http://ieeexplore.ieee.org/iel5/5610941/5624686/05624745.pdf

Power electronics

Three DC/DC converter topologies suitable for high-power-density high-power applications are presented. All three circuits operate in a soft-switched manner, making possible a reduction in device switching losses and an increase in switching frequency. The three-phase dual-bridge converter proposed is shown to have the most favorable characteristics. This converter consists of two three-phase inverter stages operating in a high-frequency six-step mode. In contrast to existing single-phase AC-link DC/DC converters, lower turn-off peak currents in the power devices and lower RMS current ratings for both the input and output filter capacitors are obtained. This is in addition to smaller filter element values due to the higher-frequency content of the input and output waveforms. Furthermore, the use of a three-phase symmetrical transformer instead of single-phase transformers and a better utilization of the available apparent power of the transformer (as a consequence of the controlled output inverter) significantly increase the power density attainable. >

A three-phase soft-switched high power density DC/DC converter for high power applications

Solid-state switch-mode rectification converters have reached a matured level for improving power quality in terms of power-factor correction (PFC), reduced total harmonic distortion at input AC mains and precisely regulated DC output in buck, boost, buck-boost and multilevel modes with unidirectional and bidirectional power flow. This paper deals with a comprehensive review of improved power quality converters (IPQCs) configurations, control approaches, design features, selection of components, other related considerations, and their suitability and selection for specific applications. It is targeted to provide a wide spectrum on the status of IPQC technology to researchers, designers and application engineers working on switched-mode AC-DC converters. A classified list of more than 450 research publications on the state of art of IPQC is also given for a quick reference.

/pdf/a-review-of-single-phase-improved-power-quality-ac-dc-2pm6h4zjxq.pdf

A review of single-phase improved power quality AC-DC converters

The performance of a high-power, high-power-density DC-to-DC converter based on the single-phase dual active bridge (DAB) topology is described. The dual active bridge converter has been shown to have very attractive features in terms of low device and component stresses, small filter components, low switching losses, high power density and high efficiency, bidirectional power flow, buck-boost operation, and low sensitivity to system parasitics. For high output voltages, on the order of kilovolts, a cascaded output structure is considered. The effects of snubber capacitance and magnetizing inductance on the soft switching region of control are discussed. Various control schemes are outlined. Coaxial transformer design techniques have been utilized to carefully control leakage inductance. The layout and experimental performance of a prototype 50 kW 50 kHz unit operating with an input voltage of 200 V DC and an output voltage of 1600 V DC are presented. >

Performance characterization of a high-power dual active bridge DC-to-DC converter

A more general averaging procedure that encompasses state-space averaging and that is potentially applicable to a much broader class of circuits and systems is presented. Examples of its application in resonant and PWM power convertors are presented. The technique is shown to be effective on a number of examples. including resonant type converters. The approach offers refinements to the theory of state-space averaging, permitting a framework for analysis and design when small ripple conditions do not hold. The method may find applications in simulation and design since it is considerably easier to simulate an averaged model than a switched model. >

/pdf/generalized-averaging-method-for-power-conversion-circuits-da237et2wc.pdf

Generalized averaging method for power conversion circuits

The inherent switching of power devices in a switch mode power supply generates electromagnetic interference (EMI) noise. This noise is dependent on several factors such as component layout, circuit parasitics, and the control techniques implemented. Several methods have been reported in literature to mitigate the EMI problem. However, until now, a metric to characterize and compare the EMI spectra of power converters is not available in literature. This paper proposes a simple metric to measure and characterize the EMI spectrum of power converters. The proposed technique is based upon the specification and thereby the size of an external passive filter required to meet the given EMI standards. The proposed metric is useful in evaluating and comparing the severity of the EMI noise generated by different implementations of a power converter. Thus, it allows the designer to choose the better implementation option from an EMI noise perspective. The use of the proposed metric is demonstrated through the comparison of the quality of spectra of a power converter with two different switching schemes.

A Metric for Evaluating the EMI Spectra of Power Converters

A tri-state boost converter with an additional boost-inductor free-wheeling interval was proposed earlier to eliminate the right-half-plane (RHP) zero that occurs in the control-to output transfer function of a classical boost converter under continuous-conduction mode of operation. A 'constant-D/sub o/' control scheme, in which the 'capacitor-charging' interval of the converter was kept constant, was employed. This resulted in a relatively large inductor current, especially under high line and load conditions, thereby causing high circuit losses. This paper proposes two variations of a novel dual-mode control (DMC) scheme that vary both the 'boost' and the 'capacitor charging' intervals. Control analysis, design, and limitations of the proposed DMC schemes are presented. Through computer simulations and hardware experiments the performance of the tri-state boost converter with DMC schemes are compared with those of the tri-state boost converter with 'constant-D/sub o/' control scheme, and the classical PI-controlled boost converter. The DMC schemes achieve a significant (about 10%) improvement in converter's efficiency for a wide load range over the 'constant-Do' control scheme.

http://ieeexplore.ieee.org/iel5/8633/27382/01218182.pdf

Dual mode control of tri-state boost converter for improved performance

A wide range zero-voltage switching (ZVS) active-clamped L-L type current-fed isolated DC-DC converter is proposed for fuel cells to utility interface application. The proposed converter maintains ZVS of all switches from full-load down to very light load condition for wide input voltage variation. Detailed operation, analysis, design, simulation and experimental results for the proposed converter are presented. The auxiliary active clamping circuit absorbs the turn-off voltage spike and also assists in achieving ZVS of main switches. The ZVS of auxiliary and main switches is achieved by the energy stored in the boost inductors and series inductor (aided by parallel inductor), respectively. Rectifier diodes operate with zero-current switching. An experimental converter rated at 200W has been designed, built and tested in the laboratory to verify the analysis, design and performance of the proposed converter for wide variations in input voltage and load.

Wide range ZVS active-clamped L-L type current-fed DC-DC converter for fuel cells to utility interface: Analysis, design and experimental results

This paper presents a study on the design and implementation of an active filter for reducing the common mode (CM) electromagnetic interference (EMI) noise suitable for off-line power converters. A current-sense voltage-feedback topology has been selected from those reported in literature. The selected topology has the advantage that its high frequency active noise compensation circuit is isolated from the mains. A simple feedback structure employing a high frequency linear amplifier and passive filter components has been designed. The major problem with active feedback filter is the stability of the feedback system, which is influenced by the parasitics of the circuit components. Special attention has been paid to both stability analysis and practical implementation of the filter. A prototype of the active CM filter has been built and tested. The analysis and the experimental results demonstrate the usefulness and limitations of such an active CM EMI filter.

Design of a current-sense voltage-feedback common mode EMI filter for an off-line power converter

Synchronous rectifiers used in high frequency, low output voltage applications are power MOSFETs specially designed to replace the usual output Schottky diodes in order to reduce converter losses. This paper deals with the analysis and design optimization of a synchronous rectifier suitable for applications of 1 to 10 MHz switching-mode power supplies. Three different MOSFET structures were studied and evaluated through detailed 2-dimensional device simulations. The internal parameters are optimized against three major performance factors, namely (1) the recovery time of the body diode, (2) the product of on-state resistance and input capacitance, i.e., the loss factor, and (3) the breakdown voltage of the body diode. Based on the evaluation, the UMOS structure produces the lowest RC loss factor and the shortest body diode reverse recovery. The final design optimization of the UMOS was then carried out and an optimized device is presented as the final design. >

Ramesh Oruganti

Papers

A Metric for Evaluating the EMI Spectra of Power Converters

Dual mode control of tri-state boost converter for improved performance

Wide range ZVS active-clamped L-L type current-fed DC-DC converter for fuel cells to utility interface: Analysis, design and experimental results

Design of a current-sense voltage-feedback common mode EMI filter for an off-line power converter

Design considerations of power MOSFET for high frequency synchronous rectification