converter. There is also a requirement to have a lower loss in the circuit and hence in the improvement of energy efficiency of the converter circuit. Operating the converter circuits at higher switching frequencies reduces the size of the passive components such as transformers, inductors, and capacitors, which results in a compact size, weight, and increased power density of the converter. At present the switching frequency of the converter circuit is limited due to the increased switching losses in the existing semiconductor devices and in the magnetic area, because of increased hysteresis and eddy current loss in the core based transformer. Based on continuous efforts to improve the new semi conductor materials such as GaN/SiC and with recently developed high frequency multi-layered coreless PCB step down power transformers, it is now feasible to design ultra-low profile, high power density isolated DC/DC and AC/DC power converters. This thesis is focussed on the design, analysis and evaluation of the converters operating in the MHz frequency region with the latest semi conductor devices and multi-layered coreless PCB step-down power and signal transformers.

An isolated flyback DC-DC converter operated in the MHz frequency with multi-layered coreless PCB step down 2:1 power transformer has been designed and evaluated. Soft switching techniques have been incorporated in order to reduce the switching loss of the circuit. The flyback converter has been successfully tested up to a power level of 10W, in the switching frequency range of 2.7-4 MHz. The energy efficiency of the quasi resonant flyback converter was found to be in the range of 72-84% under zero voltage switching conditions (ZVS). The output voltage of the converter was regulated by implementing the constant off-time frequency modulation technique.

Because of the theoretical limitations of the Si material MOSFETs, new materials such as GaN and SiC are being introduced into the market and these are showing promising results in the converter circuits as described in this thesis. Comparative parameters of the semi conductor materials such as the

vi

energy band gap, field strengths and figure of merit have been discussed. In this case, the comparison of an existing Si MOSFET with that of a GaN MOSFET has been evaluated using a multi-layered coreless PCB step-down power transformer for the given input/output specifications of the flyback converter circuit. It has been determined that the energy efficiency of the 45 to 15V regulated converter using GaN was improved by 8-10% compared to the converter using the Si MOSFET due to the gate drive power consumption, lower conduction losses and improved rise/fall times of the switch.

For some of the AC/DC and DC/DC applications such as laptop adapters, set-top-box, and telecom applications, high voltage power MOSFETs used in converter circuits possess higher gate charges as compared to that of the low voltage rating MOSFETs. In addition, by operating them at higher switching frequencies, the gate drive power consumption, which is a function of frequency, increases. The switching speeds are also reduced due to the increased capacitance. In order to minimize this gate drive power consumption and to increase the frequency of the converter, a cascode flyback converter was built up using a multi-layered coreless PCB transformer and this was then evaluated. Both simulation and experimental results have shown that with the assistance of the cascode flyback converter the switching speeds of the converter were increased including the significant improvement in the energy efficiency compared to that of the single switch flyback converter.

In order to further maximize the utilization of the transformer, to reduce the voltage stress on MOSFETs and to obtain the maximum power density from the power converter, double ended topologies were chosen. For this purpose, a gate drive circuitry utilising the multi-layered coreless PCB gate drive transformer was designed and evaluated in both a Half-bridge and a Series resonant converter. It was found that the gate drive power consumption using this transformer was less than 0.8W for the frequency range of 1.5-3.5MHz. In addition, by using this gate drive circuitry, the maximum energy efficiency of the series resonant converter was found to be 86.5% with an output power of 36.5W.

Place, publisher, year, edition, pages
Sundsvall, Sweden: Mid Sweden University, 2011. 104 p.
Series
Mid Sweden University licentiate thesis, ISSN 1652-8948 ; 62
Keyword
SMPS, High Frequency converters, Coreless PCB transformers
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:miun:diva-13964 (URN)STC (Local ID)978-91-86694-41-8 (ISBN)STC (Archive number)STC (OAI)
Presentation
2011-05-27, M102, Mid Sweden University, Holmgatan 10, Sundsvall, 10:15 (English)
Opponent
Supervisors
Funder
EU, European Research Council
Available from: 2011-06-13 Created: 2011-06-13 Last updated: 2016-10-19Bibliographically approved
2. Multilayered Coreless Printed Circuit Board (PCB) Step-down Transformers for High Frequency Switch Mode Power Supplies (SMPS)
Open this publication in new window or tab >>Multilayered Coreless Printed Circuit Board (PCB) Step-down Transformers for High Frequency Switch Mode Power Supplies (SMPS)
2011 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

The Power Supply Unit (PSU) plays a vital role in almost all electronic equipment. The continuous efforts applied to the improvement of semiconductor devices such as MOSFETS, diodes, controllers and MOSFET drivers have led to the increased switching speeds of power supplies. By increasing the switching frequency of the converter, the size of passive elements such as inductors, transformers and capacitors can be reduced. Hence, the high frequency transformer has become the backbone in isolated AC/DC and DC/DC converters. The main features of transformers are to provide isolation for safety purpose, multiple outputs such as in telecom applications, to build step down/step up converters and so on. The core based transformers, when operated at higher frequencies, do have limitations such as core losses which are proportional to the operating frequency. Even though the core materials are available in a few MHz frequency regions, because of the copper losses in the windings of the transformers those which are commercially available were limited from a few hundred kHz to 1MHz. The skin and proximity effects because of induced eddy currents act as major drawbacks while operating these transformers at higher frequencies. Therefore, it is necessary to mitigate these core losses, skin and proximity effects while operating the transformers at very high frequencies. This can be achieved by eliminating the magnetic cores of transformers and by introducing a proper winding structure.

A new multi-layered coreless printed circuit board (PCB) step down transformer for power transfer applications has been designed and this maintains the advantages offered by existing core based transformers such as, high voltage gain, high coupling coefficient, sufficient input impedance and high energy efficiency with the assistance of a resonant technique. In addition, different winding structures have been studied and analysed for higher step down ratios in order to reduce copper losses in the windings and to achieve a higher coupling coefficient. The advantage of increasing the layer for the given power transfer application in terms of the coupling coefficient, resistance and energy efficiency has been reported. The maximum energy efficiency of the designed three layered transformers was found to be within the range of 90%-97% for power transfer applications operated in a few MHz frequency regions. The designed multi-layered coreless PCB transformers for given power applications of 8, 15 and 30W show that the volume reduction of approximately 40-90% is possible when compared to its existing core based counterparts. The estimation of EMI emissions from the designed transformers proves that the amount of radiated EMI from a three layered transformer is less than that of the two layered transformer because of the decreased radius for the same amount of inductance.

Multi-layered coreless PCB gate drive transformers were designed for signal transfer applications and have successfully driven the double ended topologies such as the half bridge, the two switch flyback converter and resonant converters with low gate drive power consumption of about half a watt. The performance characteristics of these transformers have also been evaluated using the high frequency magnetic material made up of NiZn and operated in the 2-4MHz frequency region.

These multi-layered coreless PCB power and signal transformers together with the latest semiconductor switching devices such as SiC and GaN MOSFETs and the SiC schottky diode are an excellent choice for the next generation compact SMPS.

Place, publisher, year, edition, pages
Sundsvall, Sweden: Mid Sweden University, 2011. 88 p.
Series
Mid Sweden University licentiate thesis, ISSN 1652-8948 ; 61
Keyword
Multilayered Coreless PCB transformers, High frequency converters
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:miun:diva-13967 (URN)STC (Local ID)978-91-86694-40-1 (ISBN)STC (Archive number)STC (OAI)
Presentation
2011-05-20, O102, Mid Sweden University, Holmgatan 10, Sundsvall, 13:15 (English)
Opponent
Supervisors
Funder
EU, European Research Council
Available from: 2011-06-13 Created: 2011-06-13 Last updated: 2016-10-19Bibliographically approved
3. High Frequency (MHz) Planar Transformers for Next Generation Switch Mode Power Supplies
Open this publication in new window or tab >>High Frequency (MHz) Planar Transformers for Next Generation Switch Mode Power Supplies
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Increasing the power density of power electronic converters while reducing or maintaining the same cost, offers a higher potential to meet the current trend inrelation to various power electronic applications. High power density converters can be achieved by increasing the switching frequency, due to which the bulkiest parts, such as transformer, inductors and the capacitor's size in the convertercircuit can be drastically reduced. In this regard, highly integrated planar magnetics are considered as an effective approach compared to the conventional wire wound transformers in modern switch mode power supplies (SMPS). However, as the operating frequency of the transformers increase from several hundred kHz to MHz, numerous problems arise such as skin and proximity effects due to the induced eddy currents in the windings, leakage inductance and unbalanced magnetic flux distribution. In addition to this, the core losses whichare functional dependent on frequency gets elevated as the operating frequency increases. Therefore, this thesis provides an insight towards the problems related to the high frequency magnetics and proposes a solution with regards to different aspects in relation to designing high power density, energy efficient transformers.The first part of the thesis concentrates on the investigation of high power density and highly energy efficient coreless printed circuit board (PCB) step-down transformers useful for stringent height DC-DC converter applications, where the core losses are being completely eliminated. These transformers also maintain the advantages offered by existing core based transformers such as, high coupling coefficient, sufficient input impedance, high energy efficiency and wide frequencyband width with the assistance of a resonant technique. In this regard, several coreless PCB step down transformers of different turn’s ratio for power transfer applications have been designed and evaluated. The designed multilayered coreless PCB transformers for telecom and PoE applications of 8,15 and 30W show that the volume reduction of approximately 40 - 90% is possible when compared to its existing core based counterparts while maintaining the energy efficiency of the transformers in the range of 90 - 97%. The estimation of EMI emissions from the designed transformers for the given power transfer application proves that the amount of radiated EMI from a multilayered transformer is lessthan that of the two layered transformer because of the decreased radius for thesame amount of inductance.The design guidelines for the multilayered coreless PCB step-down transformer for the given power transfer application has been proposed. The designed transformer of 10mm radius has been characterized up to the power level of 50Wand possesses a record power density of 107W/cm3 with a peak energy efficiency of 96%. In addition to this, the design guidelines of the signal transformer fordriving the high side MOSFET in double ended converter topologies have been proposed. The measured power consumption of the high side gate drive circuitvitogether with the designed signal transformer is 0.37W. Both these signal andpower transformers have been successfully implemented in a resonant converter topology in the switching frequency range of 2.4 – 2.75MHz for the maximum load power of 34.5W resulting in the peak energy efficiency of converter as 86.5%.This thesis also investigates the indirect effect of the dielectric laminate on the magnetic field intensity and current density distribution in the planar power transformers with the assistance of finite element analysis (FEA). The significanceof the high frequency dielectric laminate compared to FR-4 laminate in terms of energy efficiency of planar power transformers in MHz frequency region is also explored.The investigations were also conducted on different winding strategies such as conventional solid winding and the parallel winding strategies, which play an important role in the design and development of a high frequency transformer and suggested a better choice in the case of transformers operating in the MHz frequency region.In the second part of the thesis, a novel planar power transformer with hybrid core structure has been designed and evaluated in the MHz frequency region. The design guidelines of the energy efficient high frequency planar power transformerfor the given power transfer application have been proposed. The designed corebased planar transformer has been characterized up to the power level of 50W and possess a power density of 47W/cm3 with maximum energy efficiency of 97%. This transformer has been evaluated successfully in the resonant converter topology within the switching frequency range of 3 – 4.5MHz. The peak energy efficiency ofthe converter is reported to be 92% and the converter has been tested for the maximum power level of 45W, which is suitable for consumer applications such as laptop adapters. In addition to this, a record power density transformer has been designed with a custom made pot core and has been characterized in thefrequency range of 1 - 10MHz. The power density of this custom core transformer operating at 6.78MHz frequency is 67W/cm3 and with the peak energy efficiency of 98%.In conclusion, the research in this dissertation proposed a solution for obtaining high power density converters by designing the highly integrated, high frequency(1 - 10MHz) coreless and core based planar magnetics with energy efficiencies inthe range of 92 - 97%. This solution together with the latest semiconductor GaN/SiC switching devices provides an excellent choice to meet the requirements of the next generation ultra flat low profile switch mode power supplies (SMPS).

Place, publisher, year, edition, pages
Sundsvall: Mid Sweden University, 2013. 143 p.
Series
Mid Sweden University doctoral thesis, ISSN 1652-893X ; 159
Keyword
Planar Magnetics, DC-DC Converters, Switch Mode Power Supplies, MHz Frequency Region
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:miun:diva-20270 (URN)STC (Local ID)978-91-87557-02-6 (ISBN)STC (Archive number)STC (OAI)
Public defence
2013-10-04, O102, Holmgatan 10, Sundsvall, 10:30 (English)
Opponent
Supervisors
Funder
EU, European Research CouncilVINNOVASwedish Energy Agency
Available from: 2013-11-22 Created: 2013-11-20 Last updated: 2016-10-19Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full textScopus

Search in DiVA

By author/editor
Ambatipudi, RadhikaKotte, Hari BabuBertilsson, Kent
By organisation
Department of Information Technology and Media
Other Electrical Engineering, Electronic Engineering, Information EngineeringOther Electrical Engineering, Electronic Engineering, Information Engineering

Search outside of DiVA

GoogleGoogle Scholar

Altmetric score

Total: 851 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf