Monthly Archives: March 2016

  • 23
    Feb 97

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

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.

  • 14
    Oct 97

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

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.

  • 07
    Sep 96

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

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.

  • 20
    Jun 95

The Impact Of Low Output Voltage Requirements On Power Converters

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.

 

  • 06
    May 95

The Impact Of Low Output Voltage Requirements On Power Converters

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.

  • 17
    Apr 94

High Efficiency DC-DC Converter

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

 

  • 28
    Jun 94

High Efficiency DC-DC Converter

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     

  • 13
    Feb 94

High Efficiency DC-DC Converter

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

  • 23
    May 93

Soft Transitions Power Factor Correction Circuit

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.

  • 22
    Jun 93

Soft Transitions Power Factor Correction Circuit

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.

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