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A 45W LLC resonant Converter in MHz Frequency Region for Laptop Adapter Application using GaN HEMTs
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)
Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design. (Power Electronics)
2013 (English)In: PCIM Europe Conference Proceedings, Berlin: Mesago PCIM GmbH , 2013, p. 1029-1035Conference paper, Published 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. p. 1029-1035
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:miun:diva-18402Scopus ID: 2-s2.0-84906330762Local ID: STCISBN: 978-3-8007-3505-1 (print)OAI: oai:DiVA.org:miun-18402DiVA, id: diva2:602063
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
In thesis
1. 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. p. 156
Series
Mid Sweden University doctoral thesis, ISSN 1652-893X ; 158
Keywords
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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Kotte, Hari BabuAmbatipudi, RadhikaBertilsson, Kent

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