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High Frequency (MHz) Resonant Converters using GaN HEMTs and Novel Planar Transformer Technology
Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design. (Power Electronics)ORCID iD: 0000-0001-5326-2563
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 [en]
GaN HEMTs, MHz Frequency, Resonant Converters, Planar Transformer Technology
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:miun:diva-20894Local ID: STCISBN: 978-91-87557-01-9 (print)OAI: oai:DiVA.org:miun-20894DiVA: diva2:682193
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
List of papers
1. Comparative Results of GaN and Si MOSFET in a ZVS Flyback Converter using Multilayered Coreless Printed Circuit Board Step-Down Transformer
Open this publication in new window or tab >>Comparative Results of GaN and Si MOSFET in a ZVS Flyback Converter using Multilayered Coreless Printed Circuit Board Step-Down Transformer
2010 (English)In: Proceedings of 2010 3rd International Conference on Power Electronics and Intelligent Transportation System, Shenzhen: IEEE conference proceedings, 2010, 318-321 p.Conference paper, (Refereed)
Abstract [en]

The aim of this paper is to compare two different material MOSFETs performance namely GaN (Gallium Nitride) and conventional Si (Silicon) in Zero Voltage Switching (ZVS) flyback converter circuit with Coreless PCB step down transformers. The switching frequency of the regulated converter is in the range of 3.2-5MHz. In high frequency circuits, proper selection of MOSFETs is required in order to have low gate drive power consumption so that high energy efficiency of the converter can be achieved. Even though Si MOSFET has already known for its popularity in low to medium power converters and high frequency applications, GaN MOSFET device could produce better results.  This can be done by reducing the total switching loss, conduction loss because of its low Rds-on and gate drive power consumption of the converter as a result of low gate charge, Qg. From the experimental results, it can be observed that GaN MOSFET can produce higher energy savings including gate drive power by gaining approximately 8%-10% efficiency compared to its counterpart, Si MOSFET in a regulated 45-15V isolated DC-DC converter.

Place, publisher, year, edition, pages
Shenzhen: IEEE conference proceedings, 2010
Keyword
Coreless Printed Circuit Board (PCB) step down power transformer, DC-DC Converter, GaN MOSFET, MHz frequency region, ZVS flyback converter.
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:miun:diva-14644 (URN)000306295600014 ()978-1-4244-9162-9/10 (ISBN)
Conference
2010 3rd International Conference on Power Electronics and Intelligent Transportation System
Available from: 2011-10-27 Created: 2011-10-27 Last updated: 2014-08-31Bibliographically approved
2. A ZVS Flyback DC-DC Converter using Multilayered Coreless Printed Circuit Board (PCB) Step Down Power Transformer
Open this publication in new window or tab >>A ZVS Flyback DC-DC Converter using Multilayered Coreless Printed Circuit Board (PCB) Step Down Power Transformer
2010 (English)In: World Academy of Science, Engineering and technology, Paris: World Academy of Science,Engineering and Technology , 2010, 148-155 p.Conference paper, (Refereed)
Abstract [en]

The experimental and theoretical results of a ZVS (Zero Voltage Switching) isolated flyback DC-DC converter using multilayered coreless PCB step down 2:1 transformer are presented.The performance characteristics of the transformer are shown which are useful for the parameters extraction. The measured energy efficiency of the transformer is found to be more than 94% with the sinusoidal input voltage xcitation. The designed flyback converter has been tested successfully upto the output power level of 10W,with a switching frequency in the range of 2.7MHz-4.3MHz. The input voltage of the converter is varied from 25V-40V DC.Frequency modulation technique is employed by maintaining constant off time to regulate the output voltage of the converter. The energy efficiency of the isolated flyback Converter circuit under ZVS condition in the MHz frequency region is found to be approximately in the range of 72-84%. This paper gives the comparative results in terms of the energy efficiency of the hard switched and soft switched flyback Converter in the MHz frequency region.

Place, publisher, year, edition, pages
Paris: World Academy of Science,Engineering and Technology, 2010
Series
World Academy of Science ,Engineering and Technology,ISSUE 70,OCTOBER 2010, ISSN 1307-6892 ; 70
Keyword
Coreless PCB step down transformer, DC-DC Converter, Flyback, Hard Switched Converter, MHz Frequency region, Multilayered PCB transformer, Zero Voltage Switching
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:miun:diva-12278 (URN)2-s2.0-80052088161 (Scopus ID)
Conference
International Conference on Electrical Machines and Power Electronics (ICEMPE),2010
Available from: 2010-11-24 Created: 2010-11-24 Last updated: 2016-09-26Bibliographically approved
3. High Speed (MHz) Series Resonant Converter (SRC) Using Multilayered Coreless Printed Circuit Board (PCB) Step-Down Power Transformer
Open this publication in new window or tab >>High Speed (MHz) Series Resonant Converter (SRC) Using Multilayered Coreless Printed Circuit Board (PCB) Step-Down Power Transformer
2013 (English)In: IEEE transactions on power electronics, ISSN 0885-8993, E-ISSN 1941-0107, Vol. 28, no 3, 1253-1264 p.Article in journal (Refereed) Published
Abstract [en]

In this paper, design and analysis of an isolated low profile, series resonant converter (SRC) using multilayered coreless printed circuit board (PCB) power transformer was presented. For obtaining the stringent height switch mode power supplies (SMPS), a multilayered coreless PCB power transformer of approximately 4:1 turn’s ratio was designed in a four layered PCB laminate which can be operated in MHz switching frequency. The outermost radius of the transformer is 10mm with achieved power density of 16W/cm2. The energy efficiency of the power transformer is found to be in the range of 87-96% with the output power level of 0.1-50W operated at a frequency of 2.6MHz. This designed step-down transformer was utilized in SRC and evaluated. The supply voltage of converter is varied from 60-120V DC with a nominal input voltage of 90V and has been tested up to the power level of 34.5W. The energy efficiency of converter under Zero Voltage Switching (ZVS) condition is found to be in the range of 80-86.5% with the switching frequency range of 2.4-2.75MHz. By using constant off-time frequency modulation technique, the converter was regulated to 20V DC for different load conditions. Thermal profile with converter loss at nominal voltage is presented.

Keyword
DC-DC Power Converters, High frequency magnetics, MHz frequency, Transformers
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:miun:diva-16544 (URN)10.1109/TPEL.2012.2208123 (DOI)000314697000018 ()2-s2.0-84867870182 (Scopus ID)STC (Local ID)STC (Archive number)STC (OAI)
Available from: 2012-06-24 Created: 2012-06-24 Last updated: 2016-10-20Bibliographically approved
4. A ZVS Half Bridge DC-DC Converter in MHz Frequency Region using Novel Hybrid Power Transformer
Open this publication in new window or tab >>A ZVS Half Bridge DC-DC Converter in MHz Frequency Region using Novel Hybrid Power Transformer
2012 (English)In: Proceedings of International Exhibition and Conference for Power Electronics, Intelligent Motion, Power Quality (PCIM) 2012, 8-10 May 2012, Nuremberg, Germany., Berlin: Curran Associates, Inc., 2012, 399-406 p.Conference paper, (Refereed)
Abstract [en]

The significant problems in increasing the switching frequency of isolated converters to achieve low cost and high power density are increased magnetic and switching losses. This paper presents solution with the investigation of newly designed high frequency, low profile, hybrid power transformer together with commercially available GaN MOSFETs. For achieving stringent power converters, a center tapped 4:1:1 half bridge transformer was designed in a multilayered PCB laminate with a total height of transformer as 4.2mm. The maximum obtained energy efficiency of transformer is 98% in the frequency region of 1 – 5MHz. The designed transformer possesses better high frequency characteristics in the frequency range of 3 - 5MHz with tested power density of 47W/cm3 at an operating frequency of 3MHz. This transformer has been utilized in the multi resonant zero voltage switching (ZVS) half bridge converter with synchronous rectification using GaN MOSFETs and then evaluated. The maximum achieved efficiency of multi resonant ZVS half bridge converter with this transformer is 92% in 3 – 4.5 MHz switching frequency range with characterized output power of 40W. This is to the author’s knowledge, the best energy efficiency ever reported for an isolated DC-DC converter in this frequency range and power levels. At a specified input voltage, the converter has been regulated to 15V within 1% for both line and wide load variations. This work provides considerable step for the development of next generation ultra flat low profile isolated DC-DC/AC-DC converters operating in MHz frequency region.

Place, publisher, year, edition, pages
Berlin: Curran Associates, Inc., 2012
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:miun:diva-15268 (URN)2-s2.0-84867880610 (Scopus ID)STC (Local ID)978-3-8007-3431-3 (ISBN)STC (Archive number)STC (OAI)
Conference
International Conference on Power Conversion and Intelligent Motion (PCIM) 2012, Nuremberg, Germany
Available from: 2011-12-14 Created: 2011-12-14 Last updated: 2016-10-20Bibliographically approved
5. High Performance Planar Power Transformer with High Power Density in MHz Frequency Region for Next Generation Switch Mode Power Supplies
Open this publication in new window or tab >>High Performance Planar Power Transformer with High Power Density in MHz Frequency Region for Next Generation Switch Mode Power Supplies
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, (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
Series
Annual IEEE Applied Power Electronics Conference and Exposition (APEC), ISSN 1048-2334
Keyword
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:nbn:se:miun:diva-17843 (URN)10.1109/APEC.2013.6520591 (DOI)000324988602042 ()2-s2.0-84879340967 (Scopus ID)STC (Local ID)978-1-4673-4355-8 (ISBN)STC (Archive number)STC (OAI)
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
6. A 45W LLC resonant Converter in MHz Frequency Region for Laptop Adapter Application using GaN HEMTs
Open this publication in new window or tab >>A 45W LLC resonant Converter in MHz Frequency Region for Laptop Adapter Application using GaN HEMTs
2013 (English)In: PCIM Europe Conference Proceedings, Berlin: Mesago PCIM GmbH , 2013, 1029-1035 p.Conference paper, (Refereed)
Abstract [en]

The authors report the feasibility of low profile, high power density and energy efficient isolated DC/DC converter in 3 – 4 MHz frequency region corresponding to low line input voltage of 90 – 110 Vac suitable for 45W laptop adapter application. Using novel hybrid power transformer, GaN HEMTs, the simulation and experimental results of LLC resonant converter for DC input voltage range of 127 – 155Vdc with a regulated output voltage of 22Vdc was presented. The maximum energy efficiency of converter at the full load condition is reported to be approximately 91% whereas light load efficiency was improved using pulse skip modulation technique.

Place, publisher, year, edition, pages
Berlin: Mesago PCIM GmbH, 2013
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:miun:diva-18402 (URN)2-s2.0-84906330762 (Scopus ID)STC (Local ID)978-3-8007-3505-1 (ISBN)STC (Archive number)STC (OAI)
Conference
International Exhibition and Conference for Power Electronics, Intelligent Motion, Renewable Energy and Energy Management, PCIM Europe 2013; Nuremberg; Germany; 14 May 2013 through 16 May 2013; Code 107029
Available from: 2013-01-31 Created: 2013-01-31 Last updated: 2016-10-20Bibliographically approved
7. High Speed Cascode Flyback Converter Using Multilayered Coreless Printed Circuit Board (PCB) Step-Down Power Transformer
Open this publication in new window or tab >>High Speed Cascode Flyback Converter Using Multilayered Coreless Printed Circuit Board (PCB) Step-Down Power Transformer
2011 (English)In: Proceedings of 8th International Conference on Power Electronics-ECCE Asia, IEEE conference proceedings, 2011, 1856-1862 p.Conference paper, (Refereed)
Abstract [en]

In this paper, design and analysis of the high speed isolated cascode flyback converter using multilayered coreless PCB step down power transformer is presented. The converter is tested for the input voltage variation of 60-120V with a nominal DC input voltage of 90V. The designed converter was simulated and tested successfully up to the output power level of 30W within the switching frequency range of 2.6-3.7MHz. The cascode flyback converter is compared with the single switch flyback converter in terms of operating frequency, gate drive power consumption, conduction losses and stresses on MOSFETs. The maximum energy efficiency of the cascode converter is approximately 81% with a significant improvement of about 3-4% compared to single switch flyback converter. The gate drive power consumption which is more dominant compared to conduction losses of the cascode converter using GaN MOSFET is found to be negligible compared to single switch flyback converter.

Place, publisher, year, edition, pages
IEEE conference proceedings, 2011
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:miun:diva-13248 (URN)10.1109/ICPE.2011.5944386 (DOI)STC (Local ID)978-1-61284-956-0 (ISBN)978-1-61284-958-4 (ISBN)STC (Archive number)STC (OAI)
Projects
High Speed Switch Mode Power Supplies
Available from: 2011-02-11 Created: 2011-02-11 Last updated: 2016-10-19Bibliographically approved
8. High Frequency Half-Bridge Converter using Multilayered Coreless PrintedCircuit Board Step-Down Power Transformer
Open this publication in new window or tab >>High Frequency Half-Bridge Converter using Multilayered Coreless PrintedCircuit Board Step-Down Power Transformer
Show others...
2011 (English)In: 8th International Conference on Power Electronics - ECCE Asia: "Green World with Power Electronics", ICPE 2011-ECCE Asia, IEEE conference proceedings, 2011, 1177-1181 p.Conference paper, (Refereed)
Abstract [en]

This paper introduces high frequencyhalf bridgeDC-DC converter, using multilayered coreless Printed Circuit Board (PCB) step down power transformer. The converter is simulated and then implemented on a PCB. Complementary Pulse Width Modulated (PWM) signals are generated to turn on high and low side Metal Oxide Semiconductor Field Effect Transistors (MOSFETs) alternately by a micro-controller. The isolated gate drive signals are provided to the high side MOSFET by using high frequency coreless PCB isolation transformer. We tested the converter for switching frequency range of 2 to 3 MHz, and for maximum input voltage up-to 170 V. The maximum output power achieved is 40 W and the maximum energy efficiency is approximately 82 %. © 2011 IEEE.

Place, publisher, year, edition, pages
IEEE conference proceedings, 2011
Keyword
Printed Circuit Board; Pulse Width Modulation; Switch Mode Power Supplies
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:miun:diva-14197 (URN)10.1109/ICPE.2011.5944712 (DOI)2-s2.0-80052080114 (Scopus ID)STC (Local ID)978-1-61284-956-0 (ISBN)978-1-61284-958-4 (ISBN)STC (Archive number)STC (OAI)
Conference
8th International Conference on Power Electronics - ECCE Asia May 30-June 3, 2011, The Shilla Jeju, Korea
Available from: 2011-07-19 Created: 2011-07-19 Last updated: 2016-10-19Bibliographically approved
9. Design and Analysis of 45W Multi Resonant Half Bridge Converter in MHz Frequency Region using GaN HEMTs
Open this publication in new window or tab >>Design and Analysis of 45W Multi Resonant Half Bridge Converter in MHz Frequency Region using GaN HEMTs
(English)Manuscript (preprint) (Other academic)
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:miun:diva-19797 (URN)
Available from: 2013-08-28 Created: 2013-08-28 Last updated: 2016-12-09Bibliographically approved

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