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High Performance Planar Power Transformer with High Power Density in MHz Frequency Region for Next Generation Switch Mode Power Supplies
Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design. (Power Electronics)
Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design. (Power Electronics)ORCID iD: 0000-0001-5326-2563
Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design. (Power Electronics)
2013 (English)In: 2013 Twenty-Eighth Annual IEEE Applied Power Electronics Conference And Exposition (APEC 2013), IEEE conference proceedings, 2013, 2139-2143 p.Conference paper, Published paper (Refereed)
Abstract [en]

The authors report the utilization of the core based transformer for power transfer applications with high power density and high energy efficiency in the MHz frequency region. A custom made POT core center tapped transformer of 4:1:1 turn’s ratio using novel winding strategy with the core diameter of 16mm is designed and evaluated. The designed transformer has been characterized using sinusoidal excitation for a given output power in the frequency range of 1 – 10MHz and determined the operating frequency region of the transformer. The power tests of the transformer has been carried out up to the power level of 62W at an operating frequency of 6.78MHz with a peak energy efficiency of 98.5% resulting in the record power density of ~1100W/in3. The designed transformer has been characterized using class E isolated DC-DC converter topology at an output power of approximately 18W. The simulated energy efficiency of the converter is 88.5% under the full load condition. This work provides the significant step for the development of next generation high power density isolated converters (both AC/DC and DC/DC) in MHz frequency region

Place, publisher, year, edition, pages
IEEE conference proceedings, 2013. 2139-2143 p.
Series
Annual IEEE Applied Power Electronics Conference and Exposition (APEC), ISSN 1048-2334
Keyword [en]
Center tapped transformers, High energy efficiency, High power density, Isolated converters, Isolated dc-dc converters, Operating frequency, Sinusoidal excitations, Switch-mode power supplies
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:miun:diva-17843DOI: 10.1109/APEC.2013.6520591ISI: 000324988602042Scopus ID: 2-s2.0-84879340967Local ID: STCISBN: 978-1-4673-4355-8 (print)OAI: oai:DiVA.org:miun-17843DiVA: diva2:578233
Conference
28th Annual IEEE Applied Power Electronics Conference and Exposition APEC 2013, March 17 - 21, 2013, Long Beach, California
Available from: 2012-12-17 Created: 2012-12-17 Last updated: 2016-10-19Bibliographically approved
In thesis
1. 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
2. High Frequency (MHz) Resonant Converters using GaN HEMTs and Novel Planar Transformer Technology
Open this publication in new window or tab >>High Frequency (MHz) Resonant Converters using GaN HEMTs and Novel Planar Transformer Technology
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The increased power consumption and power density demands of modern

technologies have increased the technical requirements of DC/DC and AC/DC power

supplies. In this regard, the primary objective of the power supply researcher/engineer

is to build energy efficient, high power density converters by reducing the losses and

increasing the switching frequency of converters respectively. 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. Therefore, the thesis work is

focussed on the design, analysis and evaluation of isolated converters operating in the

1 - 5MHz frequency region with the assistance of the latest semi conductor devices,

both coreless and core based planar power transformers designed in Mid Sweden

University and which are suitable for consumer applications of varying power levels

ranging from 1 – 60W.

In high frequency converter circuits, since the MOSFET gate driver plays a prominent

role, different commercially available MOSFET gate drivers were evaluated in the

frequency range of 1 - 5MHz in terms of gate drive power consumption, rise/fall times

and electromagnetic interference (EMI) and a suitable driver was proposed.

Initially, the research was focused on the design and evaluation of a quasi resonant

flyback converter using a multilayered coreless PCB step down transformer in the

frequency range of 2.7 – 4MHz up to the power level of 10W. The energy efficiency of

this converter is found to be 72 - 84% under zero voltage switching conditions (ZVS).

In order to further improve the energy efficiency of the converter in the MHz

frequency region, the new material device GaN HEMT was considered. The

comparisons were made on a quasi resonant flyback DC-DC converter using both the

Si and GaN technology and it was found that an energy efficiency improvement of 8 –

10% was obtained with the GaN device in the frequency range of 3.2 – 5MHz. In order

to minimize the gate drive power consumption, switching losses and to increase the

frequency of the converter in some applications such as laptop adapters, set top box

(STB) etc., a cascode flyback converter using a low voltage GaN HEMT and a high

voltage Si MOSFET was designed and evaluated using a multi-layered coreless PCB

transformer in the MHz frequency region. Both the simulation and experimental

results have shown that, with the assistance of the cascode flyback converter, the

switching speeds of the converter can be increased with the benefit of obtaining a

significant improvement in the energy efficiency as compared to that for 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 converter

circuit, double ended topologies were considered. Due to the lack of high voltage high

side gate drivers in the MHz frequency region, a gate drive circuitry utilizing the

multi-layered coreless PCB signal transformer was designed and evaluated in both a

half-bridge and series resonant converter (SRC). It was found that the gate drive power

consumption using this transformer was around 0.66W for the frequency range of 1.5 -

v

3.75 MHz. In addition, by using this gate drive circuitry, the maximum energy

efficiency of the SRC using multilayered coreless PCB power transformer was found to

be 86.5% with an output power of 36.5W in the switching frequency range of 2 –

3MHz.

In order to further enhance the energy efficiency of the converter to more than 90%,

investigations were carried out by using the multiresonant converter topology (LCC

and LLC), novel hybrid core high frequency planar power transformer and the GaN

HEMTs. The simulated and experimental results of the designed LCC resonant

converter show that it is feasible to obtain higher energy efficiency isolated DC/DC

converters in the MHz frequency region. The peak energy efficiency of the LCC

converter at 3.5MHz is reported to be 92% using synchronous rectification. Different

modulation techniques were implemented to regulate the converter for both line and

load variations using a digital controller.

In order to realize an AC/DC converter suitable for a laptop adapter application,

consideration was given to the low line of the universal input voltage range due to the

GaN switch limitation. The energy efficiency of the regulated converter operating in

the frequency range of 2.8 – 3.5MHz is reported to be more than 90% with a load

power of 45W and an output voltage of 22V

dc. In order to determine an efficient power

processing method on the secondary side of the converter, a comparison was made

between diode rectification and synchronous rectification and optimal rectification was

proposed for the converters operating in the MHz frequency range for a given power

transfer application. In order to maintain high energy efficiency for a wide load range

and to maintain the narrow switching frequency range for the given input voltage

specifications, the LLC resonant converter has been designed and evaluated for the

adapter application. From the observed results, the energy efficiency of the LLC

resonant converter is maintained at a high level for a wide load range as compared to

that for the LCC resonant converter.

Investigations were also carried out on isolated class E resonant DC-DC converter with

the assistance of GaN HEMT and a high performance planar power transformer at the

switching frequency of 5MHz. The simulated energy efficiency of the converter for the

output power level of 16W is obtained as 88.5% which makes it feasible to utilize the

designed isolated converter for various applications that require light weight and low

profile converters.

In conclusion, the research in this dissertation has addressed various issues related to

high frequency isolated converters and has proposed solution by designing highly

energy efficient converters to meet the current industrial trends by using coreless and

core based planar transformer technologies along with the assistance of GaN HEMTs.

With the provided solution, in the near future, it is feasible to realize low profile, high

power density DC/DC and AC/DC converters operating in MHz frequency region

suitable for various applications.

Place, publisher, year, edition, pages
Sundsvall, Sweden: Mid Sweden University, 2013. 156 p.
Series
Mid Sweden University doctoral thesis, ISSN 1652-893X ; 158
Keyword
GaN HEMTs, MHz Frequency, Resonant Converters, Planar Transformer Technology
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:miun:diva-20894 (URN)STC (Local ID)978-91-87557-01-9 (ISBN)STC (Archive number)STC (OAI)
Public defence
2013-09-26, L111, Mid Sweden University, Holmgatan 10, Sundsvall, 10:30 (English)
Opponent
Supervisors
Projects
High Frequency Switch Mode Power Supplies
Funder
EU, European Research CouncilVINNOVASwedish Energy Agency
Available from: 2013-12-27 Created: 2013-12-25 Last updated: 2016-10-20Bibliographically approved

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CiteExportLink to record
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Citation style
  • apa
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  • modern-language-association-8th-edition
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Output format
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