Publications

A Family of High Efficiency Variable Frequency Soft-Switching Off-line DC-DC Converters

  • Date of Publication 12 May 2009
  • Meeting end date 14 May 2009
  • Location Nuremberg, Germany
  • Conference/Proceedings International Conference for Power Conversion, Intelligent Motion & Power Quality, May 2009. PCIM Europe ‘09. Conference Proceedings 2009

The paper presents a family of off-line DC-DC converters for medium to high power delivering more than 95% efficiency for output levels of 12 to 48 V. The multi-layer PCB solution allows for low profile converters with multiple applications, from AC-DC adapters to TELECOM and computing. The main gain of this new design approach consist in using variable frequency topology with high frequency zero voltage switching (ZVS) and zero current switching (ZCS) for primary switchers. Theoretical considerations and practical results are presented for high frequency and high voltage soft-switching. The goal of the designs is to maintain a reasonable temperature rise of the multi-layer PCB board while delivering up to 90 W and respective 750 W power in a reduced volume and low cost.


750W High Efficiency and Soft-Switching Off-Line 12 V Converter

  • Date of Publication 15 Feb 2009
  • Meeting end date 19 Feb 2009
  • Location Washington, DC, USA
  • Conference/Proceedings Applied Power Electronics Conference and Exposition, February 2009. APEC '09. Conference Proceedings 2009, Twenty-fourth Annual

The paper presents an innovative off-line low profile converter design that delivers 750 W of power at 95%-96% efficiency for nominal input range, using variable frequency topology with high frequency zero voltage switching (ZVS) and zero current switching (ZCS) for primary switchers. Theoretical considerations and practical results are presented for high frequency and high voltage soft-switching. The goal of the design is to maintain a reasonable temperature rise of the multi-layer PCB board while delivering 750 W power in a reduced volume and low cost. The resulting product increases more than twice the power density compared to the standard two stages 400V to 12V power converters and outperforms other one stage solutions in a 125 x 70 mm2 footprint with only a 18 mm profile.


High Efficiency Adapter Using Dual Switch PFC-Flyback Single Stage

  • Date of Publication 27 May 2008
  • Meeting end date 29 May 2008
  • Location Nuremberg, Germany
  • Conference/Proceedings International Conference for Power Conversion, Intelligent Motion & Power Quality, May 2008. PCIM Europe ‘08. Conference Proceedings 2008

The paper presents an innovative design that delivers 85W of power at more than 91% efficiency in a low profile using a high frequency quasi-resonant fly-back topology with synchronous rectification, and improved power factor based on dual switch method. A closed to 0.9 power factor is achieved employing only one magnetic element and two primary side switchers. A significant power density increase is obtained due to a combination of smaller bulk capacitor and a smaller magnetic element.


High Efficiency 100W Quasi-Resonant Multi-Phases Interleaved PFC Using Planar Magnetic Components

  • Date of Publication 23 Feb 2008
  • Meeting end date 28 Feb 2008
  • Location Austin, Texas, USA
  • Conference/Proceedings Applied Power Electronics Conference and Exposition, February 2008. APEC '08. Conference Proceedings 2008, Twenty-third Annual

The paper presents an innovative PFC design that delivers 100 W of power at 96%-97% efficiency for nominal input range, in low profile using a high frequency quasi-resonant interleaved boost topology, while maintaining a reasonable low cost of the ac-dc adapter. Theoretical considerations and practical results for high frequency interleaved boost converters are described. The goal of the design is maintaining a reasonable temperature rise of the case while delivering 100W power in a reduced volume. The resulting product increases more than twice the power density compared to the standard notebook universal adapters.


ZVS and ZCS High Efficiency Low Profile Adapter

  • Date of Publication 21 Mar 2007
  • Meeting end date 23 Mar 2007
  • Location Pudong, Shanghai, China
  • Conference/Proceedings International Conference for Power Conversion, Intelligent Motion & Power Quality, March 2007. PCIM China. Conference Proceedings 2007, March 2007

The paper presents an innovative design that delivers 65W of power at more than 91% efficiency in a footprint of a business card using a high frequency quasi-resonant fly-back topology with synchronous rectification, while maintaining a reasonable low cost of the AC/DC adapter. Topology and techniques for obtaining ZVS and ZCS for high frequency and high voltage switching are described. The goal of the design is maintaining a reasonable temperature rise of the case while delivering 65W power in a reduced volume. The resulting product increases more than twice the power density compared to the standard notebook adapters.


Increasing The Efficiency In High Current And Low Voltage Application

  • Date of Publication 10 Jan 2006
  • Meeting end date 11 Jan 2006
  • On page 231-234
  • Location Pudong, Shanghai, China
  • Conference/Proceedings Delta Power Electronics Center, January 2005, DPEC Seminar Proceedings

The paper will present a converter design targeted to push the performance in respect of efficiency and power density while reducing the cost. The innovation will come from the topology, magnetic structure, drive circuit and the control method. It will present a group of innovation which together lead to a design with outstanding performance.These technologies will be implemented in a 12V output voltage bus converter for HP , delivering 450W with limited airflow.


Magnetic Integration For High Density And High Efficiency Applications

  • Date of Publication 15 Sep 2005
  • Meeting end date 16 Sep 2005
  • Location Dresden, Germany
  • Conference/Proceedings European Center for Power Electronics e. V., September 2005. ECPE ‘05. Seminar: “Power Supplies”

The tutorial will present a comprehensive overview of the integrated and quasi-integrated magnetic concepts and implementations. In the quest for higher power densities and higher efficiency integrated magnetic structures have become more popular. There will be presented many forms of integrated magnetic in close correlation with converter topologies. Included are several structures wherein the transformer and the storage elements are placed on the same magnetic core, forming the traditional integrated magnetic with emphasis on the latest trends. In addition to this will be presented structures wherein two independent power trains are placed on the same standard magnetic core and structures wherein the main transformer and a signal transformer are sharing the same magnetic core without interference. The focus for the integrated magnetic will be for low profile and or planar magnetic structures. Ripple steering in new applications will also be presented. There will be presented the advantages of different forms of magnetic integration in very high current and low voltage application. The seminar will also show present and future trends in magnetic integration and new forms of planar magnetic.


Increasing The Efficiency In High Current And Low Voltage Application

  • Date of Publication 18 Jan 2005
  • Meeting end date 19 Jan 2005
  • On page 231-234
  • Location Tongli, Wujiang
  • Conference/Proceedings Delta Power Electronics Center, January 2005, DPEC Seminar Proceedings

The continuous quest for lower voltage and higher current has created some challenges for the power designers especially if the high efficiency and high power density is pursued. This paper will underline the challenges associated with very low voltage and high current application. It will focus mostly on the reduction of effective duty cycle due to the leakage and stray inductance. It will present a magnetic structure which actually minimizes not only the leakage inductance but also the stray inductance which plays a crucial role in this application. In addition to that the magnetic structure reduces by a factor of two the footprint of the magnetic core, using a special layout structure which leads to cancellation of the magnetic filed created by the flowing current outside of the transformer the stray inductance is practically eliminated. These concepts were implemented in a 1.2V @100A quarter brick isolated DC-DC Converter which has an efficiency 2% higher than the competition at full load and reached 90% for 1.2V @ 60A, higher than many VRMs.


Magnetic Integration Through Multiple Functions In The Magnetic Cores

  • Date of Publication 18 Jan 2005
  • Meeting end date 19 Jan 2005
  • On page 225-230
  • Location Tongli, Wujiang
  • Conference/Proceedings Delta Power Electronics Center, January 2005, DPEC Seminar Proceedings

The paper presents a method of employing a magnetic core for multiple functions. For some magnetic cores shapes such EE and EI, we can implement two independent functions. These functions can be two independent power processing, can be a signal processing and power processing, or can be a power transfer and energy storage. In the continuous quest for miniaturization and cost reduction, these technologies offer a significant advantage. Several example of such implementation in high density DC-DC Converters will be presented.


Constant Voltage Reset Circuit

  • Date of Publication 20 May 2003
  • Meeting end date 22 May 2003
  • On page 119-125
  • Location Nuremberg, Germany
  • Conference/Proceedings International Power Conversion & Intelligent Motion, May 2003. PCIM ‘03. Conference Proceedings 2003, Fourty-Seventh International

This paper presents a reset mechanism, which combines the advantages of the active clamp reset and the traditional third wire reset technique. In this concept the reset voltage is constant similar to the third wire reset, wherein a constant voltage is applied to the transformer during the reset cycle. The technology has several key advantages from the active clamp reset mechanism. The energy contained in the leakage and magnetizing inductance is recycled, and the voltage across the main switch is clamped. In addition to this, the flux through the transformer is symmetrical to zero and the duty cycle can be higher than 50%, similar to the active clamp circuit. Though this circuit contains most of the active clamp circuit’s key features it does not exhibit its limitations. One of the drawbacks of the active clamp circuit is its behavior during transients wherein the duty cycle changes. During transients, until the reset capacitor charges to its optimum level, the voltage across the switch may reach uncontrollable levels. In this reset technique the voltage across the switch is constant regardless of the duty cycle and reacts to transients without any limitations. In addition to this the implementation is very simple; it does not require any additional driving and timing circuits for the reset switch. The reset switch is driven directly form the transformer by a driving winding and the reset voltage can be easily adjusted by a resistor divider. Using this technology a DC-DC converter was implemented, providing 1.2 V @ 20A, from an input voltage range of 36 V to 60 reaching an efficiency of 86% at full load. Another application of this technology in a 1/8 brick DC-DC Converter is also presented.


Self-driven Constant Voltage Reset Circuit

  • Date of Publication 09 Feb 2002
  • Meeting end date 13 Feb 2002
  • On page 893-897 vol. 2
  • Location Miami Beach, Florida, USA
  • Conference/Proceedings Applied Power Electronics Conference and Exposition, February 2003. APEC '03. Conference Proceedings 2002, Eighteenth Annual

This paper presents a reset mechanism, which combines the advantages of the active clamp reset and the traditional third wire reset technique. In this concept the reset voltage is constant similar to the third wire reset, wherein a constant voltage is applied to the transformer during the reset cycle. The technology has several key advantages from the active clamp reset mechanism. The energy contained in the leakage and magnetizing inductance is recycled, and the voltage across the main switch is clamped. In addition to this, the flux trough the transformer is symmetrical to zero and the duty cycle can be higher than 50%, similar to the active clamp circuit. Though this circuit contains most of the active clamp circuit’ key features it does not exhibit its limitations. One of the drawbacks of the active clamp circuit is its behavior during transients wherein the duty cycle changes. During transients, until the reset capacitor charges to its optimum level, the voltage across the switch may reach uncontrollable levels. In this reset technique the voltage across the switch is constant regardless of the duty cycle and reacts to transients without any limitations. In addition to this the implementation is very simple; it does not require any additional driving and timing circuits for the reset switch. The reset switch is driven directly form the transformer by a driving winding and the reset voltage can be easily adjusted by a resistor divider. Using this technology a DC-DC converter was implemented, providing 1.2 V @ 20A, from an input voltage range of 36 V to 60 reaching an efficiency of 86% at full load.


High Efficiency Flyback Converter Using Synchronous Rectification

  • Date of Publication 14 May 2002
  • Meeting end date 16 May 2002
  • On page 89-94
  • Location Nuremberg, Germany
  • Conference/Proceedings International Power Conversion & Intelligent Motion, May 2002. PCIM '02. Conference Proceedings 2002., Forty-Fifth International

This paper presents a method of driving a synchronous rectifier in a flyback topology. For optimum driving of the synchronous rectifier in a flyback converter, the primary side gate signal has to be transferred to the secondary with minimum delay. This paper presents a method of signal transfer through a power transformer without interference with the main power train. In this concept, the main transformer of the flyback converter is used to store and transfer energy to the secondary and, at the same time, to transfer the gate signal from the primary side to the secondary side with minimum delay. Both the power winding and the signal transfer winding are incorporated in a multilayer PCB, reducing the labor cost. Incorporating the signal winding and the power winding on the same magnetic core decreases the cost and increases the power density, which is a very important feature for the latest generation of DC-DC power converters. This technology is implemented in a 15 W 3.3 V@ 4.5A DC-DC converter, with an efficiency reaching 90% at full load. The power density of the converter reaches 40 W/inch3


High Efficiency Flyback Converter Using Synchronous Rectification

  • Date of Publication 10 Mar 2002
  • Meeting end date 14 Mar 2002
  • On page 867-871 vol. 2
  • Location Dallas, Texas, USA
  • Conference/Proceedings Applied Power Electronics Conference and Exposition, March 2002. APEC '02. Conference Proceedings 2002, Seventeenth Annual

This paper presents a method of driving a synchronous rectifier in a flyback topology. For optimum driving of the synchronous rectifier in a flyback converter, the primary side gate signal has to be transferred to the secondary with minimum delay. This paper presents a method of signal transfer through a power transformer without interference with the main power train. In this concept, the main transformer of the flyback converter is used to store and transfer energy to the secondary and, at the same time, to transfer the gate signal from the primary side to the secondary side with minimum delay. Both the power winding and the signal transfer winding are incorporated in a multilayer PCB, reducing the labor cost. Incorporating the signal winding and the power winding on the same magnetic core decreases the cost and increases the power density, which is a very important feature for the latest generation of DC-DC power converters. This technology is implemented in a 15 W 3.3 V@ 4.5A DC-DC converter, with an efficiency reaching 90% at full load. The power density of the converter reaches 40 W/inch3


Signal Transfer Through Power Magnetics

  • Date of Publication 17 Sep 2002
  • Meeting end date 18 Sep 2002
  • Location Bloomington, Minnesota, USA
  • Conference/Proceedings IBM Power Technology And Qualifications, 2002 Power Technology Symposium; Theme: Future Technology, September 2002

This paper presents a method of signal transfer through a power magnetic without interference with the main power train. There will be described two implementations of this concept. In the first application the concept is applied in a 15W DC-DC Converter using flyback topology. The main transformer of the flyback converter is used to store and transfer energy to the secondary and at the same time to transfer the gate signal from the primary side to the secondary side with minimum delay. Incorporating the signal winding and the power winding on the same magnetic core decrease the cost and increases the power density, which is a very important feature for the latest generation of DC-DC Converters. In the second application of this technology is implemented in a quarter brick DC-DC Converter, using a half bridge topology. In this implementation the gate signal for the primary switchers is transferred from the secondary to the primary side through the output chokes. The output chokes are used to store energy and in the same time to transfer signal from the secondary to the primary. The technology is implemented in a DC-DC Converter 132W, 3.3V @ 40A DC-DC Converter, with an efficiency of 91.5% at full load and reaching a power density of 146W/inch3


A 3kW Soft Switching DC-DC Converter

  • Date of Publication 19 Jun 2001
  • Meeting end date 21 Jun 2001
  • On page 427-435
  • Location Nuremberg, Germany
  • Conference/Proceedings International Power Conversion & Intelligent Motion, June 2001. PCIM ‘01. Conference Proceedings 2001, Forty-Third International
On page(s) 427-435
Location Nuremberg, Germany
Meeting date 06/19/2001 – 06/21/2001
Conference/Proceedings International Power Conversion & Intelligent Motion, June 2001. PCIM ‘01. Conference Proceedings 2001, Forty-Third International

This paper will present a circuit technique designed to reduce the negative impact of reverse recovery in the rectifiers for high output voltage converters. This technique works by combining reduced amplitude of the reverse recovery current and a lower voltage across the rectifier during the turn off commutation. Another major advantage of the proposed circuit is the fact that the current reflected in the primary is shaped to a triangular form with a low dI/dt during the turn on of the main switch. This will allow the completion of the resonant transition to zero voltage across the primary switchers. In the secondary section the reverse recovery current is reduced due to low dI/dt current slope at turn off and the reverse voltage is clamped to the output voltage. The maximum reverse recovery voltage does not exceed the output voltage. The soft commutation in the primary section and the secondary allows a higher frequency of operation without penalty in efficiency. A 3kW converter for on board battery charger in electric vehicles provides an output voltage between 170V to 380V. Efficiency above 96% is obtained at a switching frequency of 250 kHz while the power density of the converter exceeds 100W/inch3


A 3kW Soft Switching DC-DC Converter

  • Date of Publication 06 Feb 2000
  • Meeting end date 10 Feb 2000
  • On page 86-92
  • Location New Orleans, Louisiana, USA
  • Conference/Proceedings Applied Power Electronics Conference and Exposition, February 2000. APEC '00. Conference Proceedings 2000, Fifteenth Annual
On page(s) 86-92
Location New Orleans, Louisiana, USA
Meeting date 02/06/2000 – 02/10/2000
Conference/Proceedings Applied Power Electronics Conference and Exposition, February 2000. APEC ’00. Conference Proceedings 2000, Fifteenth Annual

This paper will present a circuit technique designed to reduce the negative impact of reverse recovery in the rectifiers for high output voltage converters. This technique works by combining reduced amplitude of the reverse recovery current and a lower voltage across the rectifier during the turn off commutation. Another major advantage of the proposed circuit is the fact that the current reflected in the primary is shaped to a triangular form with a low dI/dt during the turn on of the main switch. This will allow the completion of the resonant transition to zero voltage across the primary switchers. In the secondary section the reverse recovery current is reduced due to low dI/dt current slope at turn off and the reverse voltage is clamped to the output voltage. The maximum reverse recovery voltage does not exceed the output voltage. The soft commutation in the primary section and the secondary allows a higher frequency of operation without penalty in efficiency. A 3kW converter for on board battery charger in electric vehicles provides an output voltage between 170V to 380V. Efficiency above 96% is obtained at a switching frequency of 250 kHz while the power density of the converter exceeds 100W/inch3


Distributed Magnetics In High Power Converters

  • Date of Publication 01 May 1999
  • Location Santa Clara, California, USA
  • Conference/Proceedings High Frequency Magnetic Material, May 1999

This paper presents an actual avenue in magnetics topic, especially planar technology, related with DC-DC Power Converters. Starting from basic electric laws simple ideas could be derived and applied to practice. This leads to final interesting results that fulfill most of the initial technical requirements.


Very High Power Density Flyback Converter

  • Date of Publication 26 May 1998
  • Meeting end date 28 May 1998
  • On page 97-103
  • Location Nuremberg, Germany
  • Conference/Proceedings International Power Conversion & Intelligent Motion, May 1998. PCIM '98. Conference Proceedings 1998, Thirty-Eighth International

The paper states the concept of a very high power density flyback converter. Due to its less complex schematic flyback converters are recommended for power supplies providing low output power with inputs from low level DC voltages to high DC voltages (off-line SMPS). Main innovations are used: planar magnetics-PCB transformer and proprietary special packaging. As a result the parasitic are highly reduced and the almost ideal DC-DC converter, of 25 W, 12 V input to 48 V output reaches a power density of 100 W/inch3


Small-signal Characterization Of The Forward-Flyback Converters With Active Clamp

  • Date of Publication 15 Feb 1998
  • Meeting end date 19 Feb 1998
  • On page 626-632
  • Location Anaheim, California, USA
  • Conference/Proceedings Applied Power Electronics Conference and Exposition, February 1998. APEC '98. Conference Proceedings 1998, Thirteenth Annual

Linear equivalent models of the forward-flyback converters with active clamp are deduced, using the Vorperian model of the PWM switch. Control-to-output transfer functions are plotted against frequency, for a 36-72V to 5V converter, for different load resistances, thus allowing the design of error amplifier as to ensure circuit stability. Experimental results confirm model validity.


Power Conversion Technology For Power Levels Under 3kW

  • Date of Publication 26 May 1998
  • Meeting end date 28 May 1998
  • On page 255-263
  • Location Nuremberg, Germany
  • Conference/Proceedings International Power Conversion & Intelligent Motion, May 1998. PCIM '98. Conference Proceedings 1998, Thirty-Eighth International

We have witnessed in the last several years a transition from a technological driven to a price driven market. The power technology development was de-emphasized unless it targeted cost reduction. Though the cost is still one of the first priorities, quality and reliability made strong headway being named number one and two priority. The paper will present several technological advances, which can offer better performance in respect of reliability and quality, at a lower total cost. Different standardization techniques will be also presented. Standardization becomes the main avenue to improve the design and product quality, the reliability, to lower NRE and to reduce time-to-market.


Quasi-Integrated Magnetic an Avenue For High Power density and Efficiency In Power Converters

  • Date of Publication 23 Feb 1997
  • Meeting end date 27 Feb 1997
  • On page 395-402
  • Location Atlanta, Georgia, USA
  • Conference/Proceedings Applied Power Electronics Conference and Exposition, February 1997. APEC '97. Conference Proceedings 1997, Twelfth Annual

In order to utilize better the magnetic core of the transformer in DC-DC converters there are investigated some topologies that could fulfill this aim. The main idea is to use the transformer, usually an isolation component in a DC-DC converter, as a storage element too thus reducing the size of the choke from the filtering stage. In this way a quasi-integrated magnetic approach is set that can be seen as an intermediate step between conventional and fully integrated magnetic. Advantages and limitations are underlined. A topology using quasi-integrated magnetic was investigated with and without tap in the secondary side. As a result two methods that could eliminate the secondary winding tap are presented, one using a current doubler and the other one using two symmetrical transformers. Two experimental 100W converters providing 20A under 5V were built and evaluated using quasi-integrated magnetic approach under two different implementations.


Increasing the Utilization Of The Transformer’s Magnetic Core By Using Quasi-integrated Magnetics

  • Date of Publication 14 Oct 1997
  • Meeting end date 17 Oct 1997
  • On page 299-313
  • Location Hong Kong
  • Conference/Proceedings Power Conversion & Intelligent Motion, October 1997. PCIM '97. Conference Proceedings 1997

Several topologies leading to a better utilization of transformer’s magnetic core are investigated. To reduce the size of the output filter these topologies uses the main transformer as a storage element too. Thus a quasi-integrated magnetic is established as an intermediate step between conventional and fully integrated magnetic underlying its advantages and limitations. A quasi-integrated magnetic topology using a tap or not in the secondary side is analyzed. Two methods of eliminating the secondary winding tap will be suggested, one by using current-doubler and the second by employing two symmetrical transformers. Two 100W 5V@20A experimental converters were built and evaluated using quasi-integrated magnetic under two different implementations.


Increasing the Utilization Of The Transformer’s Magnetic Core By Using Quasi-integrated Magnetics

  • Date of Publication 07 Sep 1996
  • Meeting end date 13 Sep 1996
  • On page 238-252
  • Location Las Vegas, Nevada, USA
  • Conference/Proceedings High Frequency Power Conversion & Advanced Power Electronics Technology, September 1996. HFPC '96. Conference Proceedings 1996, Eleventh International

This paper will present several topologies that lead to a better utilization of transformer’s magnetic core. In these topologies the main transformer becomes a magnetic storage element, reducing the size of the output filter. Quasi-integrated magnetic will be presented as an intermediate step between conventional and fully integrated magnetic underlying its advantages and limitations. There will be presented quasi-integrated magnetic topologies with and without secondary winding tap. Two methods of eliminating the secondary winding tap will be suggested, one by using current-doubler and the second by employing two symmetrical transformers. Two 100W 5V@20A experimental converters were built and evaluated using quasi-integrated magnetic under two different implementations.


The Impact Of Low Output Voltage Requirements On Power Converters

  • Date of Publication 20 Jun 1995
  • Meeting end date 22 Jun 1995
  • On page 59-68
  • Location Nuremberg, Germany
  • Conference/Proceedings International Power Conversion & Intelligent Motion, June 1995. PCIM '95. Conference Proceedings 1995, Thirtieth International

Today’s power conversion trend is to use lower output voltages. This avenue sets new challenges that must be faced. The paper presents several techniques applied in power converter circuits when using low voltage Schottky rectifiers. Also it will discuss the advantages and limitations associated with synchronized rectification. A comparison between Schottky rectifiers and synchronized rectifiers made by experimental results is presented. Further the negative impact of the leakage inductance and circuit parasitic inductance on the performance is analyzed. Special care is dedicated to the copper loss minimization in the secondary winding of the transformer and the output choke. Using circuit topologies doing this one arrives to a better copper utilization especially for low output voltage applications. The paper concludes with experimental results of Rompower’s 75W 3.3V output DC-DC converter operating from an input voltage of 36V to 60V.

 


The Impact Of Low Output Voltage Requirements On Power Converters

  • Date of Publication 06 May 1995
  • Meeting end date 12 May 1995
  • On page 1-10
  • Location San Jose, California, USA
  • Conference/Proceedings High Frequency Power Conversion, May 1995. HFPC '95. Conference Proceedings 1995, Tenth International

The trend to lower output voltage sets new challenges for the power conversion industry. The paper will present circuit techniques designed to employ low voltage Schottky rectifiers and will elaborate about the advantages and limitation associated with synchronized rectification. Based on the components available today a direct comparison between the Schottky rectifiers and synchronized rectifiers is made substantiated by experimental results. This paper further presents the impact of leakage inductance and circuit parasitic inductance on the low output voltage converter’ performance. A special chapter is dedicated to minimization of copper losses in the secondary winding of the transformer and the output inductor. Using circuit topologies doing this one arrives to a better copper utilization especially for low output voltage applications. The paper concludes with experimental results of Rompower’s 75W 3.3V output DC-DC converter operating from an input voltage of 36V to 60V.


High Efficiency DC-DC Converter

  • Date of Publication 17 Apr 1994
  • Meeting end date 21 Apr 1994
  • On page 120-127
  • Location San Jose, California, USA
  • Conference/Proceedings High Frequency Power Conversion, April 1994. HFPC '94. Conference Proceedings 1994, Ninth International

A family of converter topologies employing two complementary switches in the primary and two MOSFET synchronous rectifiers in the secondary is presented. The use of two complementary switches in the primary leads to soft transitions across the switching elements, and the complementary square waveforms reflected in the secondary offers a simple and efficient driving waveform for the synchronous rectifiers. Employing one of these topological configurations, a very high efficiency and high power density 150W converter was implemented. The converter operates from an input voltage of 35Vdc to 72Vdc, providing 5V at 30A, with efficiency above 90% at full load. High efficiency combined with the use of a full-integrated multilayer PCB magnetic technology has allowed a power density of 51W/inch3

 


High Efficiency DC-DC Converter

  • Date of Publication 28 Jun 1994
  • Meeting end date 30 Jun 1994
  • On page 109-116
  • Location Nuremberg, Germany
  • Conference/Proceedings International Power Conversion & Intelligent Motion, June 1994. PCIM '94. Conference Proceedings 1994, Twenty-Eighth International

The paper presents a whole family of converters using two complementary switches in the primary side and two MOSFET synchronous rectifiers in the secondary side. These devices together with the main transformer and the filtering choke are coupled in large number of topologies. Using complementary switches one can obtain soft transitions across switching elements. Also the complementary square waveforms reflected in the secondary side offers a simple and efficient driving signal command for the synchronous rectifiers. Starting from one topology from the specified range a very efficient high-density 100W power converter was built. The converter operates from an input voltage of 35Vdc to 72Vdc, providing 5V at 20A, with efficiency above 90% at full load. High efficiency combined with the use of a full-integrated multilayer PCB magnetic technology has allowed a power density of 52W/inch3     


High Efficiency DC-DC Converter

  • Date of Publication 13 Feb 1994
  • Meeting end date 17 Feb 1994
  • On page 638-644
  • Location Orlando, Florida, USA
  • Conference/Proceedings Applied Power Electronics Conference and Exposition, February 1994. APEC '94. Conference Proceedings 1994, Ninth Annual

The paper presents a family of topologies used in DC-DC power converters employing two complementary switches in the primary and two MOSFET synchronous rectifiers in the secondary. This technique leads to soft transitions across switching devices and to a simple complementary square waveform for the driving signal of the MOSFET synchronous rectifiers. Using one topology from the family a high-efficient very dense 100W converter was built. Operating from an input voltage of 35Vdc to 72Vdc and providing 20A under 5V more than 90% efficiency at full load was obtained. Combining full-integrated multilayer PCB magnetic technology with the high efficiency target has lead to a power density of 52W/inch3


Soft Transitions Power Factor Correction Circuit

  • Date of Publication 23 May 1993
  • Meeting end date 27 May 1993
  • On page 202-208
  • Location Vienna, Virginia, USA
  • Conference/Proceedings High Frequency Power Conversion, May 1993. HFPC '93. Conference Proceedings 1993, Eighth International

The losses due to the reverse recovery of rectifiers impact significantly the performances of power converters especially at high frequency. The effect of reverse recovery time it is more severe in non isolated converters such as buck and boost topologies, due to the low impedance across the voltage source during the commutation of the diode. The current industry demand for rectifiers with high switching speed and low conduction losses has pushed the silicon based technology for power semiconductor to its performance limit. This is driving the quest for a new material such as, gallium arsine, diamond and silicon carbide, which are potential candidates for future power semiconductor devices. This paper is focused on circuit techniques, which minimize the negative effects of silicon rectifiers’ reverse recovery. There are presented two “soft” switching techniques applied to buck and boost topology, together with experimental results in a power factor correction application.


Soft Transitions Power Factor Correction Circuit

  • Date of Publication 22 Jun 1993
  • Meeting end date 24 Jun 1993
  • On page 144-150
  • Location Nuremberg, Germany
  • Conference/Proceedings High Frequency Power Conversion, June 1993. HFPC '93. Conference Proceedings 1993, Twenty-Sixth International

Reverse recovery of the diode rectifier has a negative effect on power converters’ performance when operating at high frequency. Due to the low impedance across the voltage source when the diode commutes this negative effect becomes worse in non-isolated converters using buck and boost topologies. Today’s industry requests for better power diodes rectifier regarding switching speed and low conduction losses seems to touch the technology limits. Thus the paper presents circuit techniques that minimize the negative effects of silicon power rectifiers’ reverse recovery. Two “soft” switching techniques applied to buck and boost topology are presented together with experimental results in a power factor correction application.


High Frequency, Soft Transitions Converter

  • Date of Publication 07 Mar 1993
  • Meeting end date 11 Mar 1993
  • On page 880-887
  • Location San Diego, California, USA
  • Conference/Proceedings Applied Power Electronics Conference and Exposition, March 1993. APEC '93. Conference Proceedings 1993, Eighth Annual

A high efficiency, high power density power conversion technology is presented. This topology is compatible with high output voltage applications such as 24V and 48V, where Schottky rectifiers cannot be used. The converter combines zero voltage switching across the primary switches, continuous energy transfer from the primary to the secondary and soft commutations of the output rectifiers. The soft switching of the output rectifiers minimizes the reverse recovery losses associated with ultra fast rectifiers operating at high frequency. An experimental converter using this concept is evaluated. The converter operates from an input voltage of 200V to 430V at 300 KHz, providing 400W (50V@8A) with efficiency of 95% at full load.


Constant Frequency Zero Voltage PWM Converters

  • Date of Publication 28 Apr 1992
  • Meeting end date 30 Apr 1992
  • On page 428-439
  • Location Nuremberg, Germany
  • Conference/Proceedings International Power Conversion & Intelligent Motion, April 1992. PCIM '92. Conference Proceedings 1992, Twenty-Fourth International

By utilizing a supplementary control switch, which steers the primary current back to the input source to achieve zero voltage switching conditions, a new family of ZVS-PWM converters is derived. The forward ZVS-PWM in single ended configuration is analyzed. High frequency, zero voltage switched, PWM technique is combined with continuous transfer of energy to the secondary, for double ended secondary, for double ended configuration, offering very high power density capability. Experimental results are presented for 300W converter, operating from a large input voltage range of 200V to 400V at 400 KHz switching frequency.


A New High Frequency, Zero Voltage Switched, PWM Converter

  • Date of Publication 23 Feb 1992
  • Meeting end date 27 Feb 1992
  • On page 657-664
  • Location Boston, MA, USA
  • Conference/Proceedings Applied Power Electronics Conference and Exposition, February 1992. APEC '92. Conference Proceedings 1992, Seventh Annual

A high efficiency, high power density converter, operating at constant frequency and switching at zero voltage is presented. Zero voltage switching conditions are achieved over a broad input voltage and output current range. Continuous power transfer from the input to the output minimizes the output filter requirements and by using integrated magnetic technique, high power density can be achieved. By employing the same configuration to classical PWM topologies, a new family of ZVS-PWM converters can be derived. An experimental 5V, 100A converter was designed and built. The converter operates from an input voltage of 200Vdc to 400Vdc, at 400 KHz switching frequency.

 


Constant Frequency, Forward Converter With Resonant Transition

  • Date of Publication 09 Jun 1991
  • Meeting end date 14 Jun 1991
  • On page 282-292
  • Location Toronto, Ontario, Canada
  • Conference/Proceedings High Frequency Power Conversion, June 1991. HFPC '91. Conference Proceedings 1991, Sixth International

A single ended forward converter, operating at constant frequency and switching at zero voltage is presented. By using a secondary switch, the main transformer’s core is symmetrically reset and a part of magnetizing energy is used to discharge the parasitic capacitance of the primary switch to zero. Zero voltage switching conditions are achieved over a broad input voltage and output current range. An experimental 500 KHz converter, which delivers an output power of 200W at 5V, is presented. Operating from an input voltage of 180 to 400 Vdc, the converter exhibits efficiency greater than 88% at full load.